WO2024095198A2 - Source de puissance - Google Patents

Source de puissance Download PDF

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Publication number
WO2024095198A2
WO2024095198A2 PCT/IB2023/061053 IB2023061053W WO2024095198A2 WO 2024095198 A2 WO2024095198 A2 WO 2024095198A2 IB 2023061053 W IB2023061053 W IB 2023061053W WO 2024095198 A2 WO2024095198 A2 WO 2024095198A2
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WO
WIPO (PCT)
Prior art keywords
fuel
reactor
coolant
source
power source
Prior art date
Application number
PCT/IB2023/061053
Other languages
English (en)
Other versions
WO2024095198A3 (fr
Inventor
Calym NYSCHENN
Original Assignee
Aurelia Lumina Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GBGB2216274.7A external-priority patent/GB202216274D0/en
Priority claimed from GBGB2216266.3A external-priority patent/GB202216266D0/en
Priority claimed from GB2216264.8A external-priority patent/GB2624152A/en
Priority claimed from GBGB2216267.1A external-priority patent/GB202216267D0/en
Priority claimed from GBGB2216307.5A external-priority patent/GB202216307D0/en
Priority claimed from GBGB2216276.2A external-priority patent/GB202216276D0/en
Priority claimed from GBGB2216272.1A external-priority patent/GB202216272D0/en
Priority claimed from GBGB2216265.5A external-priority patent/GB202216265D0/en
Priority claimed from GBGB2216293.7A external-priority patent/GB202216293D0/en
Priority claimed from GBGB2301873.2A external-priority patent/GB202301873D0/en
Application filed by Aurelia Lumina Ltd filed Critical Aurelia Lumina Ltd
Publication of WO2024095198A2 publication Critical patent/WO2024095198A2/fr
Publication of WO2024095198A3 publication Critical patent/WO2024095198A3/fr

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Classifications

    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C1/00—Reactor types
    • G21C1/30—Subcritical reactors ; Experimental reactors other than swimming-pool reactors or zero-energy reactors
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C7/00—Control of nuclear reaction
    • G21C7/34—Control of nuclear reaction by utilisation of a primary neutron source
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C1/00—Reactor types
    • G21C1/02—Fast fission reactors, i.e. reactors not using a moderator ; Metal cooled reactors; Fast breeders
    • G21C1/03—Fast fission reactors, i.e. reactors not using a moderator ; Metal cooled reactors; Fast breeders cooled by a coolant not essentially pressurised, e.g. pool-type reactors
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C17/00—Monitoring; Testing ; Maintaining
    • G21C17/10—Structural combination of fuel element, control rod, reactor core, or moderator structure with sensitive instruments, e.g. for measuring radioactivity, strain
    • G21C17/108—Measuring reactor flux
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C17/00—Monitoring; Testing ; Maintaining
    • G21C17/10—Structural combination of fuel element, control rod, reactor core, or moderator structure with sensitive instruments, e.g. for measuring radioactivity, strain
    • G21C17/112—Measuring temperature
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H2277/00—Applications of particle accelerators
    • H05H2277/13—Nuclear physics, e.g. spallation sources, accelerator driven systems, search or generation of exotic elements
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/30—Nuclear fission reactors

Definitions

  • POWER SOURCE The present invention relates to a power source.
  • Increasing moves towards green energy and volatility in energy markets have intensified a need for power sources that do not rely on fossil fuels or intermittent environmental factors such as sunshine and wind.
  • Thermal nuclear reactors are well positioned to meet these needs but traditionally require enormous investment, large amounts of land and long construction timetables.
  • control of conventional reactors is complicated and has, on a few occasions, failed resulting in serious accidents.
  • Another issue is the build-up of nuclear waste, often toxic isotopes with long half-lives that require secure storage over the very long term.
  • thermal nuclear reactors require enriched fuel, for example uranium with a higher proportion of the isotope U-235 than is found in naturally occurring uranium.
  • the fission cross-section is typically a U shaped curve (see accompanying Figures A13 & A14), with high values at very low energies a minimum around a couple of MeV and rising with higher energy.
  • a second reason is that convenient materials, notably water, can be used as both a coolant and a moderator for thermal neutrons.
  • thermal fission with enriched fuel happens to align with weapons programs which has often helped unlock significant state funding.
  • Fast fission has mostly only been considered practically viable in combination with thermal fission with an enriched fuel.
  • One avenue of research is in Accelerator Driven Sub-critical Reactors (ADSR). This has the promise of not requiring dangerous or expensive fuel.
  • ADSR Accelerator Driven Sub-critical Reactors
  • spallation relies on high energy particles, such as protons, disintegrating a nucleus to generate, inter alia, high energy neutrons. Spallation, however, requires an incident particle to have an energy in excess of 500million electron- volts. Particle accelerators capable of providing particles at such high energies are very large and very expensive.
  • a linear accelerator having an energy level of 800MeV or more is required, and this may be around 1km or more in length.
  • Another difficulty with US8983017 is that the reactor contains a molten salt which is extremely corrosive. This is a problem that it shares with the reactor disclosed in United States patent US9368244.
  • An IAEA paper from 2015 “Status of Accelerator Driven Systems Research and Technology Development” available at https://www.iaea.org/publications/10870/status-of-accelerator-driven- systems-research-and-technology-development is still focussed on spallation.
  • a power source as set out in accompanying claim 1.
  • Preferred features of the present invention are set out in accompanying claims 2 to 28.
  • a power source comprising: an ignition region comprising a target material arranged to receive a flux of protons and generate neutrons in response thereto; a reactor core containing a sub-critical quantity of fissionable material arranged as a structure having a plurality of layers around the ignition region; a coolant containing at least one metal; wherein the reactor core includes at least one metal incorporated with the fissionable material to modify the structural and/or thermal properties of the fissionable material such that the structure is substantially self-supporting and such that the structure has a melting point above the melting point of the coolant and below the boiling point of the coolant, an accelerator arranged to supply a flux of protons with an energy at least 5MeV and with a beam current of at least 5 ⁇ A to the target material in the ignition region,
  • an electricity generation system comprising a reactor core, a source of protons, a heat exchanger for extracting heat from the reactor and transferring extracted heat to a generating arrangement
  • the reactor comprising: a reactor vessel containing a mass of fissionable fuel arranged in at least one layer spaced from an ignition region, the ignition region containing actinide material, the at least one layer of fuel comprising a plurality of elements arranged to permit the flow of coolant around the fuel, a path through a wall of the reactor vessel permitting the passage of protons to the ignition region, and a coolant of metal or metal alloy, the coolant in thermal contact with the fissionable fuel elements, the coolant further having a melting point lower than that of the fuel and a boiling point greater than the melting point of the fissionable fuel, wherein the fuel generates insufficient neutrons by spontaneous fission in the absence of a flux of protons to the ignition region to maintain a critical or super-critical reaction.
  • a An electricity generation system comprising a reactor, a source of protons, a heat exchanger for extracting heat from the reactor and transferring extracted heat to a generator
  • the reactor comprising: a reactor vessel containing fuel arranged in at least one layer spaced from an ignition region containing actinide material and material for a proton-neutron reaction in which a parent atom and an inbound proton generates a reaction that emits one or more neutrons and a daughter element reverts to the parent element via beta decay or electron capture, whereby the material for the proton-neutron reaction is arranged to be irradiated by protons and to supply neutrons to the actinide element at the ignition region, the at least one layer of fuel comprising a plurality of elements arranged to permit the flow of coolant around the fuel, a path through a wall of the reactor vessel permitting the passage of particles to the ignition region from the source of protons, and a coolant selected from metal or metal alloy, the coolant thermal
  • an energy multiplier comprising a reactor and a particle accelerator, the energy multiplier comprising: a reactor vessel, at least one ignition region within the reactor vessel, containing material responsive to incident protons to provide neutrons for irradiating an actinide material, the actinide material responsive to incident neutrons to provide further neutrons, a particle accelerator which, in use, consumes a quantity of electrical energy, the particle accelerator being arranged to feed a path to convey particles to the at least one ignition region, actinide fuel comprising a plurality of elements supported by a structure within the reactor vessel and around the ignition region in at least one layer, a coolant comprising metal or metal alloy in thermal contact with the plurality of fast-fission fuel elements, the coolant having a melting point below a melting point of the fast-fission fuel and a boiling point above the melting point of the fast-fission fuel, and a heat exchanger for extracting heat from the coolant, and an electrical generator for generating electrical energy from the
  • an actinide fuel for use in a nuclear reactor, the fuel comprising: at least one actinide element and 2.5 to 35 atomic weight percent of material comprising at least one of tungsten, rhenium, tantalum, molybdenum, niobium, and zirconium.
  • an actinide fuel structure for a reactor comprising at least one source of neutrons, the fuel structure comprising: at least one layer comprising a plurality of elements of actinide fuel arranged on a support, the plurality of elements in a particular layer arranged to be substantially equidistant from the at least one source of neutrons in the reactor.
  • a power source comprising: a reactor vessel comprising shielding material, at least one ignition bulb, arranged within the reactor vessel, containing material responsive to incident protons to provide neutrons for irradiating an actinide material, the actinide material responsive to incident neutrons to provide further neutrons, a path to convey protons from outside the reactor vessel to the at least one ignition bulb, fast-fission fuel comprising a plurality of elements arranged within the reactor vessel and around the ignition bulb in at least one shell, at least one structure supporting the fuel in use while permitting substantially free flow of coolant around the fuel, a coolant comprising metal or metal alloy in thermal contact with the plurality of fast-fission fuel elements, the coolant having a melting point below a melting point of the fast-fission fuel and a boiling point above the melting point of the fast-fission fuel, and a heat exchanger to extract heat from the coolant.
  • a power source comprising: a reactor vessel containing, at least one neutron source, arranged within the reactor vessel, containing material capable of a proton neutron reaction, and an actinide material, the actinide material arranged to receive incident neutrons from the material capable of a proton/neutron reaction, a path to convey protons from outside the reactor vessel to the at least one neutron source, nuclear fuel comprising uranium and between 2.5 and 35 percent by atomic weight of at least one of tungsten, rhenium, tantalum, molybdenum, niobium, and zirconium, the fuel arranged as a plurality of elements in at least one layer, the fuel elements supported by a frame around the neutron source, a metal or metal alloy coolant directly surrounding the plurality of fuel elements, the coolant having a melting point below a melting point of the fast-fission fuel and a boiling point above the melting point of the fast-fission fuel, and a heat exchanger
  • a power source comprising: at least one ignition region, arranged within a reactor vessel, the ignition region containing actinide material responsive to incident protons to generate neutrons, a path to convey protons from outside the reactor vessel to the at least one ignition region, fissionable fuel comprising a plurality of fuel elements arranged around the ignition region in at least one shell,at least one structure supporting the fuel in use while permitting substantially free flow of coolant around the fuel, a coolant comprising metal or metal alloy in contact with the plurality of fast-fission fuel elements, the coolant having a melting point below a melting point of the fast-fission fuel and a boiling point above the melting point of the fast-fission fuel.
  • a power source comprising: a reactor vessel containing shielding material, at least one ignition means, arranged within the reactor vessel, containing material responsive to incident particles to provide neutrons for irradiating fast- fission fuel, a path to convey particles from outside the reactor vessel to the at least one ignition means, fast-fission fuel comprising a plurality of sub-critical elements arranged around the ignition means, at least one means for supporting the fuel in use while permitting substantially free flow of coolant around the fuel, a coolant comprising metal or metal alloy in contact with the plurality of fast- fission fuel elements, the coolant being a solid at ambient temperature and a liquid at the reactor operating temperature.
  • a nuclear reactor comprising a reactor vessel, the reactor further comprising: fissionable fuel arranged in at least one layer spaced from an ignition region, the ignition region containing actinide material, the at least one layer of fuel comprising a plurality of elements arranged to permit the flow of coolant around the fuel, a window through a wall of the reactor vessel permitting the passage of energetic particles to the ignition region, and a coolant of metal or metal alloy, the coolant in contact with the fuel elements, the coolant further having a melting point lower than that of the fuel and a boiling point greater than the melting point of the fuel, wherein the reactor is arranged such that insufficient neutrons are generated from spontaneous fission of the fissionable fuel to propagate a critical reaction in the absence of excitation by said energetic particles.
  • nuclear reactor comprising a reactor vessel, the reactor further comprising: fuel arranged in at least one layer spaced from an ignition region containing actinide material, and material for a proton-neutron reaction in which a parent atom and an inbound proton generates a reaction that emits one or more neutrons and a daughter element reverts to the parent element via beta decay or electron capture, whereby the material for the proton- neutron reaction is arranged to be irradiated by protons and to supply neutrons to the actinide element at the ignition region, the at least one layer of fuel comprising a plurality of elements arranged to permit the flow of coolant around the fuel, a window through a wall of the reactor vessel permitting the passage of particles to the ignition point, and a coolant selected from metal or metal alloy, the coolant directly in contact with the fuel, and the coolant further having a melting point lower than that of the fuel and a boiling point greater than the melting point of the fuel.
  • a method of rendering a fast fission nuclear reactor safe in response to an uncontrolled heat transfer rate comprising a reactor vessel containing at least one actinide fuel element supported by a support structure and arranged in thermal contact with a coolant, the coolant being a metal or metal alloy having a melting point lower than the melting point of the fuel and a boiling point greater than the melting point of the fuel, the method comprising: the at least one fuel element being subject to a nuclear reaction that heats the fuel element, a portion of the at least one fuel element melting, detaching at least a portion of the at least one fuel element from the support structure, the detached portion of the at least one fuel element reducing its participation in a critical or super-critical nuclear reaction, the coolant and fuel reducing in temperature, and the coolant and fuel solidifying in response to the reduction in temperature.
  • a power source comprising: an ignition region comprising a target material arranged to receive a flux of protons and generate neutrons in response thereto; a reactor core containing a sub-critical quantity of actinide material arranged as a structure having a at least one layer around the ignition region, wherein the actinide material comprises at least Thorium or Uranium and generates insufficient neutrons by spontaneous fission in the absence of the flux of protons to the ignition region to maintain a critical or super-critical reaction; a coolant containing at least one metal; an accelerator arranged to supply a flux of protons having an energy of between 4MeV and 200MeV to the target material in the ignition region, a window in the reactor core to permit the passage of said flux of protons unimpeded by coolant or actinide material; a control arrangement to control the power of the proton flux to modulate reactor core power.
  • a nuclear reactor comprising: a container containing a coolant, a central support arranged within the container, a source of a flux of protons, the central support carrying a plurality of substantially identical fuel elements extending radially outward from the support, wherein the elements generate insufficient neutrons by spontaneous fission in the absence of the flux of protons to the ignition region to maintain a critical or super-critical reaction, an ignition region arranged in proximity to the fuel elements, the ignition region being responsive to the flux of protons to generate neutrons, wherein the fuel elements are supported so as to be in thermal contact with the coolant and sustained application of protons having energies greater than 4MeV to the ignition region generates an increasing amount of neutrons in the fuel elements over time.
  • a nuclear reactor comprising: a reactor vessel for containing a coolant, the reactor vessel containing at least one element of actinide material including at least one of thorium and uranium or a mixture of both which is fissionable in response to a flux of neutrons, an ignition region arranged to produce neutrons in response to a flux of protons, wherein the actinide material generates insufficient neutrons by spontaneous fission in the absence of a flux of protons to an ignition region to maintain a critical or super-critical reaction, wherein the reactor further comprising means for forced distribution of coolant within the vessel.
  • a nuclear reactor comprising: a container containing a coolant, a support arranged within the container, the support carrying a plurality of substantially identical fuel elements, the support structure arranged to rotate within the container about an axis, an ignition region arranged in proximity to the fuel elements, the ignition region being responsive to a flux of protons to generate neutrons, a path for conveying protons from outside of the container to the ignition region, wherein the fuel elements are supported so as to be in thermal contact with the coolant, and wherein the fissionable material generates insufficient neutrons by spontaneous fission in the absence of a flux of protons to the ignition region to maintain a critical or super-critical reaction.
  • a nuclear reactor comprising: a reactor vessel comprising shielding material, at least one ignition bulb, arranged within the reactor vessel, containing material responsive to incident protons to provide neutrons for fissionable material, a path to convey protons from a particle accelerator outside the reactor vessel to the at least one ignition bulb, fissionable fuel comprising a plurality of elements arranged within the reactor vessel and around the ignition bulb in at least one shell, at least one structure supporting the fuel in use while permitting substantially free flow of coolant around the fuel, a coolant comprising metal or metal alloy having a density at room temperature of greater than 5g/cm 3 in thermal contact with the plurality of fuel elements, and a pump external to the vessel, the container comprising at least a flow line for carrying coolant to the external pump and a return line for carrying the coolant from the external pump to the container.
  • a power source comprising: an ignition region comprising a target material arranged to receive a flux of protons and generate neutrons in response thereto; a reactor core containing a sub-critical quantity of fissionable material arranged as a plurality of fuel elements of substantially the same size; a coolant containing at least one metal; an accelerator arranged to supply a flux of protons with an energy of between 4MeV and 200MeV and having a beam current of at least 100 ⁇ A to the target material in the ignition region, a window in the reactor core to permit the passage of said flux of protons unimpeded by coolant or fissionable material; a control arrangement to control the power of the proton flux to modulate reactor core power; a heat exchanger arranged to absorb heat from the molten metal coolant for transfer to a power consumer; wherein the control arrangement is arranged to model future neutron flux based on a measure of reactor state and to modulate the proton flux power based on said model.
  • a nuclear fuel element comprising; a support structure, and an actinide portion comprising at least 80% by weight of Thorium, and at least 1% of another metal selected from Iron, Nickel, magnesium and Uranium to reduce the melting point of the actinide portion, wherein the fuel element is attached to the support structure such that the actinide portion deforms under its own weight at temperatures exceeding 1700 ⁇ C.
  • a nuclear reactor comprising: a particle accelerator, a reactor vessel comprising shielding material, at least one ignition bulb, arranged within the reactor vessel, containing material responsive to incident protons to provide neutrons for fissionable material, a path to convey protons from the particle accelerator outside the reactor vessel to the at least one ignition bulb, fissionable fuel comprising a plurality of elements arranged within the reactor vessel and around the ignition bulb in at least one shell, at least one structure supporting the fuel in use while permitting substantially free flow of coolant around the fuel, a coolant comprising metal or metal alloy in thermal contact with the plurality of fuel elements, and a heat exchanger to extract heat from the coolant, the reactor further comprising a controller arranged to control the output of the particle accelerator to provide at least two distinct output levels from the nuclear reactor.
  • an energy multiplier comprising a nuclear reactor and a particle accelerator
  • the reactor comprising: a reactor vessel for containing a coolant, at least one fissionable fuel element arranged within the reactor vessel, an ignition region arranged in the reactor vessel, the ignition region comprising a first portion containing an element responsive to an incoming proton to generate a neutron and a second portion containing an element responsive to neutrons generated in the first portion to provide further neutrons, the particle accelerator coupled to supply protons to the first portion of the ignition region, whereby the particle accelerator comprises a linear particle accelerator arranged to generate protons having energies in excess of 4MeV.
  • a method of operating an electricity generation system comprising: a subcritical fast fission nuclear reactor, the nuclear reactor comprising a reactor vessel containing at least one actinide fuel element supported by a support structure and arranged in thermal contact with a coolant and a source of particles to drive the reactor into the critical or super-critical region, the method being responsive to an uncontrolled heat transfer rate and comprising: the at least one fuel element being subject to a nuclear reaction that heats the fuel element, a portion of the at least one fuel element melting and changing its geometry, the melted portion of the at least one fuel element reducing its participation in a critical or super-critical nuclear reaction, the coolant and fuel reducing in temperature, and the coolant and fuel solidifying in response to the reduction in temperature.
  • a system for treating material at high temperatures comprising: an ignition region comprising a target material arranged to receive a flux of protons and generate neutrons in response thereto; a reactor core containing a sub-critical quantity of fissionable material arranged as a structure having at least one layer around the ignition region; a coolant containing at least one metal; an accelerator arranged to supply a flux of protons with an energy of between 4MeV and 200MeV, and having a beam current of at least 100 ⁇ A to the target material in the ignition region, a window in the reactor core to permit the passage of said flux of protons unimpeded by coolant or fissionable material; a control arrangement to control the power of the proton flux to modulate reactor core power; a heat exchanger arranged to absorb heat from the molten metal coolant for transfer to a working fluid; wherein the control arrangement is arranged to model future neutron flux based on a easure of reactor state and to modulate
  • a system for treating material at high temperatures comprising a reactor vessel comprising shielding material, at least one ignition bulb, arranged within the reactor vessel, containing material responsive to incident protons to provide neutrons for irradiating an actinide material, the actinide material responsive to incident neutrons to provide further neutrons, a path to convey protons from outside the reactor vessel to the at least one ignition bulb, actinide fuel comprising a plurality of elements arranged within the reactor vessel and round the ignition bulb in at least one shell, at least one structure supporting the fuel in use while permitting substantially free flow of coolant around the fuel, a coolant comprising metal or metal alloy in thermal contact with the plurality of fuel elements, and a heat exchanger to transfer heat from the coolant to a working fluid, a kiln enclosure for containing material to be heated, and at least one conduit arranged to conduct heat from the working fluid to the kiln enclosure.
  • a system for treating material at high temperatures comprising: at least one ignition region, arranged within a reactor vessel, the ignition region containing actinide material responsive to incident protons to generate neutrons, a path to convey protons from outside the reactor vessel to the at least one ignition region, fissionable fuel comprising a plurality of fuel elements arranged around the ignition region in at least one shell, at least one structure supporting the fuel in use while permitting substantially free flow of coolant around the fuel, a coolant comprising metal or metal alloy in contact with the plurality of fuel elements, a heat exchanger to transfer heat from the coolant to a working fluid and a kiln enclosure for containing material to be heated, at least one conduit arranged to conduct heat from the working fluid to the kiln enclosure.
  • a propulsion system for driving a vehicle via a shaft
  • the propulsion system comprising: an ignition region comprising a target material arranged to receive a flux of protons and generate neutrons in response thereto; a reactor core containing a sub-critical quantity of fissionable material arranged as a structure having at least one layer around the ignition region; a coolant containing at least one metal; an accelerator arranged to supply a flux of protons with an energy of between 4MeV and 200MeV to the target material in the ignition region, a window in the reactor core to permit the passage of said flux of protons unimpeded by coolant or fissionable material; a control arrangement to control the power of the proton flux to modulate reactor core power; a heat exchanger arranged to absorb heat from the molten metal coolant for transfer to a working fluid; and a turbine arranged to rotate a shaft in response to the working fluid.
  • a propulsion system for driving a vehicle via a shaft
  • the propulsion system comprising: a reactor vessel comprising shielding material, at least one ignition bulb, arranged within the reactor vessel, containing material responsive to incident protons to provide neutrons for irradiating an actinide material, the actinide material responsive to incident neutrons to provide further neutrons, a path to convey protons from outside the reactor vessel to the at least one ignition bulb, fissionable fuel comprising a plurality of elements arranged within the reactor vessel and around the ignition bulb in at least one shell, at least one structure supporting the fuel in use while permitting substantially free flow of coolant around the fuel, a coolant arranged in thermal contact with the plurality of fuel elements, and a heat exchanger to transfer heat from the coolant to a working fluid, and a turbine arranged to rotate a shaft in response to the working fluid.
  • a propulsion system for driving a vehicle via a shaft
  • the propulsion system comprising: at least one ignition region, arranged within a reactor vessel, the ignition region containing actinide material responsive to incident protons to generate neutrons, a path to convey protons from outside the reactor vessel to the at least one ignition region, fissionable fuel comprising a plurality of fuel elements arranged around the ignition region in at least one shell, at least one structure supporting the fuel in use while permitting substantially free flow of coolant around the fuel, a coolant comprising metal or metal alloy in contact with the plurality of fuel elements, the coolant having a melting point below a melting point of the fuel and a boiling point above the melting point of the fuel, a heat exchanger to transfer heat from the coolant to a working fluid, and a turbine arranged to rotate a shaft in response to the working fluid.
  • a system for generating heat for an industrial process comprising: an ignition region comprising a target material arranged to receive a flux of protons and generate neutrons in response thereto; a reactor core containing a sub-critical quantity of fissionable material arranged as a structure having at least one layer around the ignition region; a coolant containing at least one metal; an accelerator arranged to supply a flux of protons with an energy of between 4MeV and 200MeV, and having a beam current of at least 100 ⁇ A to the target material in the ignition region, a window in the reactor core to permit the passage of said flux of protons unimpeded by coolant or fissionable material; a control arrangement to control the power of the proton flux to modulate reactor core power; a heat exchanger arranged to absorb heat from the molten metal coolant for transfer to a working fluid; and at least one conduit arranged to conduct heat from the working fluid to the industrial process.
  • a system for generating heat for an industrial process comprising a reactor vessel comprising shielding material, at least one ignition bulb, arranged within the reactor vessel, containing material responsive to incident protons to provide neutrons for irradiating an actinide material, the actinide material responsive to incident neutrons to provide further neutrons, a path to convey protons from outside the reactor vessel to the at least one ignition bulb, actinide fuel comprising a plurality of elements arranged within the reactor vessel and around the ignition bulb in at least one shell, at least one structure supporting the fuel in use while permitting substantially free flow of coolant around the fuel, a coolant comprising metal or metal alloy in thermal contact with the plurality of fuel elements, and a heat exchanger to transfer heat from the coolant to a working fluid, and at least one conduit arranged to conduct heat from the working fluid to the industrial process.
  • a system for generating heat for an industrial process comprising: at least one ignition region, arranged within a reactor vessel, the ignition region containing actinide material responsive to incident protons to generate neutrons, a path to convey protons from outside the reactor vessel to the at least one ignition region, fissionable fuel comprising a plurality of fuel elements arranged around the ignition region in at least one shell, at least one structure supporting the fuel in use while permitting substantially free flow of coolant around the fuel, a coolant comprising metal or metal alloy in contact with the plurality of fuel elements, a heat exchanger to transfer heat from the coolant to a working fluid, and at least one conduit arranged to conduct heat from the working fluid to the industrial process.
  • a system for generating heat for residential, district or commercial consumers comprising: at least one ignition region, arranged within a reactor vessel, the ignition region containing actinide material responsive to incident protons to generate neutrons, a path to convey protons from outside the reactor vessel to the at least one ignition region, fissionable fuel comprising a plurality of fuel elements arranged around the ignition region, a coolant comprising metal or metal alloy in thermal contact with the plurality of fuel elements, a heat exchanger to transfer heat from the coolant to a working fluid, and at least one conduit arranged to conduct heat from the working fluid to at least one heating consumer.
  • a nuclear reactor comprising a nuclear fuel source and a control arrangement for adjusting the power level of the reactor, wherein the thermal output of the reactor coolant is arranged to supply a first thermal consumer arranged to provide electricity and a second thermal consumer arranged to supply heat to a heating circuit and a control system arranged arranged to vary the balance of heat supplied to each of the first and second circuits and to adjust the power level of the reactor wherein the control system includes a module for estimating a prediction of demand from at least one of the first and second thermal consumers and is arranged to determine a control strategy including adjusting the balance and adjusting total reactor power wherein total reactor power level is expected to vary less rapidly than individual power demand from the first and second thermal consumers.
  • Embodiments contrast with conventional approaches to nuclear power generation which mostly deliberately slow neutrons to a region of high cross section or try to use very high energies, the higher the better, to try to operate in a higher cross section region. Instead, embodiments typically use a novel core structure with patience such that a non-critical mass of material undergoes a gradual buildup of activity under the action of a sustained but relatively low energy accelerator, with manageable power requirements.
  • the following preferred features may be applied to any aspect of the invention.
  • the ignition source or region may operate on two similar, but different principles: a two-stage process and a single stage process.
  • the target material may comprise a first material responsive to proton bombardment at energies below 20MeV to generate neutrons within a first energy range and a second material responsive to the neutrons in the first energy range to generate neutrons in a second energy range.
  • the first material may comprise material for a proton-neutron reaction in which a parent element emits a neutron and a daughter element of the parent reverts to the parent element via beta decay or electron capture. When the material exhibits a circular reaction, no material is consumed, promoting a long lifetime of the ignition source.
  • the first material is preferably selected from lithium-7, oxygen-18, nitrogen-14, nickel-64, zinc-68 and cadmium-112 which materials all exhibit a suitable circular reaction. Lithium-7 is particularly preferred.
  • the material for a proton-neutron reaction is preferably arranged to be withdrawn from the reactor without disturbing the fuel and/or the coolant. Despite the circular reaction, some degradation of the material is unavoidable, so it is beneficial to be able to replace the material with minimal disruption to the reactor.
  • the fuel bulb/region operates at 1000oC and above meaning that the material for a proton-neutron reaction is preferably contained in a tungsten or molybdenum container to withstand the high temperatures.
  • the ignition region may contain actinide material responsive to incident protons to generate neutrons.
  • actinide material responsive to incident protons to generate neutrons.
  • This “one-step” process allows for a more straightforward design of ignition bulb but requires a more powerful and expensive particle accelerator.
  • at least one further ignition bulb is provided which is arranged to receive protons from the at least one particle accelerator.
  • fuel comprising a further plurality of fast fission fuel elements arranged around the at least one further ignition bulb.
  • the further ignition bulb and the further plurality of fast fission fuel elements are controlled independently.
  • An ignition arrangement comprises a first chamber and a second chamber, the first chamber containing a first material responsive to incident protons to provide a number of first neutrons, the second chamber containing an actinide material responsive to first neutrons to provide a number of second neutrons, greater than the number of first neutrons, the first chamber being arranged, in use, to receive protons from a particle accelerator and the second chamber is arranged, in use, to receive at least a proportion of the first neutrons from the material in the first chamber, wherein the second chamber is located, in use, relative to the fissionable fuel such that at least a proportion of the second neutrons impinge on the fuel.
  • the first material preferably comprises material for a proton-neutron reaction in which a parent atom and the inbound proton generates a reaction that emits one or more neutrons.
  • the first material preferably comprises at least one of lithium-7, oxygen-18, nitrogen-14, nickel-64, zinc-68 and cadmium-112, more preferably Lithium-7.
  • the second material is preferably uranium-238.
  • the second chamber is preferably at least partially defined by the wall of a reactor vessel.
  • the first chamber is preferably separable from the second chamber.
  • the at least one actinide element comprising the fuel is preferably selected from Thorium, Uranium, Neptunium, Plutonium and Americium.
  • the actinide element comprises uranium or thorium due to a combination of abundance and cost. More preferably the actinide element is uranium due to improved reactivity when compared with thorium. More preferably still the uranium comprises uranium-238, which may comprise depleted uranium or spent uranium, available at low cost.
  • the fuel containing the actinide element may also comprise an alloy with a proportion of another metal to raise the melting point of the actinide element. This allows a reactor to be operated at a higher temperature which is more efficient.
  • the another metal preferably has a higher melting point than the actinide material and may comprise at least one of tungsten, rhenium, tantalum, molybdenum, niobium, and zirconium in a proportion from 2.5% to 35%, more preferably in a proportion between 2.5% and 10%, and still more preferably substantially 3%.
  • tungsten is preferred as the another metal since a lower proportion of tungsten is required to elevate the melting point of the actinide element.
  • a lower proportion of the another metal is preferred since it has less of an impact on the reactivity of the actinide material.
  • a fuel element comprising another metal thus contains 65 to 97.5 percent by weight of the actinide fuel material, more preferably 90 to 97.5 percent by weight of the actinide fuel material and more preferably still, substantially 3 percent by weight of the actinide fuel material.
  • the actinide element in the fuel material preferably comprises at least 90% uranium-238, more preferably at least 98% uranium-238.
  • a doped actinide fuel may be used, containing a portion of another actinide with a greater cross section to improve reaction rates. Plutonium is the most effective such doping material.
  • the fuel structure preferably comprises fuel elements are provided as self-supporting structural elements within the coolant. This simplifies the mounting of the fuel and allows faster manufacture. More preferably, the structure supporting the fuel elements comprises a cantilevered structure. This further simplifies the mounting of the fuel.
  • a fuel element according to embodiments of the invention are preferably shaped to form a cantilevered self-supporting component of a reactor core extending from a root to be attached to a base element. By using a cantilevered structure, there are fewer support elements to interrupt the flow of neutrons and coolant within the reactor.
  • the fuel elements are preferably attached to the support structure by at least one pin. For even further simplification of the structure, the fuel elements are preferably integrally formed with a base element.
  • Structural elements of the fuel preferably comprise tungsten or molybdenum to withstand the high core temperatures.
  • the fuel elements in a particular layer of fuel are preferably arranged substantially equidistant from the ignition region or bulb. This helps to ensure a predictable and consistent reaction rate within the core.
  • the fuel elements in the first layer are preferably arranged to be substantially 200mm from the source of neutrons. The exact geometry of the fuel relative to ignition source is determined from considerations of cooling and neutron flux but this distance is a good compromise in certain embodiments of the present invention.
  • the at least one fuel layer is arranged, in use, to be surrounded by coolant and at a distance from the source of neutrons selected to permit coolant flow around the layer and source sufficient to remove heat generated in use.
  • the or each layer of fuel is preferably substantially cylindrical or spherical, more preferably substantially spherical to best exploit the neutrons from the ignition bulb or region.
  • the fuel elements in a particular layer are preferably arranged to substantially surround the ignition region. This better utilises space within the reactor and neutrons from the ignition source.
  • Each layer preferably comprises a plurality of groups of three elements arranged to substantially surround the source of neutrons. This provides a good compromise between ease of assembly and number of parts required.
  • each layer may equally comprise groups of four (or even more) elements.
  • the plurality of elements in the at least one layer of fuel are preferably arranged to promote thermal convection of the coolant. This improves cooling of the fuel to prevent undue thermal stresses on the fuel which might cause deformation and/or cracking.
  • the fuel elements preferably comprise elongate structures, more preferably ribs. The ribs are preferably attached substantially centrally to the support to reduce stresses in the fuel element.
  • a reactor according to embodiments of the invention may comprise a single layer of fuel, to generate more heat
  • at least one further layer of fuel comprising a plurality of elements.
  • the at least one further layer is preferably arranged to be between 50 and 200mm, preferably substantially 100mm, from adjacent layers.
  • Each fuel element is preferably spaced from adjacent fuel elements by between substantially 15mm and 20mm.
  • Each fuel element is preferably arranged, in use, to be surrounded by coolant and at a distance from adjacent fuel elements selected to accommodate the heat transfer ability of the coolant.
  • the at least one layer arranged to be closer to the source of neutrons preferably has fewer elements than at least one layer arranged to be further away from the source of neutrons.
  • An actinide fuel structure for use with embodiments of the invention preferably comprise at least 3 layers. This provides a good power output when uranium is used as the fuel.
  • An actinide fuel structure for use with embodiments of the invention may additionally comprise at least 5 layers. This provides a good power output when thorium is used as the fuel.
  • Further layers of fuel, for example at least 7 layers, provide higher power outputs but may have a drawback in terms of coolant. Solder may cease to be appropriate at this number of layers due to absorption of neutrons (moderation) from the ignition source. LBE still provides an excellent coolant for this size of reactor.
  • a fuel structure comprises at least some fuel elements which are arranged, in use, to cause the reactor to react in a critical or super- critical manner in response to bombardment by a predetermined quantity of neutrons.
  • the plurality of fuel elements preferably comprise fast-fission fuel.
  • the coolant comprises a metal or metal alloy which is a solid at room temperature and a liquid at reactor operating temperature. This makes the reactor easy to transport when shut-down and also reduces problems of pressure within the reactor vessel. Suitable coolants include at least one of tin, lead, lead-bismuth-eutectic, lead/tin solder and Babbitt type two.
  • the coolant preferably comprises at least a proportion of lead.
  • Lead being a heavy atom, has a minimal moderating effect on the neutrons within the reactor. This is particularly important in a fast fission reactor.
  • One preferred coolant is lead bismuth eutectic or LBE which is known to have excellent performance. This comprises lead and bismuth in proportions of 44.5% and 55.5% respectively. LBE des have one drawback, however, and that is density.
  • a lighter coolant that still has excellent cooling properties is solder.
  • the solder preferably comprises at least 37% lead. Solder does exhibit a greater degree of moderation than LBE so is not preferred for larger reactors, for example, exceeding 5 layers of fuel. For 6 layers of fuel and above, LBE is preferred.
  • the coolant has a boiling point higher than the melting point of the fuel. This ensures that the fuel will melt and diminish its participation in fission before the coolant boils, ensuring that no overpressurisation of the reactor vessel occurs.
  • the boiling point of the coolant is preferably greater than the melting point of the fuel by at least, 10 degrees Celsius, more preferably 50 degrees Celsius.
  • the heat exchanger may be located internally or externally of the reactor vessel. An internal heat exchanger can be arranged to extract heat from the coolant across a large volume within the reactor vessel. The heat exchanger is preferably arranged above the fuel since the upper part of the vessel will generally contain hotter coolant.
  • an external heat exchanger that is supplied with coolant from the reactor vessel allows that vessel to be smaller and easier to manufacture.
  • Embodiments of the present invention preferably further comprise a turbine for extracting power from the reactor vessel.
  • Selection of a particle accelerator is dictated in large part by the arrangement of the ignition bulb. If the ignition bulb, or region, contains only actinide material, then more energetic protons are required to generate neutrons, necessitating a larger and more expensive particle accelerator arranged to irradiate the actinide material located at the ignition region with protons having an energy at least 20MeV on target.
  • the particle accelerator preferably generates protons with an energy of at least 20MeV.
  • the particle accelerator is preferably arranged to irradiate the material responsive to incident protons with protons with an energy of substantially 27MeV on target If, however, the ignition region is arranged to operate on a two-stage basis, a smaller and cheaper particle accelerator will suffice.
  • the at least one particle accelerator is arranged to irradiate the proton-neutron reaction material located at the ignition region with protons having an energy of at least 1.88MeV on target. This energy level is the minimum required to generate protons from a lithium 7 source.
  • the particle accelerator is arranged to irradiate the proton-neutron reaction material with protons having an energy of substantially 7MeV on target.
  • the particle accelerator In the two-step process, the particle accelerator generates energetic protons with an energy below 20MeV and more preferably between 5 and 20 MeV with a beam current of at least 50 ⁇ A.
  • a preferred output level for the particle accelerator is substantially 15MeV.
  • the particle accelerator is preferably a cyclotron.
  • a control arrangement is preferably provided and arranged to model future neutron flux based on a measure of reactor state and to modulate proton flux power based on said model. The measure of reactor state may be based at least in part on a measure of current neutron flux.
  • the neutron flux is preferably measured by at least one sensor in, on or adjacent the reactor shielding
  • the measure of reactor state may be based at least in part on a measure of reactor core temperature.
  • the measure of reactor state may be derived based on a current measure of one or more reactor physical properties and a past measure of reactor state.
  • the control arrangement may be arranged to model reactor response to power consumed and current neutron flux and to modulate proton flux power based on said model.
  • the control arrangement may be arranged to model thermal energy demand from the reactor and to modulate proton flux based on current temperature, for example reactor core temperature, and current reactor state.
  • the control arrangement is preferably arranged to deactivate the particle accelerator in response to a signal from at least one sensor, more preferably a plurality of sensors, being above a threshold.
  • That sensor may comprise at least one of a neutron sensor, a temperature sensor and a pressure sensor.
  • Embodiments of the present invention are preferably arranged so that, on heating of the reactor above a threshold cut-off temperature, the fuel elements deform before the coolant boils such that in a deformed configuration, including complete melting of the fuel, the power output is degraded. Alternatively, detached portion of the fuel elements will sink within the reactor vessel and reduce its participation in the fission reaction. These both provide a key passive safety feature that avoids vessel overpressurisation. Deactivation of the or each particle accelerator is preferably arranged to follow from a detected fault condition and a breach of the reactor vessel is preferably sealed as the coolant solidifies as it cools.
  • a fire suppression system is preferably provided in certain embodiments and is arranged to be deployed in response to a detected fault condition.
  • the fire suppression system is preferably provided to protect at least the particle accelerator.
  • Certain embodiments of the present invention preferably further comprise a shipping container housing the majority of the components.
  • the beam current of the flux of protons is at least 100 ⁇ A preferably at least 250 ⁇ A and more preferably at least 500 ⁇ A
  • the accelerator is preferably arranged to provide a flux of protons having an energy between 4MeV and 15MeV. In alternative embodiments the accelerator is arranged to provide a flux of protons having an energy of between 15MeV and 100MeV, preferably between 15MeV and 50MeV.
  • the actinide material preferably comprises at least 80% by weight of Thorium, and at least 1% of another metal selected from Iron, Nickel, Magnesium and Uranium. The proportion of the another metal is preferably selected to cause the melting point of the actinide material to be below a predetermined value.
  • the actinide material preferably comprises at least 90% by weight Thorium and more preferably 95% by weight Thorium.
  • the reactor vessel preferably further contains means for forced distribution of coolant within the vessel, for example an impeller. Forced convection of coolant may alternatively comprise at least one element of actinide material rotatable about an axis.
  • the actinide elements are preferably arranged evenly around the axis.
  • the actinide elements are preferably identical.
  • the material preferably rotates at between 1 and 25 rpm, more preferably at between 4 and 8 rpm.
  • the axis is preferably rotated by a motor and further preferably horizontal.
  • the fuel elements are preferably shaped to promote the movement of coolant within the container.
  • the flow of coolant is preferably turbulent.
  • the forced distribution of coolant comprises a pump external to the reactor vessel.
  • the means for forced distribution preferably comprise an electromagnetic pump.
  • a flow line to the motor is preferably above a return line from the motor.
  • the reactor preferably comprises a plurality of distinct output levels, wherein one the distinct output levels comprises an idle level from which the reactor can be arranged to generate full power in a shorter time than the time required from a zero output level.
  • the idle level preferably generates less than 20% of the maximum thermal output of the reactor and more preferably generates less than 10% of the maximum thermal output of the reactor.
  • the controller is preferably arranged to control the particle accelerator to provide at least three distinct output levels from the nuclear reactor.
  • the linear particle accelerator is preferably arranged to generate protons having energies in excess of 4MeV and more preferably is arranged to generate protons having energies of less than 15Mev.
  • the actinide fuel is preferably arranged to deform at excessive temperatures, whereby the the melted portion of the fuel element detaches from the remainder of the fuel element.
  • a propulsion system preferably further comprises a gearbox having an input coupled to the shaft and an output shaft.
  • the propulsion system is for a water-borne vessel
  • the propulsion system further comprising: at least one propellor coupled to the shaft or the output shaft of the gearbox.
  • the propulsion system is for a train.
  • the industrial process preferably comprises one or more of a chemical process, a drying process, refining hydrocarbons, an extrusion process and construction of composite materials.
  • the heating system preferably comprises a control system arranged to control the output of the source of protons in response to an output from at least one environmental sensor.
  • the environmental sensor may comprise a temperature sensor.
  • the control system is arranged to control the output of the system in response to weather predictions.
  • metallic, fast-fission capable fuel such as U-238 or Th-232 is capable of solving several surface-level issues such as heat transfer to a coolant at a high operating temperature and increased fuel density when compared with prior art oxide fuels.
  • the embodiments of the present invention are derived from a complete change of mindset when compared with previous approaches.
  • the general consensus has been that criticality was a core-wide concept.
  • the geometry of neighbouring cells within actinide fuel is evaluated for a “local” criticality. More details are provided in the Appendix below. Additionally, the inventor has concluded that the industry has an over-reliance on Monte Carlo mathematical methods.
  • Figure 1 is a schematic diagram of an electricity generating system in accordance with an embodiment of the present invention
  • Figure 2 is a more detailed cross section of a reactor core is accordance with an embodiment of the present invention
  • Figure 3 is a sectional view of fuel elements according to an embodiment of the present invention
  • Figures 4 to 10 show various isometric and perspective views of fuel elements in accordance with embodiments of the present invention
  • Figure 11 shows isometric views of a stem support beam for supporting the fuel elements illustrated in Figures 4 to 7
  • Figure 12 shows a bottom view and a side view of a source bulb assembly for use with a reactor according to embodiments of the present invention
  • Figures 13 to 15 show various views of a heat exchanger suitable for use with embodiments of the present invention
  • Figure 16 shows a block diagram of a control system suitable for use with embodiments of the present invention
  • Figure 17 shows a flow chart of the operation of a controller of Figure 16
  • Figure 18 shows a perspective view of an electricity generation system according
  • Figure A1 shows a graph of Nusselt number vs. P/D ratio
  • Figures A2 and A18 show properties of uranium tungsten alloy
  • Figure A3 shows properties of a uranium molybdenum alloy
  • Figure A4 shows properties of a uranium zirconium alloy
  • Figure A5 shows properties of a uranium niobium alloy
  • Figure A6 shows properties of a uranium rhenium alloy
  • Figure A7 shows properties of a uranium thorium alloy
  • Figure A8 shows properties of a tungsten molybdenum alloy
  • Figure A9 shows properties of a Tungsten-Rhenium alloy
  • Figure A10 shows a graph of neutron energy according to proton initial energy
  • Figure A11 shows particle production cross section
  • Figure A12 shows prompt neutron multiplicities
  • Figure A13 shows fast fission cross section for Th-232
  • Figures A14 and A23 show fast fission cross section for U-238
  • Figure A83 shows a thermal cycle having twin Rankine with reheat and re-gen
  • Figure A84 shows a test core having a non-rotating natural convection impeller with Thorium fuel
  • Figures A85 and A86 show heatmaps for the test core
  • Figure A87 shows the output power of the test core
  • Figures A88 and A89 show the heatmaps for the test core with Uranium fuel.
  • Figure 90 shows the output power
  • Figure A91 shows a rotating fuel micro reactor assembly
  • Figure A92 shows various views of the fuel elements for the micro reactor
  • Figures A93 and A94 show heat maps for Thorium fuel
  • Figure A95 shows the power output
  • Figures A96 and A97 show the corresponding heat maps for Uranium fuel
  • Figure A98 shows the power output
  • Figure A99 shows a control system graph for a core
  • Figure A100 shows reactor ramp up for a Thorium 5-layer core
  • Figure A101 shows reactor ramp up for thorium trinity rose core
  • Figure A102 shows various views of an alternative fuel arrangement
  • Figure 103 shows locations for neutron sensors
  • Figure A104 shows a diagram of a steam cycle
  • Figure A105 shows a block diagram of a control system.
  • Figure 1 shows a block diagram of electricity generating system 100 including a reactor vessel 102, a cyclotron 112 and a compressor/generating system 116, 118.
  • the reactor vessel contains a fuel arrangement comprising ribs of actinide fuel in a leaf arrangement 104.
  • an ignition bulb 108 comprising ignition material that converts protons to high energy neutrons.
  • the leaf arrangement 104 substantially surrounds the ignition ball.
  • the cyclotron 112 has a beam line 114 connected to the ignition bulb 108.
  • the beam line is a vacuum contained within a tungsten sheath.
  • the reactor vessel is substantially filled with a coolant 106 that is solid at room temperature and a liquid at operating temperature.
  • Towards the top of the reactor vessel is a heat exchanger 110 that is coupled to a further heat exchanger 116 for generating steam.
  • the steam drives a turbine that in turn drives a generator 118.
  • One suitable model of the turbine at least for some embodiments of the present invention is a Siemens SST200.
  • the reactor vessel 102 includes a container wall and core neutron shielding comprising Hastelloy® a nickel-chromium-molybdenum material with a very high melting point.
  • the Actinide fuel may comprise Thorium or Uranium 238 which has been alloyed with another metal to increase its melting point, as well as other actinide elements such as Neptunium, Plutonium Americium, Protactinium, Curium and Californium.
  • the fuel arrangement as a whole is designed and dimensioned to form a sub-critical core in the absence of additional neutrons emitted by the ignition bulb. This provides important controllability for the reactor and comprises a key safety feature. While three layers of fuel are illustrated any number of layers from 1 to 7 or more may be used, dependent upon the desired power output.
  • the fuel is supported on a metal structure such as a tungsten structure described further below.
  • a source of neutrons is provided at the centre of the fuel arrangement.
  • this comprises Uranium-238 located within the ignition bulb 108. When bombarded with protons from the cyclotron, the Uranium emits neutrons which maintain the reactor core in the critical or super-critical operating region.
  • the ignition bulb contains uranium-238 and another material such as lithium- 7. This provides a “two-stage” ignition process in which the lithium is irradiated by the protons from the cyclotron to generate neutrons which then impinge on the uranium. This generates further neutrons at a suitable energy to maintain the nuclear reaction.
  • the reactor will operate satisfactorily with lower-energy protons, meaning that a simpler and cheaper cyclotron or other particle accelerator may be used.
  • a linear particle accelerator may be used which is significantly cheaper than a cyclotron.
  • a higher output will be required since the output of a linear particle accelerator is pulsed.
  • Other materials besides Uranium and Lithium can be used as will be discussed further below. While a substantially hemispheric shape is shown, the ignition bulb may be replaced by other suitable shapes as dictated by the shape of the fuel arrangement such as a rod or cylinder.
  • the core is filled with a coolant 106 which, in one embodiment, comprises lead-bismuth eutectic (LBE).
  • the coolant is selected be a solid at room temperature, a liquid at the operating temperature of the reactor and also to remain a liquid at the melting point of the fuel.
  • the boiling point of the coolant is preferably higher than the melting point of the fuel. This provides a key safety feature of the reactor because, should the fuel overheat and melt, there is no risk that the coolant will boil and endanger the containment of the core. As an additional safety feature, should the fuel melt, the reaction will become sub-critical and the core will cool.
  • the boiling point of the coolant is preferably at least 50 oC greater than the melting point of the fuel to provide a safety margin.
  • the coolant is preferably in direct contact with the fuel but a heat-conducting barrier may also be placed between the fuel and the coolant.
  • coolants are also suitable, including solder which has the benefit of being substantially lighter than LBE.
  • Further alternative coolants are lead, tin and Babbitt type two. While a heat exchanger is shown that is within the reactor vessel, it may be preferred instead to provide a pair of ports on the reactor vessel comprising send and return paths for the coolant. The coolant may then be directed to flow through a heat exchanger external to the reactor vessel. This provides a simpler structure for the reactor vessel. The coolant flowing through the heat exchanger is used to heat steam for driving a turbine and generating electricity in known manner. In operation, the cyclotron is switched on and provides (via the ignition bulb) high energy neutrons to the fuel arrangement. A fast fission reaction then occurs in the fuel and the fuel starts to increase in temperature.
  • the temperature of the coolant starts to increase as well.
  • the reactor reaches operating temperature (which may take several days)
  • the coolant will travel around the fuel due to convection.
  • the shape and arrangement of the fuel is preferably designed to promote this. Coolant at a higher temperature will rise towards the top of the reactor vessel where it will encounter the heat exchanger. This has the effect of reducing the temperature of the coolant which will then descend within the vessel. Convection currents then provide lower temperature coolant to the fuel elements and the cycle continues.
  • the cyclotron will be switched on and off to maintain the reaction without permitting an uncontrolled heat transfer rate. The nature of the cyclotron and control thereof will be discussed further below.
  • FIG. 1 shows a more detailed cross-sectional view 200 of a reactor vessel 200 according to an embodiment of the present invention.
  • Wall shielding 202 is capped by a top cap 204 and contains the ignition ball 206 surrounded by fuel 208 supported by tungsten supports 210.
  • the ignition ball is fed by a beam line sheath 212 containing a vacuum.
  • a cyclotron input 224 is connected to the beam line 212 via a 90o magnet 214.
  • Beneath the magnet is extra shielding 216 because gamma rays from the ignition ball/source bulb would otherwise have a direct view along the accelerator beamline.
  • the shielding 216 comprises a boron-cement plate which is large enough to capture gamma rays in a “cone” of radiation from the source bulb.
  • the coolant will rise by convention from a cool zone 218 to a hot zone 220 where it is cooled by a heat exchanger 222 and will then drop back down towards the base of the vessel.
  • a coolant run-over zone is provided at 226.
  • FIG. 3 shows a more detailed sectional view 300 of the reactor fuel and ignition ball together with coolant flows.
  • the ignition ball 302 is coupled to a beam line 304 for receiving protons from the cyclotron (not shown).
  • the fuel is arranged in substantially spherical layers around the ignition ball of which two are shown 306, 308.
  • the fuel is supported by a tungsten support 310.
  • FIG. 4 shows isometric views of fuel elements in accordance with embodiments of the invention.
  • Figure 4 shows various views 400 of a part of a first layer of fuel, called a ring one leaf sub-assembly. Three of these would comprise the first layer of fuel. Each sub-assembly is 110o so three would occupy 330o, i.e.
  • the sub assembly comprises a number of elements, in this case 14.
  • the individual elements are elongate members called ribs and, in one embodiment, have a height of 2cm and a thickness of 5cm. Further arrangements will be clear to the skilled person on consulting the Appendix below.
  • the perspective view of the sub-assembly shows a mounting point 402 for connection to a stem support described below with reference to Figure 11.
  • a support member 404 holds each of the ribs in place.
  • the support member must have a melting point higher than the actinide fuel, preferably significantly higher than the fuel melting point to provide a safety margin.
  • One preferred material is tungsten.
  • the remaining sub-assemblies described with reference to Figure 5 to 10 have a similar support member.
  • a single layer of fuel elements is used.
  • Figure 5 shows various views of a part of a second layer of fuel, called a ring two leaf sub-assembly. Three of these would comprise the second layer of fuel with a 10o gap as for the first layer.
  • the sub assembly comprises 15 ribs, reflecting its slightly greater size than the first layer sub-assembly.
  • the perspective view of the sub-assembly shows a mounting point 502 for connection to a stem support described below with reference to Figure 11.
  • Figure 6 shows various views 600 of a part of a third layer of fuel, called a ring three leaf sub-assembly. Three of these would comprise the third layer of fuel with a 10o gap as for the first and second layers.
  • the sub assembly comprises 17 ribs, reflecting its slightly greater size than the second layer sub- assembly.
  • the perspective view of the sub-assembly shows a mounting point 602 for connection to a stem support described below with reference to Figure 11.
  • Figure 7 shows various views 700 of a three-ring tritosphere which comprises the sub-assemblies shown in Figures 4, 5 and 6.
  • Mounting points 702 attach to the stem support of Figure 11 by means of pins (not shown).
  • Three layers of fuel comprise a preferred embodiment of the present invention when the fuel is uranium-238 as this provides sufficient reaction rate and heat production for this fuel.
  • Figure 8 shows various views 800 of a part of a fourth layer of fuel, called a ring four leaf sub-assembly. Three of these would comprise the fourth layer of fuel with a 10o gap as for the lower layers.
  • the sub assembly comprises 17 ribs as for the third layer sub-assembly.
  • the perspective view of the sub-assembly shows a mounting point 802 for connection to a stem support of the type described below with reference to Figure 11.
  • Figure 9 shows various views 900 of a part of a fifth layer of fuel, called a ring five leaf sub-assembly. Three of these would comprise the fifth layer of fuel with a 10o gap as for the lower layers.
  • the sub assembly comprises 25 ribs, reflecting its greater size than the lower layer sub-assemblies.
  • the perspective view of the sub-assembly shows a mounting point 902 for connection to a stem support of the type described below with reference to Figure 11.
  • Figure 10 shows various views 1000 of a five-ring tritosphere which comprises the sub-assemblies shown in Figures 4, 5, 6, 8 and 9. Mounting points 1002 attach to the stem support of the type shown in Figure 11.
  • Three layers of fuel comprise a preferred embodiment of the present invention when the fuel is Thorium as this provides sufficient reaction rate and heat production for this fuel. While three fuel elements have been shown in each layer to substantially surround the ignition bulb, it will be understood that other arrangements such as 1, 2, 4, 5 or more are possible. Three elements provide a good compromise between complexity of support structure and ease of manufacture. While a substantially spherical arrangement of fuel has been described (bearing some resemblance to a beehive) other arrangements are possible, for example a substantially cylindrical arrangement.
  • Figure 11 shows orthographic views of a stem support beam 1100 for holding the three ring tritosphere of Figure 7. Three such stem supports would be required to hold the three sub-assemblies of the tritosphere.
  • the stem supports are attached to each of the fuel layers using a tungsten pin (not shown). A similar stem support beam would hold the sub-assemblies of five fuel layers as shown in Figure 10.
  • the appendix includes a comparison of five actinide elements that may be used as fuel.
  • Uranium-238 is preferred with Thorium as a runner up.
  • One issue with Uranium is its melting point is quite low at 1132oC and while it is preferred to operate the reactor at a higher temperature than this, it is perfectly possible to use pure U-238.
  • uranium is alloyed with Tungsten to increase its melting point. Note the constraint is that the melting point of the fuel preferably does not exceed the boiling point of the coolant.
  • a uranium/tungsten alloy with 3% tungsten has a boiling point of 1650oC, comfortably below the boiling point of LBE at 1660oC.
  • a uranium/tungsten alloy will generally require a binding agent between the two metals.
  • Molybdenum and niobium are suitable, although alternatives will be apparent to the skilled person.
  • Tungsten alloy would allow a run over event before damage and some elements within the core may operate at varying temperatures (bulb may operate above 1200oC while edges of the core may operate at 800 oC).
  • Bulb may operate above 1200oC while edges of the core may operate at 800 oC.
  • Alloys of the other 4 actinide elements with tungsten may also be used. This alloying permits the reactor to run on depleted uranium (i.e. nearly pure U-238 extracted from natural uranium as part of the conventional fuel-enrichment process).
  • U-238 Since U-238 is minimally radioactive, the reactor requires very few shielding precautions in its dormant state. Even the decay products of U-238, Th-234 and Pa-234, only emit beta particles. This also addresses a problem of stockpiling of low-level nuclear waste.
  • Alternatives to tungsten include Rhenium, Tantalum, Molybdenum, Niobium and Zirconium. However, these are less desirable as the uranium alloy must contain a greater proportion of these materials to achieve the same melting point (rhenium at 25%, zirconium and niobium at 35%). This is less desirable since the fuel will then contain a lower proportion of uranium with negative consequences for reaction rate.
  • FIG. 20 shows a graph of first law mirror function for the most common actinides.
  • the excluded elements are not available in any significant quantity due to their half-lives, or, in the case of actinium due to having an unknown fission cross section. It will be seen that while all of the common actinides exhibit an exponential growth in the function over time, plutonium far exceeds that of any of the other isotopes.
  • FIG. 21 shows a graph of the first law mirror function with plutonium excluded and an expanded vertical axis to better illustrate the relative performance of the other actinides. These graphs illustrate that doping of actinides such as Th-232, Pa-231, U-238, Np-237, Am-241, Cm-246 and Cf-250 with some plutonium (or other actinide with a higher cross section) will improve performance, particularly at reactor start-up. against this, of course, are the known issues with plutonium.
  • Figure 12 shows a view from below and a sectional view on the line A-A of a source bulb assembly 1200 for use with a reactor according to embodiments of the present invention.
  • the bulb has an external cylindrical wall 1202 that is closed off by a hemispherical portion 1204.
  • An internal wall 1206 isolates a cavity 1208 within the hemispherical portion. This cavity contains the uranium 238 source of neutrons that sustain the fast fission reaction in the core of the reactor.
  • the wall 1206 comprises a smaller hemispherical portion 1210 that protrudes into the cavity 1208 at the centre of the cylindrical wall. Fitting snugly within this portion 1210 is another hemispherical member 1212 defining another cavity 1214.
  • This cavity contains the first ignition material such as Lithium 7.
  • a beam line 1216 defined by a smaller cylindrical wall 1218 is provided within the cylindrical wall.
  • Protons from the cyclotron 112 ( Figure 1) travel along this beam line and irradiate the Lithium 7.
  • the Li-7 emits neutrons in a reaction described fully in the Appendix.
  • These neutrons pass into the cavity 1208 containing uranium which in turn provides further neutrons at a high enough energy to sustain the fast fission reaction in the core.
  • the ignition bulb also includes a window 1220 through which the protons from the particle accelerator have to pass to reach the Li-7 material. Ideally, this window reduces the energy of the protons by the smallest possible amount.
  • the window is preferably titanium which imposes a minor energy reduction on the protons (e.g. a proton from a 15MeV cyclotron may still possess an energy of 13Mev on target.
  • the conduction of heat from the reactor core to the ignition bulb will cause the temperature of the titanium to rise too high.
  • the window may comprise tungsten which will impose a greater reduction in proton energy – for example from 15MeV to around 9MeV.
  • Li-7 has a peak reaction at 7MeV (see Appendix) so a tungsten window may be used with a 15 MeV accelerator.
  • the hemispherical member 1212 containing the Li-7 can be removed from the reactor without disturbing the coolant, fuel or neutron- providing material in the cavity 1208. To do this the reactor is shut down and allowed to return to ambient temperature, the proton feed from the cyclotron is disconnected and the hemispherical member 1212 can be withdrawn.
  • Nitrogen-14 bombardment with deuterium particles produces a neutron and Oxygen-15, Oxygen 15 rapidly decays into Nitrogen-15 which is stable. Hitting a newly formed Nitrogen-15 with the same reaction would likely create Oxygen-16 and another neutron.
  • This reaction scheme requires a deuterium accelerator – increased cost – and deuterium particles – an isotope of hydrogen found in “heavy water”.
  • the Oxygen-15 decay into Nitrogen-15 is another circular decay function. 3.
  • Nickel-64 proton bombardment creates Copper-64 and a neutron with Copper-64 decaying back to Nickel-64 via a dual-branch decay where one branch leads back to Nickel-64 and another leads to Zinc- 68.
  • the branch decay back to Nickel-64 only happens 61% of the time, with the remainder going back to Zn-64.
  • the Nickle-64 reaction has a peak production at 18 MeV, a 15 MeV cyclotron is still viable for this reaction. There’s room for viability in this, but once again, Nickel-64 has a low natural abundance and doesn’t share the same industrial backbone as Oxygen-18. High purity Nickel-64 can be purchased at around 48200 USD/g and about 9grams would be required for at least some embodiments. 4.
  • Zinc-68 proton bombardment creates Gallium-68 and a neutron, much the same as the Nickel-64 reaction, at a similar cost but without the branch decay (100% decay of Gallium-68 back into Zinc-68 in another circular decay function).
  • the cost of Zinc-68 is a 10 th of that of the Nickel-64 target at 4850 USD/g making it a better choice than that of the Nickel-64 target.
  • This reaction is also viable under a 15 MeV cyclotron. 5.
  • Cadmium-112 under proton bombardment creates Indium-111 with a p-2n reaction.
  • Indium-111 decays back to Cadmium-111 – so this isn’t a perfect circular reaction – but Cadmium-111 is also a viable target for a singular p-n reaction within the same energy spectrum creating a circular decay function with Indium-111. This reaction is viable at a 15 MeV cyclotron but is beginning to become ineffective at this atomic weight. Natural Cadmium may be used and a wide variety of p-xn reactions will occur to create various Isotopes of Indium that all decay back into Cadmium. As will be seen from the Appendix, only a small proportion of impinging protons actually participate in a reaction with the Li-7 (or other material) but the “unused” protons cause no difficulties as follows.
  • the third case where hydrogen fills the beam line, is slightly more consequential as it may reduce the efficiency of the beam line over time, but this will also provide a trivial effect.
  • the ignition bulb shown in Figure 12 may readily be adapted to provide the one-step neutron generation using, for example, uranium 238 and a higher power cyclotron, having an energy on target of at least 26.8 MeV. In practice, to address efficiency issues as discussed, this requires a cyclotron having an output in the region of 35MeV. Described embodiments of the invention use LBE as the coolant and, as discussed further in the appendix, this is an excellent material for the purpose.
  • LBE is a eutectic alloy of lead and bismuth in the atomic proportion 44.5% and 55.5% respectively. It has a boiling point of 1660oC which suits the current application very well. However, it does have a drawback and that is its density at around 13g/cm 3 . This may cause problems in a reactor that is designed to be mobile. As an alternative, tin/lead solder (in, for example, proportion 63%/37%) also functions well as a coolant and has a much lower density than LBE at 8.6/cm 3 . It is also cheaper than LBE. This may thus be a preferred coolant in a smaller, portable reactor. Some of the possible coolants have the following advantages/disadvantages.
  • Solder contains tin, which has a very low cross-section of interaction with neutrons but a smaller atomic mass than bismuth – the effect is that tin has a lower chance of having a neutron collide into it, but a larger effect on the neutron when it does collide.
  • the scattering reaction slows neutrons down in a moderation process. This may take the neutrons out of the fast spectrum, which in a fast reactor is something to avoid.
  • Tin is unique in that its stable isotope range is very wide; 112, 114, 115, 116, 117, 118, 119, 120, 122. If it absorbs a neutron, it will simply move up the chain of stable isotopes. The cross section for absorption is also very low in the fast spectrum.
  • the unstable isotopes, 113 and 121 are on opposite ends of the spectrum which also helps.
  • 112 needed to absorb a neutron and it only has a natural abundance of 0.97%.
  • 121 decays into Antimony-121 which is stable and part of Babbitt type 2. You can follow a multi-stage absorption on that line and you'll land on a chain of stable tellurium until 127.
  • Figures 13 to 15 show an embodiment of a heat exchanger for use with a reactor according to embodiments of the present invention.
  • FIG 13 shows a side view and a view from below of a fuel arrangement and a heat exchanger according to an embodiment of the present invention.
  • a fuel arrangement 1302 is shown mounted beneath a heat exchanger 1304 comprising 10 layers of piping in which adjacent layers have pipes arranged orthogonally.
  • the side view illustrates a suitable spacing for the fuel core and the heat exchanger.
  • the view from below gives a good sense of the relative size of the core and the heat exchanger – the heat exchanger has a larger diameter than the core to ensure efficient capture of the heat from the circulating coolant (not shown).
  • Figure 14 shows an orthographic and an isometric view of the heat exchanger 1400. The orthographic view shows that there are 13 heat conducting pipes in each orthogonal direction.
  • the isometric view shows more clearly the ends of the pipes which are linked together by short U-shaped pipes to provide a serpentine path through the heat exchanger.
  • the heat exchanger is preferably constructed from Hastelloy® a nickel-chromium-molybdenum material with a very high melting point although Inconel 601 may also be used.
  • Figure 15 shows a single layer of the heat exchanger showing the paths of the parallel cooling pipes 1502. This figure also illustrates the modular nature of the heat exchanger, in that each of the layers may be identical to facilitate manufacture. It also facilitates variation of the capacity of the heat exchanger by selection of the number of layers used.
  • a heat exchanger may be located outside and be coupled to receive and return coolant from within the reactor.
  • Figures 22 and 23 show the power generated by a 7 layer core at switch-on and switch-off respectively.
  • the graphs show the power developed by each ring separately and also by the ignition bulb.
  • the core takes several hours to heat up but, as shown in Figure 23, the corresponding cool down (once the particle accelerator is switched off) is very rapid. This provides an excellent level of safety for embodiments of the invention.
  • the entire electricity generating apparatus is mounted in a standard 40ft shipping container.
  • Figure 16 shows an isometric view of such an arrangement 1600 mounted on the floor 1602 of a shipping container.
  • a cyclotron 1604 is mounted between two reactor cores 1606 and 1608. This exploits the fact that cyclotrons generally have two outputs so makes more efficient use of this expensive component. Having two reactor cores also provides redundancy and allows the use of smaller cores for an equivalent energy output. Between the cores is an Electronic Control Unit (ECU)/transformer 1610. Reactor core two 1608 is coupled to a Siemens SST-200 turbine 1610 which in turn is coupled to transmission 1612. The transmission is coupled in turn to an AC generator 1614 and an intercooler 1616. Beneath the turbine 1610 are a pair of compressors 1618, 1620. This provides a 20MWe system.
  • ECU Electronic Control Unit
  • FIG. 17 shows an orthographic view 1700 of the arrangement of Figure 16 showing the cyclotron 1704 is mounted between the two reactor cores 1706 and 1708. Between the fuel cells is the Electronic Control Unit (ECU)/transformer 1710. Reactor core 1708 is coupled to the Siemens SST-200 turbine 1710 which in turn is coupled to the transmission 1712.
  • ECU Electronic Control Unit
  • FIG. 18 shows a block diagram of a control arrangement 1800 for use with the embodiments of the present invention.
  • a reactor core 1802 comprises a number of sensors, such as neutron flux sensors 1804, 1806 embedded in the reactor shielding. Temperature sensors 1808, 1810 are also provided. These sensors are coupled to a controller 1812 which is also connected to control a cyclotron 1814.
  • FIG 19 shows a flow chart 1900 illustrating the operation of the controller 1812 (Figure 18).
  • the operation starts at 1902 and at 1904 sensor outputs from the neutron flux sensors and the temperature sensors is collected.
  • the neutron flux sensor outputs and the temperature sensor outputs are compared with predetermined safe values and, if the values are within acceptable limits, processing proceeds to 1908 in which the controller activates the cyclotron (or allows it to remain activated, if it is already on). If the values are not within acceptable limits, the control returns to step 1904 via step 1910 in which the cyclotron is deactivated (or remain deactivated if it is already off). After step 1908, control reverts to step 1904 at which the sensor outputs are collected again and the process repeats.
  • a more sophisticated control strategy may be applied, for example one that uses hysteresis to prevent unduly frequent switching of the cyclotron. That is to say that the flux and/or temperature levels at which the cyclotron is activated are lower than those at which the cyclotron is deactivated. While only temperature and neutron flux sensors have been described, other types, quantities and locations of sensors may be deployed, in particular gamma ray sensors. A control strategy may be deployed that uses an algorithm to combine various sensor inputs to make on/off decisions.
  • Such a strategy may be arranged to take account of sensor failure (neutron flux sensors occupy a rather hostile environment) by analysing outputs from a plurality of sensors and, taking account of their location and typical relations in their readings, determine whether a sensor output is trustworthy.
  • the reactor may be provided with a “shut-down” mode in which sensor levels that do not reduce when the cyclotron is deactivated result in no further activation of the cyclotron until troubleshooting has taken place.
  • Figure 24 shows a block schematic diagram 2400 of an application of the reactors comprising embodiments of the present invention. Certain industrial processes require materials and components to be treated at very high temperatures.
  • FIG. 2402 shows a reactor 2402 driven by a particle accelerator 2404.
  • the reactor is coupled to a steam heat exchanger 2406 that transfers heat from the reactor coolant to superheated steam (also referred to as working fluid) at a temperature of around 1000 degrees Celsius.
  • superheated steam also referred to as working fluid
  • the steam is piped to a kiln 2408 and is arranged to heat the kiln via pipework 2410 within the kiln.
  • the pipework effectively comprises a steam-to-air heat exchanger. This provides enough thermal energy to the kiln to maintain the temperature of 700 degrees Celsius.
  • the skilled reader will appreciate that other arrangements for transfer of the heat will also be suitable.
  • the kiln includes at least one temperature sensor 2412 whose output is coupled to a controller 2414 arranged to control the operation of the accelerator 2404. This feedback loop maintains the temperature of the kiln at the desired level.
  • the reactor 2402 may comprise any and all of the features disclosed herein, for example with regard to the number of fuel elements, fuel materials, single or two-stage ignition, coolant material and so on.
  • Figure 24 also shows an optional turbine/generator 2416 which may be as described previously and an optional further kiln 2418.
  • This arrangement coverts the superheated steam from the heat exchanger 2406 to electrically heat kiln 2418.
  • Some industrial processes require higher temperatures than the direct heating of kiln 2408 can achieve.
  • the carbon fibre brake discs discussed above also need to be treated at around 1600 degrees Celsius for a short time later in their manufacture.
  • the reactor 2402 cannot generate such high temperatures due to operating temperature limits of the fuel and the coolant.
  • a reactor according to embodiments of the present invention may also be arranged to power the higher-temperature kiln.
  • the turbine/generator also provides the electrical power to the accelerator 2404.
  • the turbine/generator arrangement may be provided to provide electrical power to the accelerator 2404.
  • the output of the reactor 2402 may be adjusted and the balance of heat output between the first kiln and the turbine/generator adjusted to operate the reactor to meet the energy demands of both kilns.
  • the arrangement shown in the figure may be modified to provide a source of heat to other industrial processes such as chemical processes, drying processes, extrusion processes and refining or cracking of hydrocarbons. Broadly speaking, this arrangement is applicable to any industrial process that requires heat but particularly those that require temperatures above 400 degrees Centigrade.
  • FIG. 25 shows a block schematic diagram 2500 of another application of reactors according to embodiments of the present invention, namely a propulsion system for a vehicle.
  • a reactor 2502 driven by an accelerator 2504 is coupled to a steam heat exchanger 2506, in turn connected to a turbine 2508 to convert the thermal energy in the superheated steam to mechanical energy in a rotating shaft 2510.
  • the shaft is coupled to an optional gearbox 2512 and to a propeller or screw 2514.
  • a speed sensor 2516 provides feedback to a controller 2518 which in turn controls the particle accelerator 2504.
  • Also shown in the figure is an optional arrangement of a generator 2520, motor 2522 and propellor 2524. The output of the generator is connected to supply electrical energy to the accelerator 2504.
  • the further motor and propellor may be replaced by a hybrid drive arrangement that uses the electricity generated by the turbine/generator 2520 to drive the propellor 2514. While an arrangement with a propellor or screw is shown in the figure, the propulsion system may equally be applied to land-based vehicles such as trains. Also, while a single propellor is shown in the figure, multiple propellers may be employed.
  • the presently-disclosed reactors have a particular benefit when applied to water- and land-based propulsion systems which is that the reactor may be quickly placed in a standby or idle mode by reducing the output of the accelerator 2504. Appendix figures A98, A99 and A100 together with their descriptions illustrate graphs of output power against time for such arrangements.
  • the reactor may thus be operating normally at a desired power output but when the drive to the particle accelerator is reduced the output power of the reactor reduces very quickly to around 1MWt. While this may appear to still be a significant amount of heat, it may very easily be dissipated to water surrounding a vessel or even to air around a land-based vehicle.
  • the controller is arranged to maintain the reactor at this output level until more power is required and the accelerator output is increased.
  • the reactor can attain full power output quite quickly from an idle state. Although the resumption of power output is slower than the reduction, this is seldom an issue in practice. For example, a ship leaving port will be forced to travel more slowly until it is in open water and the speed of trains is often constrained while they are in urban areas (i.e. near the station).
  • An alternative to placing the reactor in an idle mode comprises selling electricity to the grid.
  • a diesel-powered ship or boat When a diesel-powered ship or boat is in port, it is usually connected to a land-based source of electricity usually called shore-power so that no engine is required to run on the ship or boat.
  • shore-power a land-based source of electricity usually called shore-power
  • shore-power a land-based source of electricity usually called shore-power
  • shore-power a land-based source of electricity usually called shore-power so that no engine is required to run on the ship or boat.
  • shore-power a land-based source of electricity usually called shore-power
  • shore-power a land-based source of electricity usually called shore-power
  • shore-power a land-based source of electricity usually called shore-power
  • shore-power a land-based source of electricity usually called shore-power
  • shore-power a land-based source of electricity usually called shore-power
  • a reactor 2602 is coupled to a first heat exchanger 2604 and a second heat exchanger 2606.
  • the first heat exchanger is connected to a turbine 2608 and a generator 2610 to generate an electrical output.
  • This output may be coupled to a particle accelerator (not shown) to drive the reactor as previously discussed. It may also be arranged to provide electricity to other consumers such as an electricity grid.
  • the second heat exchanger 2606 is coupled to a working fluid path 2612 comprising send 2614 and return 2616 paths.
  • the working fluid path may pass through a building, a number of buildings or an entire neighbourhood. Multiple fluid paths may be provided to serve different locations and/or different classes of consumers. Heating consumers such as a house 2618, an apartment block 2620 or commercial premises 2522 are arranged to derive heat from the working fluid path 2612.
  • FIG. 27 shows a diagram 2700 of a forced-convection reactor which uses the fuel as an impeller.
  • a reactor vessel 2702 contains actinide fuel 2704 of any of the disclosed varieties mounted to a hollow shaft 2706 which is driven by a motor 2708 under control of a controller 2710.
  • the controller is responsive to at least one temperature sensor 2712 or other suitable sensors for detecting the state of the reactor.
  • FIG. 2702 At the top of the vessel 2702 is a heat exchanger 2714 and the vessel is filled with a coolant 2716. External connections to the heat exchanger, particle accelerator and further control connection are omitted for clarity.
  • the ignition region (not shown) is housed within the hollow shaft 2706 and receives particles from a particle accelerator via a path 2718 as previously discussed.
  • the motor 2708 rotates the actinide fuel 2704 to force convection within the coolant 2716.
  • the shape of the fuel elements is preferably selected to enhance the convection flow. Further details of suitable fuel elements are given in the Appendix. By forcing convection within the reactor vessel, the reactor performance and control are enhanced.
  • Figure 28 shows a diagram 2800 of a forced-convection reactor using an external pump.
  • a reactor vessel 2802 contains elements of actinide fuel 2804 surrounding an ignition region 2806. Further details of the fuel elements are provided in the Appendix.
  • the ignition region is supplied, as before, by a particle accelerator and proton path (not shown).
  • the vessel also contains a heat exchanger 2812 towards the top of the vessel.
  • a pump 2814 is provided externally of the vessel and connected between the send pipe 2816 and a return pipe 2818. The send line is connected towards the top of the reactor vessel and the return pipe is connected towards the bottom of the reactor vessel.
  • the pump is controlled by a controller 2820 responsive to one or more sensors such as a temperature sensor 2822.
  • the pump is an electromagnetc pump as described in“Optimization of an extra vessel electromagnetic pump for Lead-Bismuth eutectic coolant circulation on a non-refueling full-life small reactor” by Tae Uk Kang et. al. published in the journal of Nuclear Engineering and Technology 20223919-3927 (Elsevier). Electromagnetic pumps do not operate with high efficiency. However, in this application this is not a major concern as waste heat generated by the pump will mostly be returned to the reactor and/or coolant and will thus be used by the reactor’s thermal cycle. In operation, the pump operates to move coolant from the top of the reactor vessel (where the coolant will generally be hotter) to the bottom of the reactor vessel (where the coolant will generally be cooler).
  • the reactor performance and controllability are enhanced by the addition of forced coolant circulation.
  • An optional heat exchanger 2824 may be placed in the send or return pipes to permit the extraction of heat from the reactor either to extract energy or to improve cooling (or both).
  • APPENDIX Embodiments of the present invention are based upon an understanding that, instead of spallation, it is possible to instead target the reactor fuel directly. The following analysis illustrates the viability of this principle.
  • the European Spallation source uses a linear accelerator, well over a kilometre in length, to induce spallation – the shattering of an atom into many smaller pieces – within the GW range of the lead coolant of a fast fission core.
  • total neutrons per interaction is an average summation of all neutrons which include immediate neutrons of the proton, x-neutron reaction as well as fission reaction neutrons.
  • the fission reaction is induced due to the increased energy imparted onto the target atom as well as the loss of the neutrons caused by the proton bombardment reaction.
  • the amount of neutrons pre-fission and post are heavily dependent on the target atom.
  • Lead-bismuth eutectic is a eutectic alloy comprising 45% Lead (Pb) and 55% Bismuth (Bi).
  • the alloy itself is often abbreviated to LBE.
  • LBE Properties LBE is an excellent coolant for high-temperature applications as – unlike water – does not require additional pressurisation to adequately be used as a working fluid at high temperatures. LBE also serves as a coolant that does not moderate due to its exceptionally low scattering and absorption cross-section and heavy elemental nature.
  • the handbook concludes an immense difficulty and lack of knowledge on pool thermo-hydraulics.
  • LBE behaves similar to a liquid metal with a low Prandtl number of between 0.041 at its melting point and 0.007 at 900 degrees Celsius. Effectively, the heating dynamics of a pool of LBE should instead be viewed as a highly conductive unit.
  • Establishing heat transfer dynamics for a fully three-dimensional solution using computational fluid dynamics methods based on the Navier-Stokes equation is the preferred method of evaluation.
  • the report is highly detailed for heat transfer dynamics with the use of cylindrical pipes – the most likely case for heat transfer units – and suggests similar performance in the use of LBE in a shell and tube type heat exchanger in a turbulent flow dynamic.
  • Figure A1 shows the Nusselt numbers in fully developed flow in rod bundles arranged in a triangular array as a function of the Peclet number Pe and P/D for constant wall heat flux.
  • Uranium Alloys for High Temperature Applications Regarding fuel, a key component in reactors according to embodiments of the invention is the density of uranium. It is of great importance that as much fissionable material as possible is located as close to the source plate as feasibly possible. The obvious choice then is to use Uranium metal, however, due to the metal’s lower melting point, this would create a structural issue as the core would begin to melt down. Natural Uranium metal has a melting point of 1135°C or roughly 1400K which would greatly limit the operating domain of the LBE coolant.
  • FIG. 1 is a phase diagram created by Dr Wang of the Department of Materials Science and Engineering, College of Materials, and Research Centre of Materials Design and Applications, Xiamen University, Xiamen, PR China. Even a moderately low atomic percentage of Tungsten drastically increases the melting point of Uranium.
  • a 3% atomic abundance of Tungsten within the Uranium metallic alloy would increase the melting point to roughly 1650°C – which would match that of the LBE boiling point.
  • Newton’s law of cooling means that a margin of just 10o is adequate as the fuel will melt before the coolant is at risk of boiling. Even with no margin, a small amount of localised boiling of the coolant is permissible as discussed further below.
  • one issue with the uranium tungsten alloy is a failure to bond and, thus, having the uranium separating from the tungsten.
  • a simple solution lies within the method used to alloy the metal; powder bed fusion, with its high-temperature laser, has a tendency to create different bonding structures within two different metals.
  • FIG. 1 is a phase diagram for a Uranium-Molybdenum alloy. Uranium has a better bonding effect with the molybdenum than tungsten but requires a higher percentage of the added alloy – in this case, Molybdenum –to reach a melting point of 1650 ⁇ C (around 40% molybdenum) which would severely impact reaction rates within the alloy. Meaningful improvements to the alloy melting temperature only begin at 33%.
  • Figure A4 is a phase diagram for a uranium zirconium alloy.
  • FIG. 5A is a phase diagram for a uranium niobium alloy. Niobium underperforms in comparison to the other alloys within this section. At least 70% of the alloy would need to be Niobium to create an alloy having a melting point of 1650 ⁇ C.
  • Figure A6 is a phase diagram for a uranium rhenium alloy. Rhenium performs well with only Tungsten able to outperform in terms of effect-per-mass-unit added. 25% Rhenium is significant enough to produce an alloy having a melting point of 1650 ⁇ C.
  • Figure A7 shows properties of a uranium thorium alloy.
  • This approach binds Uranium with the lower reacting Actinide to form a pure fast-fission alloy.
  • the alloy would benefit from Thorium’s higher melting temperature (1755 ⁇ C) while having the potential to not heavily impact reaction rates due to the secondary element added to the matrix – thorium – also being able to fission under the bombardment of fast protons.
  • Alloys of Uranium – Thorium has been well studied under the 1960s breeder reactor program (thermal neutron breeder) to enhance the efficiency of the use of Uranium. Further approaches comprise three-metal systems.
  • One such system is a Uranium, Tungsten and Molybdenum triple system exist.
  • the phase diagram for the alloy also shows a negatively impacting relationship between the two metals which suggests the elements do not favour bonding together.
  • Rhenium may fail to produce a binder to Uranium-Tungsten if the Uranium cannot balance the system.
  • An alternative is to use a zirconium binder. Zirconium additions exert a pronounced effect on the alloy structures, a wide variety of structures being obtained as the uranium and zirconium content and the heat treatment are varied. In alloys quenched from elevated temperatures, the uranium is present as a gamma solid solution. On slow cooling, the gamma transforms to the intermediate uranium- zirconium delta phase.
  • Niobium additions to the zirconium-containing alloys stabilize the gamma phase.
  • the study looked at small quantities of doping of Zirconium (under 10%) with various Thorium dominant alloys (75% and above Thorium). More analyses would be needed on a heavy Uranium- based alloy. Summary table for estimates of the constitution of a suitable binary alloy Binary Alloys Alloy name Constitution Variability Notes Uranium – U-97, W-3 2.5 – 10% ⁇ Higher than 4.5% Tungsten produces an Tungsten W alloy that would fail to melt at the boiling point of lead, thus, removing the passive safety element of controlled meltdown. ⁇ Requires a binder in the form of an additional element or in the method of fabrication.
  • Powder bed fusion by laser has a tendency to form bonds that produce different metallurgical effects (similar to how quenching produces thermos-chemical effects).
  • Uranium based alloy More Uranium is preferred, thus, the upper limit of a Uranium based alloy is chosen.
  • This alloy has never been Rhenium (1.35 Re) studied.
  • Rhenium must be less than 30% of the atomic percentage of Tungsten or greater than 70%. Since Tungsten is the preferred Alloy, values for the lower limit have been given.
  • the thermal Niobium doping melting point was not a massive consideration for the study, only the Ternary Alloys crystalline structure for thermal breeding impacts. ⁇ Briefly mentioned was the use of zirconium doping, when quenched, created a heart-treated Uranium- gamma-zirconium state that was stable beyond the melting temperature of Uranium.
  • Lithium-7 Neutron ADS source In preferred embodiments of the present invention, a two-stage ignition process is employed at the ignition source (bulb/ball). Firstly, incoming protons impinge on an atom such as LI-7 to generate neutrons. The following illustrates the process.
  • Equation 2 Electron capture decay of Beryllium-7 ⁇ 53.2 ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ 7 + ⁇ ⁇ ⁇ ⁇ 7 This is an important feature of Li-7 as the first material in the two-stage neutron generation process, meaning that the material performing the p-n reaction is not consumed over the longer term.
  • the study suggested a number of key findings: i. A resonance peak interaction probability of 580 mbarns at 2.25 MeV. ii. A wider peak interaction spectrum around 5 MeV of 400 mbarns. iii. A 200 mbarns sustained interaction beyond 5 MeV until a decline to 50 mbarns at 10 MeV.
  • the results suggested a slight bias for a forward conical production of neutrons (Storm et. al.,2013).
  • the Los Alamos National Laboratory conducted an investigation into particle emission from the proton-induced reaction of a Lithium target in the energy range of between 2 MeV and 150 MeV.
  • Equation 4 the double alpha emission from Beryllium-8 is the dominant reaction at lower energies with the single neutron emission reaction becoming dominant after 2 MeV.
  • the peak interaction point is 340 mbarns at 5 MeV. This does conflict with the reports of the follow-up study from Storm et al. suggesting a 580 mbarn peak at 2.25 MeV but is consistent with the value of 400 mbarns at 5 MeV.
  • the alpha reaction peak at 13 MeV is the dominant reaction that eventually decreases the neutron production between 13 MeV and 25 MeV – this is also consistent with Storm et al.
  • Fast-Fission Cross-Sections for Uranium and Thorium Reaction rates for the two main fuels of interest, Uranium-238 and Thorium-232 depend upon the cross section of the nuclei.
  • Fast fission – upon which most embodiments of the present invention rely — is a type of atomic fission employing the use of fast neutrons. While the fast neutron mechanism has a more effective use of source neutrons – in that neutrons aren’t lost to diffusion in great quantities – the chance of interactions in the fast spectrum is far lower than in the thermal spectrum. This is directly counteracted by both the neutron multiplicities and the easily available fuel. Neutron multiplicities in the fast region vary proportionally to the incident neutron.
  • Figure A12 is a collection of cross-sectional data and prompt neutron multiplicities for Uranium-238 (the standard stable isotope of uranium with 99.3% natural abundance) and Thorium-232 (an element three times more common than Uranium). Both Uranium-238 and Thorium-232 have been considered fuels for fast fission. Both natural Uranium and Thorium have near-complete abundance in these isotopes and the energy output of fast fission is nearly identical. Where Thorium falls short is its lower fission cross-section compared with U-238. Compare Figure A13: Th-232 Fast Fission cross-section and Figure A14: U-238 Fast Fission cross- section. Fast fission has a number of fuel-related advantages.
  • ⁇ 15.726 ⁇ ⁇ Principles of Accelerator Driven Fission according to embodiments
  • the basic explanation of the method is to break up high- density fuel into a finite element mesh grid and analyse each element from its centre point node, from here one node is selected to be a source node (the impacted node from the accelerator) and all other nodes are considered inert fuel pieces.
  • the source is multiplied by the second law mirror equation – which is based on the geometry of the surrounding fuel – and this second law function carries on to create a neutron impact field neighbouring fuel.
  • Neighbouring elements, impacted by the source node are then treated as source nodes, individually, with an initial fission rate stemming from the source element and, thus, with a corresponding neutron source rate.
  • the process begins again by assigning a second state to this field. All states are then superimposed onto one another to get a governing equation for each nodal source element commanded by the same time step as the source function. During the superposition step, the original neutron field is extended beyond its boundaries as the neighbouring fuel elements help create the source functions for these out-of-bound elements.
  • Equation 1 time-dependent source multiplication equation 2 2 2 ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇
  • the overall effect we have appreciated pursuant to the invention is that, when computing fast fission rates, the geometry of the neighbouring fuel cells becomes a far more important factor than conventionally assumed. To complicate matters, in a metallic fast-fission core, the lack of moderation increases the “area-of- effect” of this multiplication effect.
  • the example given is small, but apply it to a large mass of fuel, and even small source functions eventually build to produce large-scale energy outputs.
  • the current gold-standard computation method for nuclear reactions is the Monte-Carlo method. However, despite being the accepted model it doesn’t take into account geometry with such a high degree of accuracy. The method computes a number of particles in a system and computes them for the lifetime of the particle.
  • the multiplication factor for metallic uranium cores is: ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇
  • This gap in traditional presents an un-appreciated; a reaction mode of secondary fissions adding to an original, external source that is impactful enough, over time, to drastically impact energy values while, on a first computational basis, would seldom be picked up by Monte-Carlo code and conventional modelling methods. In our arrangement this becomes as important as the reaction equation itself. This is not meant to discourage or disprove the Monte-Carlo method but rather to compensate for the shortfall in the particular situation which is exploited in embodiments of the invention. However in a core such as in embodiments, the additional flux becomes important over time.
  • Equation 13 First law of semi-transparency from energy conservation [ ⁇ ⁇ fission ⁇ , ⁇ , ⁇ + ⁇ ⁇ absorption ⁇ , ⁇ , ⁇ ]
  • ⁇ ⁇ Area of the node under review in respect to the source
  • ⁇ ( ⁇ , ⁇ , ⁇ ) local flux point remaining from the source Assuming a mid-point analysis once more alongside a one-dimensional analysis for simplification – which we’re allowed to do according to the symmetry of a spherical source, generates the system of a linear set of elements as shown in Figure A16.
  • Equation 19 Sum of all elements 1 1 1 1 ⁇ 4 Substituting in Equation 19: ⁇ 0 ⁇ 0 ⁇ ⁇ ⁇ ⁇ N ⁇ 4 Equation 20: Maximum flux radii ⁇ ⁇ Equation 21: Maximum flux radii with ⁇ ⁇ Second law of local Criticality functions
  • Figure A18 which repeats Figure A2, two identical elements are adjacent to one another. These two elements are homogenous, fissionable materials with element one undergoing a nuclear reaction to produce neutrons. The control of this initial source reaction is entirely independent of the system and will continue to bombard the target element at a constant rate.
  • Equation 22 Spherical source function ⁇ ⁇ 0 Equation 22 is constant for all spherical sources to a 2D flux field for neutrons emanating from the source a radial distance “r” away.
  • Equation 23 Mirrored source function ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇ Equation 23 may combine with the source to a combined source multiplication function: Equation 24: Source multiplication ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇
  • This new source is then used in a repeating function as these neutrons impact element two in the same manner: ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇
  • Equation 12 establishes the time-dependent equation.
  • Equation 25 time-dependent source multiplication equation 2 ⁇ ⁇ ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇ It may be necessary, as discussed in accuracy, to expand the accuracy beyond a simple singular reciprocating function and expand to a secondary or tertiary reciprocating function. In this case, the mirrored neutron’s effects are considered significant enough to be considered in Equation 12. The requirements for “significant” are outlined within the zeroth law. Equation 32 outlines an expanded notation for multiplication factors to increase the accuracy of a solution.
  • Equation 26 Mirrored source addition extended and expanded ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ 2 ⁇ ⁇ ⁇ ⁇ ⁇ 2 2 ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ 2 3 ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ 2 n ⁇ 2 2 2 2 2 2 2 2 2 ⁇
  • Figure A19 represents a system of 6 equally adjacent elements surrounding a source element. Since the material is homogenous, Equation 25 would become: 2 ⁇ ⁇ ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇
  • Figure A20 displays twelve elements of equidistance from the source element (red).
  • Equation 25 now becomes: ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇
  • Equation 25 no of semi- transparency.
  • Equation 28 General second law mirror ⁇ ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ N ⁇ 2 Third Law of Interaction Accuracy While the universe is to expand that chaos, it is not random. This law aims to justify the tug-of-war between accuracy and computational ability; or rather, usefulness.
  • Equation 30 Secondary mirrored event source ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇
  • These neutron events are then become: ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇
  • the red block indicates the source element
  • the blue blocks represent elements within the mirror effect region, with only primary mirror effects, that will directly increase the local criticality of the source node and, the yellow region indicates elements effected by the source element but that do not contribute to the mirror effect.
  • the source function as shown in the second law for the three-dimensional cube, equates to Equation 27 as a function of time; ⁇ This equation now governs the fission effect of all the elements within the neutron field.
  • the red block indicates the source element under investigation
  • blue – once again – represents elements within the mirror effect region, with only primary mirror effects, that will directly increase the local criticality of the source node and, the yellow region indicates elements effected by the source element but that do not contribute to the mirror effect
  • green represent newly-added elements that were previously out of the field and, grey represent the original source node.
  • the neutron fields are superimposed on one another, additively, and thus for this example, after two fields have been computed, the source function of the original primary source becomes; ⁇ Due to this particular example, it is easy to deduce the superimposed total source function by a simple symmetric analysis; six nodes are a distance one elemental node length away, twelve are a distance ⁇ 2 elemental node lengths away and, eight are a distance ⁇ 3 elemental node lengths away.
  • Equation 2 The source function, after superimposing all twenty-one flux fields that are directly adjacent to the source element, creates; ⁇ Equation 2: Superimposed cubic source function from “blue-zone” adjacent to the original source node ⁇ ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇ ⁇ ⁇ ⁇ 2
  • Equation 48 Cubic mirror function ⁇ 2 ⁇ ⁇ 2 ⁇ N ⁇ 2 ⁇ 2 ⁇ ⁇ 2 ⁇ N ⁇ 2 ⁇ 2 ⁇ ⁇ 2 ⁇ N ⁇ 2 and thus, Equation 49: Simplified superimposed cubic source function from “blue-zone” adjacent to the original source node (see Figure A25): ⁇ ⁇ ⁇ 2 ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ 6 12 8 Analysing a fields.
  • Equation 50 Source function from source plane, a nodal distance root-8 away t 2 2 ⁇ 2 ⁇ ⁇ 2 ⁇ N ⁇ ] (4 ⁇ ( ⁇ 3l) ) only change being the distance from the source: Equation 51: Source function of an element root-8 nodal lengths away with the second law 2t Upon analysis of a five-by-five-by-five element cube presents a set of distances from the centre (source) element: • 6 centre faces of nodal distances 2 with four elements accompanying a distance ⁇ 5 and four elements of a distance ⁇ 6 in addition to those.
  • Equation 52 Superimposed cubic source function from “blue-zone” adjacent and "yellow-zone” second adjacent to the original source node ⁇ ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇ ⁇ ⁇ ⁇ 2 the following super imposed equation: Equation 53: general 4th-law source element function ⁇ 2 ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ Once the 4 th -law value for the element. To construct source functions within the “green-zone” – i.e.
  • Equation 53 Equation 54: 3rd neutron plane starting source ⁇ ⁇ ⁇ 2 ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇
  • Equation 553 3rd plane starting source including 2nd law ⁇ ⁇ ⁇ 2 ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇
  • Equation 56 3rd plane source effects on a neighbouring fuel element at a distance "r" from the element ⁇ ⁇ ⁇ 3 2 ⁇ ⁇ ⁇ ⁇ 1 ⁇ ⁇ ⁇
  • Equation 574 3rd plane source effects on a neighbouring fuel element at a distance "r" from the element ⁇ ⁇ ⁇ 3 2 ⁇ ⁇ ⁇ ⁇ 1 ⁇ ⁇ ⁇ ⁇
  • Equation 574 3rd plane source effects on a neighbouring fuel element at a distance "r" from the element ⁇ ⁇ ⁇ 3 2 ⁇ ⁇ ⁇ ⁇ 1 ⁇ ⁇ ⁇ ⁇
  • Equation 574 3rd plane source effects
  • Equation 58 general 4th-law source element function for the superposition of planes 3 and 4 2 2 ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ The i. Source multiplied by 2 nd law mirror effect. ii. Construction of neutron plane [1] from the source. iii. Effects of prior neutron plane establish the source functions of neighbouring elements. iv. Source functions from the prior step establish a new neutron plane [2]. v. Old neutron [1] and new neutron [2] planes superimpose additively. vi. These planes are marked as “fixed”. vii.
  • the first and second laws are both built upon the basic understanding of spherical sources, neutron multiplicity through chain fission and basic geometry.
  • the inaccuracies of the method arrive at two key locations; the simplification of cubic elements into dimensionless point sources and the use of superposition to establish a system-wide relationship.
  • the reason for both comes from the computational ability to track the locations of individual particles within the fuel material.
  • nodal elements may have their dimensional units changed to reflect a smaller cube (changing the cm standard unit to mm) but I warn against this: this method already pushes the boundary on modern computational ability, utility-sized reactor cores computed down to the millimetre could require months of computations to compute even with modern technology.
  • Equation 47 For the argument that using superposition effectively doubles the mirror effect there is the following rebuttal: From Equation 47: ⁇ ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ 2 ⁇ ⁇ ⁇ 2 account twice is thus invalid. In practice this second half of the equation is always substantially less than the first (see Figure A26).
  • the red line (Equation 47) represents the growth in source function for U238 under a source value of one and included the 4 th -law superposition of the “blue zone” elements.
  • This source flux effectively means that 7.22% of all protons within the beam line interact with the target plate with the intended reaction.
  • Equation 59 when used according to the volume of 1cm 3 , is consistent with MCNP and FLUKA simulations.
  • Figure A28 illustrates these results.
  • Each of the above actinide elements has its respective advantages and disadvantages. Considering the multiplicities of a fast neutron reactor, even a minor change in neutron source has an enormous effect on the reactor flux as it expands through the material.
  • Uranium-238 has an atomic density of 1.6 times greater than thorium-232.
  • Two stage Neutron ADS source Preferred embodiments of the present invention utilise a two-stage neutron source in which protons from a particle accelerator impinge on a first material to produce neutrons that go on to impinge on a second material.
  • the previous section discussed a source that was conducting direct proton fission on a target material where the target material is also fissionable under fast neutrons.
  • the minimum requirement is 26.7 MeV on target (Isaev et. al., 2008).
  • a minimum of a 35 MeV particle accelerator is required as the beamline would need to pass through a window that separates the Uranium and the LBE coolant.
  • a 35 MeV cyclotron is a costly investment in two ways; the amount of low-carbon steel required to make the magnet can drain a local supply chain (increasing production time) and the financial investment grows exponentially for every MeV that a particle accelerator is capable of. That is not to say that a commercially viable reactor cannot be made and indeed one can, particular for higher power applications.
  • the most commonly produced particle accelerator is a 15 MeV cyclotron designed for the medical industry to produce PET drugs. This is under the threshold minimum for direct proton fission. It would be a yet further and independently advantageous step if a system taking advantage of the multiplication discussed above could be made to function with excitation deriving from such a source, or a cyclotron with energy below 20MeV. According to a further innovative aspect, this can be achieved. Medical cyclotron sources are can be used with a refinement. 15MeV is adequate to excite a lithium-7-based neutron ADS source, the threshold for which is 1.88 MeV.
  • Lithium-7 does have a fast neutron reaction with a minimum threshold of 2.47 MeV, reaching a peak interaction cross-section of 0.6 barns at 7.5 MeV (Hernandez & Pereslavtsev, 2018). Within the upper echelon of neutron production, Lithium-7 will likely begin to degrade over time if at the centre of a fast-fission reactor core. Another concern is the lack of a “primary” mirror effect in terms of the second law, instead, the source unit will have to have lithium surrounded by fast-fissionable material to generate any source multiplication.
  • the Lithium-7 source unit will favour the Lithium-7 (p, n) reaction creating Berylium-7 – which will decay back into Lithium-7 with a half-life of 53 days.
  • the fast-neutron reaction with a minimum threshold of 2.47 MeV, will be the only destruction of the Lithium-7 source unit due to this unique circular decay function.
  • the Lithium, or equivalent material in the ignition bulb is preferably replaceable (with the reactor shut down) without disturbing the fuel or the coolant.
  • An integer winding number gives the curve a topological invariant, or property that does not change even while the curve is continuously deformed.
  • To determine whether a point is inside or outside of a polygonal mesh in the complex plane utilize the winding number. To do this, one can build intricate curves from the mesh’s vertices to the target point and then calculate each curve’s winding number. The point is inside the mesh if the sum of the winding numbers for all the curves is non-zero, and outside the mesh, if the sum is zero.
  • This technique known as the "winding number algorithm,” is popular and effective for determining whether a point is within or outside of a polygonal mesh because it only involves quickly calculating the winding numbers of each curve.
  • the code needs to create a mesh of nodes, assigning to each node if it is fuel or not. This is done by loading the stl meshes using the numpy-stl module and getting the number of nodes that will be required in the x,y, and z directions. The meshes are then centered on the nodes.
  • the code can be run on multiple cores and therefore save computational time.
  • Each process then iterates through the y and z coordinates calculating the winding number for each node. To improve the speed each point’s coordinates are compared to the minimum and maximum coordinates of the mesh. If the point lies outside of these bound it is not necessary to calculate the winding number as the point cannot be inside the mesh. Multiplicities Of Nodes For each step of the code, the same optimization is done in the initializing of the nodes (splitting the code into processes for each x-coordinate). In order to optimize further concept from the First Law Of Semi Transparency is used to eliminate calculations if the node is outside the area of effect. First, the multiplicities for the source node are calculated.
  • the first plane is calculated using the concepts from the Fourth Law Of Neutrons Field Superposition.
  • the code iterates through each of the nodes treating it as the secondary source then it iterates through the nodes again calculating each of the nodes’ contribution to the secondary source’s multiplicity. These multiplicities are then added together for each secondary source.
  • the second plane is calculated using once again the concepts from the Fourth Law Of Neutrons Field Superposition. For this part the code iterates through each of the nodes treating it as the secondary source then it iterates through the nodes again calculating how the secondary source affects the nodes’ multiplicity.
  • Average secondary neutron energy is shown in Figure A50 (First moments (average energies) of 235,238U and 239Pu prompt fission neutron spectra for endf/B-VII.0 calculated with the Los Alamos model [69] in comparison with those of endf/B-VI.
  • Fission Cross Sections Cross section Element value Reasoning Thorium- 0.15 barn From the data collected from the cross-section working group, the 232 cross section for Thorium-232 fast fission to be 0.15 barn between 1.5- 5 MeV fast neutrons.
  • Uranium- 0.6 barn From the data collected from the cross section working group, the cross 238 section for Uranium-238 fast fission is fairly consistent at 0.6 barn between 1.5-5 MeV fast neutrons.
  • Uranium- 0.04833 A multiplier of 0.97 was also used in conjunction with this value 238 to simulate the need for at least one alloy.
  • ADS Neutron Source We accurately predict the neutron source that could be expected from both a single step ads source (direct proton induced fission) and a two-step ads source whereby the target is Lithium-7 (targeting the (p,n) reaction).
  • the analyses took a weighted total, capture and total scattering cross section of the isotopes with available data – 44.3% and 62.8% of all fission products for Th232 and U238 respectively.
  • the weighted, adjusted, total scattering cross section (assuming 100% of the material) is shown at the bottom of each table and again in the analyses of each core type.
  • Mo-95 was assumed to be 100% of all atoms when considering the scattering effects – as it’s the lightest atom – while maintaining the adjusted total scattering cross section.
  • the fission products are assumed to have scattered evenly throughout the cores coolant which then establishes the atomic density accordingly.
  • Fission WIMS U-238 Total Weighted Capture Weighted Total Weighted product ID Scattering 42-Mo- 4095 5,13E-02 7,864 4,03E-01 0,3244 1,66E-02 7,5396 3,87E-01 95 43-Tc- 99 4099 6,24E-02 9,126 5,69E-01 0,658 4,10E-02 8,468 5,28E-01 44-Ru- 4101 6,21E-02 7,78 4,83E-01 0,7557 4,69E-02 7,0243 4,36E-01 101 45-Rh- 4103 0,00E+00 8,321 0,00E+00 0,7325 0,00E+00 7,5885 0,00E+00 103 45-Rh- 4105 4,09E-02 8,321 3,41E-01 0,7325 3,00E-02 7,5885 3,11E-01 105 47-Ag- 4109 2,52E-03 8,335 2,10E-02 0,6336 1,59E-03 7,7014 1,94E-02 109 54-Xe- 4131 3,29E-02 7,8
  • This core separates fuel into a Tritosphere configuration with up to seven layers (or more) of “petals” or shells that substantially surround the ignition bulb.
  • Each petal layer features 97% Uranium- 238, 3% Tungsten and comprises ribs or blades 5cm in depth and 2cm in height that is separated according to a constant angle for that layer. Every blade peers directly into the centre with a flat face of a height of 2cm, i.e. each blade is aligned with the ignition bulb so that its 2cm flat face is substantially perpendicular to a line between it and the ignition bulb.
  • Figure A37 shows a side view and a top view of a rose core while Figure A38 shows an individual fuel Tritosphere.
  • Each petal is supported by a tungsten support stem which is attached to a central base that allows each petal to move in layers: similar to the movement of a rose in bloom.
  • the advantage of allowing each petal to move is related to the 4th law and the influence of distance on the establishment of neutron planes in terms of local criticalities: removing fuel elements out of the ability to establish a “mirror” overlap of neutron planes ensures the destruction of the local criticality function and thus a prompt shutdown or, forcing some layers to function entirely as irradiated passive fuel in a “subcritical” format.
  • a level four is a partial meltdown and release of reactor fuel resulting in exposure to radiation.
  • the meltdown of the rose core lacks the latter –radiation exposure – but satisfies the first requirement.
  • a meltdown would have caused an over- pressurisation of water within the vessel which would lead to a subsequent rupture of the containment vessel in the event of a disaster – Chernobyl.
  • the shape of the spiral elements of the Trinity core may be defined by rotating a line about a point in an x-y plane while steadily increasing the value on the z-axis to define a 3-dimensional element.
  • the rotation is preferably about one fifth of a full turn.
  • Addition Of Movement With Reference To The 4th Law Spiral movement does not change the distances between nodes as the entire reactor is spinning about a symmetric axis.
  • Metallic Core concept – Willow Run Figure A56 shows a side and top view of a five fuel-element design suitable for incorporation into the reactor shown in Figure 27.
  • the Willow Run core was designed with the desire to improve the Rose core on the basis of ease of manufacturing.
  • the Rose core features a large number of unique components and requires a larger reactor vessel due to the natural convection requirement.
  • Willow run features five spiral fins designed to direct coolant through the axis of the reactor to incorporate forced convection in the lead coolant, thus making the reactor far smaller.
  • the Rose core has a very spread-out multiplicity heat map as shown in the figures. This is desirable because it means that the fuel will burn at roughly the same rate.
  • the rise time is shown in Figure A59 which is longer than that for an equivalent Uranium core (Figure A62) but is still viable.
  • Figures A60, A61 and A62 duplicate Figures A57 – A59 with Uranium as the fuel.
  • the Thorium Rose core has a projected life of 55.39 years and a half-life (when half the power output is reached) of 127.97 years.
  • the Uranium Rose core is better at a projected life of 88.28 years and a half-life of 203.97 years.
  • Figures A63, A64 and A65 duplicate Figures A57 – A59 for a Trinity core with Thorium as the fuel and Figures A66 – A68 have Uranium as the fuel.
  • Trinity has a slightly less spread out heat-map as shown in the figures, therefore a larger core would be more desirable to increase the lifespan.
  • Trinity has a faster rise time than rose as shown in Figures A65 and A68.
  • the Thorium Trinity core has a projected life of 9.66 years and a half-life of 22.32 years
  • the Uranium Trinity core is better at a projected life of 15.40 years and a half-life of 35.57 years.
  • FIGS A69, A70 and A71 duplicate Figures A57 – A59 for a Thorium Willow Run core, that is to say a five-element rotating core, while Figures A72 – A74 illustrate a Uranium core. From Figures A69, A70, A72 and A73 it can be seen that Willow Run is shown to have a well spread out heat-map. Willow Run is shown in Figures A71 and A74 to have a longer rise time. This is expected to be due to the angle of the blade, allowing less of the blade to be influenced by the source bulb.
  • the Thorium Willow Run core has a projected life of 16.06 years and a half-life of 37.11 years, the Uranium Willow Run core is better at a projected life of 25.60 years and a half-life of 59.15 years.
  • Heat Transfer Methodology The on Eutectic Alloy And properties, Materials Compatibility, Thermal- Hydraulics And Technologies Extensive use of the Handbook on Lead-bismuth Eutectic Alloy and Lead Properties, Materials Compatibility, Thermal-hydraulics and Technologies was conducted to construct a simplistic thermal capability modal of the ade system.
  • Figure A75 shows a Trinity Three Pipe Modal and Figure A76 shows a Trinity five Pipe Modal illustrate this pseudo pipe formation.
  • the fluid flow rate is dictated by rpm, which then in tern dictates the heat transfer rate.
  • Fluid velocity is governed by the following equation: 2 ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇
  • Figure A78 shows the density of melted LBE versus temperature and Figure A79 shows the dynamic viscosity of melted LBE versus temperature at normal pressure.
  • Figure A80 shows the Molecular Prandtl number as a function of temperature for different fluids.
  • the thermal conductivity of Lead and lbe has been established as 20 W/mK and 17 W/mk respectively.
  • Figure A81 shows Thermal Conductivity Of Molten Lead, Bismuth And lbe Versus temperature.
  • Thermal Cycle Figure A83 shows a thermal cycle having twin Rankine with reheat and re-gen as an alternative to those shown in Figures A45 and A46.
  • the Uranium-Tungsten alloy will sink to the bottom of the chamber due to the density difference between the alloy and the lbe medium. The alloy will also separate into tungsten and Uranium respectively. Uranium will solidify at 1132°C in the cooler lbe (return temperature of 480°C) and will also be out of range of the neutron field planes established in the 4th law – creating only irradiated fuel with no mirror effects. If the entire core melts down and is out of range of the source bulb’s mirror field, the reaction rate becomes entirely subcritical at the bulb with a very low flux field – even at utility-scale, this irradiation amount is only a few kilowatts.
  • Decommissioning and lbe heat exchanger are designed to be repository ready. The purpose of this is to simplify the decommissioning process in that the entire unit is placed into retirement without the need to process and separate waste or destroy components.
  • Each reactor core has a large half-life. The reactor may continue beyond a single half-life, but it is theorized that the unit’s structure may have integrity problems after one half-life (69.3% material remaining). Every fission event creates a local discontinuity within the material and, while each member is not load-bearing, the weight itself at such a point may become too much to hold and crack under the thermal stress. It may be recommended to construct a specialized facility for decommissioned units.
  • Test Cores Figure A84 shows a test core having a non-rotating natural convection impeller with Thorium fuel.
  • Figures A85 and A86 show the heatmaps and Figure A87 shows the output power.
  • Figures A88 and A89 shows the heatmaps and Figure A90 the output for the test core with Uranium fuel.
  • the heat-maps in figures A85, A86, A88 and A89 show the multiplicities inside the test cores, as expected the outside of edges have the lowest multiplicities while those closest to the source bulb have the highest.
  • the heat-map also shows that the shape of the source bulb has low effect on the distribution of multiplicities, but that it instead only requires fuel to be close to the source node, allowing for the mirror effect to increase the source node’s multiplicity.
  • FIG. 8 shows a rotating fuel micro reactor assembly and Figure A92 shows various views of the fuel elements.
  • Figures A93, A94 and A95 show the corresponding heat maps and power output for Thorium fuel.
  • Figures A96, A97 and A98 show the corresponding heat maps and power output for Uranium fuel.
  • Figure A99 shows a control system graph for a core (thorium shown but the principle is valid for all fuels) in which the reactor output is varied up and down in response to demand. This has particular application to the transport field as it allows a ship or train to “throttle back” on the output of the reactor when the vessel is not moving or is moving very slowly. The technique is, of course, usable in all applications.
  • Figure A99 shows a diagram for the response of the system.
  • the output can be controlled by changing the accelerator current.
  • Upper 2 is a safety limit, if this limit is reached the power to the accelerator is cut until troubleshooting and operator re-activation occurs.
  • ⁇ ⁇ ⁇ ⁇ 1 is replaced by ⁇ ⁇ ⁇ ⁇ ⁇ 1 ⁇ ⁇ ⁇ ⁇ , ⁇ ⁇ ⁇ ⁇ ⁇ by ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ and ⁇ ⁇ ⁇ ⁇ ⁇ 2 with ⁇ ⁇ ⁇ ⁇ ⁇ 2 ⁇ ⁇ ⁇ ⁇ .
  • FIG. 1 shows reactor ramp up for a Thorium 5-layer core.
  • Figure A101 shows reactor ramp up for thorium trinity rose core.
  • Figure 103 shows two possible placements for neutrons detectors.
  • Neutron Detectors can either be placed inside the fuel cell or above the fuel cell under the capstone. This is possible because there is no neutron shielding between the top of the fuel cell and the capstone.
  • Figure A104 shows the steam cycle for the fuel cell, temperature and pressure sensors are placed at 1-4 a high temperature sensor is placed at ⁇ ⁇ . In case off shutdown the backup power needs to be able to power the system for at least 2 restarts, 2 hour cool down period and power the compressor and inter-cooler fans during this time.
  • Figure A105 shows a block diagram of a control system for the fuel cell.
  • neutron detectors will be used to monitor the neutrons per second, this will then be fed into an analogue controller and fuel cell control software or a PID controller.
  • the analogue controller sole purpose is to monitor the neutrons per second and if it is above the ⁇ ⁇ ⁇ ⁇ ⁇ 2 safety limit shown in Figure A99 it will shut down the accelerator.
  • the fuel cell control software will also monitor the neutrons per second and keep it within the desired range. If the ⁇ ⁇ ⁇ ⁇ ⁇ 2 limit is sensed by the software it to can cut power to the accelerator. A mechanical shutoff is also needed.
  • the inter-cooler fans are also set to max speed and mass flow in the steam cycle is increased to allow for better cooling.
  • the fuel cell temperature sensor feeds into the analogue controller, fuel cell software and steam cycle controller.
  • the fuel cell software and steam cycle controller can communicate and together keep the fuel cell temperature within the desired range, this is done by either changing the desired neutrons/second, mass flow in the steam cycle or increasing the inter-cooler fan speed. If the fuel cell temperature is too high the same shutoff sequence is used as the one used in the neutron sensor.
  • the steam side pressure and temperature sensors also have max values that can cause the shutdown protocol to be initiated.
  • the steam side pressure and temperatures sensors are fed into the steam cycle controller, the controller keeps these two values within the desired range. If pressure is to high the blow-off valve can be activated, the blow-off valve also has a mechanical limit after which it will release pressure. The pressure is released into a tank, this allows for the water to be used to refill the loop if needed. Entrance breach, Restart and Fire Safety If the fuel cell is breached or fire is detected the shutdown procedure is triggered. In the case of fire CO 2 are deployed to automatically extinguish the fire. If the fuel cell needs to be restarted a master key must be given to the system, the person with this key must ensure that it is safe for the fuel cell to be restarted.
  • the idle state control system is very similar to that of the normal operating conditions except for the upper and lower limits that are changed and the bypass valve is set to bypass the turbine at all times. All other safety and control methods are kept in place. Inherent safety of the innovative design The benefits of the design of inherent safety will be appreciated. Whereas a conventional nuclear reactor requires positive damping of neutrons to prevent thermal runaway, with the current design it is simply a matter of switching off power to the accelerator to stop the reaction almost instantly. An “emergency off” capability which does not require positive action or mechanical components is thus readily provided. Moreover in less extreme scenarios the reaction rate can be precisely modulated by varying the accelerator input with a much faster response time several orders of magnitude more responsive than physically moving bulky and sometimes fragile control rods.
  • the source bulb undergoes a full analysis under the same dimensions of Equation 52.
  • iii The source bulb equation referenced in the above point is the only time-dependent equation for the reactor dynamics in both start-up and shutdown.
  • the rose core is analysed as an average density within a spherical zone – i.e. no gaps exist between fuel blades but the mass is the same as if there were gaps. Chain fission neutrons are seen as travelling “outward” from the centre and are added to the flux as it attempts to escape the centre.
  • Figure A41 is an excerpt from the code that computes the fission reaction rate in the material.
  • the multiplicity of three is derived from the cross-section evaluation group’s date on Uranium fast fission and aims to be a good conservative estimate considering the high neutron energies exiting the ADS flux.
  • the fission cross-section is taken to be 1 barn – the average for the fast fission group.
  • the volume for these fuel rings is “hard-coded” from the 3D CAD evaluation of the respective petals
  • the functions shown in the code have been replicated to host up to 7 fuel layers and total several hundred lines of python code.
  • the following table identifies the fuel mass by layer according to one embodiment of the present invention.
  • Layer Mass (grams) Total mass (grams)
  • an output of 5MWe is provided, that is to say 5MW of electricity. With an output of 5MWe, the thermal output of the core would need to be in the range 12-14 MWt to adequately supply the electrical demand after system efficiencies.
  • Figure A37 is a 3- layer rose core with a lithium-7 source designed for a compact power delivery system.
  • Figure A43 is a comparable graph for a 7 layer core with a single stage.
  • Figure A44 shows a single tritosphere for a 3-layer core.
  • the largest configuration described for the Rose core is a seven-layer single-stage reactor.
  • the maximum output, while still maintaining a half-life above 100 years, is 135 MWt at a half-life of 104 years.
  • this core will generate approximately 50 MWe. If a larger facility is desired, it is recommended to add additional layers in the same configuration, in the range of 8-10 layers. Increasing the number of layers improves efficiency. However the individual core becomes large and maintenance if needed is complicated.
  • multiple cores can be co-located and indeed can be powered and controlled from a single accelerator source.
  • Thermal to electrical conversion considerations Those skilled in the art of power station and nuclear reactor design in particular are familiar with arrangements for extracting heat with flows of multiple MW from a high temperature source at several hundred degrees (up to approaching 1000C) to provide useful electrical output. This disclosure will not therefore concentrate on that so as not to re-invent the wheel, or steam turbine. An important consideration though is the very high temperature regime the embodiments allow, potentially improving thermodynamic efficiency. A practical consideration is that materials should be used which can withstand the high temperatures of the coolant (LBE) without softening.
  • LBE coolant
  • Inconel® 600 is a suitable material used in heat exchangers with a melting point of about 1350 degrees C and tungsten or titanium-tungsten alloys can be used for higher temperatures up to 3000C.
  • the following examples are purely for illustration and not intended to be limiting. The primary purpose of the disclosure is to show that the thermal power generated can be comfortably handled using largely off-the shelf conventional components without excessive physical or practical issues arising. Of course for efficiency an optimised heat exchanger will likely be made for a particular application.
  • Example of steam power generation a closed cycle LBE to an open cycle steam power generator. As illustrated: i. Hot LBE at 1000°C ii. Cooled LBE (500° - 600°) iii. Open feedwater at 300k iv.
  • Figure A46 shows this three-working-fluid system and will be the focus of analyses.
  • a Siemens® SST-200 turbine was chosen as the steam turbine with inlet parameters of 10 MPa and 500°C. Due to the unique nature of an ultra-high temperature LBE heat source, it is possible to have the entire system in the superheated steam region – drastically improving thermal efficiencies. Designing the entire steam cycle to be in the superheated region allows for steam to be treated as an ideal gas.
  • the NTU method for heat exchangers also applies as no two-phase heat transfers exist.
  • the compressor unit is a multistage process to supply steam at 10 MPa at 350°C.
  • the use of a lead-based alloy as coolant is a partial shielding for gamma rays (not neutrons) so a combination of 35cm Concrete at a Ferro-boron content of 50% (FeB-2 in the graphs) and the coolant’s 15 cm radius beyond the core is more than sufficient as a shielding material.
  • Passive Safety The rose core is designed to use the thermodynamics of two-phase heat transfer to strategically destroy fuel elements before allowing the LBE coolant to vaporise – thus ensuring no pressurisation of the reactor core. During a phase change, the temperature of the medium stays constant and this, in combination with Newton’s law of cooling, ensures that the vaporisation of LBE is impossible.
  • Uranium will solidify at 1132°C in the cooler LBE (return temperature of 480°C) and will also be out of range of the neutron field planes established in the 4 th law – creating only irradiated fuel with no mirror effects. If the entire core melts down and is out of range of the source bulb’s mirror field, the reaction rate becomes entirely subcritical at the bulb with a very low flux field – even at utility-scale, this irradiation amount is only a few kilowatts. This is how the reactor core was designed from the start - with complete safety in mind.
  • active safety The most straightforward element of active safety is the control of the accelerator: varying the input or shutting it down entirely will reduce/collapse the neutron mirror fields rapidly in a highly predictable way. This, in itself, is also a passive safety element as the shutdown of electrical power is typically the first occurrence in the event of a disaster: floods, electrical short, terrorism etc.
  • the reactor core does not feature control rods; the particle accelerator provides the control. Every law of fission, neutron reaction dynamics and thermodynamics actively oppose this reactor core from functioning without the particle accelerator. The rate of reaction is monitored via neutron detectors embedded in the shielding and will be the first indication of an increased reaction rate.
  • the beamline intensity is varied rhythmically to balance the core in the vicinity of the desired output. All of this can readily be done automatically with no human input. Moreover the rapid response time allows more sophisticated control algorithms to be deployed which predict future neutron flux based on reactor state and temperature and measured or predicted load and can proactively adjust beam to give fine control. This proactive modelling can be performed in addition to parallel fail-safes which simply reduce excitation as temperature increases, for example reducing at a first temperature threshold and shutting down at a second threshold. To protect equipment – a potential financial loss not a potential exposure risk – the following measures are to be put in place: I. Fire suppression systems should be installed near all of the electronics with a preference for protecting the cyclotron. II.
  • Cycle pressure and temperature systems should monitor for any unexpected change or loss in pressure triggering an immediate shutdown.
  • Radiation detection monitors surrounding both thermal cycles – a spike in radiation should trigger an immediate shut-down. However it should be noted that there is not much radiation as compared to a conventional reactor.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Particle Accelerators (AREA)

Abstract

L'invention concerne une source de puissance (100) comprenant une région d'allumage (108) comprenant un matériau cible agencé pour recevoir un flux de protons et générer des neutrons en réponse à celui-ci. Un cœur de réacteur contenant une quantité sous-critique de matériau actinide (104) est agencé sous la forme d'une structure ayant au moins une couche autour de la région d'allumage (108). Le matériau actinide comprend au moins du Thorium ou de l'Uranium et génère des neutrons insuffisants par fission spontanée en l'absence du flux de protons vers la région d'allumage pour maintenir une réaction critique ou supercritique. La source de puissance comprend en outre un accélérateur (112) agencé pour fournir un flux de protons ayant une énergie comprise entre 4 MeV et 200 MeV au matériau cible dans la région d'allumage (108) et un agencement de commande pour commander la puissance du flux de protons pour moduler la puissance du cœur de réacteur.
PCT/IB2023/061053 2022-11-02 2023-11-02 Source de puissance WO2024095198A2 (fr)

Applications Claiming Priority (46)

Application Number Priority Date Filing Date Title
GBGB2216266.3A GB202216266D0 (en) 2022-11-02 2022-11-02 Energy multiplier
GB2216293.7 2022-11-02
GB2216276.2 2022-11-02
GB2216264.8 2022-11-02
GB2216264.8A GB2624152A (en) 2022-11-02 2022-11-02 Power source
GBGB2216267.1A GB202216267D0 (en) 2022-11-02 2022-11-02 Actinide fuel structure
GBGB2216274.7A GB202216274D0 (en) 2022-11-02 2022-11-02 Power source
GBGB2216307.5A GB202216307D0 (en) 2022-11-02 2022-11-02 Power source
GB2216267.1 2022-11-02
GBGB2216276.2A GB202216276D0 (en) 2022-11-02 2022-11-02 Nuclear reactor safety method
GB2216265.5 2022-11-02
GBGB2216272.1A GB202216272D0 (en) 2022-11-02 2022-11-02 Actinide fuel
GB2216307.5 2022-11-02
GBGB2216265.5A GB202216265D0 (en) 2022-11-02 2022-11-02 Electricity generation system
GBGB2216293.7A GB202216293D0 (en) 2022-11-02 2022-11-02 Nuclear reactor
GB2216274.7 2022-11-02
GB2216266.3 2022-11-02
GB2216272.1 2022-11-02
GBGB2301873.2A GB202301873D0 (en) 2022-11-02 2023-02-09 System for treating material
GB2301869.0 2023-02-09
GBGB2301874.0A GB202301874D0 (en) 2022-11-02 2023-02-09 A system for generating heat
GB2301875.7 2023-02-09
GBGB2301878.1A GB202301878D0 (en) 2022-11-02 2023-02-09 Propulsion system
GB2301879.9 2023-02-09
GBGB2301865.8A GB202301865D0 (en) 2022-11-02 2023-02-09 Nuclear fuel element
GBGB2301868.2A GB202301868D0 (en) 2022-11-02 2023-02-09 Nuclear reactor
GB2301877.3 2023-02-09
GB2301876.5 2023-02-09
GB2301874.0 2023-02-09
GBGB2301869.0A GB202301869D0 (en) 2022-11-02 2023-02-09 Nuclear reactor
GB2301878.1 2023-02-09
GBGB2301875.7A GB202301875D0 (en) 2022-11-02 2023-02-09 System for generating heat
GBGB2301872.4A GB202301872D0 (en) 2022-11-02 2023-02-09 Nuclear reactor
GBGB2301871.6A GB202301871D0 (en) 2022-11-02 2023-02-09 Energy multiplier
GB2301880.7 2023-02-09
GBGB2301876.5A GB202301876D0 (en) 2022-11-02 2023-02-09 Electricity generation system
GBGB2301866.6A GB202301866D0 (en) 2022-11-02 2023-02-09 Power source
GB2301866.6 2023-02-09
GB2301871.6 2023-02-09
GB2301873.2 2023-02-09
GBGB2301879.9A GB202301879D0 (en) 2022-11-02 2023-02-09 Nuclear reactor
GB2301868.2 2023-02-09
GB2301872.4 2023-02-09
GB2301865.8 2023-02-09
GBGB2301880.7A GB202301880D0 (en) 2022-11-02 2023-02-09 Power source
GBGB2301877.3A GB202301877D0 (en) 2022-11-02 2023-02-09 Nuclear reactor

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