WO2009138756A1

WO2009138756A1 - Electrical power generating systems using spent nuclear fuel and other radioactive materials

Info

Publication number: WO2009138756A1
Application number: PCT/GB2009/001224
Authority: WO
Inventors: Alexander Keith Bushell; Michael James Doggwiler
Original assignee: Permastar Ltd
Priority date: 2008-05-15
Filing date: 2009-05-14
Publication date: 2009-11-19
Also published as: GB0808805D0

Abstract

An electrical power generating system comprises a pod which contains spent nuclear fuel (1) or other radioactive materials that generate heat and electromagnetic radiation. A fluid (16) circulates, driven by heat transfer, within the pod generating electrical power via a turbine (4). Alternatively a thermophotovoltaic array (13) is used to generate electricity from the heat and electromagnetic emissions from the spent fuel or radioactive material.

Description

Electrical Power Generating Systems Using Spent Nuclear Fuel and Other Radioactive Materials

FIELD OF THE INVENTION

The present invention relates generally to electrical power generating systems and in particular to such systems which utilise spent nuclear fuel rods and radioactive waste in various configurations to create heat or radiation which is converted into electrical power by specifically adapted steam turbines, heat transference and heat convection turbines, and thermophotovoltaic systems.

BACKGROUND OF THE INVENTION

The use of spent nuclear fuel to generate electrical power is known in the art - see, for example, RU 2,145,129.

US 5,771,265 discloses a method and apparatus that utilizes this principle in deep underground waste repositories such as mines in order to generate electricity through convection.

The use of this concept for capturing energy from nuclear waste is also known, for example see RU 2,231,837 and JP 2000,08,8987.

However, significant challenges exist in creating an economically viable electrical generating systems based on the principle of driving electrical turbines through the use of heat derived from spent nuclear fuel rods and waste radioactive material, in terms of achieving an appropriate cost efficiency of energy production, largely as a result of the efficiency of electrical power produced and the engineering challenges associated with construction of the reactor, for example in deep underground mines.

Prior art systems require the spent fuel or waste material to undergo significant re-processing before they can be used to generate electricity or require extensive underground facilities that present significant civil and geotechnical engineering issues to be overcome that have economic and technical impact on the ability to generate electricity efficiently and safely.

It is an object of the present invention to provide an improved electrical power generating system.

It is a further object of the present invention to provide an electrical power generating system which may be easily built, operated and maintained, and is modular, in both size and output generation.

It is a further object of the present invention to provide an electrical power generating system which may be easily scaled in size.

It is a further object of the present invention to provide an electrical power generating system which may be modular in construction and application so the failure of one component does not cause the entire system to shut down and allows independent modules to continue to function. It is a further object of the present invention to provide an electrical power generating system that can be operated without a requirement for major attention to safety issues.

It is a further object of the present invention to provide an electrical power generating system that does not require solutions to the significant engineering and economic challenges required by prior art systems.

It is a further object of some embodiments of the present invention to prove an electrical power generating system with improved power production efficiency over prior art systems .

SUMMARY OF THE INVENTION

The present invention provides an electrical power generating system comprising a plurality of shielded pods each of which is lined with spent nuclear fuel rods or pellets or radioactive waste that may be covered in silica glass or other coatings to improve heat retention and dissipation, and which generate heat in a fluid filling the pod that may be in liquid or gaseous form driving a turbine by convection of or conduction through the fluid to generate electrical power. Another embodiment of the present invention is to use calibrated thermophotovoltaic cells that generate electrical power from the heat emitted by spent nuclear fuel rods, fuel pellets or radioactive waste thermophotovoltaically.

Other desirable and advantageous embodiments of the invention are set out in the dependant claims 2 to 34. In some embodiments, the present invention provides methods for using the spent nuclear fuel in its component pellet form to increase heat output which is not covered in prior art.

In some embodiments, the present invention coats the spent nuclear fuel or radioactive waste in various combinations of silica, ceramics and other materials that influence the heat emitting properties of the spent nuclear fuel or radioactive waste to influence efficiency and longevity of the electrical power generation system which is not covered in prior art.

In some embodiments, the present invention uses photovoltaic cells that have been tuned to optimise the generation of thermophotovoltaic electrical power increasing the efficiency of the electrical power generation system which is not covered in prior art.

In some embodiments the present invention uses various fluids in liquid or gaseous form that optimise the heat transference characteristics of the spent nuclear fuel or radioactive waste enhancing the efficiency of electrical power generation which is not covered in prior art.

Further objectives and advantages of the invention will become apparent from a consideration of the ensuing description and drawings, which, by way of example, describe embodiments of the invention in which multiple arrays of complete pods are used as a modular electrical power generation system and failure of one element of a module does not require the closure of the entire reactor as with most existing power stations. BRIEF DESCRIPTION OF THE DRAWINGS

Figure IA: A schematic perspective drawing of a first embodiment of a system according to the invention;

Figure IB: A schematic perspective drawing of a pod containing spent fuel rods of a first embodiment of a system according to the invention;

Figure 1C: A schematic perspective drawing showing a cross section of a pod containing spent fuel rods, convection funnel and turbine of a first embodiment of a system according to the invention;

Figure 2: A schematic perspective drawing of a pod showing the spent fuel rod connectors and safety shielding of a first embodiment of a system according to the invention;

Figure 3A: A schematic perspective drawing of a pod of a first embodiment of a system;

Figure 3B: A schematic perspective drawing of a pod showing the pod cap, fluid transfer apparatus and turbine of a first embodiment of a system;

Figure 4 : A schematic perspective drawing of the turbine assembly of a pod of a first embodiment of a system; Figure 5: A schematic perspective drawing of a pod showing the convection hood of a first embodiment of a system;

Figure 6A: A schematic perspective drawing of an alternative configuration of the spent nuclear fuel of a second embodiment of a system according to the invention;

Figure 6B: A schematic perspective drawing of an alternative configuration of the spent nuclear fuel as a modular array of a second embodiment of a system;

Figure 7 A schematic perspective drawing of a third embodiment of a system according to the invention.

Figure 8: A schematic perspective drawing of a fourth embodiment of a system according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

In figure IA a modular reactor contains a scaleable number of pods. Each pod can be loaded with a plurality of spent fuel rods (1) encased in safety shielding (9) to prevent escape of excess heat, fluids and radioactivity. To maximise safety features and minimise risk the pod array should ideally be located within the bounds of an existing nuclear facility, although this is not essential. Figure IB shoes the spent fuel rods (1) linked by their mounting frames (2) that can be removable depending on the recycling and reprocessing requirement of the fuel within the safety shielding (9) . The mounting frames are configured for a mechanical loading process allowing safe and convenient insertion and removal of the fuel rods. The mechanical loading feature allows single or multiple fuel rods to be removed in the event of rupture or maintenance and testing requirements.

The pod is shown in cross section in figure 1C. The fuel rods (1) are loaded into their frames (2) surrounded by safety shielding (9) with a removable cap (8) similarly safety shielded such that insertion and removal of the fuel rods (1) is allowed. Fluid filling the pod (16) , as a gas or liquid, and circulation occurs when it rises into the convection funnel (3) , through the turbine blades (5) and into a circulation or reprocessing facility (6) . Re-circulated fluid enters the pod (7) to complete the cycle.

Spent fuel rods (1) in their mounting frames (2) are arrayed around the internal circumference of the fluid filled (16) pod in figure 2. The safety shielding (9) and mounting frames (2) are constructed of materials to reflect and divert heat towards the centre of the pod to maximise heat concentration and convection.

Figure IB shows the spent fuel rods (1) in detail with the safety shielding (9) cut-away illustrating how the mounting frames (2) are configured not to obstruct the front of the spent fuel rods (1) and heat transference. The safety shielding (9) in figure 3A is constructed from a plurality of materials that maximise radiation shielding and heat reflection and insulation properties.

Heat from the spent fuel rods drives strong convection currents in the fluid (16) , either liquid or gas, contained in the pod that are channelled into the convection funnel (3) in figure 3B. The design of the convection funnel (3) is such that is maximises the hydraulic pressure of the convecting fluid (16) as it reaches the turbine blades (5) optimising the speed of the turbine blades (5) as they rotate to generate electrical power through the turbines (4) .

Once through the turbines, the fluid (16) leaves the pod for treatment (6) and may be returned to the pod (6) to be injected into the bottom of the pod (7) to complete the convection and fluid circulation cycle. An alternative embodiment of the pod is to retain the fluid in a sealed circulation system within the pod. Constant fluid circulation is ensured by the regular heat output of the spent fuel rods and the convection funnel (3) to provide steady, regulated electrical power generation.

In figure 4 the cap (8) and entire turbine assembly and fluid transfer apparatus can be removed to allow replacement, repair and maintenance of the spent fuel rods. The turbine blades (5) can be optimally configured for the nature of the fluid (16), in gas or liquid form and using a gas or liquid that optimises the power generation and economic efficiency of the reactor system. If a liquid is used, for example water, the radioactivity of the spent fuel rods is reduced preparing them for subsequent storage and reprocessing after their useful second life.

As shown in figure 5, the spent fuel rods (1) in their mounting frames (2) generate the heat which is focused towards the centre of the pod, reflected and focused by safety shielding (9) . The fluid (16) is forced upwards through convective pressure into the optimally designed convention funnel (3) .

In an alternative embodiment the spent fuel rods (1) are coated with materials that will affect the heat retention and emission properties of the spent fuel rods (1) . The materials, such as silica based glass, can allow a much higher degree of retained and useable thermal temperature, a decrease in heat decay and thus longer utilisation of the heat potential, increased radiation depletion and prior encasement in preparation for next stage recycling and reprocessing.

A further enhancement of heat density can be seen in figure 6A, where the spent fuel rods have been dismantled and their component fuel pellets (10) extracted. The pellets are encased in a pellet tray (11) made from highly efficient heat conducting materials on one side facing the centre of the pod and highly reflective and insulating on the other facing outwards which significantly increases the heat density and focuses heat on the conducting and convective fluid in the pod.

The pellet trays (11) shown in figure 6B are linked by removable clasps (12) that allow a plurality of pellet trays arrayed around the circumference of the pod. The pellet trays are loaded and removed using a mechanical process that allows repair, maintenance, and removal of the pellet trays at the end of their life for recycling and reprocessing.

Increased heat density will increase the convection flow of the fluid through the turbine blades resulting in an increased electrical power generation capacity and efficiency.

The individual pellets themselves and the full pellet trays can be coated in a similar fashion to the spent fuel rods with materials, for example silica and glass, which change the heat transference properties of the pellets and the pellet trays. This results in a longer life, higher efficiency and a regulated heat flow. This is also a cost effective solution for the use of recycled glass .

An alternative embodiment of the invention is the use of thermophotovoltaic technology to generate the electrical power. Figure 7 shows a pod in which a cylindrical array of thermophotovoltaic cells (13) constructed from specially modified photovoltaic diodes is suspended within the circumference of spent fuel rods (1) in their mounting frames (2), within the safety shielding (9) constructed from reflective and thermal and radioactivity insulating materials (9) . The spent fuel rods (1) supply the electromagnetic radiation, in the form of heat and light radiation, which powers the thermophotovoltaic cells.

The efficiency of the thermophotovoltaic cells (13) is maximised by tuning the molecular structure of the photovoltaic diodes to the specific radiomagnetic wavelengths of the radiation emitted by the spent fuel cells (1) .

The architecture of the thermophotovoltaic cells contained in the cylindrical array (13) is constructed to maximise the amount of radioactivity that can reach the photovoltaic diodes, minimising the blockages caused by cell components.

A coating can be applied to the surface of the thermophotovoltaic cells in the cylindrical array (13) to magnify the intensity of the electromagnetic radiation emitted by the spent fuel or radioactive material.

The fluid (16) filling the pod is optimised in its makeup and molecular structure to maximise the heat and electromagnetic radiation transfer from the spent fuel (1) to the thermophotovoltaic cells in the cylindrical array (13) . Alternatively, a vacuum may exist in the pod to maximise efficiency.

Electrical power generated by the cylindrical array of the thermophotovoltaic cells is channelled into the power control and sensor unit (14) in the pod. The electricity then contributes to the electrical grid, or the device being powered, via electrical transmission apparatus such as cabling (15) . Sensors detect the output of the cylindrical thermophotovoltaic cell array detecting performance and alerting operators of the pod in the event of damage of failure of a cell.

A mechanical device within the power control and sensor unit (14) can also allow the array to be inserted into and retracted from the spent fuel rods (1) . The cylindrical array of thermophotovoltaic cells (13), sensors, power control and mechanical apparatus (14) are all designed from materials that can withstand the high temperature and radioactivity caused by the spent fuel or radioactive material within the pod.

An additional benefit of the embodiment of the invention that utilises thermophotovoltaic cells as the power sources is that there are much fewer moving parts, reducing maintenance requirements and the possibility of component failure.

An alternative embodiment of the invention is to use pellet trays as the source of heat for thermophotovoltaic electricity generation.

Figure 8 shows an alternative embodiment of the system shown in figure 7. Instead of spent fuel rods, this embodiment of the system has the pod lined with thermophotovoltaic cells (13) . The spent fuel rods (1) in their mounting frames (2) are lowered using a mechanical device (17) into the pod which has thermophotovoltaic cells (13) lining the circumference. The power control and sensors (14) are located in a suitable place connected to the thermophotovoltaic cells (13) . The thermophotovoltaic cells (13) generate electrical power when the spend fuel rods (1) emit heat when lowered into the thermophotovoltaic cells' (13) radius.

An alternative embodiment of the invention shown in figure 8 is to use pellet trays as the source of heat for thermophotovoltaic electricity generation. The alternative embodiments of the invention are scaleable within the pod, with additional layers of spent fuel rods or pellet trays possible in both the horizontal and vertical axis and in the base and cap of the pod. The pods are scaleable within the reactor depending on the power output required.

The modular nature of both heat source within the pods and the reactor array of pods means that the failure of one component does not significantly affect the overall electrical power output of the reactor and allows for downtime of individual pods for refuelling, repair and maintenance .

An individual pod can be used as an independent standalone electrical power source for specific applications.

Claims

1. An electrical power generating system comprising:

- at least one pod in which spent nuclear material is received; a layer of heat retaining material, which in use, surrounds the spent material and defines an annular cavity with an inner wall of the pod; - a fluid, which in use, circulates, within the pod; a funnel located in the pod for directing fluid towards a roof region of the pod; and - a turbine located in the roof region of the pod whereby circulating fluid impinges the turbine thereby generating electricity

2. An electrical power generating system according to claim 1 in which the spent nuclear material is a nuclear fuel rod from a nuclear reactor.

3. An electrical power generating system according to claim 1 in which the spent nuclear material is in the form of fuel pellets.

4. An electrical power generating system according to any of the preceding claims in which the heat retaining material includes silica glass.

5. An electrical power generating system according to any preceding claim wherein the funnel is configured to optimise the flow of fluid towards and through the turbine blades.

6. An electrical power generating system according to any preceding claim wherein a shield of a material is provided for reflecting heat and radiation towards the centre of the pod, the shield surrounds the spent nuclear material.

7. An electrical power generating system according to claim 7 wherein the shield surrounding the spent nuclear fuel is a radiation shield and protects against radiation.

8. An electrical power generating system according to any preceding claim in which a cap of the pod can be removed to allow the fuel to be replenished and for inspection, repairs and maintenance.

9. An electrical power generating system according to any preceding claim wherein the turbine can be removed from the pod for recycling or decontamination.

10. An electrical power generating system according to claim 1 in which the spent radioactive material is loaded and unloaded from the pod using a mechanical system.

11. An electrical power generating system according to claim 1 in which the spent radioactive material is in mounting frames within the pod that allow loading and unloading.

12. An electrical power generating system according to claim 3 in which the pellets are coated in silica glass or ceramics in order to improve the heat retention properties of the fuel pellets.

13. An electrical power generating system according to claim 3 in which the fuel pellet trays are made of materials that reflect heat and radiation towards the centre of the pod.

14. An electrical power generating system according to claim 3 in which the pellet trays are arrayed around the circumference of the pod in a modular fashion.

15. An electrical power generating system according to claim 15 in which the pellet trays are connected using removable clasps to allow ease of loading and unloading of the pellet trays.

16. An electrical power generating system according to any of the preceding claims further comprising:

- a cylindrical array of thermophotovoltaic cells to generate electricity;

- a cylindrical array of thermophotovoltaic cells; and

- a sensor and power control unit which monitors the electrical power output of the thermophotovoltaic cells and transfers electricity at desired instant.

17. An electrical power generating system according to claim 17 in which the molecular structure of photovoltaic diodes in the thermophotovoltaic cell has been optimised to the wavelengths of the electromagnetic radiation emitted by the spent fuel or radioactive material.

18. An electrical power generating system according to claim 17 in which the thermophotovoltaic cell are shaped to maximise the amount of electromagnetic radiation that can reach the photovoltaic diodes.

19. An electrical power generating system according to claim 17 in which the thermophotovoltaic cells are coated with materials that focus electromagnetic radiation emitted by the radioactive material.

20. An electrical power generating system according to claim 17 in which the fluid in the pod includes a material with a molecular structure that optimises the heat and electromagnetic radiation transfer between the spent fuel and the cylindrical array of thermophotovoltaic cells.

21. An electrical power generating system according to claim 17 in which a vacuum optimises the transfer of heat and electromagnetic radiation between the spent fuel and the cylindrical array of thermophotovoltaic cells.

22. An electrical power generating system according to claim 17 in which the photovoltaic diodes in the thermophotovoltaic cell are resistant to high temperatures and levels of radioactivity within the pod.

23. An electrical power generating system according to any of the preceding claims in which the number of pods used to generate electrical power are scaleable.

24. An electrical power generating system according to any of the preceding claims in which the size of the pods are scaleable.

25. An electrical power generating system according to any of the preceding claims in which the pods are modular.

26. An electrical power generating system according to any of the preceding claims in which the heat and electromagnetic radiation fuel source in the pod is scaleable .

27. An electrical power generating system according to any of the preceding claims in which each pod has an array of sensors to detect power output, safety levels and performance of the components of the pod.

28. An electrical power generating system according to any of the preceding claims in which a pod may function independently as an individual reactor for a specific application.