Highly irradiated fuel behaviour up to melting : JOG tests in CABRI

Abstract The existence and growth of a layer of fission product compounds at the fuel-clad interface induces uncertainties in the power-to-melt determination of fuel at high burn-up. To solve this problem, a programme of in-pile experiments, called JOG tests, has been designed and one test has already been performed. This programme presently consists of two tests performed in the CABRI reactor. Each test simulates a control rod withdrawal event, stopped at a power sufficient to provoke fuel melting, but lower than that required to fail the pin. The first test, JOG2, has been performed and the first results show that no pin failure occurred and the post-test gamma-scans coupled to pin neutronography indicate that significant fuel melting occurred during the test. The second test, JOG1, is now planned for mid 1993 and will give, coupled with JOG2, valuable information concerning high burn-up fuel pin behaviour and related modelling.