Risk ranking methodology for radiological events
Risk ranking schemes have been used in safety analysis to distinguish lower risk accidents from higher risk accidents. This is necessary to identify those events that might warrant additional study/quantitative analysis and to ensure that any resources allocated for risk reduction are properly directed. A common method used for risk ranking utilizes risk matrices. These are typically 3x3 or 4X4 matrices, having event consequences along one ixis and event frequency along the other. Each block on the risk mitrix represents some level of risk, and blocks presenting similar risk are often grouped together into one of 3 or 4 risk regions. Once a risk matrix has been identified, events are placed on the matrix based on an estimate of the event consequence and event frequency. Knowing how the blocks on the risk matrix relate to one another with respect to risk, the relative risk of the events will be known based on where they are placed on the matrix. In most cases, the frequency axis of the matrix has some numerical values associated with it, and this typically spans several orders of magnitude. Often, the consequence axis is based on a qualitative scale, where consequences are judgment based. However, the consequence scale generally has implicit qualitative values associated with it, which may or may not be recognized. Risk regions are often arbitrarily assigned (or assigned on the basis of symmetry). This presents a problem in that if the blocks of the risk matrix are incorrectly grouped, then incorrect conclusions can be drawn about the relative risk presented by events at a facility. This paper first describes how risk matrices have typically been established in the past. Problems associated with these risk matrices are identified and discussed. A methodology for logically establishing risk matrices, with specific application to radiological risk is provided. The paper provides guidance on how matrices should be tailored to their specific application, and then closes with some summary remarks.
- Research Organization:
- Lawrence Livermore National Lab., CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 563146
- Report Number(s):
- UCRL-JC--126175; CONF-970661--; ON: DE98051161
- Country of Publication:
- United States
- Language:
- English
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