Document: NUREG-0800
Document ID: 09810f04-ae4d-4062-8e3a-bcd25f5f6e84
Document Type: srp
Title: EVALUATION OF POTENTIAL ACCIDENTS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340562.pdf
Revision Date: 2023-06
Chapter: 2
Section ID: 2.2.3
CFR Part: 
CFR Title: 

Content:
r Auxiliary Systems Branch (ASB), regarding possible effects of external events on plant structures or components. The applicant's probability calculations are reviewed, and an independent probability analysis is performed by the'staff if the potential hazard is considered significant enough to affect the licensability of the site or is important to the identification of design basis events. All stochastic variables that affect the occurrence or severity of the postulated event are identified, and judged to be either independent or conditioned by other variables. f 2.2.3-2 Rev. 2 Probabilistic models should be tested, where possible, against all available information. If the model or any portion of it, by simple extension, can be used to predict an observable accident rate, this test should be performed. The design parameters (e.g., overpressure) and physical phenomena (e.g., gas concentration) selected by the applicant for each design basis event are reviewed to ascertain that the values are comparable to the values used in previous analyses and found to be acceptable by the staff. Each design basis event is reviewed to determine that the effects of the event on the safety features of the plant have been adequately accommodated in the design. If accidents involving release of smoke, flamuable or nonflammable gases, or toxic chemical bearing clouds are considered to be design basis events, an I evaluation of the effects of these accidents on control room habitability should be made in SAR Section 6.4 and on the operation of diesels and other safety-related equipment in SAR Chapter 9. Special attention should be given to the review of standardized designs which propose criteria involving individual numerical probability criteria for individual classes of external man-made hazards. In such instances the reviewer should establish that the envelope also includes an overall criterion that limits the aggregate probability of exceeding design criteria associated with all