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This page contains answers to common questions handled by our support staff, along with some tips and tricks that we have found useful.

Q. What are the limits in constructing an Event Tree?

A. Within an individual Event Tree there is a limit of 25 events (1 initiating event and 24 functional events) and 150 sequences. If additional headings or sequences are desired, this is accomplished using an event tree transfer. Multiple transfers can occur such that there is effectively no limit to the number of headings or the number of sequences.

Q. What are the limits in constructing a Fault Tree?

A. The limits within an individual Fault Tree (LGC file) and in a Linked Fault Tree (LKC file) are shown in the table below. In general, the capability to link fault trees expands the numerical size limits and allows analysts to develop 1 fault tree per system or 1 tree per system group such as AC Power.

Tree Component LGC File Maximum LKC File Maximum
Gates 500 40,000*
Unique Basic events 500 10,000*
Basic events 1,000 10,000*
Unique Internal Transfers 500 Not used
Unique External Transfers 500 Not used
Internal + External Transfers 1,000 N/A
Pages 100 N/A
Minimal cutsets in solution Not Applicable 60,000
Cutset elements (Boolean terms) Not Applicable 1,000,000

* These values are dependent on the Fault Tree Solution Engine Licensed. Contact SCIENTECH for your values. Events are counted by name, not as event-occurrences.

Q. What Fault Tree features are there in WinNUPRA to support the analysis of spatial events or multiple states such as different operating alignments or different shutdown plant states?

A. WinNUPRA supports House events to turn On or Off portions of any fault tree. This feature supports modeling alignments and differing success criteria. The Data Module is designed such that multiple sets of House events can be constructed to adjust the fault tree based on variations in the initiating events or variations in plant state. Additionally, any Basic Event can be designated as a Logical event type to support spatial analyses.

Q. How many basic event types are there in WinNUPRA?

A. Six: Repairable, Periodically Tested, Failure on Demand, Running Failure, Module, and Logical.

Q. When linking fault trees, it is possible to introduce a logical loop.   How does WinNUPRA help locate these loops?

A. The fault tree solution algorithm notes the logical loop and assists in identifying the affected gates.

Q. How is WinNUPRA structured to support data updates such as required by the Maintenance Rule?

A. In the Data Module both the Unavailability file and the Parametric data file are structured with Data Import and Data Export features to support linking to a spreadsheet or external data programs.

Q. Does the software allow selecting data subsets of a common group such as component, system, failure mode, or human interactions?

A. Given a consistent naming scheme, the Sensitivity Module and the search portion of the Data Module allows selecting a group of basic events.

Q. What are the limits in results manipulation analyses?

A. Uncertainty and Importance analyses can be conducted on cutset equations containing up to 60,000 cutsets. The limits within WinNUPRA are re-visited by the User's Group annually and adjusted as needed.

Q. Sometimes a basic event is always paired with another (such as Loss of Offsite Power and Non-Recovery probability). Can WinNUPRA calculate the importance of this event combination?

A. The Importance module of WinNUPRA can calculate joint importance. Joint importance treats the specified combination like a single basic event and calculate Risk Reduction Worth, Risk Achievement Worth, and Fussell-Vesely importance.

Q. What type of quality assurance program is WinNUPRA maintained under?

A. WinNUPRA is maintained under the SCIENTECH Quality Assurance program to 10CFR50 Appendix B quality assurance levels. This program has been successfully audited by NUPIC in 1999. Validation and Verification summary reports are available for review and are provided with the Users Manual during software delivery.

Q. What capabilities have been added to WinNUPRA 2.0?

A. Significant capabilities worth noting:

bulletCopying Event Trees and Fault Trees to the clipboard, and into documentation.
bulletCompatibility with the new WinNUCAP (Level 2 + 3).
bulletTools for searching and comparing Data Files and Equations.
bulletCutset Tracer showing the path from the Fault Tree top down to the basic events in a cutset.

Q. What capabilities have been recently added to WinNUPRA 2.1?

A. Click here to see the changes and new features in Version 2.1


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WinNUPRA is a trademark of Scientech. All other products mentioned are registered trademarks or trademarks of their respective companies.
Copyright 2000-2011 Scientech All rights reserved.
Last modified: Wednesday October 05, 2011.

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