Probabilistic quantitative assessment software code on NPP safety improvement, as result of different modernization measures

Every modernization measure results in failure probability improvement of a specific component, group of component or system. This failure probability improvement leads to the NPP safety improvement, by core damage frequency reduction. The calculation of this frequency by PSA requires profound knowledge of PSA theory and practice, available and installed PSA and rights to use it. This makes impossible for wide range of specialists to do quick calculation of safety change, in case of a component (group, system) reliability change. The presented software code enables core damage frequency change calculation in seconds, without using of the PSA models. Instead, the code automatically uses the PSA results, which are more available. The code can calculate not just the core damage frequency reduction, but the core damage frequency increase as well, for example in case of component (group, system) outage for planned or unplanned repair, component failure or reliability reduction, test outage etc. The code can calculate the core damage frequency changes due to common cause failure as well. There is a possibility to compare the effect of the different modernization measures (or activities within a measure), by the core damage frequency changes. The code lists the changed event trees, the changed accident scenarios and the values of their core damage frequency changes. The code calculates the core damage frequency change in the following cases: Failure probability change of a component (group, system); Seismic fragility change of a component (group, system); Outage of a component (group, system). (author)