Risk Assessment: Tools, Techniques, and Their Applications

15.6 Quantitative Risk Assessment

The performance of quantitative risk assessment is a more detailed process than the qualitative assessment process. Expert system/process knowledge is a prerequisite to begin the assessment process. This expert knowledge is gained through system knowledge, event/process knowledge, knowledge of normal and abnormal conditions and casualty operating procedures, and research on specific failure information. Failure information is not merely the rate at which the equipment fails. Other factors include modes of failure, the sample sizes (how many failures, how many of a particular component are utilized), environments that were utilized, operating time/cycles, repair time, frequency of periodic maintenance, or testing. Sources for information on the failure can come from a wide variety of sources including manufacturer and government testing, maintenance databases, and databases on existing or suspected failures from the Nuclear Regulatory Commission (NRC), NASA, and National Transportation Safety Board (NTSB), among others. Since these analyses are often performed on complex systems, this process is often costly and time consuming. Because of these factors, this type of assessment is only performed when required by regulation and liability management, or when an appreciable cost benefit is expected to be achieved.

The risk assessment process consists of determining possible events that could occur with detrimental consequences; for example, loss of ...