Application of pore former for density control of TRU nitride pellets

Takaki, Seiya; Otobe, Haruyoshi; Takano, Masahide

no journal, , 

Nitride fuel with ZrN inert matrix has been studied as a candidate for the transmutation fuel of minor actinides (MA) in an accelerator-driven system (ADS). The pellet densities were designed to be about 85 % of the theoretical density to ensure a margin against swelling, but a dense microstructure is required. One of promising method of controlling the sintering density is by using a pore former (PF). This study aims to investigate the appropriate PF using (Dy,Zr)N as a surrogate nitride fuel with MA and evaluate its technical feasibility through sintering tests of (TRU,Zr)N (TRU: Np, Pu). Three types of polymer particles (A: stearic acid, B: polyester, C: polyethylene) as PF were mixed with (Dy,Zr)N powder respectively, and then the mixed powder was compacted and sintered to obtain the pellets. The dependence of oxygen and carbon impurity concentrations on PF type and concentration was not clear, whereas the pellets mixed with A had numerous cracks formed perpendicular to the direction of compaction. From the above, B and C were used as candidate PFs in the demonstration tests of (TRU,Zr)N. The sintered pellets were prepared using (TRU,Zr)N powder mixed with selected PFs. The sintered density of the pellets decreased linearly with PFs addition concentration as in the (Dy,Zr)N tests, and the almost no clacks occurred in the pellets. We can therefore conclude that B and C are fully applicable to control the sintering density of MA-containing pellets for ADS.

Exploring magnetic order in actinide dioxides using adiabatic connection fluctuation dissipation theory

Nakamura, Hiroki; Machida, Masahiko

no journal, , 

One of the most reliable simulation methods for predicting the physical properties of actinide dioxides is density functional theory (DFT). DFT can evaluate various physical properties including magnetism, but does not always succeed in predicting the correct magnetic ordering. For example, although plutonium dioxide is nonmagnetic, the ground state calculated by DFT is magnetic even if the strong correlation effect and spin-orbit coupling are considered. To address this issue, we adopt adiabatic connection fluctuation dissipation theory (ACFDT), which is expected to be more effective for actinides dioxide since it considers higher-order correlation and exchange interaction effects more efficiently. In this paper, we calculated energy for PuO and UO with ACFDT for various magnetic orders and evaluated the ground-state magnetic order. We found that ACFDT is more likely to predict the correct magnetic order than DFT. Thus, it is expected that ACFDT can improve the accuracy in the prediction of the physical properties of fuel materials.

Measurement and modelling of properties of (U,Pu)O doped with simulated FP elements

Hirooka, Shun; Horii, Yuta; Vauchy, R.; Hayashizaki, Kohei; Owada, Hideaki*; Furusawa, Naoya*; Yamada, Tadahisa*; Sunaoshi, Takeo*; Uno, Hiroki*; Naganuma, Masayuki; et al.

no journal, , 

Synthesis of zirconolite with U-Ce mixed oxide for stable storage of nuclear fuel materials

Hayashizaki, Kohei; Hirooka, Shun; Akiyama, Daisuke*; Kirishima, Akira*; Saito, Kosuke

no journal, , 

Thermal validation of a multi-dimensional analysis Code BISON for MOX; Okami

Ozawa, Takayuki; Hirooka, Shun; Kamei, Miho; Oki, Takumi; Novascone, S.*; Medvedev, P.*

no journal, , 

It is well known that the most typical behavior of MOX fuels irradiated in a fast reactor (FR) would be radial pore migration along the temperature gradient causing fuel restructuring with radial density distribution and finally central void formation. In order to analyze the fuel restructuring behavior, MOX fuel properties and a pore migration model that depends on fuel composition were applied in a multi-dimensional analysis code BISON with specialized MOX features, called Okami, which was developed in cooperation with INL. Since the fuel restructuring takes place at the early stage of irradiation and fuel temperature strongly affects the pore migration behavior, the fuel temperature calculation in Okami was validated by using in-pile fuel center temperature obtained in the INstrumented Test Assembly (INTA) tests, INTA-1 and INTA-2, and power-to-melt (PTM) test, B5D-2, in Joyo. The fuel restructuring behavior calculation in Okami was validated by using Am-MOX irradiation test, B14, in Joyo, in which O/M dependence on central void formation at the early stage of irradiation could be observed. As a result of thermal validation for fuel temperature and fuel restructuring calculations, Okami could precisely represent the MOX fuel behavior at the early stage of irradiation in FR.

Development status and plan of MOX fuel production technology for SFR in Japan

Ishii, Katsunori; Sano, Yuichi; Kaito, Takeji; Takeuchi, Masayuki

no journal, , 

In Japan, research has been conducted on various fast reactor technologies, such as sodium cooling, light water cooling, and thorium molten salt cooling, in accordance with the Strategic Roadmap for Fast Reactor Development, which was approved by the Cabinet in 2018. As a result, sodium cooling was evaluated as the most promising from the perspective of technological maturity and marketability. The roadmap was revised in 2022 to clarify future development policies, etc., and to specify the image of the development target and the progress method. According to the revised roadmap, the selection of fuel technology (oxide fuel and metal fuel) is scheduled to be made around 2026, and various evaluations necessary for comparative selection will be carried out. Regarding MOX fuel fabrication technology, technological development will be focused on technologies that are in a low development stage. This report introduces the development status of MOX fuel fabrication technology, the challenges for practical application, and an overview of future plans.