Actinide Transmutation in PWRs Using CONFU Assemblies
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Expansion of domestic use of nuclear power to provide energy security and environmental sustainability requires minimization of the nuclear waste. To achieve this goal in the short term, transmutation of transuranic (TRU) elements in COmbined Non-Fertile and UO2 (CONFU) Generation-III pressurized water reactor (PWR) assemblies is evaluated. These assemblies are composed of a mix of standard UO2 fuel pins and pins made of recycled TRU in an inert matrix and are designed to fit in currently deployed PWRs. Previous studies have shown the feasibility of a CONFU-Equilibrium (CONFU-E) assembly design with a net TRU balance between production and destruction and a CONFU-Burndown (CONFU-B) assembly design with net destruction of TRU coming from several reactors. In this paper, a CONFU-self-Contained (CONFU-C) assembly is shown to achieve net TRU destruction in a self-contained TRU multirecycling system. Both the CONFU-B and CONFU-C designs are presented in this paper in detail.For these designs a detailed assembly-level neutronic analysis has been performed using CASMO-4 to investigate cycle length, TRU management performance, and key reactor reactivity parameters, along with detailed intraassembly power peaking factors (IAPPFs). Various fuel mixing schemes and cooling times were evaluated. Using the IAPPF results, a full core thermal-hydraulic analysis using VIPRE was performed to validate thermal margins, and a loss-of-coolant-accident event was assessed using RELAP5. Based on the TRU management characteristics of these designs, metrics were developed to reflect the material handling difficulties of the multirecycled fuel, along with its repository impact. These parameters were compared to a standard once-through UO2 cycle, along with other Pu or TRU multirecycling schemes [mixed oxide with enriched uranium (MOX-UE) and COmbustible Recyclage A ILot (CORAIL)]. Finally, an economic analysis has been conducted to compare the fuel cycle cost (FCC) associated with these designs.TRU management results of CONFU-B and CONFU-C showed a net TRU destruction of 2 to 20 kg/TW·h(electric) generated, with an FCC of 12 to 15 mills/kW·h(electric), depending on the mixing strategy and cooling time chosen. Reactor control parameters and thermal margins were found to be comparable to an all-UO2 assembly. While both designs offer significant repository benefits, the accumulation of minor actinides may limit the practicality of fuel multirecycling.Keywords:
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The chemistry of the actinides is still a fruitful area of research more than half a century after the discovery of plutonium by Seaborg et al. However, the fields of interest have shifted from the pioneering work establishing the basic inorganic and extraction chemistry to areas that are more focused on environmental aspects and long-term storage of transuranium materials. The hydrolysis behavior of actinide cations is basic to all environmental studies. This paper reviews recent work in this area.
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In the view of transmutation of transuranium (TRU) elements, molten salt fast reactors (MSFRs) offer certain advantages compared to solid fuelled reactor types like sodium cooled fast reactors (SFRs). In the first part these advantages are discussed in comparison with the SFR technology, and the research challenges are analyzed. In the second part cycle studies for the MSFR are given for different configurations--a core with U-238 fertile, a fertile free core, and a core with Th-232 as fertile material. For all cases, the transmutation potential is determined and efficient transmutation performance for the case with thorium as a fertile material as well as for the fertile free case is demonstrated and the individual advantages are discussed. The time evolution of different important isotopes is analyzed. In the third part a strategy for the optimization of the transmutation efficiency is developed. The final aim is dictated by the phase out decision of the German government, which requests to put the focus on the determination of the maximal transmutation efficiency and on an as much as possible reduced leftover of transuranium elements at the end of the reactor life. This minimal leftover is achieved by a two step procedure of a first transmuter operation phase followed by a second deep burning phase. There the U-233, which is bred in the blanket of the core consisting of thorium containing salt, is used as feed. It is demonstrated, that transmutation rates up to more than 90% can be achieved for all transuranium isotopes, while the production of undesired high elements like californium is very limited. Additionally, the adaptations needed for the simulation of a MSFR, and the used tool HELIOS 1.10 is described.
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was for the separation of Am and Cm. The elution behavior of small amounts of transuranium elements was also studied in the classical EDTA rare earth cation exchange system. Separation of the elements Am, Cm, Bk, and Cf was obtained, each being eluted at the overlap region of their respective rare earth homolog and the heavier adjacert rare earth. The techniques are also being considered for the separation of macro amounts of transuranium elemerts since neither requires high concentrations of acid or light elemert salts, and in the EDTA case dilution of the actinide elements on the column is attained by the presence of inactive rare earths. (auth)
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Coprocessing is conceived as a method in which the plutonium is never available in a separate stream. In addition, it is possible to keep the transuranium actinides with the plutonium and uranium streams rather than allowing them to leave with the fission products and terminate in the high level waste. The recovered actinide product can be reconstructed as a fuel and recycled in light water reactors. But even after nine cycles the fuel composition does not reach equilibrium. Since the plutonium is never separated from other actinides, the potential of proliferation can be reduced.
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Results are presented of a conceptual design study of a transuranium (TRU) fuel assembly consisting of only plutonium and minor actinide (MA) oxides for transmutation of MAs in a pressurized water reactor (PWR). The average plutonium content of the TRU transmutation fuel assembly in this study is 38 wt% Putot, and the average MA content is 62 wt%. The fuel rod arrangement and the plutonium content are optimized to suppress the internal power peaking in the fuel assembly. Core characteristics and TRU inventory change are evaluated for an 870-MW(electric) PWR core loaded heterogeneously with a few TRU transmutation fuel assemblies. The maximum loading of the TRU transmutation fuel is limited to nine assemblies to maintain a negative moderator temperature coefficient at the beginning of cycle, while satisfying a cycle length of 15.2 GWd/tonne U. By loading nine TRU transmutation fuel assemblies, the total MA inventory in the core decreases by ∼65 kg/cycle, which is approximately equivalent to that produced from three UO2 reactors. The heterogeneous loading of a few fuel assemblies with highly concentrated TRU in a PWR is found to be feasible for the effective transmutation of MAs while maintaining reactor safety.
Nuclear transmutation
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