Document: NUREG-0800
Document ID: 4e1d86bd-74a5-4678-8bc0-ffce3ba28ea0
Document Type: srp
Title: RISK-INFORMED INSERVICE TESTING
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0428/ML042880272.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.9.7
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CFR Title: 

Content:
r non-proceduralized actions (e.g. for the recovery of failed components). This ensures that the change preserves defenses against human errors. Another element of the integrated decisionmaking is the assurance that sufficient safety margins are maintained. In applications that seek relaxations in the IST strategy, safety margins could be decreased. The level of justification required for such changes in margin should depend on how much uncertainty is associated with the performance parameter in question (e.g., component failure rate as a function of time for applications that seek to extend test intervals), the availability of alternatives to compensate for adverse performance, and the consequences of functional failure of the affected components. For example, safety margin is maintained if: * ASME Codes or alternatives approved for use by the NRC are met. * Safety analysis acceptance criteria (e.g., USAR, supporting analyses) are met. * In applications that propose to extend test intervals, component degradation is accounted for, either by quantitative methods (analysis and data) or by qualitative arguments which show that significant degradation will not occur. Component degradation can also be addressed by the use of enhanced testing methods and the trending of the required performance parameter to determine an acceptable test interval. * The component categorization process is robust, and the components identified for relaxation in IST because of their low safety significance based on this categorization will only have a small effect on plant risk. In addition, test intervals are based on a margin to failure (by trending of performance characteristics) that is commensurate with the risk significance of the component. The categorization of components will be based in part on results from importance/risk rankings from a PRA. Since importance measures are only applicable to components taken one at a time, these measures are not an adequate measure of the change in