Application of the effective convectivity model to an PWR in-vessel retention scenario

For the very improbable scenario of a severe accident with core meltdown and for-mation of a melt pool in the lower plenum of a Light Water Reactor (LWR) Pressure Vessel (RPV) computer codes are developed to assess the thermal and mechanical behaviour of the RPV wall. If the RPV wall fails within the lower head region, the melt is discharged into the reactor pit, which can result in severe thermal and mechanical loads for the containment. One accident management strategy could be to stabilize the in-vessel debris or melt pool configuration in the RPV via external flooding.
Based on the successful simulation and analysis work of the FOREVER-experiments (cf. Fig. 1 and [1]) coupled thermo-mechanical models have been developed further to simulate the prototypical scenario of an In-Vessel-Retention in large PWRs [2]. According to the recent publication “An Effective Convectivity Model (ECM) for Simulation of In-Vessel Core Melt Progression in a Boiling Water Reactor” by Tran and Dinh [3] the thermal part of the FE-model developed at FZD is now improved to be able to apply the new ECM approach.