DESIGN STUDY ON A FAST REACTOR METAL FUEL ATTAINING VERY HIGH BURNUP

摘要

Innovative fuel design measures to attain a much higher burnup than that obtained using the conventional concept were investigated for a fast reactor (FR) metal fuel. Considering the typical mechanism of metal fuel degradation, three innovative design measures were proposed: (a) a decrease in plenum pressure by adopting the fission gas vent design, (b) prevention of fuel-cladding chemical interaction by lining the cladding inner wall, and (c) mitigation of fuel-cladding mechanical interaction by reducing the fuel smear density. The effects of these design measures on increasing the burnup were analyzed with ALFUS, an irradiation behavior analysis code for FR metal fuels. The ALFUS analysis revealed that a very high burnup of ＞40 at. % can be attained under the conventional design criteria for securing fuel integrity by applying these innovative measures. Neutronic analysis of a metal fuel core employing these design measures indicated that a high burnup of ＞40 at. % at the assembly peak can be attained while suppressing the burnup reactivity swing to almost the same level as that of conventional cores with normal burnup through the use of a minor actinide-containing fuel.