Two-component Nuclear Energy System Research Articles

On plutonium-241 and americium in the two-component nuclear energy system

The paper deals with the influence of the strategy for using separated plutonium from spent fuel of thermal and fast reactors, as well as homogeneous burning of americium in the BN reactor core on the balance of americium in the Russian nuclear fuel cycle throughout the 21st century. The assessment is carried out with the use of mathematical modeling of nuclear materials movement including nuclide transformations throughout the nuclear energy system based on the CYCLE code. Scenario modeling of the americium and Pu-241 accumulation was carried out in Russia’s two-component nuclear energy system model with thermal (VVER) and fast (BN) reactors. In so doing, spent nuclear fuel (SNF) reprocessing was simulated in 2 options: as priority reprocessing of SNF of VVER reactors (1) or SNF of BN reactors (2). In addition to americium accumulation in the system without burning, the accumulation of this actinide was studied taking into account its homogeneous burning in the MOX-fuel of fast reactors at the level of its equilibrium content of ~1%. It has been shown that the priority reprocessing of VVER spent fuel makes it possible to reduce the americium accumulation by the end of the century by ~8 tons, and the effect is achieved by using freshly separated plutonium with short-term cooling, thus, by priority the americium source is eliminated, without directly handling it. Homogeneous addition of americium to the fuel of fast reactors of the BN-1200 type at a level of ~1% makes it possible to stop accumulation of americium in a two-component energy system by 2070, stabilizing it at a level of ~40 tons in the scenario with priority reprocessing of VVER SNF and ~50 tons in the scenario with priority reprocessing of BN SNF.

Some economic aspects of reducing americium production in a two-component system of thermal and fast reactors

The article analyzes the economic aspects of reducing the production of americium during the transition from a single-component nuclear energy system (NES) based on thermal reactors in an open fuel cycle to a two-component system with thermal and fast reactors in a closed nuclear fuel cycle. Scenarios for the development of these systems in Russia up to the end of the century are modeled. Two methods are considered for reducing the production of americium in a two-component NES with fast sodium reactors. The first method, closing the fuel cycle for plutonium in BN reactors of SFR type, is based on the use of plutonium separated from spent nuclear fuel of thermal reactors with the shortest possible (according to technical specifications) time for MOX fuel preparation and use thus preventing the main part of plutonium-241 from decay into americium. The second way is transmutation of americium. The study was carried out by using the mathematical code CYCLE designed for modeling of the NES with closed nuclear fuel cycle (NFC). The technical and economic data used in the paper was taken from published studies of Russian specialists and materials of European Union specialists presented in the IAEA/INPRO SYNERGIES project. The results of the research show that the efficiency of closing the NFC by using plutonium from thermal reactors in MOX fuel of fast sodium reactors is comparable to the efficiency of the homogeneous transmutation considered in the paper. The combination of the americium accumulation prevention method and transmutation method might significantly reduce the rate of the americium accumulation in a nuclear energy system, but the estimated costs of the considered homogeneous transmutation can significantly worsen the economic performance of sodium fast reactors.

Physical feasibility of minor actinides transmutation in a two-component nuclear energy system in Russia

A transition to a two-component nuclear power structure with a reactor fleet consisting of thermal and fast reactors as envisioned in the Russian nuclear power development strategy to 2050 and outlook to 2100 will require optimal spent nuclear fuel and radioactive waste management solutions. A core issue in this regard is managing the long-lived minor actinide (MA) inventory that affects overall nuclear power ecological safety. The study examines several options for homogenous MA (Am and Np) transmutation using modern calculation codes with MA transmutation rate and material balances taken into account. Results demonstrate that if fast reactor installed capacity reaches 92 GWe by 2100 there would not be any need for dedicated MA-burners as the MA issue would be gradually resolved within the two-component nuclear energy system by the end of the century.

Программный модуль оценки достижения радиологической эквивалентности (РОЗА-РАО)

The main problem of the large-scale development of nuclear energy in the world is the safe dis-posal of accumulated radioactive waste (RW). The hazard of RW at the time of their formation to human health far exceeds the hazard of the source natural uranium ore, after the use of which these wastes were formed. Due to the natural processes of radioactive decay, the hazard of radi-oactive waste decreases over time. The hazard of waste can also be reduced by artificial trans-mutation or incineration of the radionuclides that make up RW composition. For uranium nuclear fuel cycles, the natural reference level of RW hazard is the hazard level of the uranium ore, upon reaching which decisions can be made on the final disposal of RW. The article presents a meth-od for estimating the time of achieving radiological equivalence of the mass of accumulated RW of nuclear energy and the source mass of natural uranium raw materials used in this case. A de-scription of the software module "Radiological support of protection – radioactive waste" (PM ROZA-RAO), which implements this method, is also presented. Radiological equivalence herein refers to the equality of the corresponding radiation risks for the population. The methodology used is determined by the current recommendations of the International Commission on Radio-logical Protection (ICRP) and the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) on the calculation of human radiation risks from internal exposure based on equivalent doses in organs and tissues. The determination of equivalent doses to organs and tissues was based on dose coefficients of radioactive substances provided for widespread use by the United States Environmental Protection Agency (EPA). Calculations by means of the PM ROZA-RAO showed that within the framework of the most likely scenario for the development of two-component nuclear energy system in Russia, for radioactive waste accumulated by 2100, the time of onset of radiological equivalence is less than 100 years (98.8 years). With the help of the developed software module, for the first time in the nuclear industry, the parameters of the processing of exposed nuclear fuel (the composition and activity of radionuclides for controlled storage, combustion and transmutation) and the management of RW can be determined, minimizing the potential radiation risks of the population, which corresponds to the best practice of developed countries in the field of radiation protection.

System levelized fuel cost of electricity generation in a two-component nuclear energy system with a closed uranium-plutonium NFC

The authors propose an approach to the calculation of the levelized unit fuel cost (LUFC) of electricity generation for a fast reactor in a two-component nuclear energy system (NES) with regard for plutonium production. The approach is based on taking into account the additional economic effect, which can be achieved through the sale at the market price of the natural uranium released due to the substitution of thermal reactors by fast reactors with MOX fuel based on the plutonium bred in a fast reactor. This requires considering simultaneously the reactor parts of the fuel cycle for fast and thermal reactors. Relationships have been obtained which connect the key neutronic and fuel characteristics with the NPP and fuel cycle economic performance. The described methodology was used for the computational study of the LUFC for a fast sodium-cooled reactor. Calculations have shown that, in the considered case, taking into account the plutonium production leads to the LUFC reduction by nearly half and, therefore, to a major decrease in the total unit cost of electricity generation (levelized cost of electricity or LCOE).

Comparative study of a stationary two-component nuclear energy system with light water and fast breeder reactors versus one-component one with self-sufficient non-breeding fast neutron reactors

Russia is currently in its initial phase of transitioning to a two-component nuclear power structure, consisting of nuclear power plants with thermal and fast reactors operating in a closed nuclear fuel cycle. Alternative approaches to closing the nuclear fuel cycle often have different assumptions regarding the role of fast reactors in this new structure. They can either imply that fast reactors are self-sufficient and are economically viable in such a way, that they can completely replace existing thermal reactor technology, or that they are used for breeding fuel for the whole nuclear energy system and are essentially complementary to VVER reactors in a permanent two component symbiotic structure. The results of this study show that nuclear power scenarios favoring the development of a large-scale fast reactor fleet with a breeding ratio ∼1 without any additional VVER type component in the nuclear power structure is optimal from an economic standpoint.

Multi-criteria evaluation and ranking of potential scenarios for the development of Russian two-component nuclear energy system with thermal and sodium-cooled fast reactors

The paper presents the results from a multi-criteria comparative evaluation of potential deployment scenarios for Russian nuclear power with thermal and sodium-cooled fast reactors in a closed nuclear fuel cycle (the so-called two-component nuclear energy system). The comparison and the ranking were performed taking into account the recommendations and using the IAEA/INPRO software tools for comparative evaluation of nuclear energy systems, including tools for sensitivity/uncertainty analysis with respect to weighting factors. Ten potential Russian nuclear power deployment scenarios with different shares of thermal and sodium-cooled fast reactors were considered, including options involving the use of MOX fuel in VVER reactors. Eight key indicators were used, estimated as of 2100 and structured into a three-level objectives tree. The comparative evaluation and the ranking were carried out based on the multi-attribute value theory. The model for assessing the key indicators was developed using the IAEA/INPRO MESSAGE-NES energy system planning software tool. The information base for the study was formed by publications of experts from JSC SSC RF-IPPE, NRC Kurchatov Institute and NRNU MEPhI. The presented results show that it is possible to enhance significantly the sustainability of the Russian nuclear energy system, when considering multiple performance indicators, through the intensive deployment of sodium-cooled fast reactors and the transition to a closed nuclear fuel cycle. Tasks have been outlined for the follow-up studies to make it possible to obtain more rigorous conclusions regarding the preferred options for the evolution of a two-component nuclear energy system.

Current status of BN-1200M reactor plant design

• Fast sodium reactors provide the background for two-component nuclear energy system. • The engineering solutions for BN-1200M aim at enhancing safety and performance. • The results of the R&D ensure the competitive level required for BN-1200 power units.

АНАЛИЗ КОНКУРЕНТОСПОСОБНОСТИ ПРОЕКТА ЭНЕРГОБЛОКА БН НОВОГО ПОКОЛЕНИЯ С УЧЁТОМ СИСТЕМНЫХ ТРЕБОВАНИЙ

The development of an energy system, including nuclear, is a long and multi-stage process. The complexity of the process is determined by the deep degree of workforce decomposition at nuclear power facilities, high capital and science intensity of the industry. When assessing the prospects, it is necessary to take into account many significant external factors and uncertainty of the future macroeconomics development trends. In the process of analysis and decision-making on the development of the country's energy system, there are many participants of technological concepts are involved, often with divergent interests. The main task of justifying decisions on the development of the energy industry and, in particular, nuclear power are coordination of interests of all subjects of relations and methodology the formation of mechanisms to ensure the development process. In such an assessment, the ultimate goal is sustainable development. To determine the technological development of the energy system with nuclear and non-nuclear power technologies for the next 5-10 years, it is necessary to assess the long-term prospects of such scenarios. This task requires a multi-criteria approach to analyze the competitiveness of technology using a list of criteria of competitive advantages, combining economic indicators and indicators that characterize safety, environmental impact, risks of implementation, development prospects. This paper discusses the results of multi-criteria system analysis using international assessment tools. The transfer of Russian nuclear power to the two-component nuclear energy system with VVER and BN reactors and the expansion of the international fuel business by providing a full range of NFC services was evaluated using a set of key criteria.

Multi-criteria analysis of the efficiency of scenarios for the development of the Russian nuclear industry in view of the uncertain prospects for the future

Multi-criteria analysis is used in many areas of research where it is required to compare several alternatives according to a selected set of criteria. Of particular interest is the application of this method for a comparative assessment of the efficiency of scenarios for the development of innovative nuclear systems. The article proposes an approach to the computational substantiation of the step-by-step transfer of the Russian nuclear industry to a two-component nuclear energy system (NES) with a centralized closed nuclear fuel cycle (NFC) based on the multi-criteria analysis method. At the same time, consideration is given to options for the development of the domestic nuclear industry in view of the uncertain prospects for the future. Taking into account various trends in the nuclear energy development, the authors identify the following three groups of possible scenarios. The first group includes ‘growing’ scenarios in which the number of units and their total installed capacity grow over time. The second group assumes that after a certain time of growth of the installed capacities, the stationary level will be reached, in which there will be no time-dependent capacity changes. The third group simulates a decrease in the installed nuclear energy capacities in the country after some growth. To select the most preferable ways of technological development and assess the efficiency of a nuclear energy system, a limited set of selection criteria and performance indicators are used, covering the economy, export potential, competitiveness, efficient SNF and RW management, natural uranium consumption, and innovative development potential. An important part of this work was a detailed analysis of the uncertainties in the weights and input data used to derive the criteria.

Possibilities and Features of REMIX Technology as an Initial Stage in the Establishing of a Full-Scale Two-Component Nuclear Energy System

According to the Energy Strategy of Russia for the period up to 2035, the direction of the transition of the nuclear industry is to be headed to a two-component nuclear energy system (NES. In this paper, in order to identify the features of recycling MOX and REMIX fuel and to analyze possible strategies for two-component NES, the changes in the isotopic composition of the plutonium fraction during multiple recycling of fuel has been evaluated, and the consumption of plutonium in various strategies of establishing a two-component NES has been quantitatively assessed. The data obtained can be used for the further analysis of the possibility of developing the two-component NES concept with the involvement of REMIX fuel in the nuclear fuel cycle of thermal reactors at the initial stage of the establishing of a full-scale two-component NES.

Prospects of creation of the two-component nuclear energy system

Possible options of organization of two-component energy system with closed nuclear fuel cycle (CNFC) and new business potential associated with provision of CFC services to foreign customers are examined. Dominating role in the development of nuclear power generation is assigned to VVER reactors with gradually increasing fraction of sodium-cooled fast breeder reactors (FR) incorporated within the joint nuclear fuel cycle operated on MOX-fuel. Components of such energy system perform the following functions: 1. Fast reactors: Generate electric power in base-load mode (possibility of fine tuning of reactor power within limited range (100 – 75 – 100%) is assumed); Utilize waste and/or regenerated uranium for re-fueling power reactors, produce plutonium applicable to the maximum extent for manufacturing MOX-fuel for VVER reactors; Incinerate long-lived highly radioactive wastes – minor actinides separated during reprocessing spent nuclear fuel of FR and VVER reactors. 2. VVER reactors: Generate electricity in compliance with manoeuvrability requirements imposed by the utility company operating the energy system; Utilize MOX-fuel instead of UO2 fuel; Are offered for export with the option of returning SNF back to Russia; Plutonium extracted from VVER spent fuel is used for manufacturing MOX-fuel for SFR. 3. Nuclear fuel cycle facilities: Provide reprocessing of SNF from VVER and SFR with extraction of nuclear materials for recycling; Use depleted or reprocessed uranium and plutonium extracted from spent nuclear fuel for manufacturing MOX-fuel; Provide partitioning of RAW for subsequent utilization of minor actinides and reduction of risks of proliferation of nuclear materials, conditioning and disposal of RAW. Russia possesses capacities for establishing the two-component system with CNFC, as well as the new business approach to rendering CNFC services to foreign customers.

Neutron balance in two-component nuclear energy system

Abstract Most nuclear reactors under operation are thermal reactors, which consume 235U in once-through fuel cycle resulting in ineffective resource utilization and dramatic SNF volume growth. However, sustainable nuclear energy system (NES) should provide NFC closing for all hazardous radionuclides to minimize its life-time within NES and to make risk to be proportional to NES capacity, rather than total energy produced. These two basic principles require enough amount of neutrons for both energy generation and hazardous radionuclides transition to fission products. Therefore, taking into account politic, economic and technological risks and uncertainties, these issues can be solved in terms of two-component NES consisting of both thermal and fast reactors. In this work two methods to estimate neutron balance in NES are discussed. The fist method is based on the analysis of nuclear transformation chain due to radioactive decays and neutron induced reactions. The second one is the most complete one and relies on reaction rates comparison. Neutron balance estimation approach is demonstrated for two-component NES case study.

ИССЛЕДОВАНИЯ ПОТЕНЦИАЛА ДВУХКОМПОНЕНТНОЙ СИСТЕМЫ ЯЭ В РАЗНЫХ УСЛОВИЯХ ЕЁ РАЗВИТИЯ

The aim of the work is to study the possibility of long-term management of a developing or non-developing nuclear power system. The concept of fuel supply control is introduced. Nuclear power systems with different structural organization of generating capacities and a closed nuclear fuel cycle are considered. A comparison is made of these systems in terms of their development potential, ratio between the number of thermal and fast reactors and the possibilities of fuel supply. It is noted that the ratio is determined by the breeding characteristics, the balance of plutonium and natural uranium in the system, as well as the needs for NP development. A feature of the two-component systems of nuclear reactors considered in the work, consisting of thermal reactors of different types and fast reactors BN-1200, is that the SNF stocks of all types of reactors are completely processed during the considered time interval and all the excess separated plutonium is used to manufacture MOX fuel. The requirements to the characteristics of fast reactor breading are put forward. The important role of mastered and promising technologies with the possibility of their flexible adaptation to changes in the nuclear power development scale and rate is emphasized. It is shown that the system including advanced fast neutron sodium reactors having flexible breading can offer increased tolerance to possible changes in the nuclear power development rate. The results of simulation of fuel cycle scenarios for the considered two-component nuclear energy system are presented.

РЕШЕНИЕ ПРОБЛЕМЫ ОЯТ ТЕПЛОВЫХ РЕАКТОРОВ В ДВУХКОМПОНЕНТНОЙ СИСТЕМЕ АТОМНОЙ ЭНЕРГЕТИКИ

To date, several conceptual models of the organization of a two-component nuclear power system have been proposed in the world. This report presents the schematic diagrams of these models, briefly describes their main tasks and prospects for their implementation with time. As a result, based on the preliminary analysis, a model of a two-component nuclear energy system with thermal and fast reactors operating in a single closed nuclear fuel cycle is proposed. Such a model, based on existing and demonstrated technologies of thermal and fast reactors, can solve the main problems of current nuclear power, consisting in the uncontrolled accumulation of SNF volumes of thermal reactors and the inefficient use of natural uranium.

Optimization models of a two-component nuclear energy system with thermal and fast reactors in a closed nuclear fuel cycle

The article presents a description and some illustrative results of the application of two optimization models for a two-component nuclear energy system consisting of thermal and fast reactors in a closed nuclear fuel cycle. These models correspond to two possible options of developing Russian nuclear energy system, which are discussed in the expert community: (1) thermal and fast reactors utilizing uranium and mixed oxide fuel, (2) thermal reactors utilizing uranium oxide fuel and fast reactors utilizing mixed nitride uranium-plutonium fuel. The optimization models elaborated using the IAEA MESSAGE energy planning tool make it possible not only to optimize the nuclear energy system structure according to the economic criterion, taking into account resource and infrastructural constraints, but also to be used as a basis for developing multi-objective, stochastic and robust optimization models of a two-component nuclear energy system. These models were elaborated in full compliance with the recommendations of the IAEA’s PESS and INPRO sections, regarding the specification of nuclear energy systems in MESSAGE. The study is based on publications of experts from NRC “Kurchatov Institute”, JSC “SSC RF-IPPE”, ITCP “Proryv”, JSC “NIKIET”. The presented results demonstrate the characteristic structural features of a two-component nuclear energy system for conservative assumptions in order to illustrate the capabilities of the developed optimization models. Consideration is also given to the economic feasibility of a technologically diversified nuclear energy structure providing the possibility of forming on its base a robust system in the future. It has been demonstrated that given the current uncertainties in the costs of nuclear fuel cycle services and reactor technologies, it is impossible at the moment to make a reasonable conclusion regarding the greatest attractiveness of a particular option in terms of the economic performance.

Оптимизационные модели двухкомпонентной ядерной энергетики с тепловыми и быстрыми реакторами в замкнутом ядерном топливном цикле

Оптимизационные модели двухкомпонентной ядерной энергетики с тепловыми и быстрыми реакторами в замкнутом ядерном топливном цикле