IRRADIATION BEHAVIOR OF HTGR COATED PARTICLE FUEL AT ABNORMALLY HIGH-TEMPERATURE

Irradiation behavior of high temperature gas-cooled reactor (HTGR) coa ted particles under temperature transient conditions was investigated in accordance with a design-base accident scenario for HTTR, a 30 MWth HTGR under construction at JAERI. One of the scenarios predicts that the fuel temperature of the block-type fuel element rises to abnormall y high temperature by blocking a coolant channel with some foreign sub stance. For simulating this scenario the fuel compacts incorporating t he coated particles were irradiated at normal temperature in three cap sules, followed by temperature transient up to a maximum of approximat ely 2000 degrees C. The post-irradiation examinations, including surfa ce inspection, metrology, ceramography and a measurement of coated par ticle failure were applied to the fuel compacts to investigate the the rmal-transient effect on the fuel integrity. Integrity of the fuel com pact was also assessed by an estimation of tangential stress introduce d into the compact by the temperature transient.