压水堆平衡堆芯钍铀燃料循环初步研究

建立WIMSD5-SN2-CYCLE3D和CASMO3-CYCLE3D物理分析系统作为钍铀燃料循环研究工具.以大亚湾第1机组压水堆为参考堆型,不改变反应堆栅元、组件和堆芯的结构与几何尺寸,设计出含36根钍棒、4.2#5U富集度的新型含钍组件,并对含钍组件和3.2%富集度的铀组件进行中子学计算和分析.模拟并分析了大亚湾压水堆12个月换料从初始循环到铀钚平衡循环的换料过程.再从平衡铀堆芯出发,逐步加入含钍组件代替铀组件,对铀钚平衡循环到钍铀平衡循环的换料过程进行了模拟与分析.计算结果表明:钍铀平衡循环比铀钚平衡循环每天节省裂变核素质量约18.4%,并减少了长寿命放射性核废料的产生.不利因素是使得循环长度减少90EFPD,缩短了换料周期,增加运行费用,并给燃料管理、安全控制以及乏燃料的处理带来困难.建议提高组件的235U富集度,在压水堆上进行钍利用研究.     

Optimization of the core composition for a sodium-cooled fast reactor with oxide fuel and fuel-utilization improvement by adopting a closed fuel cycle

The transition to a closed fuel cycle after several years of operation of the BN-800 with oxide uranium fuel in an open fuel cycle is examined. It is shown that there is an advantage to using new fuel assemblies with 91 fuel elements with diameter 8.6 mm in a regime with four refuelings. On the basis of new fuel assemblies with mixed uranium-plutonium oxide fuel, transitional recycling to a closed fuel cycle without separating uranium and plutonium and without external plutonium makeup is examined. It is confirmed that a negative sodium void effect of reactivity is achieved with admissible values of the linear power density of a fuel element. It is shown that a regime with four refuelings can be obtained by adding uranium with enrichment no higher than 15% to replace the poison which is removed. __________ Translated from Atomnaya énergiya, Vol. 104, No. 2, pp. 94–99, February, 2008.     

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.     

重水堆钍铀燃料增殖循环方案研究

论文的目的是研究重水堆钍铀燃料增殖循环方案。基于前期设计的技术路线,以CANDU-6堆芯为参考堆芯,研究了钍基堆芯燃料管理策略,分析了中子学特性,并对乏燃料特性进行了评估,包括放射性毒性、衰变热和伽马射线。在此基础上,建立了钍铀燃料增殖循环方案,其在可持续性关键指标方面优于常规天然铀一次通过循环。     

The closed on-site fuel cycle of the brest reactors

The BREST fast reactor with nitride fuel and lead coolant is being developed as a reactor of new generation, which has to meet a set of requirements placed upon innovative reactors, namely efficient use of fuel resources, nuclear, radiation and environmental safety, proliferation resistance, radwaste treatment and economic efficiency. Mixed uranium-plutonium mononitride fuel composition allows supporting in BREST reactor CBR≈1. It is not required to separate plutonium to produce “fresh” fuel. Coarse recovered fuel purification of fission products is allowed (residual content of FPs may be in the range of 10⁻² – 10⁻³ of their content in the irradiated fuel). High activity of the regenerated fuel caused by minor actinides is a radiation barrier against fuel thefts. The fuel cycle of the BREST-type reactors “burns” uranium-238, which must be added to the fuel during reprocessing. Plutonium is not extracted during reprocessing being a part of fuel composition, thus exhibiting an important nonproliferation feature.

The radiation equivalence between natural uranium consumed by the BREST NPP closed system and long-lived high-level radwaste is provided by actinides (U, Pu, Am) transmutation in the fuel and long-lived products (I, Tc) transmutation in the blanket. The high-level waste must be stored for approximately 200 years to reduce its activity by the factor of about 1000.

The design of the building and the entire set of the fuel cycle equipment has been completed for the demonstration BREST-OD-300 reactor, which includes all main features of the BREST-type reactor on-site closed fuel cycle.     

聚变裂变混合堆钍基增殖锕系元素嬗变包层中子学初步研究

聚变裂变混合堆比纯聚变堆在工程及技术方面要求低,且在产生核燃料、嬗变长寿命核废料以及固有安全性方面具有一定优势,因此,越来越受到人们的重视。增殖包层是混合堆系统的关键部件,已有的包层研究基本上是基于较成熟的铀-钚燃料循环技术。针对我国铀资源相对较少而钍资源较丰富的现状,本文就一种新型的钍基燃料增殖锕系元素嬗变包层进行了初步的中子学研究,利用一维离散纵标法燃耗程序BISONC以及Monte-Carlo粒子输运程序MCNP,对包层的关键核参数,诸如氚增殖比、少量锕系元素的嬗变质量、233U产量以及热功率等,进行了较详细的计算分析。计算结果表明,生成的核燃料233U的富集度可达到3.65%,从而满足压水堆燃料富集度要求。分析结果为下一步的包层优化设计提供了依据。     

使用均匀混合型燃料组件的压水堆钍-铀增殖循环研究

为提升压水堆燃料利用率,设计了一种包含适量²³²Th和²³³U的均匀混合型燃料组件。对该型燃料组件的核特性分析表明,其具备随燃耗增加k_inf下降更缓慢的特性,有利于堆芯获得更长的循环长度。以岭澳核电厂一号机组为例,对包含均匀混合型含钍燃料组件的堆芯进行了分析,结果表明,当前压水堆中采用均匀混合型含钍燃料组件是可行的,并且具备²³⁵U利用率高、堆芯循环长度长的优势。     

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.     

Necessity of nuclear fuel cycle closure

The results of a systems study confirming on a new level the need to develop fast reactors with a closed nuclear fuel cycle and the best transition times to a closed nuclear fuel cycle are presented. The results obtained show that nuclear fuel cycle closure is a necessary step for developing large-scale nuclear power in the country. Nuclear fuel cycle closure using fast reactors with inherent safety is justified economically even now.     

Use of Recovered Uranium and Plutonium in Thermal Reactors

A possible version of the VVER-1000 fuel cycle without separation of uranium and plutonium during reprocessing of spent fuel is examined. In this fuel cycle, the uranium-plutonium regenerate obtained, from which other actinides and fission products have been removed, is used after enriched natural uranium is added for preparing VVER fuel. The results of a calculation of the content of uranium and plutonium isotopes in the spent uranium-plutonium fuel after one and two recycles in VVER-1000 are presented. The main advantages of the fuel cycle are discussed: lower risk of plutonium proliferation, savings of natural uranium, and less spent fuel as compared with an open uranium fuel cycle. __________ Translated from Atomnaya Energiya, Vol. 99, No. 2, pp. 136–141, August 2005.     

Fast reactors in the energy security for the stable development of Russia

New aspects of the development of a future nuclear power system based on the advanced technologies of a closed nuclear fuel cycle with fast-neutron reactors are discussed on the basis of an analysis of systems problems pertaining to present-day nuclear power. The systems requirements ensuring adequate fuel for nuclear power with any installed capacity and maximum use of natural uranium and thorium brought into the fuel cycle are formulated. Sodium-cooled fast reactors, which thus far possess the highest level of technological readiness for commercialization, are given a special role in the formation of a new technological platform for large-scale nuclear power of the 21st century.     

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.     

钍铀核燃料循环研究

本文报道了中国科学院上海原子核研究所在开展钍铀燃料循环研究方面的进展和取得的成果。这些研究主要为克级量纯~(253)U的提取、钍基燃料后处理技术研究、新的铀钍萃取体系的研究、钍铀镤分离和分析方法研究、中子辐照ThO_2时产生有关核素的累积与中子积分通量和中子能谱的关系、钍的零功率试验等。本文还对钛的利用进行了评估和展望。     

Single-purpose electronuclear installation using natural uranium as fuel

The results of investigations of the parameters of an electronuclear setup, operating on solid fuel, for producing useful power are presented. The objective of the investigations is to show the attractiveness and practical possibility of producing a safe (subcritical) setup for producing energy with unlimited fuel resources. The setup contains an accelerator, two targets, and two blankets. The fissioning isotopes accumulate in one blanket, supplied with natural uranium. Actually, his blanket performs the function of enrichment for the uranium-plutonium fuel cycle in modern nuclear power. Power is generated mainly in the other blanket, which is supplied with fuel assemblies that are extracted from the first blanket. In contrast to reactors operating on natural uranium, in an electronuclear setup a high degree of fuel burnup can be achieved by converting part of the generated energy into neutrons. 1 figure, 9 references. State Science Center of the Russian Federation—Institute of Theoretical and Experimental Physics. Translated from Atomnaya énergiya, Vol. 87, No. 3, pp. 199–204, September, 1999.     

An assessment of the effectiveness of fuel cycle technologies for the national energy security enhancement in the electricity sector

Energy security, in the 21st century, draws significant attention in most countries worldwide, because the national security and sustainable development depend largely on energy security. The anticipated fossil energy depletion and the instability of their supply drive many countries to consider nuclear energy as their alternative energy source for the enhancement of their national energy security. In this study, indicators measuring the level of energy security in the electric power sector are developed and applied for the assessment of the effectiveness of four electric power system schemes which deploy different nuclear fuel cycle technologies, with consideration for the diversification of the energy markets and the vulnerability to economic disruption. Results show that the contribution of the closed fuel cycle scheme is larger than the once-through fuel cycle scheme in the perspective of energy security. In addition, the completely closed fuel cycle with the spent fuel recycling enhances the national energy security to the maximum extent compared to all other fuel cycle schemes. Since a completely closed fuel cycle is hardly affected by the uranium price changes, this scheme is found to be the most favorable scheme, ensuring the stable profit of utilities and stabilizing the electricity tariff. In addition, the completely closed fuel cycle scheme provides the best enhancement of national energy security with respect to energy supply, under reasonable price conditions. The indicators developed in this study can be utilized as a useful instrument for the measurement of the level of the energy security, especially by the countries importing energy resources for the generation of electric power.     

Safety assessment methodology and analysis of production during plutonium recycling at the State Science Center of the Russian Federation—Scientific-Research Institute of Nuclear Reactors

The methodology and criteria for safety assessment of nuclear fuel cycle technological processes are proposed, substantiated, and checked in large-scale recycling of plutonium (500 kg). The results of comprehensive investigations of the radiation-ecological conditions during the experimental production of mixed uranium-plutonium fuel and fuel assemblies at the State Science Center of the Russian Federation— Scientific-Research Institute of Nuclear Reactors are presented. A methodology and an experimental data bank can be used for safety assessment of commercial recycling of plutonium and Np, Am, and Cm in the nuclear fuel cycle. 4 figures, 3 tables, and 13 references. State Science Center of the Russian Federation—Scientific-Research Institute of Nuclear Reactors. Translated from Atomnaya énergiya, Vol. 87, No. 4, pp. 266–275, October, 1999.     

Status of and possible approaches to the standardization of the safety of elements of the nuclear fuel cycle

Conclusions In summary, the foregoing analysis shows that the systems of standardizing documents for fuel-cycle elements must be developed as quickly as possible. The proposed system must have at the upper levels a hierarchical structure of documents of the regulating agencies and at the lower level it must contain the industry documents. Two principles must be observed: on the one hand, the requirements for the safety of the elements of the nuclear fuel cycle must be satisfied by approaches and principles corresponding to modern approaches to guaranteeing the safety of installations posing a nuclear and radiation hazard and, on the other, the extensive industrial experience accumulated and the corresponding industrial standardizing documentation should be used. An important question in formulating such a system of requirements is: What are the further prospects for the development of the entire nuclear fuel cycle? If the future development of nuclear power in this country is based on a closed fuel cycle, then the entire infrastructure of the elements of the nuclear fuel cycle will have to be modified. The next century, when these enterprises will be operating, will have its own safety requirements, and we must think about this now. If the fuel cycle will be open and several of the presently operating elements of the fuel cycle survive, then we have a different formulation of the problem and different scientific and technical problems. Scientific-Research Center of Gosatomnadzor of the Russian Federation. L. Ya. Karpov Scientific-Research Institute of Physical Chemistry. Institute of Physics and Power Engineering. Gosatomnadzor of the Russian Federation. Translated from Atomnaya énergiya, Vol. 76, No. 4, pp. 264–273, April, 1994.     

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.     

Use of weapons plutonium in VVÉR-1000 reactors

One scenario for using excess Russian weapons plutonium is to load it into VVéR-1000 reactors. It is proposed that up to 40% of the fuel assemblies with uranium fuel be replaced with structurally similar fuel assemblies with mixed uranium-plutonium fuel. The stationary regime for burning fuel has the following characteristics: the run time is about 300 or 450 eff. days, the yearly plutonium consumption reaches 450 kg, the neutron-physical characteristics are close to the corresponding regimes with uranium fuel. The nuclear safety criteria and the irradiation dose for workers handling fresh and spent mixed fuel remain within the limits of the normative values. The use of mixed fuel makes it necessary to upgrade certain systems at nuclear power plants. A substantial quantity of weapons plutonium can be loaded every year into VVéR-1000 reactors, effectively using the energy potential of this plutonium. __________ Translated from Atomnaya énergiya, Vol. 103, No. 4, pp. 215–222, October, 2007.