Facility Vulnerability with VISAC

View Results

After each incident is defined or after all of them have been defined, the user can view the results. For each incident, there are several things the user can look at by first selecting an incident from the left panel of the main window, and then selecting an option under the Incident menu: (note - the results shown are cumulative, up to the selected incident)

1. Incident Summary - Gives the user just the basic information calculated for each aspect of the facility - the probability of each outcome and the expected downtime (if any).

2. Incident Event/Fault Trees - Uses EFTed to in its Results mode to display the event trees and fault trees showing which sequences are the most probable and which components contributed to facility kill and core damage.

3. Incident Calculation Report - Is the report generated by the event/fault tree solver, EFcalc. This is supplied for the user to look for any problems in the event/fault trees, such as undefined gates or circular logic errors, that might have been introduced into the logic model during editing. This also gives the user the uncertainties on the probabilities calculated, if the Monte Carlo method was used to solve the trees.

4. Incident Details - Gives the user all of the details about what the state of the plant was before this incident, what this incident damages, what the cumulative damage is, and what systems are contributing how much to the downtime estimate.

5. Incident Downtime Graph - Displays a probabilistic distribution for downtime. The graph can be used to answer the question, "What is the probability the facility will be down for at least X months?"

For downtime results, there are three different downtimes listed: CDS algorithm, parallel and serial. The parallel and serial methods assume that all systems contributing to downtime have indepenent failure probabilities. The parallel repair schedule assumes that for a combination of systems, the repair time is that of the longest system repair time. The serial repair schedule assumes that the repair time for any given set of failed systems is the total repair times of those systems. The CDS algortihm finds the shortest downtime possible using the assumption that the failure probabilities are correlated and a parallel repair schedule is used. These downtimes should be considered rough estimates since repair/replacement times can change due to specific circumstances.

The above results can viewed on screen and also printed to the local printer. These reports (except the graph) all exist in the project area, under the subdirectory of the project name, as ASCII text files that can be imported into word processors.

For any incident, the cumlative damage can be shown graphically using the Triple View Slicer, the QuickView 3D or the 3D Ray Tracer viewer.

Oak Ridge National Laboratory, 2004

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