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:
sting are those that leave equipment unavailable until the condition is discovered during a subsequent test or until the equipment is demanded (i.e., a restoration error). Reviewers should verify that the assumptions, models, and data used to quantify this error are consistent with the revised test strategies. The quantification of compensating human actions refers to the credit taken for actions for purposes of deciding on IST changes. Reviewers should confirm that credit for compensating human actions is limited to proceduralized actions taken to actuate systems and that repair of failed equipment is not considered. The intent of this review is to ensure that licensees do not relax IST on the basis of relatively uncertain quantification of recovery probabilities. * Component Failure Rates: The reviewer should establish that failure rates for components that are important in the justification of the IST change are consistent with plant-specific data. Failure rates that are appreciably less than generic data (e.g., those that are more than a factor of 3 lower than generic data) should be justified. To use the lower plant-specific failure rate, it must be demonstrated that the plant-specific failure rate data came from a population statistically different from the generic population and an engineering rationale should be provided. The reviewer should ascertain whether the failure rate takes account of special environmental stresses or aging. If not, this should figure in the evaluation of the performance monitoring and feedback activity. 3.9.7-21 Rev. 0 - August 1998 Quantification of Risk Impact: Reviewers should ensure that the evaluation of the change has not been performed non-conservatively by, for example, using a pre- determined cutset solution and requantifying the basic event probabilities, rather than resolving the equations with the higher values. In addition, because of the simultaneous increase in basic event probabilities associated with like