BENCHMARK ANALYSIS OF SAFETY SIGNIFICANT EVENTS AT THE IGNALINA NUCLEAR POWER PLANT USING STATE OF THE ART CODES

摘要

The Ignalina nuclear power plant (INPP) is a twin unit with two RBMK-1500, graphite moderated, boiling water, multichannel reactors. Several important design functions of RBMK-1500 reactors are unique and extremely complex with respect to those of western reactors. The RBMK-1500 reactor, with one coolant loop, having a flow length of more than 200 m, consists of 1661 parallel pressure tubes and numerous components, such as collectors, pumps and valves. This complex main circulation circuit is divided into two halves. Each half is cooled by water from three operating main circulation pumps (MCPs). The fourth MCP at each side of the reactor is normally idle and in standby mode. The MCPs feed the common pressure header on each side of the reactor. Each pressure header provides coolant flow to 20 group distribution headers, each of which in turn feeds 38-43 pressure tubes. The reactor fuel assemblies within these pressure tubes are contaminated. Core exit piping connects each pressure tube with one of the four steam separators. The steam separators are connected via a common main steam header, providing coolant flow through control valves to each of the two high pressure turbines. Liquid is recircu-lated to the MCPs through downcomer pipes from the separators to a common pump suction header on each side. Feedwater is provided to the steam separator to make up for the steam flow to turbines.