PROCEDURES AND TOOLS COMPARING PSA IN THE FRAME OF PERIODIC SAFETY REVIEWS

摘要

Different procedures and tools have been developed by GRS for improving efficiency and comprehensibility of PSA review tasks. They are based on the database interface of a widely applied PSA software tool using SQL queries and the scripting language Ruby. Changes in fault and event trees are identified and presented as "difference graphs" by drawing an overlay of the fault/event trees of the different versions and flagging the differences. It is also possible to trace the influence of changes of a specified fault tree to all corresponding TOP-gates, to the affected function events and event trees. For a given fault tree an "expanded" view can be created consisting of all fault trees connected to it by transfer gates either "upwards" to all affected TOP-gates or "downwards" to the basic events. Another feature of the GRS tools is the merging of data from different sources such as specifications of basic events (e.g. failure rates, test intervals, repair times). For quantifying the changes in the core damage frequency (CDF) between different versions of a PSA the quantitative differences are split up in contributions by the changes of the initiating event frequencies, changes in the modeling of fault trees and event trees respectively, as well as changes in the reliability data for the basic events.