A computerized safety assessment and post-trip analysis system for the Forsmark Unit 2 control room, integrating a real-time expert system and a modern graphic display system

Approximately 50 percent of the electricity generated in Sweden comes from nuclear power. More than half of this is produced at the Ringhals and Forsmark nuclear power stations. The Forsmark station is situated on the east coast of Sweden, 140 km north of Stockholm. The plant consists of three boiling water reactor units, Forsmark 1, 2, and 3. Units 1 and 2 are twins. They were taken into operation in 1980 and 81. Net electrical output from these units are 970MW. Records show that the Swedish nuclear power plants have been operated without any serious accidents. They also have a high availability, recent figures indicate a yearly average energy availability of close to 90 percent for the nine BWRs. In spite of these good records, there is a continuous objective to improve safety at the Swedish nuclear plants. One way to meet such an objective is to introduce computerized support systems in the control rooms. This paper describes one such system called SAS 2. It is being developed under a joint research and development program between Unit 2 at the Swedish nuclear plant Forsmark, the Swedish Nuclear Inspectorate (SKI) and the OECD Halden Reactor Project in Norway. The purpose is to develop a function oriented advisory system to assist the shift supervisor in his observation and evaluation task after plant disturbances leading to scram. To monitor this emergency shut-down process the supervisor today applies a set of function oriented emergency procedures. When SAS 2 is installed the idea is that the system continuously gives information to support the work with the emergency procedure as well as alarm if and explain why critical safety functions are challenged