Radiation Characteristics of Fuel and Wastes in the Uranium–Plutonium and Thorium–Uranium Fuel Cycle

The radiation characteristics of fuel cycles of various reactors – replacement candidates in the future nuclear power – are compared. Proceeding from the basic requirements (safety, fuel supply, and nonproliferation of fissioning materials), inherently safe fast reactors of the BREST type can be used as the basis for large-scale nuclear power. Thermal reactors, which can burn enriched uranium, thorium–uranium fuel, or mixed uranium–plutonium fuel with makeup with fissioning materials from fast reactors, will operate for a long time simultaneously with fast reactors in the future nuclear power. VVÉR-1000 and CANDU reactors are examined as representatives of thermal reactors; for each of these reactors the operation in various variants of the fuel cycle is simulated. It is shown that with respect to radiation characteristics of the fuel and wastes the thorium–uranium fuel cycle has no great advantages over the uranium–plutonium cycle.     

Radiation Balance in Nuclear Power Growth with BREST-1200 and VVÉR-1000 Reactors

The role of irradiated VVÉR-1000 and RBMK-1000 fuel and irradiated fuel from foreign PWRs in the strategy for growth of future nuclear power production up to 300 GW using BREST-1200 reactors as the main component is examined. The growth time up to 300 GW varies in different variants from 90 to 180 yr. Analysis of the dependence of the potential biological hazard of the wastes on the holding period, taking account of the migrational characteristics, taken by comparing the retainment coefficients of elements in rocks, shows that the time for reaching a balance between the potential biological hazard of the wastes and the raw materials at the end of the period of growth of nuclear power production lies in the range 1–1.5 thousand years. The time to reach radiation equivalence is short at the initial stages of growth and increases gradually; this requires gradual improvement of the fuel reprocessing technology with fewer elements going into the wastes.     

Calculation of the time for establishing radiation equivalence of high-level wastes

The potential harm of long-lived radionuclides estimated as the product of the activity of a radionuclide and the dose coefficient is examined. The potential harm of actinides in high-level wastes is calculated taking account of the harm due to their decay products. At the same time, an analogous calculation is performed for the uranium isotopes ²³⁸U, ²³⁵U, and ²³⁴U consumed in the reactor. The value obtained, which depends on the time, can be regarded as the averted harm. The time for establishing radiation equivalence between the high-level wastes and the consumed uranium is determined as the time in which the potential harm from actinides becomes equal to the averted harm. It depends on the holding time of the spent fuel before radiochemical reprocessing. For a 5 yr holding period, it is 49000 yr.__________Translated from Atomnaya Énergiya, Vol. 98, No. 2, pp. 123–129, February, 2005.     

Possibility of long-term nuclear power development based on today’s technology

The possibility of long-term nuclear power development with a uranium fuel cycle based on ²³⁸U burnup and todays industrial technology is investigated. It is shown that such development is possible with fast reactors, including with sodium coolant. In this case, incomplete fuel reprocessing is admissable in a closed fuel cycle employing a pyroelectrochemical technology, which allows some fission products and actinides to be present in the fresh fuel prepared for reloading after reprocessing. These fission products and actinides can be burned in a reactor, thereby decreasing the quantity of radioactive wastes compared with the complete reprocessing with chemical separation of the fuel elements and decreasing the radiation load on the environment.Translated from Atomnaya Ènergiya, Vol. 97, No. 4, pp. 252–260, October, 2004.     

Radiation Equivalence and Natural Similitude in Handling Radioactive Wastes

The possibility of long-term safe disposal of radioactive wastes based on their radiation and radiation-migration balance with the initial fuel component and taking account of the thermal, radiation, and elastic loads due to waste dispoasl on the natural medium is examined. The specific radiation and radiation-migration equivalence is established on the basis of the radiotoxicity of uranium and the components of the decay of uranium and individual radionuclides as well as the sum of the latter.     

Assessment of the quality and activity of the radionuclides in the fuel cycles of a three-component structure of nuclear power

A three-component structure of nuclear power with a closed nuclear fuel cycle is examined. In addition to the existing thermal and fast reactors the system contains a liquid-salt reactor for closing the fuel cycle with respect to actinides. The quantity and activity of the radionuclides are analyzed for promising variants of the structure of nuclear power and the uranium-plutonium, thorium-uranium, and uranium-plutoniumthorium closed fuel cycle. It is concluded on the basis of calculations and analysis, taking into account the life cycle from production of the fuel to the burial of the wastes, that the uranium-plutonium-thorium fuel cycle is more advantageous than the uranium-plutonium and thorium-uranium fuel cycles. __________ Translated from Atomnaya énergiya, Vol. 101, No. 3, pp. 214–221, September, 2006.     

Plutonium fuel and fuel elements for power reactors

Conclusions The use of plutonium in the fuel cycle during complex utilization of thermal and fast reactors in nuclear energetics permits solving the problem of ensuring nuclear fuel for a long period. Oxide uranium-plutonium fuel facilitates the development of technology of fast reactors and so far it is considered as the basic type of fuel. At the same time, oxide fuel cannot ensure the required rate of plutonium accumulation, in view of which the investigations of more efficient fuel and constructional materials become a pressing problem. The use of uranium-plutonium oxide fuel in thermal reactors requires improvements in the construction of fuel elements and organization of large-scale completely automatic production.Translated from Atomnaya Énergiya, Vol. 43, No. 5, pp. 412–417, November, 1977. Editors' Remarks. For the completeness of the discussion of the problem it is, of course, necessary to consider the possibility of using plutonium in fast and thermal reactors as done by the authors. However, it should be kept in mind that by its nuclear-physical parameters plutonium as a nuclear fuel is more suitable for use in fast reactors than in thermal reactors. The use of plutonium in thermal reactors can reduce the demands of natural uranium for the development of nuclear power in all by 10–15%, whereas its use in fast reactors reduces the demand for uranium by a factor of 10.All this indicates the feasibility of using plutonium only in fast reactors even if its accumulation is required over a certain period.     

The raw material and waste activity balance in the projected nuclear power of Russia

Under discussion is the management of long-lived high-level wastes in the nuclear energy sector of Russia, the development of which on a large scale in the next century is motivated by the need for arresting the increasing consumption of fossil fuels. The prerequisites for the nuclear power growth consists in the design of naturally safe reactors and development of a transmutational nuclear fuel cycle (NFC) technology. The choice of operations in such a cycle and of their quantitative characteristics, is aimed at minimizing the wastes to approach the radiation balance with the natural uranium extracted and put to use. The paper discusses the way the approximation to the balance between the raw material and waste activity is influenced by introduction of the transmutational NFC (in case 2), inclusion of transmutation reactors into the energy mix (case 1), partial disposal of actinide wastes into outer space, and by recycling of protactinium (case 3). It is shown that such a balance can be sustained for a considerable time in cases 2 and 3 or throughout the operation stage of the future nuclear power (case 1).     

BN-800 as a New Stage in the Development of Fast Sodium-Cooled Reactors

The role of fast reactors in a strategy for developing nuclear power in Russia because of the inevitable exhaustion of natural uranium deposits in the foreseeable future is discussed. The BN-800 reactor, which is under construction and incorporates unique solutions – greatly enhancing the safety of the reactor – to technical and constructional problems, is examined. Cost assessments taking account of the complete life cycle show that fast reactors could be no more expensive than the most widely reactors in the world – water-moderated water-cooled reactors.Closing the BN-800 nuclear fuel cycle will make it possible to solve the problem of utilizing plutonium and actinides. This makes fast reactors safer for the environment.     

The neutronic potential of nuclear power for long-term radioactivity risk reduction

An analysis to evaluate the comparative neutronic transmutation potential of different nuclear power system (standard or advanced fission reactors and accelerator driven hybrids) is presented. The analysis is based on an evaluation of neutronic constraints for the reduction of both long-lived fission product toxicity and fuel waste toxicity integrated over the life of the nuclide families, taking into account the overall neutron balance of the systems being considered.     

Possibilities of BREST reactors and transmutation fuel cycle under conditions implementing modern plans for the development of nuclear power

The possible dynamics of the development of BREST-1200 fast reactor capacities after 2030 on the basis of plutonium and other actinides accumulated in the spent fuel of thermal reactors is examined. It is shown that by 2100 the power BREST reactors could be 114–176 GW, and subsequently they will develop as a result of their own breeding of plutonium. Calculations have shown that the rate at which BREST reactors are put into operation can be doubled by using enriched uranium obtained from natural uranium and regenerated spent fuel from thermal reactors. It is shown that the development of fast reactors with a closed fuel cycle solves the problem of transmutation of long-lived high-level actinides and makes it possible to implement a transmutation fuel cycle in nuclear power. __________ Translated from Atomnaya énergiya,Vol. 103, No. 1, pp. 21–28, July, 2007.     

Effect of fission products yield library on the calculation of the nuclide composition of the fuel in sodium-cooled fast reactors

The calculation of the composition of irradiated fuel for different degrees of burnup is a basic problem in the analysis of nuclear-radiological safety of objects holding spent fuel assemblies. The yield of fission products is one of the important initial indicators in burnup calculations. Methods for compiling libraries of fission products yield on the basis of the ENDF/B up-to-date evaluated nuclear data files are described. The nuclide composition of uranium oxide and uranium-plutonium-zirconium metal fuel in sodium-cooled fast reactors is analyzed by means of high-precision calculations performed with different fission product yields libraries using different computer codes MONTEBURNS–MCNP5–ORIGEN2 and the results are presented.     

Choice of the capacity of a fast reactor for nuclear power

Analytical assessments, associated with the choice of the unit capacity of a serially built fast reactor under conditions of the future advancement of nuclear power, are presented. It is shown that considering the limited resources of natural uranium, the development of a reliable raw materials base must be based on the development of fast reactors with expanded breeding of fuel and fuel cycle closure. Since fast reactors, together with energy production, are also producers of new fuel, their parameters must be optimized taking account of this factor on the basis of systems analysis. Calculations show that the optimal capacity for fast reactors is in the 1 GW range. __________ Translated from Atomnaya énergiya, Vol. 103, No. 2, pp. 83–88, August, 2007.     

Economic aspects of the development of nuclear power and fuel cycle plants in the USSR

Conclusion Plutonium breeding in fast reactors themselves will not have any significant effect in the next 20–25 years on growth rate of the capacity of nuclear power stations with fast reactors.The character of the distribution of the capital expenditures on nuclear power stations and on the fuel cycle shows that the bulk of the expenditures is spent on the construction of the nuclear power stations and only 20% on the development of the fuel-cycle plants. For this reason, greatest savings of capital expenditure are given by a reduction in the construction costs of nuclear power stations by means of improvements in the design and of the reactor and the thermal and mechanical equipment of the plant.In the fuel cycle the biggest economic effect is produced by measures that lead to a reduction in the specific consumption of natural uranium since the capital expenditure on the mining operations constitutes about one-half of the total capital expenditures on the fuel cycle. The natural uranium costs also make up roughly one-half of the fuel component of the cost of electricity generated by a nuclear power station. As the price of uranium rises, this fraction of costs will also increase.Translated from Atomnaya Énergiya, Vol. 43, No. 5, pp. 365–369, November, 1977.     

Self-consistent model of nuclear power and nuclear fuel cycle

Under discussion are such major aspects of the nuclear energy sector as cost effectiveness, nuclear and environmental safety of reactors and nuclear fuel cycle facilities, sustained fuel supply, and proven feasibility of a proliferation-resistant technology. These requirements can be met, for instance, by a two-circuit nuclear facility with an inherently safe fast reactor of the BREST type which is expected to produce electricity at a cost not higher than that at modern LWRs. Fuel supply to such facilities and to a relatively small number of thermal reactors with BR<1, could be provided by fast reactors using depleted uranium as makeup fuel and having a small breeding gain in the core (CBR≈1.05) and bottom blanket (full BR≈1.1). Use of a high-boiling metallic coolant (lead) affords deterministic nuclear, technical and environmental safety of the plants in design-basis and hypothetical accidents. Introduction of a transmutational NFC is viewed as one of the avenues to global environmental safety, when the equivalent activity of long-lived high-level waste is made lower or close to the activity of the source material going into energy production. With such a balance in place, nuclear power could be regarded, in a sense, as waste-free.     

Assessment of the effectiveness of mixed uranium-plutonium fuel in VVÉR

An assessment of the cost-effectiveness of burning mixed uranium-plutonium fuel in VVéR reactors is made as a function of the price of natural uranium. It is shown that for the present price structure, based on the main technological processes used for fabricating fuel, mixed fuel becomes cost-effective when the price of natural uranium is about $300/kg. The results of systems investigations of the development of nuclear power in our country with an orientation toward fast reactors are also presented. In this case, the systems price of plutonium at the stage where fast reactors are first introduced increases. This indicates that the growth prospects must be taken into account in order to develop an efficient fuel-use strategy. __________ Translated from Atomnaya énergiya, Vol. 103, No. 5, pp. 275–277, November, 2007.     

Innovative development of nuclear power in Russia

The basic principles for performing analysis and the systems requirements for large-scale nuclear power in our country are formulated. The problems of modern nuclear power are examined and ways for modern nuclear power to transition to innovative development while satisfying these systems requirements for fuel use, handling spent fuel and wastes, and nonproliferation are indicated. The basic scenario of innovative development in the near term (up to 2030) is based on using predominantly ²³⁵U as fuel and water-moderated water-cooled reactors, which have been well mastered, for increasing nuclear capacities with limited introduction of fast reactors for solving the problem of spent fuel from thermal reactors. In the long term (2030–2050), a transition to ²³⁸U as the primary raw material with fast reactors predominating and complete closure of the nuclear power fuel cycle will be made. The journal variant of a report “New-Generation Nuclear Energy Technologies” presented at a meeting of the Scientific and Technical Council of Rosatom, Moscow, September 27, 2006. __________ Translated from Atomnaya énergiya, Vol. 103, No. 3, pp. 147–155, September, 2007.     

Nuclear power technologies at the stage of sustainable nuclear power development

It is not simple to solve the problem of competitiveness of nuclear power technologies in evolutionary upgrading the conventional nuclear power plants (NPP) such as light water reactors (LWR), which requires high expenditure for safety. Moreover, the existing LWRs cannot provide nuclear power (NP) for a long time (hundreds of years) because the efficiency of use of natural uranium is low and closing the nuclear fuel cycle (NFC) for those reactors is not expedient.The highlighted problem can be solved in the way of use of innovative nuclear power technology in which natural uranium power potential is used effectively and the intrinsic conflict between economic and safety requirements has been essentially mitigated.The technology that is most available and practically demonstrated is the use of reactors SVBR-100 — small power multi-purpose modular fast reactors (100 MWe) cooled by lead-bismuth coolant (LBC). This technology has been mastered for nuclear submarines’ reactors in Russia.High technical and economical parameters of the NPP based on RF SVBR-100 are determined from the fact that the potential energy stored in LBC per a volume unit is the lowest.The compactness of the reactor facility SVBR-100 that results from integral arrangement of the primary circuit equipment allows realizing renovation of power-units LWRs, the vessels’ lifetime of which has been expired. So due to this fact, high economical efficiency can be obtained.The paper also validates the economical advantage of launching the uranium-fueled fast reactors with further changeover to the closed NFC with use of plutonium extracted from the own spent nuclear fuel in comparison with launching fast reactors directly with on uranium-plutonium fuel on the basis of plutonium extraction from spent nuclear fuel of LWRs.     

Current and Future Problems of the Fuel Supply for Nuclear Power

The structure of the nuclear fuel cycle, consisting of the technological stages of uranium production, refining, enrichment, fabrication of nuclear fuel, and reprocessing of the spent fuel for reuse of the fissioning materials, is examined. Supplying fuel includes supplying fuel for Russian nuclear power plants, propulsion and research reactors, export of fuel for nuclear power plants and research reactors constructed according to Russian designs, export of low-enriched uranium and fuel for nuclear power plants constructed according to foreign designs. The explored deposits of natural uranium, the estimated stores of uranium in reserve deposits, and warehoused stores will provide nuclear power with uranium up to 2030 and in more distant future with the planned rates of development. The transition of nuclear power plants to a new fuel run will save up to 20% of the natural uranium. The volume of reprocessing of spent fuel and reuse of ²³⁵U makes it possible to satisfy up to 30% of the demand for resources required for Russian nuclear power plants. The most efficient measure of the resource safety of Russian nuclear power is implementation of an interconnected strategy at each stage of the nuclear fuel cycle.     

Study of a self-regulated nuclear burn wave regime in a fast reactor based on a thorium–uranium cycle

The possibility of a wave of slow nuclear burning in a fast reactor in thorium–uranium fuel cycle is investigated. The calculations were performed using a model based on the solution of a nonstationary nonlinear diffusion equation for a cylindrical homogeneous reactor using the concept of a radial geometric factor (buckling) and the effective multigroup approximation taking account of the nuclear kinetics of the precursors of delay neutrons and burnup and production of the main nuclides of the thorium–uranium fuel cycle. The calculations showed that the generation and propagation of a wave of nuclear burning traveling with velocity approximately 2 cm/yr are possible in a thorium–uranium medium. However, the addition of even small quantities of a construction material and coolant to the composition of the reactor makes it impossible to obtain the burn wave regime. A self-maintained nuclear burn regime is also established in this case and exists for a long time (∼5 yr), but the system does not transition into a regime with a nuclear burn wave propagating along the axis of the reactor.