A Probabilistic Risk Assessment of Mound's Tritium Emissions Reduction Facility (TERF)

A probabilistic risk assessment was made on the TERF process in order to establish its expected degree of reliability and to locate places in the system which could be improved by revision of the equipment or the operating procedures. The equipment design of the TERF was evaluated using a fault tree study. The probability of human failures was then evaluated by adding their probabilistic effects to the fault tree and then reevaluating it. It was found that 1) the TERF system is expected to be very reliable, with an annual expected downtime of only 2.35 hours, 2) the expected downtime comes almost entirely from process equipment failure rather than human errors, and 3) that certain equipment changes could be made that increased the system reliability. These equipment changes included 1) making provision for blocking off certain automatic control valves with more reliable manual valves to facilitate their repair and 2) making the two sources of power to the TERF totally independent of each other.