SE1551606A1 - Method for conversion of nuclear energy into heat and devicetherefor - Google Patents

Abstract

The present invention refers to the domain of nuclear power engineering and, more specifically, to a method for conversion of nuclear energy into heat and a device therefor. The essence of the method is as follows. A relativistic ion beam is generated, accelerated, and directed onto a deeply under-critical target to destroy its nuclei. A beam of secondary particles, including neutrons, is produced, which is used to split nuclei of isotopes of heavy chemical elements. The process results in release of nuclear energy. The condition of the target of a size ensuring the transfer of the beam's kinetic energy and that of the secondary particles to the target is monitored, and the duration of accumulation and replacement of nuclear fission products is determined. The aforesaid relativistic ion beam is accelerated to an energy level at which at least two generations of nuclear multi-fragmentation products are produced by means of target material decay, and nuclear energy is released within a time interval that exceeds the duration of the accumulation and replacement of the decay products with a material to be exposed. The flux of secondary particles is then recycled and the exposed material is cooled down and forwarded for recycling as work material for extraction of materials suitable for further recycling. The invention increases the efficiency of conversion of nuclear energy into heat and recycling of a wide range of long-lived radionuclides.(Fig.)

Description

1O METHOD FOR CONVERSION OF NUCLEAR ENERGY INTO HEATAND DEVICE THEREFOR TECHNICAL FIELD This invention refers to the domain of nuclear power engineering, morespecifically, to a method for conversion of nuclear energy into heat, anddevice for conversion of nuclear energy into heat and is particularly suitablefor recycling of any industrial waste, including nuclear, radioactive, chemical and biological waste.BACKGROUND RF patent No. 2267826, G21G1/02 of 2001, “Method for Incineration ofTransuranic Chemical Elements and Nuclear Reactor Therefor” describes amethod and a device using a weakly subcritical core of the nuclear reactorwhere long-lived radionuclides of heavy elements are placed. Additionalneutrons required for criticality of the core are inj ected from an externalsource such as a proton accelerator with energy of 1 GeV with a lead or lead-bismuth target as proposed therein. However, this prior art engineeringsolution does not allow a significant increase in the efficiency of conversion ofnuclear energy into heat due to conceptually insurmountable restrictionsinherent in the method based on proton beams. Moreover, it also does notremove the sources for production of an unacceptably high amount of long-lived radionuclides or risks relating to production of materials suitable for nuclear terrorism.

In RF patent No. 2238597, G21C1/3o dated 2oo3 ”The Method forConversion of Nuclear Energy into Heat“, it is proposed to use a relativisticproton beam to trigger nuclear cascade processes in a deeply under-criticaltarget made of heavy chemical elements (lead, bismuth, thorium anddepleted uranium, as well as their combinations), with the target contentemployed concurrently as fuel and heat transfer medium. The inventorsnoted an increase in probability of a deeper splitting of target nuclei with a rise in energies of accelerated particles. However, this engineering solution 1O suffers from similar shortcomings as noted above, which are due to the use ofa relativistic proton beam, and does not address the issues associated withthe utilization of the beam of secondary neutrons produced in the proposed target and leaving the target.

The closest prior art is the invention according to RF patent No. 2413314dated 2008, “Method and System for Conversion of Nuclear Energy intoHeat”. This solution employs the acceleration of a beam of heavy chargedparticles (e.g. multiple-charged ions of uranium, thorium, bismuth and leadisotopes) up to an energy causing the origination of a flux of cascade nucleonsin a deeply under-critical core used as a target, to which such a flux isdirected and the condition of which is monitored with, if necessary,replacement of its content. To raise the intensity of the said flux, the core isproposed to be made, in part or in full, of spent nuclear fuel. The device forthis method comprises an accelerator of relativistic multiple-charged ions, aunit for beam transportation and introduction onto the target to couple theaccelerator and the target, the latter being normally placed in a strong case,often cylindrically shaped. The excess of heat produced in the reactor (target)is removed with the help of a subsystem comprising first and second circuitcoolant, heat-into-electricity conversion units with the function of a heat transformer.

The claimed advantages of the said prototype, however, are accompanied byseveral disadvantages related to incomplete utilization of accelerated ionbeams for increasing the efficiency of conversion of nuclear energy into heat,recycling of long-lived radionuclides, including plutonium and minor actinides (neptunium, americium and curium).SUMMARY The herein proposed invention eliminates the above disadvantages of the prior art inventions and the prototype. 1O An object of this invention is to increase the efficiency of conversion ofnuclear energy into heat and recycling of a wide range of long-lived radionuclides.

Long-lived radionuclides in this case are those with a half-life longer than 15 years.

The technical effect of the invention consists in an increased efficiency ofconversion of nuclear energy into heat, recycling of a wide range of long-lived radionuclides, and production of materials suitable for further use.

The technical effect of conversion of nuclear energy into heat is achieved asfollows. A relativistic ion beam is produced and accelerated, the beam isdirected to a regularly refreshable material of a deeply under-critical target,which results in fission of target nuclei, the flux of secondary particles isproduced, including neutrons, the secondary particles are arranged to splitthe nuclei of isotopes of heavy chemical elements, which, in its turn, resultsin release of nuclear energy, the condition of the target of a size ensuring thetransfer of the beam”s kinetic energy and that of the secondary particles to thetarget is monitored, and the duration of accumulation and replacement ofnuclear fission products is determined. The aforesaid relativistic ion beam isaccelerated to an energy level at which at least two generations of nuclearmulti-fragmentation products are produced by means of fission of the targetmaterial, and nuclear energy is released within a time interval that exceedsthe duration of the accumulation and replacement of the nuclear fissionproducts by a material prepared for exposure. The flux of secondary particlesis recycled and the exposed material is cooled down and forwarded forrecycling as work material for extraction of materials suitable for further use according to the claimed method.

The technical effect in the device for conversion of nuclear energy into heat isachieved as follows. In the first embodiment of the device, which comprises arelativistic ion beam accelerator, a unit for beam transportation andintroduction onto the target, a deeply under-critical target made of heavy chemical elements suitably enclosed in a fire-, radiation- and corrosion- 1O resistant case with an open upper end, and a heat transformer unit, allarranged in series, the target case, according to the invention, has a conical orspherical shape relative to the energetic axis of the device and is connectedthrough pipelines to the heat transformer and through a pipeline and shutoffgear to a backup unit that allows its replenishment and is located above thetarget. As a result, the simplest and hence more reliable design of the device for conversion of nuclear energy into heat is provided.

In the second embodiment of the device, which comprises a relativistic ionbeam accelerator, a unit for beam transportation and introduction onto thetarget, a deeply under-critical target made of heavy chemical elements,suitably enclosed in a fire-, radiation- and corrosion-resistant case with anopen upper end, and a heat transformer unit, all arranged in series, the targetcase, according to the invention, is made of two sections consecutivelydisposed relative to the unit for beam transportation and introduction ontothe target, the lateral surface of the sections relative to the energetic axis ofthe device has a similar cylindrical or conical shape, the base part of the firstsection, that can be replaced and fixed, is made planar or spherical, thesecond section is connected through pipelines to the heat transformer andthrough a pipeline and shutoff gear to a backup unit that allows itsreplenishment and is located above the target. This embodiment of the deviceis distinguished in that along with power production it offers the possibilityto concurrently transmute, under a relativistic ion beam, radioactive wastewith a prevailing portion of long-lived radionuclides into radioactive wastewith predominantly short-lived radionuclides through potential replacementof the target”s first section formed of radioactive waste and/ or actinides and/ or spent nuclear fuel.

In the third embodiment of the device, which comprises a relativistic ionbeam accelerator, a unit for beam transportation and introduction onto thetarget, a deeply under-critical target made of heavy chemical elementssuitably enclosed in a fire-, radiation- and corrosion-resistant case with anopen upper end, and a heat transformer unit, all arranged in series, the target case, according to the invention, is made of three sections consecutively 1O disposed relative to the unit for beam transportation and introduction ontothe target, the lateral surface of the sections relative to the energetic axis ofthe device has a similar cylindrical or conical shape, the base part of the firstsection, that can be replaced and fixed, is made planar or spherical, the baseparts of the second and third section s are spherical and separated from eachother to a distance equal to the difference of their radii, wherein the thirdsection of the target case is connected through pipelines and shutoff gears tothe second section and a backup unit, respectively, with the second sectionconnected through pipelines to the heat transformer, while the design of thebackup unit allows its replenishment and the said unit is located above thethird section of the target. This embodiment features, in addition to theadvantages of the second embodiment, the possibility to achieve the utmostpower production through increasing the portion of fissile radionuclides in the second section of the target.FIGURES The features of the claimed method and device will be better understood by reference to the accompanying drawings of Figures 1 - 13 and Table 1.In the drawings: Fig.1 displays the first six stages of an avalanche process of multi-fragmentation of uranium target nuclei, triggered by a multiple-charged 238U ion with energy of 1 GeV per nucleon.

Fig.2 presents a general view of the device for conversion of nuclear powerinto heat, which comprises a single-section conical target, to implement the method proposed herein.

Fig. 3 displays a sectional view of the proposed device for conversion of nuclear energy into heat.

Fig.4 depicts a general view of the device for conversion of nuclear energyinto heat, which uses a single-section spherical target to implement the method proposed herein. 1O Fig.5 presents a sectional view of the said device for conversion of nuclear energy into heat.

Fig. 6 displays a general view of the device for conversion of nuclear energyinto heat, wherein a two-sectioned cylindrical target with a cylindrical first section is used.

Fig. 7 provides a sectional view of the said device for conversion of nuclear energy into heat.

Fig. 8 displays a sectional view of the device for conversion of nuclear energyinto heat, wherein a two-sectioned cylindrical target is used, the base part of the target”s first section being spherical.

Fig.9 provides a sectional view of the device for conversion of nuclear energyinto heat, wherein a two-sectioned conical target with a frustum-like first section is used.

Fig.1o presents a sectional view of the device for conversion of nuclear energyinto heat, wherein a two-sectioned conical target and spherical base parts of both sections are used.

Fig. 11 shows a general view of the device for conversion of nuclear energyinto heat, wherein a three-sectioned cylindrical target is used, with the firstsection made cylindrical, the second and third ones having a spherically shaped base part.

Fig.12 presents a sectional view of the same device for conversion of nuclear energy into heat.

Fig. 13 shows a diagram of the nuclear fuel cycle closed on long-lived radionuclides.

Table 1 contains a list of long-lived radionuclides. 1O DETAILED DESCRIPTION OF EMBODIMENTS The present invention refers to the domain of nuclear power engineering and,more specifically, to a method for conversion of nuclear energy into heat anda device therefor. A relativistic ion beam is generated, accelerated, anddirected onto a deeply under-critical target to destroy its nuclei. A beam ofsecondary particles, including neutrons, is produced, which is used to splitnuclei of isotopes of heavy chemical elements. The process results in releaseof nuclear energy. The condition of the target of a size ensuring the transfer ofthe beam”s kinetic energy and that of the secondary particles to the target ismonitored, and the duration of accumulation and replacement of nuclearfission products is determined. The aforesaid relativistic ion beam isaccelerated to an energy level at which at least two generations of nuclearmulti-fragmentation products are produced by means of target materialdecay, and nuclear energy is released within a time interval that exceeds theduration of the accumulation and replacement of the decay products with amaterial to be exposed. The flux of secondary particles is then recycled andthe exposed material is cooled down and forwarded for recycling as workmaterial for extraction of materials suitable for further recycling. Theinvention increases the efficiency of conversion of nuclear energy into heat and recycling of a wide range of long-lived radionuclides.

The proposed method is based on the results obtained in the course of a systematic study into power aspects of multifragmentation of radionuclide nuclei (ranging from 3H to 251Cf) when exposed to a relativistic beam ofheavy particles (ranging from neutrons, protons, deuterons to multiple-charged uranium ions). The effect of nuclear multifragmentation has beenknown for a long time (“Experimental Nuclear Physics”, in two volumes, K.N.Mukhin, Moscow, Energoatomizdat Publishing House, 1993, ch.11, para 73).Yet, no systematic calculations for power aspects of nuclearmultifragmentation as a result of, among other factors, fragments of such decay have been carried out. The effect of power release from decay of target 1O nuclei by fragments of the second and further generations has not been discovered or investigated.

This work has been performed by the authors who used their own computerprogram based on the method for calculation of energies of nuclear reactionsin targets made of various chemical elements and exposed to relativistic ionbeams (Physical values. Handbook. I.S. Grigoriev, E.Z. Melikhov. Moscow,Energoatomizdat Publishing House, 1991), as well as an array of estimatednuclear data on mass defect values for neutron and 3288 nuclides, which isprovided on the website of the Brookhaven National Laboratory(http: / / www.nndc.bnl.gov/ nudat2 / ). Results of the calculations are supposed to be corroborated with experimental data.

The bottom line of the carried out work is the discovery of significantfeatures, more specifically, advantages of power characteristics of nuclearmultifragmentation of long-lived radionuclides, including actinides, when thetarget is exposed to relativistic heavy particles (with release of nuclear energyand absorption of kinetic energy of the relativistic particles), whichdemonstrates a positive contribution of electrically charged nuclearfragments to a rise in the efficiency of energy release. As a result, the authorspropose a novel way for practical utilization of the said effect to address thechallenges and problems of power engineering, environment and publichealth.

Fig.1 illustrates the first six stages of the process of multifragmentation of 238U nuclei, triggered by a 32-charged 238U ion with an energy of 1 GeV per nucleon with the appearance (as the first generation) of six electricallycharged fragments of comparable masses and 39 neutrons taken as an example: 1. Collision of an accelerated 238U ion a ainst a tar et nucleus.8 8 2. Appearance of high-energy first-generation fragments with release of 194 MeV (~ 3*1o12 implementation options). 1O 3. Separation of first-generation fragments.4. Collisions of the first-generation fragments against target nuclei.

. Appearance of high-energy second-generation fragments with release of ~19o MeV (calculated) (over 2*1o8 implementation options).6. Separation of second-generation fragments.

Thus, an avalanche process of nuclear fission is triggered and startsescalating, including, among other factors, under the effect of electricallycharged fragments of decayed nuclei with energies that exceed the Coulombbarrier of the nuclei along the trajectories of such fragments, with their subsequent destruction.

The significance of the said effect of multiplication of decay of target material nuclei is as follows.

Firstly, by adequately placing and exposing various materials (including thelong-lived radionuclides listed in Table 1) to relativistic beams of heavycharged particles in the target section facing the beam, one can achieve theirpractically complete recycling through a multiple recycling process on therespective irradiated target material by means of coupled radiochemical regeneration and refabrication.

Secondly, radioactive waste recycling products (for both separated waste, i.e.that with a predominant portion of long-lived radionuclides, and non-separated (and/or chemical) waste, as well as spent nuclear waste fromresearch, industrial and power reactors) may find application in diverse fieldsof national economy after such recycling products are cooled down andradiochemically or otherwise converted. It is due to that the aforesaidproducts are chiefly stable and neutron-deficit nuclides. As known, the latterones (in their vast majority) differ from neutron-excessive ones, which are produced in fuels of existing reactor types, by sizably lower half-life values. 1O Thirdly, under conditions of full absorption of the flux of secondary neutronsin the respective target section, fissile radionuclides are produced with arespective rise in power production in the target and conversion into electricpower, in particular for compensation of the electric power spent for theacceleration of the particle beam. The excess of power so produced can be taken off by other power consumers.

The proposed device comprises an accelerator, a deeply under-critical target,a unit for beam transportation and introduction onto the target, a heat transformer, and a backup unit.

Reference numbers in the figures denote the following:1 - relativistic ion beam accelerator; 2 - unit for beam transportation and introduction onto the target;3 - target; 4 - backup unit; - heat transformer; 6 - target makeup pipeline; 7 - backup unit shutoff gear; 8, 9, 10, 11 - coolant pipelines; 12 - first section of the target; 13 - second section of the target; 14 - third section of the target; - pipeline for makeup of the target”s second section with material of the third section; 16 - shutoff gear for the target”s third section. 1O 11 The beams of relativistic heavy ions are generated with the help of abackward travelling wave linear accelerator 1 (BTWLA, see A.S. Bogomolov,T.S. Bakirov, “Ion Accelerators for Industrial Use”, Moscow, Kuna, 2012, 87pp.) with achieving an energy of accelerated multiple-charged ions of not lessthan 100 MeV per nucleon. Exceeding the said energy level by multiple-charged ions allows using them practically in full for triggering the afore- mentioned diversity of nuclear processes.

The distance from the unit for beam transportation and introduction onto thetarget, wherefrom the beam is directed immediately onto the target sectionadjacent to the unit, to the target is derived from the condition ofminimization of negative impact of the ionizing radiation from the saidsection upon the unit for beam transportation and introduction onto the target.

The material of a single-section target 3 and a first section 12 of two- andthree-sectioned targets is formed of radioactive waste, other substances thatcontain long-lived radionuclides intended for direct destruction, includingsmall actinides (plutonium and minor actinides), and/ or spent nuclear fuel inthe form of a low-melting U-Fe type eutectic. Such materials can initially bein a solid or liquid phase. The thickness of the layer of these materials alongthe beam trajectory is derived for the single-section target 3 from thecondition of complete absorption therein of not only the primary beam, butalso the flux of secondary particles, including neutrons. The layer thicknessand the accelerator beam intensity determine the capability for full melting ofthe material of such a target. The thickness of the first section 12 in the caseof two and three -sectioned targets is derived from the condition ofconversion of a greater part of primary particles in the beam into a secondaryflux with the formation (in this section) of a prevailing amount of neutron-deficit fission products. Due to release of nuclear energy even in the case of arelatively deep nuclear multi-fragmentation, the temperature of the materialin the first section 12 rises to values sufficient for at least partial melting ofthe material. The duration of the exposure to the beam (with accumulation of nuclear fission products) of the first section 12 in a two or three -sectioned 1O 12 target is normally determined numerically, proceeding from the necessity toachieve an appropriate portion of decayed target material with, yet, keeping asufficient strength of the respective case. Once a specified irradiation dose isreached, the material of the section is replaced with new (prepared) one withsubsequent cooling-down and handover of the exposed material to aradiochemical enterprise as stock for fabrication of next-in-turn batches ofmaterials with radionuclides meant for burnout under the accelerator beamdevice. For such burnout, radionuclides of a wide range of chemical elements(see Table 1) can be employed. In this context, it should be noted that aservice life of the proposed device can be achieved which is incomparablylonger than the time needed for accumulation of nuclear fission products not only in the target”s first section, but also in the target as a whole.

The material of a second section 13 of the target (see Figs 6 - 10 and 12) isfabricated mainly of actinides, including depleted and/ or regenerateduranium and/ or spent nuclear fuel with absolute adherence to therequirement of deep under-criticality. In this target section, the greater partof energy is released from all kinds of destruction giving way to nuclearenergy release. Therefore, the material of the second section is fabricated as alow-melting U-Fe type eutectic that, once exposed to an intense flux ofparticles, reaches its melting point and its melt is then used as a primarycoolant to remove heat from the target via pipelines 8 - 11 (see Figs 6 - 12).Along with removal of excess heat from the target, the pipelines provide alsothe homogenization of the target material through factual mixing. A similareutectic is used for conversion of the material of a third section 14 into aliquid phase (see Figs 11 and 12) in the case of a three-sectioned target meant to utilize the flux of neutrons that lost their capacity (in the second section 13) to destruct 232Th and/or 238 U nuclei with reproduction of fissilenuclides. Such an eutectic in all the three sections and all the threeembodiments may be replaced with a liquid salt melt of respective chemical elements or their compositions. 1O 13 The amount of material in the third section 14 of the three-sectioned target istaken with a sufficient surplus that allows timely compensation of inevitabledecrease in the material in the second section 13 due to not only thetransition of the material into a liquid phase after the heating, but also as aresult of a prolonged burnout under a beam. For this purpose, an appropriateamount of the molten material from the third section 14 of the target issupplied from a heated backup unit 4 (see Figs 11 and 12) placed above thethird section of the target at the natural head level, via a makeup pipeline 6and a shutoff gear 7. The same function is performed by the backup unit 4 inembodiments of the device with single and two-sectioned targets (see Figs 2-10). Out of there, via the makeup pipeline 6 and the shutoff gear 7, decreasesare compensated in the level of material in those sections of the target wherethe greater part of heat is released. In this connection, it is worth noting that the main position of shutoff gear ('closed') is shown in Figs 1 - 12.

To compensate the material decrease in the second section 13 of the three-sectioned target, a required amount of exposed material enriched with fissilenuclides from the third section 14 of the target is supplied from the case ofthe third section 14 by means of the pump forming part of a shutoff gear 16, via a pipeline 15 (see Figs 11 and 12).The device operates as follows.

In a steady-state operation mode, an accelerator beam 1 of multiple-charged 238U ions with an average current of ~ 1 mA and an energy of ~ 1 GeV per nucleon is directed, with the help of a unit for beam transportation andintroduction onto the target 2, onto either the target 3 of the device with asingle-section target (see Figs 2 - 5) or the first section 12 of the two or three -sectioned target (see Figs 6 - 12).

In the case of the single-section target 3 (Figs 2 - 5) with a conical orspherical case and the material fabricated of radioactive waste and/oractinides and/ or spent nuclear fuel, the beam of primary particles generates a flux of secondary particles, first generations of which also destruct target 1O 14 nuclei. In the bottom part of the target 3, the secondary flux of particles isutilized. Wherein nuclear energy is released, which is converted into heat inthe target. The decrease in the target material is compensated from thebackup unit 4 via the pipeline 6 fitted with the shutoff gear 7. Excessive heatis removed from the target 3, via the pipelines 8, 9, 10, 11 to a heat transformer 5, where it is converted into electric power.

In the second embodiment of the device, it has a two-sectioned target (Figs 6- 10) with the case whose lateral surface has cylindrical or conical shape.Also, the base part of the first section 12 is made planar or spherical, thecontents of the first section is identical to that of the target as per the firstembodiment, whereas the second section 13 is filled with actinides and/ orspent nuclear fuel with strict adherence to the condition of deep under-criticality. The primary beam generates a flux of secondary particles in thefirst section, thereby making nuclei of the material therein neutron-deficit.The flux of secondary particles in the second section provides the greater partof energy release and is utilized similarly to the case of a single-section target.The decrease in the target material is replenished from the backup unit 4 viathe pipeline 6 fitted with the shutoff gear 7. Excessive heat from the secondsection 13 is removed via the pipelines 8, 9, 10, 11 to the heat transformer 5 where it is converted into electric power.

In the third embodiment of the device (see Fig.12) where the target is madethree-sectioned, the lateral surface of the sections is cylindrical or conical, thebase part of the first section is made planar or spherical, the base parts of thesecond and third sections are spherical and separated from each other to adistance equal to the difference of their radii. The distance between the casesof the second and third sections is derived from the condition of fullabsorption in the third section of the flux of secondary neutrons leaving thesecond section. In the third section, complete utilization of the neutron flux isensured. The third section of the target is coupled by means of the pipelinesand the shutoff gear to the second section and the backup unit respectively.The first section 12 and the second section 13 are filled with the same materials as the respective sections of the above two-sectioned target, while 1O the material of the third section 14 is fabricated from depleted and/or regenerated 238U and/ or 232Th. The second section ensures energy release, in the third section 14 the secondary flux of neutrons that lost their capacity to destroy 238U and/ or 232 Th nuclei through converting them into fissile radionuclides is recycled.

The aforesaid purposes of the device (generation of heat and electric power,utilization of long-lived radionuclides) allows the development of anexhaustive plurality of relevant closed cycles based on long-livedradionuclides, including production of heat and electric power through release of nuclear energy, on chemical waste.

As an example, the diagram of a nuclear fuel cycle closed by long-livedradionuclides is provided in Fig.13. According to the diagram, practically allspent nuclear fuel and radioactive waste, including that containing plutoniumand minor actinides that are produced in such a fuel cycle, are fed to acoupled recycling cycle comprising the proposed device, a storage facility tocool down irradiated materials, radiochemical processing, a productionfacility for preparation of materials with long-lived radionuclides (and/or chemical waste) for exposure. In this case, such materials include also those containing 232Th and/ or 238 U, which are used for, among other purposes,reproduction of fissile nuclides within the device. Products of the long-livedradionuclide recycling process are heat and electric power that are in demand in not solely the nuclear fuel cycle, but also beyond its limits.

The above recycling process can involve radioactive waste from mining, hydrometallurgical and other production facilities, depleted uranium produced in the course of uranium enrichment (by 235U isotope), spentnuclear fuel, regenerated uranium, plutonium and minor actinides, as well as radioactive waste from radiochemical production facilities.

The diagram presented in Fig.13 is applicable to formation of all types of nuclear fuel cycles (U, U-Pu, Th-U and so on) closed on long-lived 1O 16 radionuclides, for feasible combinations, using fast-neutron reactors or not,with involvement of other types of devices and production facilities thatinevitably produce radioactive waste, with total refusal, on principle, from burial of such waste, which is practiced nowadays.

It should be noted that the above recycling process has a self-consistent valueas well when its input includes not only spent nuclear fuel, radioactive wastecoupled with its reprocessing, thorium, uranium, plutonium and minoractinides, but also radioactive waste of other nature, for instance, thatproduced in the course of dismantling of nuclear reactors and/or similarfacilities with service life expired or decommissioned ahead of schedule for whatever other reasons.

In a similar way, closed cycles are formed for any industries on respectivechemical and/ or biological waste fed as input of a recycling cycle similar tothe cycle depicted in Fig.13 and using the proposed recycling device, yetadapted for predominant burnout of chemical elements forming the bulk ofwaste in the given industry. In such a case, the industry will receive heat andelectric power for its needs and the adjacent nuclear fuel cycle will provide the above mentioned consumables and assembly parts for the recycling cycle.

Thus, a full-scale implementation of the proposed method and device forconversion of nuclear energy into heat will allow achieving not only logicalcompleteness and environmental consistency of existing types andmodifications of nuclear fuel cycles and those in the process of design in fullcompliance with applicable IAEA requirements (unlimited amount of fuelstock, invariability of the Earth”s radiation background, inviolability of thenon-proliferation regime, inherent safety of nuclear power facilities), but alsodeveloping, in a purposeful and consistent manner, a deeply under-criticalenvironmental-friendly power engineering capable of ensuring, among otheraspects, adequate justification of human activities in industrial sphere as a whole, including its nuclear segment.

Table 1 List of long-lived radionuclides 17 N LLR TV2, yfS N LLR TV2, yfS N LLR T1/2 , yfS1 Be-10 1.387(12)+6 31 I-129 1.57(4)+7 61 Th-229 7932(28)2 C-14 5700(30) 32 CS-135 2-3(3)+6 62 Th-230 7-54(3)+43 A1-26 7.17(24)+5 33 Cs-137 3o.o8(9) 63 Th-232 1.4o(1)+1o4 Si-32 153(19) 34 La-137 6(2)+4 64 Pa-231 3.276(11)+45 Cl-36 3-01(2)+5 35 Pm-145 17-7(4) 65 U-232 68-9(4)6 Ar-39 269(3) 36 Sm-146 1o.3(5)+7 66 U-233 1.592(2)+57 Ar-42 32-9(11) 37 Sm-151 90(8) 67 U-234 2-455(6)+58 K-40 1.248(3)+9 38 Eu-150 36.9(9) 68 U-235 7.o4(1)+89 Ca-41 1.o2(7)+5 39 Gd-148 7o.9(1o) 69 U-236 2.342(4)+710 Ti-44 6o,o(11) 40 Gd-150 1.79(8)+6 70 U-238 4.468(3)+911 Mn-53 3-74(4)+6 41 Tb-157 71(7) 71 Np-236 153(5)+312 Fe-60 2.62(4)+6 42 Tb-158 18o(11) 72 Np-237 2.144(7)+613 Ni-59 7-6(5)+4 43 Dy-154 3-0(15)+6 73 Pu-238 87-7(1)14 Ni-63 1o1.2(15) 44 Ho-163 457o(25) 74 Pu-239 2411o(3o)15 Se-79 2.95(38)+5 45 Ho-166m 1.2o(18)+3 75 Pu-240 6561(7)16 Kr-81 2.29(11)+5 46 Hf-178m 31(1) 76 Pu-242 3.75(2)+5 18 17 Sr-90 28.90(3) 47 Hf-182 8.90(9)+6 77 Pu-244 8.00(9)+718 Zr-93 1.61(5)+6 48 Re-186m 2.0+5 78 Am-241 432.6(6)Am-19 Nb-91 6.8(13)+2 49 Ir-192m 241(9) 79 141(2)242m20 Nb-92 3-47(24)+7 50 Pt-103 50(6) 80 Am-243 7370(40)Nb-21 ggm 16,12(12) 51 Hg-194 444(77) 81 Cm-243 29.1(1)22 Nb-94 2.03(16)+4 52 Pb-202 52.5(28)+3 82 Cm-244 18.1(1)23 M0-93 4-0(8)+3 53 Pb-205 1-73(7)+7 83 Cm-245 842304)24 Tc-97 4.21(16)+6 54 Pb-210 22.20(22) 84 Cm-246 4706(40)25 T0-08 4-2(3)+6 55 Bi-207 31-55(4) 85 001-247 1-56(5)+726 Tc-99 2.111(12)+5 56 Bi-208 3.68(4)+5 86 Cm-248 3.48(6)+527 Pd-107 6.5(3)+6 57 Bi-210m 3.04(6)+6 87 Cm-250 8.3+3Ag-28 438(9) 58 Po-209 102(5) 88 Bk-247 1380(250)108mSn-29 43-0(5) 50 Ra-226 1600(7) 80 Cf-240 351(2)121m30 Sn-126 2.30(14)+5 60 Ac-227 21.772(3) 90 Cf-251 898(44) Note: LLR - long-lived radionuclide; T1 / 2 - half-life; 1.387(12)+6 - (1.387 i 0.012) * 106

Claims (4)

1. A method for conversion of nuclear energy into heat consisting in that arelativistic ion beam is produced and accelerated, the beam is directed to aregularly refreshable material of a deeply under-critical target, which resultsin decay of target nuclei, the flux of secondary particles is produced,including neutrons, the secondary particles are arranged to split the nuclei ofisotopes of heavy chemical elements, which, in its turn, results in release ofnuclear energy, the condition of the target of a size ensuring the transfer ofthe beam kinetic energy and that of the secondary particles to the target ismonitored, and the duration of accumulation and replacement of nuclearfission products is determined, characterized in that the aforesaid relativisticion beam is accelerated to an energy level at which at least two generations ofnuclear multi-fragmentation products are produced by means of the fissionof the target material, and nuclear energy is released within a time intervalthat exceeds the duration of the accumulation and replacement of the nuclearfission products by a material prepared for exposure, the flux of secondaryparticles is recycled, and the exposed material is cooled down and forwardedfor recycling as work material for extraction of materials suitable for further use in conformity with the claimed method.

2. A device for the method according to Claim 1, which comprises arelativistic ion beam accelerator, a unit for beam transportation andintroduction onto the target, a deeply under-critical target made of heavychemical elements in a fire-, radiation- and corrosion-resistant case with anopen upper end, and a heat transformer unit, all arranged in series,characterized in that the target case has a conical or spherical shape relativeto the energetic axis of the device, is coupled through pipelines to the heattransformer and through a pipeline and shutoff gear to a backup unit that allows its replenishment and is located above the target.

3. A device for the method according to Claim 1, which comprises arelativistic ion beam accelerator, a unit for beam transportation and introduction onto the target, a deeply under-critical target made of heavy 1O chemical elements in a fire-, radiation- and corrosion-resistant case with anopen upper end, and a heat transformer unit, all arranged in series,characterized in that the target case is made of two sections consecutivelydisposed relative to the unit for beam transportation and introduction ontothe target, the lateral surface of the sections relative to the energetic axis ofthe device has a similar cylindrical or conical shape, the base part of the firstsection that can be replaced and fixed is made planar or spherical, the secondsection is connected through pipelines to the heat transformer and through apipeline and shutoff gear to a backup unit that allows its replenishment and is located above the second section of the target.

4. A device for the method according to Claim 1, which comprises arelativistic ion beam accelerator, a unit for beam transportation andintroduction onto the target, a deeply under-critical target made of heavychemical elements in a fire-, radiation- and corrosion-resistant case with anopen upper end, and a heat transformer unit, all arranged in series,characterized in that the target case is made of three sections consecutivelydisposed relative to the unit for beam transportation and introduction ontothe target, the lateral surface of the sections relative to the energetic axis ofthe device has a similar cylindrical or conical shape, the base part of the firstsection, that can be replaced and fixed, is made planar or spherical, the baseparts of the second and third sections are spherical and separated from eachother by a distance equal to the difference of their radii, wherein the thirdsection of the target case is connected through pipelines and shutoff gears tothe second section and a backup unit respectively, herewith the secondsection connected through pipelines to the heat transformer, while the designof the backup unit allows its replenishment and the said unit is located abovethe third section of the target.