Analyses of PACTEL passive safety injection experiments with APROS, CATHARE and RELAP5 codes

The European Commission fourth framework programme project 'Assessment of p assive safety injection systems of advanced light water reactors' involved experiments on the PACTEL test facility and computer simulations of selecte d experiments. The experiments focused on the performance of passive safety injection systems (PSIS) of advanced light water reactors (ALWRs) in small break loss-of-coolant accident (SBLOCA) conditions. The PSIS consisted of a core make-up tank (CMT) and two pipelines. A pressure balancing line (PBL ) connected the CMT to one cold leg. The injection line (IL) connected it t o the downcomer. The project invoked 15 experiments in three series. The ex periments provided information about condensation and heat transfer process es in the CMT, thermal stratification of water in the CMT, and natural circ ulation flow through the PSIS lines. The project included validation, of th ree thermal-hydraulic computer codes (APROS, CATHARE and RELAP5). The analy ses showed the codes are capable of simulating the overall behaviour of the transients. The codes predicted accurately the core heatup, which occurred when the primary coolant inventory was reduced so much that the core top b ecame free of water. The detailed analyses of the calculation results showe d that some models in the codes still need improvements. Especially, furthe r development of models for thermal stratification, condensation and natura l circulation flow with small driving forces would be necessary for accurat e simulation of the phenomena in the PSIS. (C) 2000 Elsevier Science S.A. A ll rights reserved.