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Ternary alloy fuel will be used as driver fuel for future fast reactors. Reprocessing of this spent alloy fuels will be carried out by pyrochemical reprocessing which is based on molten salt electrorefining at high temperature. During electrorefining, fission products get accumulated in the electrolyte along with some actinides in the form of their chlorides. The presence of fission products in the salt will add to the radioactivity levels and hence have to be stripped off. Melt crystallization is pursued to remove fission products from contaminated salt and to reuse the purified salt for electrorefining. Numerical modeling and experimental studies on tracking the phases during solidification of molten sodium nitrate salt were carried out. The numerical predictions closely matched with the experimental results. A resistance measurement technique was developed to accurately track the solidification interface so as to validate the numerical predictions. [ABSTRACT FROM AUTHOR]

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With the increasing interest in small modular reactors or microreactors, developers are working to design and submit licensing approval requests of U–10Zr-fueled fast reactors. The developers and their proponents cite prior metal fuel experience (worldwide, but U.S. experience in particular for many developers) as the motivation and justification for their reactor concepts. The experience with metal fuel deployment in sodium-cooled fast reactors as well as the underlying irradiation testing database, provide a suitable basis for analytically justifying the use of metal fuel in new reactors. The evolution of metal fuel design and capability illustrates the importance of key fuel design parameters to consider in new applications of the prior experience: fuel smeared density, plenum-to-fuel volume ratio, the ratio of cladding radius to thickness, fuel composition, and cladding and duct materials. In-service operating and deployment conditions to be considered include fuel linear heat generation rate, fuel temperature, cladding temperature, peak burnup and peak fast fluence. Fuel designs and in-service conditions that are bounded by the database and experience are most easily addressed, but deviations from those previous parameters and conditions can be addressed by considering impacts on previously established behavior and applying other mitigating conservatisms, as appropriate. The authors recommend any new deployment proceed with fuel surveillance and monitoring to mitigate risk, application of conservative measures to address uncertainties, and a fuel qualification program that addresses a range of in-service operating conditions with production fuel. The work reported should be of interest to students and regulators unfamiliar with metal fuel in fast reactors. • Metal fuel deployment in SFRs can be technically supported by prior experience. • Evolution of metal fuel design illustrates the importance of fuel design parameters to consider. • Fuel designs bounded by the database and experience are most easily addressed. • Deviations from previous designs can be addressed by considering impacts and mitigations. • New deployment should include fuel surveillance and monitoring to mitigate risk. [ABSTRACT FROM AUTHOR]

• An SFR-based Small Modular Reactor (SMR), SALUS-100 is developed by KAERI. • The reactor features incorporate a long fuel-cycle core concept with a metallic alloy fuel. • The inherent safety and reliability features focuses on preventing severe accidents. • The key research and development activities for technology advancements are introduced. • The innovative design of SALUS-100 offers diverse applications in future SMR markets. The paper introduces the innovative development of an SFR-based Small Modular Reactor (SMR) known as SALUS-100, with a 100 MWe electrical output, developed by KAERI. This innovative design, derived from the previous TRU transmutation burner SFR concept, represents a significant step forward in establishing a new model for SMRs and offers diverse applications, including on– and off-grid electricity generation, district heating, and industrial heat supply. The reactor features of SALUS-100 incorporate an integrated pool-type primary system configuration and a long fuel-cycle core concept with a metallic alloy nuclear fuel. Its design concept prioritizes preventing severe accidents by capitalizing on the inherent safety and reliability features achieved through emphasizing passive design characteristics. The paper describes the engineering design and safety analyses of SALUS-100, highlighting advanced design concepts in reactor core, fuel, materials, and systems. Additionally, the key research and development endeavors, focusing on vital areas such as enhancing system design capability, validating designs, demonstrating safety, and innovating in metal fuel technology, are briefly discussed, emphasizing the potential of SALUS-100 in revolutionizing the SMR market and utilizing efficient nuclear energy in the future. [ABSTRACT FROM AUTHOR]

Ceramic plasma-spray coatings with single and multiple layers have been applied to melting crucible material substrates for the development of a reusable crucible for the fabrication of metal fuel slugs for a sodium-cooled fast reactor (SFR). Various combinations of vacuum plasma-spray (VPS) coated specimens have been applied to investigate the bonding effect on the crucible substrate and the interaction between the metal fuel and the VPS-coated crucible substrate. All VPS-coated methods maintained a sound coating state after a dipping test with U-10 wt%Zr melt. A single coating of a Y2O3(150) layer and a double coating layer of TaC(50)- Y2O3(100) showed some degradation or penetration, respectively, after 2 cycles of dipping test with an aggressive U-10 wt%Zr-5 wt%RE melt. Injection castings of U-10 wt%Zr and U-10 wt%Zr-5 wt%RE fuel slugs were also conducted to investigate the feasibility of a reusable melting crucible of metal fuel slugs. The U-10 wt% Zr fuel slugs were soundly fabricated without significant interactions of the graphite crucibles; however, the U-10 wt%Zr-5 wt%RE fuel slugs had some degradation or penetration, respectively, after injection casting. [ABSTRACT FROM AUTHOR]

• Molten metal fuel was pressure injected into the coolant channel with pressure. • The Real Time X-ray Video System was able to capture the metal fuel relocation behavior. • The injected metal fuel was simultaneously dispersed downward and upward. • Relocation of metal fuels can potentially result in negative reactivity feedback effects. A pool-type sodium-cooled fast reactor (SFR) using metal fuels has a number of inherent safety features that can support benign consequences for design basis accidents (DBAs). Even in postulated severe accident conditions, the core is designed to remain under sub-critical condition in a passive coolable geometry. In case of the postulated severe accidents in SFRs, fuel relocation in the core region along the coolant channel is an important negative reactivity feedback factor that lowers the reactor power level and consequently eliminates the possibility of recriticality. Therefore, understanding the relocation behavior of fuels and the coolability of the relocated fuels in the postulated severe accident is one of the most important factors in the safety assessment of SFRs. In the present study, the relocation behavior of the metal fuel in a pin bundle geometry was investigated by injecting the metal fuels into the coolant channels with pressure. The first metal fuel relocation with pressure injection (RPI-1) experiment showed that many of the metal fuels levitated to upper plenum. In case of RPI-2 experiment, the Real Time X-ray Video System (RTXVS) was constructed and used to obtain a real time X-ray video of the experiment. This real time X-ray video clearly showed the relocation behavior of the pressure injected metallic uranium in the sodium coolant channel. Through this video, it was confirmed that part of the fuel was dispersed downward and part of the fuel was dispersed upward, and the relocation behavior of the injected fuel proceeded simultaneously in the downward and upward directions. It can be concluded that in case of pressure injection of the metallic fuel, there is a possibility that the metallic fuel can be quickly removed from the core region, resulting in a negative reactivity feedback effect. [ABSTRACT FROM AUTHOR]

The purpose of this study was to demonstrate the neutronic feasibility and competitive fuel cycle economics of sodium fast reactors operating with uranium metal (UZr)fuel on a once-through fuel cycle. Uranium startup fast reactors (USFRs) decouple their deployment from that of expensive reprocessing and recycle facilities. This could facilitate and speed up the deployment of conventional fast reactors, which, in their traditional designs, heavily depend on the availability of reprocessing facilities for transuranic fuel production. The uranium requirement and fuel cycle cost of studied USFR core designs are calculated to be comparable to those of typical light water reactors. The main design constraint is the fast neutron fluence imposed on the cladding material, which is required to be below 5.0 x 1023 n/cm² even for advanced oxide dispersion strengthened steels. Therefore, moderators need to be inserted in the fuel assemblies to lower the fast neutron flux so that the fuel residence time limited by neutron fluence can be extended to match the reactivity limited fuel residence time. In this study, magnesium oxide is used for reflectors as well as for the moderator. [ABSTRACT FROM AUTHOR]

Abstract: Minor actinide recycling in a fuel cycle is a potential technology to minimize the environmental radioactivity burden in waste disposal in the fast reactor era after 2050. Pyroprocessing technology with metal electrorefining expects that no additional process is required to separate minor actinides and short- cooled fuels can be treated due to no-use of organic solvent that degrades by radiation. Pyroprocessing has been explored for metal fuel cycle and nitride fuel cycle in Japan. Metal fuel fast reactor, which can achieve a high breeding ratio over 1.3, and its fuel cycle is a compact system by integrating pyroprocessing. Oxide fuel can be also treated by converting to metals by reduction. Separation of transuranium elements from high level liquid waste originating from aqueous reprocessing has been challenged. Verification of the process and development of an engineering scale device are the current interests for study. In addition, irradiation study of metal fuel with minor actinides currently much advances from the point of fundamental investigation. Accelerator-driven system (ADS) for transmutation of minor actinides is integrated with pyroprocessing for recycling system. The denitriding at anode and azotizing at cathode together with electrorefining have been fundamentally studied by use of plutonium. [Copyright &y& Elsevier]

A small modular fast reactor is thought to be one of the solutions to meet future energy security with low research and development (R&D) risk. In the present study, a new small reactor concept for a modular power source is proposed. A minimum configuration with a compact reactor vessel, one-loop main cooling system, and simple fuel-handling system is adopted, enhancing cost reduction. In the present one-loop main cooling system, there are double electromagnetic pumps in series considering pump failure. To show the reliability of the one-loop main cooling system, pipe-break transient analyses have been carried out. In addition, the construction cost of a set of a first-of-a-kind reactor and small fuel cycle plant is evaluated to show the economical potential at the demonstration stage. A major advantage of the present concept is that the demonstration reactor and fuel cycle plant can be directly appropriated for first commercial modules and the power plant can easily increase its capacity adding reactor and electrorefiner modules. Commercialization of the nuclear fuel cycle fusing the present modular concept is thought to reduce R&D risk since the total budget for demonstration is small and the facilities for demonstration are directly appropriated to commercial use. [ABSTRACT FROM AUTHOR]