Radiation and Nuclear Safety Authority of Finland (STUK) started to develop living PSA computer code SPSA in 1988. Level 1 part of this code was taken into use in 1991. Since then, the algorithm has been continuously developed, and its efficiency and robustness have been demonstrated in many benchmarks [1,2] and in practical PSA use. FinPSA is a new version of SPSA for Microsoft Windows.
1. Fault tree reduction and quantification code Benchmark exercise, by H.Ohlmeyer, S. Dinsmore, TUV Norddutschland GmbH under the auspices of BMU, 1992.
2. J. Sandberg, R. Virolainen, Comparison of the core damage probability by the SPSA computer program and by analytical methods - a simplified loss of offsite power. Validation of the SPSA program. STUK-YTO-TR 62. Helsinki: Painatuskeskus Oy, 1993: 1-28.
Teamwork
FinPSA is developed for teamwork. PSA models can be shared or private models. Shared models reside in a server, and can be accessed and edited simultaneously by several users. A locking mechanism prevents two users from editing the same part of the PSA model at the same time. PSA models can be copied between shared and private locations.
Multithreading
In a multi-core computer, FinPSA uses multithreading to fully utilize the computing power of new computers. When minimal cut set search for a PSA projects is started, each CPU performs its own cut set search.
Parallel calculation
The PSA team can solve minimal cut sets together with several computers utilizing parallel computation. Every user can join or quit the parallel computation on the fly. With a click of a single button, computers can be defined as calculation resources, and whenever a cut set search is started, the resources automatically join the computation. The user may then even abort his own computation, leave the resources running, and prepare the next calculation. Calculations are fail-safe: an interrupted calculation can be resumed later. The already calculated parts are available for analysis even before restart.
Power of clusters
With these features, several multi-core computers can be connected together with a dedicated network to build powerful PSA clusters. STUK has a cluster of 3 dedicated quad-core servers, which makes solution PSA models incredibly fast. For example, complete minimal cut set solution for full-scope Olkiluoto 1 PSA model takes only two and a half minutes.
Hierarchical results
FinPSA searches for cut sets for each event tree sequence. After the search, the cut sets of individual sequences are automatically combined and grouped according to user-defined hierarchy of consequences. On the top level, FinPSA produces cut set files classified by consequence only. Any number of intermediate levels can be defined.
FinPSA introduces new level of traceability
Each minimal cut set can be traced back to the event tree and accident sequence, and visualized in the automatically generated sequence fault tree - with one mouse click.
![[screenshot]](/ydinturvallisuus/ydinvoimalaitokset/en_GB/finpsa/_files/12222632510021172/default/finpsa_screenshot1.jpg "[screenshot]")
Efficient and versatile cut set handler
Calculations with already searched minimal cut sets are quick and versatile. They can be performed for one cut set file, or automatically for all accident sequences in one event tree or the whole PSA model. Results are always up-to-date. FinPSA automatically detects the modified parts of model and performs related update calculations.
Interface to other programs
FinPSA works together with common Windows programs for importing and exporting data base tables, fault trees, events trees, and almost every item in the model. Results are available in several formats to Windows clipboard, printer and files.
New features increase productivity
FinPSA contains new features like Hazard table. It lists external events and their dependencies and maps them automatically to system fault trees during cut set search. For each dependency, conditional failure probabilities with uncertainty can be defined. There is no need to modify system fault trees or use house events.
Importance map is an interactive tool for risk-informed applications. It displays basic event probability, safety margin, Fussell-Vesely importance and Risk increase factor for all or selected basic events.
Current status of FinPSA
Preliminary version of FinPSA level 1 is available. The development of FinPSA will continue with new features like
- task-oriented model for control systems (from RELVEC code)
- asymmetric common cause failures, additional CCF models
- level 2 (dynamical containment event trees already implemented in SPSA).
Price for integrated level 1 and 2 FinPSA approximately 50 000 Euro for company license (no restrictions within a company).
More information: ilkka.niemela [at] stuk.fi.
