Analysis of new safety criteria for CABRI reactor core

As the technical support of the French Safety Authority, IRSN has examined the new criteria proposed by the operator of the CABRI reactor to insure the clad integrity of the driver core fuel rods during fast reactivity insertion transients. The main issues of the extensive analysis of the clad failure phenomena and of the additional justifications on the choice of the strain limit are presented and discussed. The evaluation of the methodology to compute the thermo-mechanical behaviour of the fuel rods (based on the use of the SCANAIR code) is comprehensively described. The main results of a complementary study aimed at comparing the energy deposit required to match the criteria proposed for CABRI with those leading to failures in SPERT-CDC (USA) and NSRR (Japan) experiments are also presented. As the operator has included in the safety demonstration all the additional requirements identified by IRSN, it can be concluded that the present safety demonstration is sufficiently robust and guarantees the absence of rod failure during fast transients. (author)