Document: NUREG-0800
Document ID: a2870fde-2b77-4036-900e-2e0e8ccaf2fa
Document Type: srp
Title: - 2.2.2.28
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070222.pdf
Revision Date: 2023-06
Chapter: 2
Section ID: 2.2.1
CFR Part: 
CFR Title: 

Content:
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, flammable or nonflammable gases, or toxic chemical- bearing clouds are considered to be design basis events, an evaluation of the effects of these accidents on control room habitability should be made in SAR Safety Analysis Report (SAR)29 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 manmade 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 of the identified external manmade hazards. Similarly, special attention should be given to the review of a site where several manmade hazards are identified, but none of which, individually, has a probability exceeding the acceptance criteria stated herein. The objective of this special review should be to assure ensure that the aggregate probability of an outcome that 30 may lead to unacceptable plant damage meets the acceptance criteria of subsection II of this SRP section. (A hypothetical example is a situation where the probability of shock wave overpressure greater than design overpressure is about 10 per reactor year from accidents at a -7 nearby industrial facility, and approximately equal probabilities of exceeding design pressure from railway accidents, highway accidents, and from shipping accidents. Individually each 31 may be judged acceptably low; the aggregate probability may be judged sufficiently great that additional design features are warranted.) For standard design certification reviews under 10 CFR Part 52, the procedures above should