Study on thermal behavior of the obstructed region in a bottom column of annular fuel

Naganuma, Masayuki  ; Maeda, Seiichiro ; Nemoto, Junichi*

In JSFR, annular fuel is planned to be adopted because of the superior features such as easiness in fabrication and capability for high linear power and high burnup. On the other hand, the annular fuel has some issues. One of the important issues is central void blockage by falling of fuel debris from annular surface. The blockage induces local increases of linear power and smear density due to deposition of fuel material, affecting the mechanical and thermal integrities. Thus, it is necessary to evaluate effects of the blockage on mechanical and thermal integrities for adoption of the annular fuel. For investigation of the blockage, JAEA have conducted irradiation tests of annular fuel in EBR-II as a collaborative program with ANL in the 80s, and detailed PIEs had been conducted. In this study, the effect on thermal integrity was picked up, and the thermal model that can estimate the PIE results (such as the fuel restructuring around the blockage region) appropriately was evaluated.