Accident sequence development

The Risk Assessment Technology Group at Westinghouse Hanford Company has participated in a number of full and partial reactor risk assessments, including that for the N reactor, Fast Flux Test Facility, WNP-1, and the SP-100 ground test facility. As the mission of the Hanford site was changed from special nuclear material production to environmental cleanup, the emphasis for performing risk assessments has shifted from evaluating the risk from the operation of reactors to that from operating nonreactor facilities such as the following: (1) waste storage tanks; (2) waste treatment facilities, such as Grout and the Hanford Waste Vitrification Plant; and (3) waste processing facilities such as the 242-A evaporator. In addition, risk assessment techniques are being used to support engineering design studies, safety analysis report development, and environmental remediation efforts. The opportunities for the use of risk assessment methodology are great, but care must be taken to ensure that they are correctly and properly employed. This paper describes how this is being done at Hanford