ANALYSES OF PACTEL PASSIVE SAFETY INJECTION EXPERIMENTS GDE-21 THROUGH GDE-25

In advanced light water reactors (ALWR), gravity-driven passive safely injection systems (PSIS) replace pump-driven emergency core cooling s ystems. PSISs often rely on small density differences and driving forc es for natural circulation. In a typical loss-of-coolant accident (LOC A). interactions between different parts of the emergency core cooling system also take place. VTT Energy in Finland, in co-operation with t he Lappeenranta University of Technology (LUT), performed five experim ents in tile PACTEL loop to study PSIS performance during SBLOCAs. The purpose of the PSIS, a passive core make-up tank (CMT). was to provid e high-pressure safety injection water to the primary circuit. The pur pose of these experiments was to produce data to validate the current thermal-hydraulic safety codes, and to study the effects of break size on the PSIS behaviour. In all experiments the CMT ran as planned. No problems with rapid condensation in the CMT: as seen in earlier passiv e safety injection experiments in PACTEL. The main reason was the new CMT arrangement, with a Bow distributor (sparger) installed. The analy ses of the test data supported the use of McAdams correlation for calc ulating the heat transfer from the hot liquid layer to the CMT wall. T he use of Nusselt film condensation correlation for condensation at th e CMT walls seems correct. The APROS code simulated successfully the o verall primary system behaviour in the GDE-24 experiment, such as timi ng of the core heat-up al the end of the experiment. The code had some problems, in the simulation of thermal stratification in the CMT. (C) 1998 Elsevier Science S.A. All rights reserved.