Facility Vulnerability with VISAC

Post-Project

Timelines

For all of the incidents together, timelines can be made to show how probabilities of different outcomes change with each incident. Two versions are available: a graph where the total of the bad conquences for each aspect is shown or a graph where every consequence of a single aspect is shown. These graphs can be viewed by using the Post-Project/View Timeline menu. JPEG images of the graphs can be saved to disk for use in reports.

MBLM Calculation

MBLM 54d, developed by SAIC, can be used to calculate the amount of materials released to the atmosphere. Once the incidents have all been added to the project, the information about damaged compents and incident types can be combined with the MLBM inventory files to create an input deck for an MBLM calculation. MblmGui can be used to fill in any missing details in the MBLM model and run MBLM 54d. This is done in two steps:

• After all the incidents have been defined, incorporate the VISAC damage into the MBLM model (Post-Project/Incorporate Damage into Base Model). This will determine the gas generators and dust amounts, depending on the VISAC Incidents. Some user interaction may be required to fill in any gaps.
• Run MBLM (Post-Project/Review-Run Already Modified Model). This again uses MblmGui, this time with a "Run" button. Select "Run". The user can use MmblGui to corrent any errors with the model reported during the run.

Full implementation of MBLM in VISAC is currently on hold, pending other issues with HPAC integration.

MELCOR Calculation

Releases used by VISAC for nuclear power plant core damage were calculated using MELCOR for six different combinations of core damage:

• small, early release
• large, early release
• small, intermediate release
• large, intermediate release
• small, late release
• large, late release

In the future, the capability to run MELCOR after a project may be added to VISAC. This would allow VISAC to model more precisely what was released, instead of restricting it to one of six pre-calculated outcomes. VISAC would calculate which components of the core were damaged to a significant level, and then create a MELCOR input deck by relating the VISAC damage to MELCOR modeled flow paths.

MELCOR - a computer code for analyzing severe accidents in nuclear power plants and other facilities, was developed at Sandia National Laboratories for the US Nuclear Regulatory Commision.

Oak Ridge National Laboratory, 2004

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