Thermal conductivity of MOX with simulated fission products

Horii, Yuta ; Hirooka, Shun ; Kato, Masato   ; Uno, Hiroki*; Ogasawara, Masahiro*; Tamura, Tetsuya*; Yamada, Tadahisa*

The low-decontaminated fuel which contains significant amount of fission products (FPs) has been investigated as a fuel for the advanced fast reactor cycle. In this cycle, it is expected to reduce reprocessing cost and strengthen nuclear proliferation resistance of recovered plutonium accompanying high radiation dose FPs. However, FPs could affect on thermal properties of MOX. In particular, thermal conductivity is one of the most important properties for fuel design. Many studies have been reported on the thermal conductivity of MOX that evaluated the effect of plutonium and minor actinide (Am, Np) contents. However, the number of studies on the thermal conductivity of MOX containing FPs are limited; only Nd, Eu and Zr. In this study, thermal conductivity of MOX including NdO and SmO, which are expected to be the main FPs remaining as solid solutions in low-decontaminated fuel, was evaluated by measuring thermal diffusivity of sintered pellet. NdO powder and SmO powder was added into raw MOX powder of 20% plutonium content and they were milled by ball-mill. Sintered pellets were obtained by pressing and sintering this powder. The thermal diffusivities were measured by a laser flash method from 973 K to 1673 K at every 100 K. The thermal conductivities up to 1400K are expressed by classical phonon transport model as =(A+BT) where A(mK/W)=2.010+4.810C and B(m/W)=2.510. This means the thermal conductivity decreased with enhancement of phonon scattering by adding NdO/SmO, similar to the previous studies.