Degraded core quench: a status report

An important accident management measure for controlling severe accident transients in light water reactors (LWRs) is the injection of water to cool the degrading core. This report for the CSNI summarises the status of experimental and theoretical knowledge of fuel behaviour aspects concerning the quench of degraded cores, where the fuel rods are in a mainly rod-like geometry at the time of quench; consideration of quench of late phase core configurations such as debris beds is outside its scope. Initially the review addresses thermal hydraulic aspects of reflood and quenching in non-degraded reactor cores, this is relevant because the models developed here are often extrapolated into the severe accident regime. The review then considers the phenomena exhibited in the bundle experiments LOFT LP-FP-2, PBF SFD-ST, and the CORA tests 12, 13 and 17. Following this, the extent to which the experimental knowledge has been translated into computer models is considered by reviewing the status of the treatment of quench in four major code systems; SCDAP/RELAP5, ICARE/CATHARE, ATHLET-CD/KESS and MELCOR