Quantitative Risk Assessment Use in Facility Siting and Consequence Analysis

<>Quantitative Risk Assessment use in Facility Siting and Consequence Analysis

Erin P. Collins and Elizabeth Cook

JENSEN HUGHES

The authors were involved in several QRAs used to help efficiently manage and minimize the risk associated with facility siting, design and operations, as part of an overall Risk Management Plan (RMP).  A principal goal of these assessments was to identify those systems, components, and activities that govern the risks associated with disposal of chemical munitions and agents.  Insights derived from the QRAs were used to identify potential improvements in systems or operations that could further reduce the public and worker health risks during disposal operations.  In addition, the QRAs were able to be easily modified to allow evaluation of whether proposed modifications to the facility, operating procedures, or the schedule for disposal would be expected to avert a significant amount of risk relative to the complexity of the change.  The QRA provides the plant-specific inputs for the facility RMP as documented in the RMP requirements document.  For example, the QRA models were used for evaluation of modifications, studies of incidents and near misses, and emergency preparedness activities.  The evaluation of risk also served as the basis for communicating the risk insights to the operating staff and other interested parties.

Key objectives of the QRAs included:  1) developing an analytical model that could be used as the basis for ongoing risk management and to evaluate proposed modifications, and could be updated as changes were made to the facility or as additional insights into accident behavior become available, 2) incorporating the model into a computer workstation, and 3) documenting the analyses in a manner that both supported the results and provided the necessary bases for external reviewers to determine that the work was accomplished in a thorough and competent manner.

The QRAs were used to examine the design of the facilities as part of siting and prior to construction.  For example, QRAs resulted in a re‑design of a portion of two facility structures to reduce possible earthquake damage.  The amount of stored liquefied petroleum gas (LPG) was reduced based on risk findings.  As part of a formal Change Management Plan, sensitivity studies were performed on the amount of chemicals stored in tanks on-site.  The reliability models developed for the QRAs were also used to study issues of the need for redundancy, such as in emergency power systems.

This paper will discuss the use of PRA/QRA in addressing facility siting, design and operations concerns as well as addressing other RMP issues, such as input to a site Environmental Impact Statement (EIS).