BG106217A - Power from fission of spent nuclear waste - Google Patents

Abstract

A linear accelerator, preferably of the monochromatic type, accelerates electrons to an energy of about 10 MeV which are directed onto a high Z target such as tungsten to generate gamma rays which are directed onto the fuel material such as U238 which results in the (gamma,f) reaction, thus releasing about 200 MeV. A reactor built to this principle requiring an accelerator driven by 1 MW will develop about 20 MW of power. The reaction is not self-sustaining and stops when the beam is turned off. This accelerator driven reactor may be used to "burn-up" spend fuel from fission reactors, if simply operated at 10 MeV. The photo-fission results in typical spent fuel waste products such as Cs137 and Sr90 which undergo photodisintegration by the (gamma,n) reaction, resulting in short-lived or stable products. 18 claims, 6 figures

Description

RECEIVING ENERGY FROM THE DISPOSAL OF WASTE WASTE

TECHNICAL FIELD

This invention generally relates to the treatment of spent nuclear waste. More specifically, this invention relates to the generation of electrical energy from heat in reactions from the decay of spent nuclear waste and to the efficient use of nuclear waste.

BACKGROUND OF THE INVENTION

A typical 1000 megawatts (MWe) PWR of 75% capacity generates about 25 tonnes of spent fuel with a combustion efficiency of 43 gigawatts (GWe / t). 21 tonnes of fuel consumed (containing 42 PWR fuel cells with a total volume of about 11 m ³ ) will produce electricity of about 6.6 TWh (6.6 billion kWh). The production of this energy corresponds to the combustion of 2 million tonnes of coal in a conventional heat plant, producing 120,000 tonnes of ash, 5.4 million tonnes of CO and 50,000 tonnes of SO.

The spent fuel from a nuclear reactor includes uranium (U), which by weight represents about 96% of the spent fuel released from industrial reactors. In the case of light water reactors (of the most commonly used LWR type, which include the PWR type), spent fuel contains about 0.90% U, such as natural uranium

includes only 0.70% of this isotope. Pluton represents about 1% by weight of spent fuel. Pluton is degradable, which means it can be used as fuel in nuclear reactors. Low actinides represent about 0.1% by weight of the spent fuel. These include about 50% Np, 47% Am, and 3% Cm, which are highly radiotoxic. Decomposition products (iodine, technician, neodymium, molybdenum, cerium, cesium, ruthenium, palladium, etc.) make up 2.9% by weight of the spent fuel.

The two decomposition products of particular importance due to their significant thermal impact on the storage site and presenting a health hazard are Sr ⁹⁰ and Cs ¹³⁷ . These two radioisotopes have been the main contributors to the release of heat from spent fuel for at least the first few decades. Cs also represent a major source of penetrating radiation emitted from spent fuel. Both decomposition products are of particular importance because of their potential contribution to health hazards are Tc ⁹⁹ and I ¹²⁹ . They are of particular importance because they have a long life, are produced in considerable quantities during the process of decomposition, are usually soluble in geological conditions and are relatively rapidly distributed in groundwater.

The long-term toxicity of spent fuel dominantly is determined by actinides such as Np ²³⁷ , U ²³⁴ , U ²³⁶ and Ri ²³⁹ , Ri ²⁴⁰ , Ri ²⁴² . The conversion of long-lived isotopes into highly radioactive waste into stable or short-lived isotopes through induced nuclear reactions is one desirable alternative approach for reducing highly radioactive nuclear waste.

There are about 300 different radioactive species generated by the operation of a nuclear reactor, mainly as a result of neutron capture and neutron-induced decay. The adverse effect of different radioisotopes is altered by differences in chemical behavior in the body and radiation emitted by radioisotopes. The risk of radioisotopes is related to the location of the storage of nuclear waste. The most common mechanisms for the release and exposure of radioisotopes from the storage site include groundwater contact with nuclear waste, followed by slow dissolution, transfer of radioisotopes to the accessible environment, distribution in the biosphere and their likely uptake from food and water. . Although there are hundreds of isotopes in spent fuel or nuclear waste, only some of them are important for storage and storage. These are the four isotopes Cs ¹³⁷ , Sr ⁹⁰ , I ¹²⁹ and Tc ⁹⁹ , which are the main concerns for spent fuel from light water reactors, ie. nuclear waste due to their high heat dissipation, groundwater solubility or health hazards.

The disposal of spent fuels must ensure that the biosphere is protected under economically acceptable conditions without adverse effects in the near future, and the public must be convinced of the effectiveness of the methods used. Because spent fuel contains long-lasting radioisotopes, some precautionary measures are required for at least 100,000 years. There are two options:

1. We can wait for the natural disintegration of radioactive elements by physically isolating them from the biosphere by installing sequential bulkheads at an appropriate depth underground. This strategy is called deep geological deposition.

2. We can use nuclear reactions that will convert long-lived waste into lower radioactive products or products with a shorter life span. This strategy is called transformation.

The problem with storing nuclear waste underground is that there is no material to retain the radioactive content, the radioactive waste continuously produces heat, hydrogen and helium, and other unstable products.

The defense-grade transuranic wastes are temporarily stored in 23 locations throughout the United States, while mixed radioactive and hazardous wastes are currently stored at 40 locations nationwide.

There are 114 nuclear reactors in the United States and around 400 operating industrial nuclear power plants worldwide, including about 120 GWe of nuclear power in Western Europe and 45 GWe operating in the former USSR and Eastern European countries. In the US alone, we have accumulated 34,000 tonnes of nuclear waste. Currently, the United States produces 3000 tonnes of highly active waste (mainly spent fuel) annually. An average industrial power plant stores 60 used fuel charges in a temporary warehouse each year, and this is expected to continue until 2000, when the waste will be transferred to the DOE. This does not include low-activity wastes such as gloves, filters, tools, clothing, etc. that come from nuclear power plants, research centers, and hospitals that use radioactive materials. There are about 100,000 facilities in the United States that use radioactive materials. They produce 1.6 million cubic feet of low-activity waste annually.

Current project costs for the US Environmental Management Program are approximately $ 7.5 billion per year. Theoretical studies currently spend about 20% of the budget on environmental restoration. According to the Basic Environmental Management Report, the total cost of cleanup in the nuclear weapons program is $ 230 billion over a 75-year period, including the Hanford cleanup project.

Most of the current industrial nuclear reactors are light water reactors with high capacity and 400 MWe electricity capacity. A boiling water reactor, which is known as a kind of light water reactor, has a pressure vessel and a reactor core located in the pressure vessel. The reactor core includes a plurality of fuel cartridges. The reactor power control rods are designed to fit into the core of the reactor. The boiling water reactor has a system for recycling the cooler in the core of the reactor, and the cooler also serves as a means of fine-tuning the power of the nuclear reactor. The steam generated in the reactor pressure vessel is introduced into a steam turbine to drive it and then cooled into a condenser. The resulting condensate is recycled as a coolant in a pressure vessel.

Another typical example of a light water reactor is a pressurized water reactor comprising a pressure vessel comprising a core

of a multi-fuel tank reactor, a steam generator, and a main cooling system that forms a closed circuit comprising a pressure vessel and a steam generator. The hot coolant, after being heated in the reactor core, is introduced into the steam generator through a pipe from the main cooling system to produce heat exchange with the supply water supplied to the steam generator. The coolant, whose temperature has decreased as a result of the heat exchange, is returned from the steam generator to the pressure vessel through the pipe into the main system. On the other hand, the supplied water is evaporated as a result of the heat exchange and converted into steam. The steam is fed to the turbine to drive it, and then cooled in a condenser. The condensate returns as feed water to the steam generator.

The nuclear decay of heavy elements after ingestion of electromagnetic radiation (photodecomposition) was first predicted by Bohr and Wheeler in their famous 1939 article. Huxby, Schup, Stevens, and Wales (1941) were the first to receive decay in gamma rays.

One literature study shows that the photonuclear response in actinide nuclei has been a goal pursued by several laboratories over the last 40 years, using several types of gamma ray sources. The main objective of these studies was to obtain nuclear information in the field of excitation of energies in the resonance region of a giant dipole and in the low energy region, near the thresholds of photodecay and photoneutron. The giant dipole resonance (WGD) has been found to radically improve the effective cross section that is provided to random photons incident on the target nucleus.

Bauman, using a quasi-monochromatic photon obtained from annihilation during the flight of monochromatic positrons, was the first to detect the characteristic separation of the resonance of a giant dipole into a decaying nucleus into two components, a phenomenon also observed in other permanently deformed nuclei. In doing so, it was discovered that the photon-induced I ' _n / I' j ratio is highly energy-dependent, a result that is in complete contradiction to the data obtained from neutron-induced decay, delayed radiation-induced decay and decay, caused by a charged particle.

The systematic resonance of the giant dipole, which characterizes the absorption of electromagnetic radiation from the nucleus over an energy range of 5 to 30 MeV, was of interest in the discovery of the giant dipole itself. Over the years, photoneutron cross sections of many nuclei have been measured in many laboratories using mono-energy photons. All of these data are presented in the Atomic and Nuclear Data Tables. For most of the cases examined, the compliance is remarkably good.

The classical description of the process of absorption of photons by a dipole implies that for spherical nuclei the complete section for absorption of photons is characterized by a Lorentz curve,

0 (^) = 0 ^ / (1 + (^ ² ¾ ² ) ² ¾ ² ^] (Equation 1) where a _sh is the peak cross section, Still is the resonant energy and D is the full width at half maximum. deformed (spheroid) nuclei, the overall picture implies the separation of the giant resonance into two components corresponding to the oscillations, parallel and perpendicular to the axis of symmetry of the nucleus.

For medium to heavy nuclei, the Coulomb barrier suppresses the emission of charged particles at giant resonance energies and photon scattering cross sections are always small at the (γ, η) threshold; therefore, the full photoneutron cross section is a good approximation of the full photon absorption cross section.

The internal four-pole moment Q _o for a deformed nucleus can be calculated from the expression,

Q _o -2/5 ZR ² e -2/5 ZR ² (η-1) η ^2/3 (Equation 2)

Where R = RoA ^1/3 , Z and A are the number of atoms and the atomic weight, respectively, is the eccentricity of the nucleus and the parameter η is the ratio of the large to the small axis (for elongated nuclei) given by the formula,

E _m (2) / E _m (1) = 0.911 η + 0.089 (Eq. 3)

Where Eht (1) and Eht (2) are the low and high levels of resonant energies, respectively, from the correspondence of the two-component Lorentz curve to the giant resonance.

The dipole resonance energy is so low that a much simpler process, such as (γ, π), (γ, p), (γ, 2n), and photodecomposition reactions can occur in the region of the giant resonance. The competition between these processes is governed by the normal statistical considerations for reducing excitation between the compound-nucleus, so that neutron emission is usually predominant.

The resonance characteristics of a giant dipole for actinide nuclei are of particular interest. For such nuclei with high - Ζ and high Coulomb barriers, the total cross section for photon absorption is equal to the sum of the cross sections of the following reactions, σ (γ, Πίοΐ) = σ (γ, π) + 2σ (γ, 2π) + νσ (γ, ί) (Equation 4) where ν is the neutron multiplicity of the decay phenomenon.

In addition, the total cross section for neutron production is, (Eq. 5)

The competition between neutron emission and decay can be expressed by, r '/ Tf (E) = σ (γ, π) / σ (γ, ί) (Ε) (Eq. 6)

The value of r _a / Tf decreases exponentially with the ability of the nucleus to decay. The theoretical expression for D _and / yy that explains the behavior of competition neutron emission and decay is extracted from the Permanent core temperature level density is expressed by

D _n / D _d = 2 ^2/3 TA / 10 exp {(Ef - Bn ') / T} (eq. 7) where (Ef - Bn') are the effective thresholds for the respective fotoyadreni processes and T is the nuclear temperature.

The fact that more than one neutron is emitted for decay when decaying such isotopes as Th ²³² , U ²³³ , U ²³⁵ , U ²³⁸ and P ²³⁹ leads to the possibility of a chain reaction of a mass of disintegrating material. How stable the chain reaction will remain, develop or die depends on the competition between neutron decay production and neutron loss through various processes such as non-decay neutron capture, mainly from (η, γ) system reactions and neutron leakage through the surface of the system.

Energy is released at 200 MeV level for the decay of one atom or about 23X10 ⁶ kWh for the decay of one kilogram of U ²³⁵ . The decay fragments account for 82% of the energy in the form of kinetic energy. Fast neutrons account for another 2.5%, fast gamma particles account for 3.5%, beta decay accounts for 4%, and neutrinos account for the remaining 5%. Neutrino particles and their energy are lost because the possibility of interacting with neutrino is very small. Some decay also occurs with a fast neutron impact in a U ²³⁸ atom. Plutonium is also produced by burning the fuel, with a large percentage of the energy coming from the decay of the R ²³ atoms. About 80% of neutron uptake in U ²³⁵ results in decay, the remaining 20% are (η, γ) reactions. The average kinetic energy released at Th ²³² photodecomposition is about 0.8 of that released at decay of U ²³⁵ with slow neutrons or about 160MeV.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a nuclear reactor powered by depleted or non-depleting radioactive material such as spent fuel from a conventional nuclear reactor.

Another object of the invention is to provide a nuclear reactor with increased safety through the use of a sub-critical mass of fuel.

It is another object of the present invention to provide a small size and capacity nuclear reactor.

According to this invention, which is made to achieve the above objectives, a system is provided in which electrons are accelerated to achieve energy of at least 6 MeV from an accelerator and the accelerated electrons or gamma photons obtained from the impact of the accelerated electrons in the target are introduced into the fuel of a nuclear reactor, causing the fuel to decay through a nuclear reaction process known as photodecomposition. Fuel decomposition produces heat and neutrons, as in a conventional reactor, although decomposition is not maintained on its own due to the use of subcritical mass and non-decaying fuel elements. In this way, the process of photo-decay stops immediately when the electron beam is stopped. The resulting heat and neutrons can be used in a conventional nuclear reactor, such as for the production of electricity.

The disclosed invention is a method and means for producing nuclear energy from heavy but not disintegrating elements. The reaction is not driven by the well-known self-sustaining chain reaction of

U ²³⁵ , and by means of an accelerator. The fuel for this type of accelerator reactor may be spent fuel from decay reactors. The mechanism by which nuclear energy is released from non-degradable material is known as photodecomposition, in which energy above the photodecomposition threshold is introduced into a photon or gamma particle, resulting in the decay of the attacked nuclei. For example, at U ²³⁸ , the photodecay threshold is about 6 MeV and decay of U ²³⁸ nuclei is obtained, releasing energy of about 200 MeV.

EXPLANATION OF THE FIGURES Attached

FIG. 1 is a flow chart of the invention

FIG. 2 is a schematically preferred embodiment of the electronic accelerator of the invention.

FIG. 3 is a graph of the partial and full photo-nuclear cross section for U showing the reactions (γ, η), (γ, 2η), (γ, d) and the cross-section (γ, complete).

FIG. 4 is a graph of photonuclear cross sections for Th ²³² , U ²³⁸ , Np ²³⁷ .

FIG. 5 is a graph for the photonuclear cross section for Ri ²³⁹ .

FIG. 6 is a graph of gamma spectroscopic analysis of the resulting product of 30 MeV photodecomposition of U ²³⁸ .

EXAMPLES FOR THE IMPLEMENTATION OF THE INVENTION

In FIG. 1 shows an embodiment of the present invention, where a linear accelerator 1, preferably of the monochromatic type, accelerates electrons to energy of about 5-30 MeV, preferably about 10 MeV, which hit a high-Z converter such as tungsten to obtain a gamma rays which focus on a combustible material such as

U ²³⁸ in reactor 2, resulting in a (γ, f) reaction also known as photodecomposition, thus releasing about 200 MeV of energy.

A primary cooling pump 3 is passed through the reactor 2

coolant to transfer heat from the reactor to a heat exchanger 4 in which heat is introduced into a secondary cooling system driven by a secondary cooling pump 5. The heat dissipated from the secondary cooling system is used to drive the turbine 6 before the coolant passes in capacitor 8 and recycle. Turbine 6 drives generator 7 to generate electricity.

A reactor constructed according to the invention requiring an accelerator 1 having a beam power of 1 MW will develop a power of about 20 MW. The photodecomposition reaction that occurs in reactor 2 is not self-sustaining and stops when accelerator beam 1 is turned off. This invention can be used to refuel spent fuel from conventional light water decomposition reactors simply by operating at 10 to 20 MeV. As a result of the invention, typical waste products such as Cs ¹³⁷ and Sr ⁹⁰ are produced, which undergo photodisintegration by (γ, η) reaction in reactor 2, resulting in short-lived or stable products. Chemical separation of isotopes from spent fuel is not necessary. Of course, to achieve higher power, more than one accelerator 1 can be used to drive reactor 2, as well as for an accelerated afterburning process. Ideally, about 4.8 MW of power is required to operate four spacecraft, resulting in about 100 MW of reactor power. The fact that the reaction is not self-supporting is a safety feature that allows immediate stopping in case of a problem.

The primary significant nuclear reactions that occur in the reactor are listed in Table 1.

Table I. Reactions in Accelerator-driven Reactor

PHOTO DISPOSAL REACTIONS (T.L σ “t“ ЧNL M RUB ”,“ Ri ”. P“ * “. T“, and “i®, and“. DISPOSAL REACTIONS (only one of many) fiU “+ on * 4 mSt * + iHe ¹ * + 2 «c * β (stable) mX · ¹ * 4 jjC $ ^{, 4} ° + β 4 iVa ^'49 + β' 4 nLa '* + β * 4 ICE ^{, 4c} + β ^ ςτβ0Η.ιίΗ8 (γ, η) ENHANCEMENT nU ⁿ '+ y »eU ^B ' + an ' _W U» + T 4 ntf * + 2 · α * + τ> wU ^Mi + en' and Ash ²⁴¹ + y 4 tsAm ³ * + «in * + - | in ^4« JPu ²⁴⁰ «Νρ ° * + τ 4 oNp ³³³ + 2" in ¹ + e ⁹ 4 nU ^ai wU ³ "+ γ-» «(J® ' + βπ * ♦ γ-¼ + «a ¹ * T« U ²³⁵ * β® ¹ n? and ^w + γ 4 mRi ° * + 2 ¢ 0 ¹ + γ 4 mRi ³⁵ + «a ¹ +., e * 4« Νρ ° ³ + -, e ^e 4 "ϋ ³³³ “ "+ 7 4 *" η ¹ 4 lMr ¹ + β '+ 7 ">" Νρ "+ 2" η ¹ + ..e * 4 ηϋ ²³⁵ mR ^w +7 4 iRi * ⁷ + 2 on '+7 4 ^ + 2 ^ ¹ + f * 4 »Np ^DJ +.,« * 4 «V ⁰³ 9 * Pu ^2J9 + 7-» wtr ^DS + a

NEUTRANE ENHANCEMENT ^ + ^ 4 ^ + 7 nd ° * + on '4 nd * + 7 4 iR® · + β · 4 ^ Pu ³⁹ + β' 4 " ^Ρ * ^ο3 + β · 4βυ ^η, + β · (γ η) NEUTRALIZATION:

, Η ³ * 7 4 ιΗ ³ ♦ «a * (stable) <C ¹⁴ + * 4 <C ¹³ + oo. ¹ (stable) »Υ * + 74» Υ * + on * (stable) I jjNi® 4 jjNi * ³ + on * (stable) µg ^m + γ 4 j ^ Kr * ⁴ + on * (stable) pSO * ° + 74 «Co ³⁹ + oh * (stable) aiTl ²⁰ * +74« ΤΙ ³ ® + ^ '(stable) aSr * + 7 4 3tSr ** + 2 «a ¹ (stable) I dBi ^3W + y 4 oBi ³⁰⁹ + oQ ¹ (stable) mVA ¹³³ + at 4 uBa ¹³³ + op ^! (stable) gjPb ^{3, e} + y 4 pJ ³ ® + 2 ^ '(stable) «Sr * + y 4« Sr * + oa ¹ 4 »Y * ⁹ + p * (stable) jjl' ³⁹ + 7 4 el ¹³⁹ + ¢ 0 ¹ 4xHe ^w + β * (ίτβ6 ™ ΐΗβ) »jCs ^{, 3T} + γ 4 5jC $ ¹³⁴ + on ¹ 4« Ba ¹³ * + β * (ctable) «Fe * + 7 4 seFe +« η ¹ 4 «Co ³⁹ + p * (stable) tjPb ²¹⁰ + 7 4 nPb ³⁰⁹ + oa ¹ 4« Bi ³⁰⁹ + β (stable) NEUTRAL NEUTRALIZATION:

• jTc ⁹⁹ + ofl ¹ 4 «Tc ¹ * + y 4« xRu ¹⁰⁰ + β * (ctable) nl ^'39 + oa' 4 «I ¹³⁰ + y 4 iHe ^'30 + β' (stable) i1 * ²⁷ + on '4' ί ' ³ * + y4 mHe ¹³ * + · β (stable) nNa ^g »pn ¹ 4 nNa ³³ + γ (stable)

The photodecay and neutron decay thresholds for the respective isotopes are given in Table II.

Table II - Threshold energy for decay of selected isotopes

NUCLEID PHOTOGRAPHY NEUTRON-DECOMPOSITION At ²⁴¹ PRAGUE (MeV) 6.0 PRAGUE (MeV) At ²⁴² - 6.4 Th ²³² 5.8 1.3 Np ²³⁷ 5.6 0.4 Np ²³⁸ - 6.0 and ²³³ 5.7 0.025 and ²³⁴ 6.0 0.4 and ²³⁵ 5.3 0.025 and ²³⁶ - 0.8 and ²³⁷ - 6.3 and ²³⁸ 5.8 1.2 Ri ²³⁹ 5.8 0.025

The invention requires a high-power, low energy (lOMeV) electron accelerator 1 or linear accelerator to produce gamma rays to drive the reactions in reactor 2, the preferred embodiment of which is shown in FIG. 2. The current technological level involves the use of a PillIB traveling electronic accelerator 1, triggered by two 1.2 MW continuous wave (CW) L-band clusters 11, preferably operating at 1249 MHz RF to obtain an electron beam with energy of 10 MeV is a current of 100 mA.

Pill IB was selected to amplify the beam breaking threshold current and to obtain high accelerator efficiency, which is achieved by low attenuation constant value and high multiplier field factor, which is only allowed with P1111B. The advantages of using P1111B over the standing wave as a guide accelerator are: simplified cavity design, larger aperture size, easier manufacturing, easy mechanical separation from the recirculating wave guide, all of these things simplify operation in a high radiation field.

The klystrons 11 are preferably powered by a 90 KVDC power supply to produce 1.2 MW RF. The power of 1.2 MW RF is fed into the P1111B through the directional switches 12. The electron injector consists of a 200 KVDC electronic tool 13, two magnetic lenses, one RF switch, a pre-modulator 15 and a modulator 16. The electronic tool requires a circuit breaker 14 and the modulator 16 is designed to produce a peak current of 400 mA with a beam energy of 200 KeV.

Accelerator 1 consists of seven accelerator guides 18.

Each individual section of the accelerator forms an RPF. Each of the accelerator guides 18, 1.2 m in length, includes voids with

Form 13 2π / 3 and two connecting voids. All accelerator guides 18 s of type construction have a constant gradient, provided they are loaded with a beam of 100 mA.

The first klystron triggers one modulator and three guides from the accelerator, while the second klystron activates the remaining four guides from the accelerator. The RF power supplied to the modulator and each accelerator guide is 220 to 250 KW, respectively.

U ²³⁸ can be used for gamma transducer and for photodecomposition target, thus avoiding a separate electron converter to gamma particles such as tungsten and the target material U as an X-ray source can be used. The advantage here is in the recovery of heat, which is usually emitted by the converter and which is in the order of 70% of the radiant energy.

It is important to note that, although the reactor is of sub-critical mass and is driven by gamma rays, the neutrons obtained still induce both fast and slow neutron decay, as with any conventional reactor. These neutron reactions result in additional energy, which increases the I / O ratio by 1/20 to the design value.

FIG. 3 represents the photonuclear cross section of U ²³⁸ and the competing reactions (γ, η), (γ, 2η) (γ, f) and (γ, complete). Note that at the preferred energy level, 10 MeV, the two photonuclear reactions are (γ, η) and (γ, f).

FIG. 4 shows the full photonuclear cross sections for Np ²³⁷ , U and Th, while FIG. 5 shows the full photonuclear cross section for Ri. Comparing the cross sections of the two figures, it can be seen that the cross sections are almost identical; in particular up to about 10%. This is important because the photon source cannot distinguish between these four fuel sources. This means that

23S tm 232 237 performance is the same when used for fuel from U, Th, Νρ,

Ri ²³⁹ or other photodecomposition materials.

FIG. 6 is a gamma-ray spectroscopic analysis of the products obtained from actual photodecomposition of U. The only long-life products are Na ²² , Kg ^85, and Cs ¹³⁵ , which, when subjected to a continuous stream of photons with a power of 10 MeV, are photo-disintegrated.

Calculations show that efficient (γ, η) burning of waste 1 Q decay products requires a gamma flow of 10 γ / cm s to accelerate the decay time 180 times.

The number of nuclei (γ, η) reacting during irradiation can be determined by the following differential equation:

dNi / dt = - (λι + σΐφ) Nj + Σ Xji + σρφ) Ν ₃ , i = l, 2 ..., N _a (Equation 8) where

Брой = number of Ι-το nucleus λί = decay constant of i-th nucleus σ, = complete photo-nucleus cross-section of the ith nucleus λμ = decay constant from j-th nucleus transmitting to i-th nucleus φ = flux γ-rays

N _a = number of cores reported in the model.

Using matrix representation, equation (8) is written as follows:

dN / dt = Α · Ν, (Equ. 9) where

- (λί + σΐφ) (i = j),

Az = {λρ + σ ^ φ (i * j).

The kernel matrix N at time t = At can be obtained from the Taylor expression:

N (t + At) = N (t) + Σ (At) 7r! dN ^<n) (t) / dt, (Equation 10) i = l where dN ⁽ⁿ⁾ (t) / dt, is the rth derivative of N (t) φ

Combining equations (9) and (10), we can obtain N (t + At) as follows:

N (t + At) = N (t) + Σ (At) 7r! A ^ t) (Equ. 11) ι = 1

Matrix A contains two types of data: decay constants and photonuclear cross sections.

Also, by means of fast neutrons directed at nickel, the φ Η ⁵⁸ (η, γ) Nj ⁵⁹ reaction achieves Compton scattering rays, yielding gamma rays with energies from 5 to 9 MeV. In our application, if the reactor contains transducer material such as nickel, this means installing a "repeating station" each time a nickel collision occurs. For example, if the reactor contains layers of nickel and U ²³⁸ :

1. The accelerator produces a gamma ray of 10 MeV directed at a uranium target to produce photodecomposition as a result of fast neutrons;

2. The attenuation of gamma rays as they pass through the first uranium layer reduces their energy below the reaction threshold (γ, η); and

3. Absorption of fast neutrons in the first nickel layer produces 5 to 9 MeV gamma rays, which will affect photodecomposition in the next layer of uranium.

Using this multilayer approach, there is no limit to the thickness of the reactor core as the accelerator beam is continuously amplified in each nickel layer.

In addition to or instead of nickel, other elements or compounds or mixtures of elements, for example sulfur, dysprosium, yttrium, calcium, titanium, beryllium, manganese, lead, iron, aluminum and copper, may be used as a "repeating station".

Despite the clarification of this invention set forth above with respect to specific agents, materials and embodiments, it should be clear that the invention is not limited to these disclosed features, but extends to all equivalents within the scope of the following claims.

Claims (18)

Patent Claims A heat source comprising a nuclear reactor triggered by an accelerator, said accelerator accelerating electrons to energy of about 5 to 30 MeV, and said reactor containing spent nuclear fuel. 2. The heat source of claim 1, wherein said accelerator operates on a continuous wave principle. The heat source of claim 1, wherein the accelerator is a traveling wave resonant ring type accelerator. The heat source of claim 1, wherein said accelerator is actuated by L-band klystrons. The heat source of claim 4, wherein said klystrons operate at a frequency of 1249 MHz. The heat source of claim 1, wherein the nuclear reactor comprises a transducer material for converting fast neutrons to gamma rays by (η, γ) reaction. 7. The heat source of claim 6, wherein the transducer material is nickel. 8. The heat source of claim 6, wherein the converter material is sulfur. 9. The heat source of claim 6, wherein the transducer material is dysprosium. 10. The heat source of claim 6, wherein the converter material is yttrium. The heat source of claim 6, wherein the transducer material is calcium. The heat source of claim 6, wherein the transducer material is titanium. 13. The heat source of claim 6, wherein the transducer material is beryllium. 14. The heat source of claim 6, wherein the converter material is manganese. 15. The heat source of claim 6, wherein the converter material is lead. 16. The heat source of claim 6, wherein the transducer material is iron. 17. The heat source of claim 6, wherein the transducer material is aluminum. 18. The heat source of claim 6, wherein the converter material is copper.