TRANSIENT-BEHAVIOR OF LOW ENRICHED URANIUM SILICIDE PLATE-TYPE FUEL FOR RESEARCH REACTORS DURING REACTIVITY INITIATED ACCIDENT CONDITIONS

This paper describes the results of transient experiments using a low enriched uranium silicide miniplate fuel for research reactor. The pul se irradiation was performed in the Nuclear Safety Research Reactor (N SRR) at the Japan Atomic Energy Research Institute (JAERI). The result s obtained in this study are summarized as follows : (1) The tested fu el plates were damaged with energy depositions above 94 cal/g.fuel, bu t remained intact below 82 cal/g.fuel. A failure threshold should ther efore exist between these two values. (2) Four of the fuel plates that showed peak cladding surface temperatures <330-degrees-C were damaged by the thermal stress during quenching. These damaged fuel plates rev ealed small intergranular cracks that propagated perpendicularly to th e axial direction of the plate, from the Al cladding surface to the fu el core, without significant dimensional changes. On the other hand, w hen peak cladding surface temperatures were >400-degrees-C, the test f uel plates were damaged mainly by melting of the Al cladding, accompan ying significant dimensional changes. (3) The thermal stress of the da maged fuel plates calculated on the basis of the maximum transient tem perature drop during quenching was greater than the tensile stress tha t occurred during fabrication.