Analysis of the Effectiveness of the Pressure Suppression System in BWR Plants in Beyond-Design-Basis Accidents Involving Main Steam Pipe Break and Simultaneous Leak between the Pressure and Condensation Chambers

作者：Schittek Ulf^*; Ohlmeyer Hermann; Gall Uwe; Koch Marco K

来源：ATW - International Journal for Nuclear Power, 2010, 55(3): 178-+.

The containment of a boiling water reactor (BWR) is subdivided into a pressure chamber (PC) and a condensation chamber (CC). In a loss-of-coolant accident within the containment PC, e.g. as a consequence of a break of a main steam pipe or a feed water pipe, these chambers act as a pressure suppression system. Because of the overpressure generated in the PC, the steam released in this case flows through the condensation pipes into the water pool of the CC where it condenses. This effectively limits the maximum accident pressure in the containment.
In an assumed beyond-design-basis leakage between the PC and the gas region of the CC, the functioning of this pressure suppression system may be restricted because complete condensation of the steam released in the water pool is no longer guaranteed. In order to be able to assess the relevance of such accident scenarios with a bearing on probabilistic studies, the effectiveness of the CC in a break of a main steam pipe with a superimposed leak between the PC and the gas region of the CC of a BWR of the 69-line was studied. The leak size and the number of legs available of the residual heat removal system, TH, were varied in the process.
The analyses were based on the COCOSYS containment code developed by the Gesellschaft fur Anlagen- und Reaktorsicherheit (GRS).
The results of this analysis show that the pressure suppression system was designed with very large margins because effective limitation of the maximum pressure in the containment allows leakages between the PC and the CC to be tolerated which are at least 2orders of magnitude above the leaks considered permissible at the time the plants were built.

• 出版日期2010-3