This paper briefly discusses the history of software tools for PRA and their development from the Jirst commercial PRAs to the present. The characteristics of a usable ('living') PRA are then described (i.e., accessibility, maintainability and quality). A description of the small event tree~large fault tree approach to PRA is discussed, with special attention paid to the interaction of the various PRA codes. Finally, four different applications of PRA are listed, showing the functions and interactions of SAIC's PRA workstation codes.
The software tools developed to support Probabilistic Risk Analyses (PRAs) have had a profound impact on the PRAs role in the utility regulatory environment. By providing the needed automation, integration and optimization, the costs of performing analyses have been greatly decreased while the timeliness of PRA results has improved. Automation and integration let the engineer focus on the analysis and not the procedures needed to perform the analysis, while optimization has allowed computations to be performed on a top-end personal computer, reducing costs. The resulting effect of the PRA workstations has been to change the nature of a PRA, from a static report that sat on a shelf to a living document which could be quickly updated, modified and analyzed.
During the time of the first commercial PRAs (e.g. Zion & Oconee), 1 the only software tools supporting PRA were large mainframe fault tree quantification tools. In addition to the model quantification, there were 355 Reliability Engineering and System Safety