Sustainability-oriented prioritization of nuclear fuel cycle transitions in China:a holistic MCDM framework under uncertainties

A sustainability-oriented assessment of the nuclear energy system can provide informative and convincing decision-making support for nuclear development strategies in China.In our previous study,four authentic nuclear fuel cycle(NFC)transi-tion scenarios were proposed,featuring different development stages and exhibiting distinct environmental,economic,and technical characteristics.However,because of the multiple and often conflicting criteria embedded therein,determining the top-priority NFC alternative for a sustainability orientation remains challenging.To address this issue,this study proposed a novel hybrid multi-criteria decision-making framework comprising fuzzy AHP,PROMETHEE GAIA,and MOORA.Initially,an improved fuzzy AHP weighting model was developed to determine criteria weights under uncertainty and investigate the influence of various weight aggregation and defuzzification approaches.Subsequently,PROMETHEE GAIA was used to address conflicts among the criteria and prioritize alternatives on a visualized k-dimensional GAIA plane.As a result,the alternative for direct recycling PWR spent fuel in fast reactors is considered the most sustainable.Furthermore,a sensitivity analysis was conducted to examine the influence of criteria weight variation and validate the screening results.Finally,using MOORA,some significant optimization ideas and valuable insights were provided to support decision-makers in shaping nuclear development strategies.

Preliminary analysis of fuel cycle performance for a small modular heavy water-moderated thorium molten salt reactor

Heavy water-moderated molten salt reactors(HWMSRs)are novel molten salt reactors that adopt heavy water rather than graphite as the moderator while employing liquid fuel.Owing to the high moderating ratio of the heavy water moderator and the utilization of liquid fuel,HWMSRs can achieve a high neutron economy.In this study,a large-scale small modular HWMSR with a thermal power of 500 MWth was proposed and studied.The criticality of the core was evaluated using an in-house critical search calculation code(CSCC),which was developed based on Standardized Computer Analyses for Licensing Evaluation,version 6.1.The preliminary fuel cycle performances(initial conversion ratio(CR),initialfissile fuel loading mass,and temperature coefficient)were investigated by varying the lattice pitch(P)and the molten salt volume fraction(VF).The results demonstrate that the temperature coefficient can be negative over the range of investigated Ps and VFs for both 233U-Th and LEU-Th fuels.A core with a P of 20 cm and a VF of 20%is recommended for 233U-Th and LEU-Th fuels to achieve a high performance of initial CR and fuel loading.Regarding TRU-Th fuel,a core with a smaller P(~5 cm)and larger VF(~24%)is recommended to obtain a negative temperature coefficient.

Nuclear Power in the Fuel and Energy Complex of Ukraine

Nuclear power is a powerful and effective energy branch in Ukraine. There are currently 4 active nuclear power stations （NPS） and 13 operational VVER energy units, producing a total power of 11880 MW, in the country. According to the data collected from the International Agency of Nuclear-Power Energy, Ukraine is in seventh place for the largest supply of uranium on the planet. The use of nuclear power in Ukraine includes： extraction and processing uranium ore, production of UF6, production of zirconia rental and purveyances from a zirconia alloy, production of heat-radiating collections, storage of exhaust nuclear fuel and nuclear wastes. The realisation of uranium isotopic enrichment is the main problem in the structure of organisation in nuclear fuel production in Ukraine. This country has a unique station, non-operative Chemobyl NPS, where different types of wastes are located. Two factories are currently being built there in order to process the liquid and solid radio-active wastes. In perspective, Ukrainian nuclear-power energy will be enriched with new nuclear-power units and security systems to ensure safe manufacturing.

Tianwan sets a national record for continuous and safe operation in first fuel cycle

On May 1st, China National Nuclear Corporation(CNNC) announced in Beijing that unit 1 and unit 2 ofTianwan Nuclear Power Plant cooperatively constructedby China and Russia have completed in succession thefirst fuel cycle operation continuously and safely. It is

Safety and effective developing nuclear power to realize green and low-carbon development

This paper analyzes the role of nuclear power of China's energy structure and industry system. Comparing with other renewable energy the nuclear power chain has very low greenhouse gas emission, so it will play more important role in China's low-carbon economy. The paper also discussed the necessity of nuclear power development to achieve emission reduction, energy structure adjustment, nuclear power safety,environmental protection, enhancement of nuclear power technology, nuclear waste treatment, and disposal, as well as nuclear power plant decommissioning. Based on the safety record and situation of the existing power plants in China, the current status of the development of world nuclear power technology, and the features of the independently designed advanced power plants in China, this paper aims to demonstrate the safety of nuclear power. A nuclear power plant will not cause harm either to the environment and nor to the public according to the real data of radioactivity release, which are obtained from an operational nuclear plant. The development of nuclear power technology can enhance the safety of nuclear power. Further, this paper discusses issues related to the nuclear fuel cycle, the treatment, and disposal strategies of nuclear waste, and the decommissioning of a nuclear power plant, all of which are issues of public concern.

Burnup optimization of once-through molten salt reactors using enriched uranium and thorium

The advantages of once-through molten salt reactors include readily available fuel,low nuclear proliferation risk,and low technical difficulty.It is potentially the most easily commercialized fuel cycle mode for molten salt reactors.However,there are some problems in the parameter selection of once-through molten salt reactors,and the relevant burnup optimization work requires further analysis.This study examined once-through graphitemoderated molten salt reactor using enriched uranium and thorium.The fuel volume fraction(VF),initial heavy nuclei concentration(HN_(0)),feeding uranium enrichment(E_(FU)),volume of the reactor core,and fuel type were changed to obtain the optimal conditions for burnup.We found an optimal region for VF and HN_(0) in each scheme,and the location and size of the optimal region changed with the degree of E_(FU),core volume,and fuel type.The recommended core schemes provide a reference for the core design of a once-through molten salt reactor.

Americium Transmutation in the SVBR-100 Reactor

One of the postponed problems of nuclear power (NP) is the problem of the management of long-lived radioactive waste (RAW), and, first of all, with minor actinides (MA), of which americium-241 is the most difficult. The aim of this work is to study the efficiency of americium transmutation in a fast reactor with a heavy liquid metal coolant lead-bismuth eutectic alloy. The article presents the results of calculations of the transmutation of americium in the SVBR-100 reactor using standard uranium oxide fuel with the addition of americium-241. The obtained values of the rate of transmutation of americium are compared with similar values for the SVBR-100 reactors on MOX-fuel and in the BN-800 reactor.

Prospects of Technological Improvement of Nuclear and Environmental Safety of World Energy

Today, the most urgent problem of the existing and future nuclear power industry is to ensure the nuclear and environmental safety of the operation of nuclear power reactor units (NPPs) and nuclear power plants (NPPs). It is solved thanks to the application of deeply echeloned protection and an anti-accident complex of methods and means for effective control of the operation of active reactor zones (AZR). However, the danger of existing NPPs in the world from time to time manifests itself in the form of severe post-project accidents and catastrophes with the release into the environment of a significant amount of radioactive materials dangerous for all living things. The results of the analysis show that the unconditional fulfillment of the main requirements of nuclear environmental safety and biocompatibility is possible only in the so-called wave nuclear reactor of the G-V generation, which, unlike reactors of the previous generations III, II+ and IV, does not require supercritical loading of the core with nuclear fuel. In the active zone of this reactor, nuclear-physical processes governed by physical law are implemented, which exclude the operator’s participation in regulating the reactivity of the reactor’s active zone, which makes it the reactor with the highest level of nuclear and environmental safety today, which is based on the principles of so-called internal safety, free from the human factor. The possibility of burning nuclear fuel based on U238 and Th232 in it expands the reserves of energetic nuclear fuel almost to inexhaustibility. The technology of nuclear reactors of the G5 generation through the secondary use of spent irradiated nuclear fuel (SNF) for the production of energy and energy raw materials with simultaneous burning of it to an environmentally safe state is able to quickly reduce the available stocks and further production of dangerous SNF, guarantee the nuclear and environmental safety of NPPs with reactors G5 and to technologically make nuclear post-project accidents and disasters impossible at the level of physical law with the complete elimination of the human factor.

Resourceability on nuclear fuel cycle by transmutation approach

A resourceability on nuclear fuel cycle by transmutation of fission products in the spent fuel of nuclear reactors is discussed in this paper to investigate the feasibility of ＂creation and utilization＂ of Apr6s ORIENT from Adv.-ORIENT cycle, in which chemical ＂separation and utilization＂ of nuclear rare metals （platinum group metals, Mo, Tc, rare earth, etc.） has been proposed since FY2006. Apr6s ORIENT research program was newly initiated in FY2011 for nuclear transmutation of fission products into stable or short-lived highly-valuable elements. In the resourceability of rare earth metals from fission products, non-radioactive Nd and Dy can be created from Pr and Tb, respectively, by transmutation. Especially, the Dy creation has relatively high feasibility of about 10-20 %/y in creation rate. A proper moderation of neutrons in blanket of fast reactors may be required to provide a high creation rate of La from Ba. In light platinum group metals, non-radioactive Ru can be created from Tc by transmutation, of which creation rate is about 4-5 %/y in blanket of fast reactors. Pd created from Rh is almost non-radioactively depending on the isotope fraction of 107pd. Rh creation from Ru is not feasible under the neutron irradiation of typical nuclear reactors.

Thorium-Based Fuel Cycles in the Modular High Temperature Reactor

Large stockpiles of civil-grade as well as weapons-grade plutonium have been accumulated in the world from nuclear power or other programs of different countries. One alternative for the management of the plutonium is to incinerate it in the high temperature reactor （HTR）. The thorium-based fuel cycle was studied in the modular HTR to reduce weapons-grade plutonium stockpiles, while producing no additional plutonium or other transuranic elements. Three thorium-uranium fuel cycles were also investigated. The thorium absorption cross sections of the resolved and unresolved resonances were generated using the ZUTDGL code based on existing resonance data. The equilibrium core of the modular HTR was calculated and analyzed by means of the code VSOP＇94. The results show that the modular HTR can incinerate most of the initially loaded plutonium amounting to about 95.3% net 239pu for weapons-grade plutonium and can effectively utilize the uranium and thorium in the thorium-uranium fuel cycles.

Feasibility of Burning Civilian Grade Pu in the Modular HTR with Th Fuel Cycle

The Modular High Temperature Gas-Cooled Reactor (HTR) can be used to burn plutonium fuel to reduce Pu stockpiles because of its inherent safety characteristics and ability to burn a variety of fuel mixtures. The equilibrium core is calculated and analyzed for Pu enriched fuel. Fuel spheres with 7g heavy metal including the civilian grade Pu and thorium are loaded into the reactor. An enrichment of 11% is chosen to provide the desired equilibrium core reactivity. The fuel and moderator temperature coefficients are both negative. The maximum fuel element temperature during normal operation and during a loss of coolant accident is less than 1500℃. 92% of 239 Pu will be burnt during nomal operation. Therefore, a thorium fuel cycle in the modular HTR is an effective method for burning civilian grade plutonium.

E-pO^(2–) diagram for rare earth elements in molten salt

Electro-reduction of spent nuclear oxide fuels in molten salt was the key step of pyroprocessing for oxide fuel treatment. In the present study, the E-pO^2- diagram for rare earth elements in molten Li Cl-KCl at 450 oC were developed based available experimental data. E-pO^2- diagrams could show the stability of each chemical compound in the salt, and therefore, the diagrams could be applied to predict experimental conditions for electro-reduction of spent nuclear fuel efficiently. Compared with the available E-pO^2-diagrams, the present study concerned the activity coefficient of the element studied in the molten salt in all reactions, which made the diagram be more reliable and accurate.