MODELING BUBBLE CONDENSER CONTAINMENT WITH COMPUTER CODECOCOSYS: POST-TEST CALCULATIONS OF THE MAIN STEAM LINE BREAKEXPERIMENT AT ELECTROGORSK BC V-213 TEST FACILITY

摘要

Containment of the WWER-440 Model 213 nuclearpower plant features a Bubble Condenser, a complexpassive pressure suppression system, intended to limitpressure rise in the containment during accidents. Due tolack of experimental evidence of its successful operation inthe original design documentation, the performance of thissystem under accidents with ruptures of large high-energypipes of the primary and secondary sides remains a knownsafety concern for this containment type. Therefore, anumber of research and analytical studies have beenconducted by the countries operating WWER-440 reactorsand their Western partners in the recent years to verifyBubble Condenser operation under accident conditions.Comprehensive experimental research studies at theElectrogorsk BC V-213 test facility, commissioned in 1999in Electrogorsk Research and Engineering Centre (EREC),constitute essential part of these efforts. Nowadays this isthe only operating large-scale facility enabling integral testson investigation of the Bubble Condenser performance.Several large international research projects, conducted atthis facility in 1999-2003, have covered a spectrum of pipebreak accidents. These experiments have substantiallyimproved understanding of the overall system performanceand thermal hydraulic phenomena in the BubbleCondenser Containment, and provided valuableinformation for validating containment codes againstexperimental results.One of the recent experiments, denoted as SLB-G02,has simulated steam line break. The results of thisexperiment are of especial value for the engineers workingin the area of computer code application for WWER-440containment analyses, giving an opportunity to verify validity of the code predictions and identify possibilities formodel improvement. This paper describes the results of thepost-test calculations of the SLB-G02 experiment,conducted as a joint effort of GRS, Germany and Ukrainiantechnical support organizations for Regulatory Authorityusing computer code COCOSYS. The code has beendeveloped in GRS for the analysis of the containmentresponse under design basis and severe accidentconditions in light water reactors of different design,including WWERs. Comparison of the code calculationswith experimental results has demonstrated reasonableaccuracy of the code predictions. The paper describes thetest facility and the SLB-G02 experiment, conducted byEREC, the COCOSYS model of the test facility, andcompares the code predictions to the experimental results.