Risk-based fault tree analysis method for identification, preliminary evaluation, and screening of potential accidental release sequences in nuclear fuel cycle operations

A method is described for identification, preliminary evaluation, and screening of potential accident sequences leading to uncontrolled release of radioactive materials. Included is a procedure for estimating the risk sum of all identified sequences. In addition, portions of the procedures have been developed for detailed analysis of the dominant (highest risk) sequences so screened. This method was developed for the ERDA-sponsored risk analysis of systems for managing high-level waste, part of the Waste Fixation Program (WFP). The method begins with certain preliminary analyses. The facility and operation are described and analysis bounds are established. A type of fault tree construction, the ''to/through'' approach, was chosen for the WFP waste management system. The to/through fault tree approach offers advantages over others in several respects. The analysis is considered more complete because the system is treated as a whole. The screening process was successfully demonstrated on a conceptual waste management system for the Waste Fixation Program. Fault trees were constructed and evaluated for processing, handling, transporting, and storing high-level waste. Trees of up to 14,000,000 release sequences (BICS-Boolean-indicated cut sets) were screened and the top few hundred or thousand sequences preliminarily ranked. An estimate of the total risk represented in the faultmore » tree was also obtained. (auth)« less