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
CFR Part: 
CFR Title: 

Content:
n the eventual occurrence of a PRA initiating event. * The component is not a part of a system that acts as a barrier to fission product release during severe accidents. * The failure of the component will not result in unintentional releases of radioactive material even in the absence of severe accident conditions. 7. Evaluating the Effect of Proposed Changes on Overall Plant Risk The change in risk from proposed changes to the IST program should be consistent with the guidelines provided in Section 2.2.2 of Regulatory Guide 1.174. In comparing the calculated risk to the guidelines, the licensee should address the model and completeness uncertainty as 3.9.7-1 0 Rev. 0-August 1998 discussed in Regulatory Guide 1.174. In addition, the licensee should address parameter uncertainty either by propagating the uncertainty during sequence quantification or by demonstrating that the "state-of-knowledge correlation" effect (Ref. 8) is not significant especially in cutsets where the RI-IST changes affect multiple components which are similar. In evaluating the change in overall plant risk from proposed changes in the IST program, the licensee should perform the following: * Evaluate the risk significance of extending the test interval on affected components. This requires that the licensee address the change in component availability as a function of test interval. The analysis should include either a quantitative consideration of the degradation of the component failure rate as a function of time, supported by appropriate data and analysis, or arguments which support the conclusion that no significant degradation will occur. * Consider the effects of enhanced testing to the extent needed to substantiate the change. Other issues that should be addressed in the quantification of the change in risk include the following: * The impact of the IST change on the frequency of event initiators (those already included in the PRA and those screened out because of low frequency) should