Document: NUREG-0800
Document ID: e32f0820-4e33-476e-aa36-4ca8c2c64af0
Document Type: srp
Title: Use of Probabilistic Risk Assessment in Plant-Specific, Risk-Informed Decisionmaking:
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0119/ML011940192.pdf
Revision Date: 2023-06
Chapter: 19
Section ID: 19.0
CFR Part: 
CFR Title: 

Content:
shutdown conditions). However, reviewers should recognize that many PRAs are not full-scope assessments and the use of less than full-scope PRA information may be acceptable as discussed later. There are two acceptance guidelines, one for CDF and one for LERF, and both should be used. The guidelines for CDF are as follows: If the application can clearly be shown to decrease CDF, the change is considered to satisfy the relevant principle of risk-informed regulation with respect to CDF. (Because Figure Il1-1 is drawn on a log scale, it does not explicitly indicate this region.) * When the calculated increase in CDF is very small (less than 1 x 106 per reactor year), the change should be considered regardless of whether there is an assessment of total CDF (Region III). While there is no requirement for the licensee to quantitatively assess the total CDF, information should be provided to show that there is no indication that the total CDF could considerably exceed 1 x 10' per reactor year. Such an indication could result, for example if the contribution to CDF calculated from a limited-scope analysis (such as that from the IPE or the IPEEE) significantly exceeds 1 x 10' per reactor year, if the licensee has identified a potential vulnerability from a margins-type analysis, or if plant operating experience has indicated a potential safety concern. SRP 19-19 When the calculated increase in CDF is in the range of 1 x 10'6 to 1 x 10' per reactor year, applications should be considered only if the licensee can reasonably show that the total CDF is less than 1 x 10' per reactor year (Region II). Applications which increase CDF by more than 1 x 10' per reactor year (Region I) should not normally be considered. The CDF-related guidelines listed above are to be applied together with the guidelines for LERF. That is, both sets of guidelines should be satisfied. Specifically, the guidelines for LERF are as follows: If the application can clearly be shown to decrease LERF, the