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:
. As indicated therein, the identification of design basis events resulting from the presence of hazardous materials or activities in the vicinity of the plant is acceptable if the design basis events include each postulated type of accident for which the expected rate of occurrence of potential exposures in excess of the 10 CFR Part 100 guidelines is estimated to exceed the NRC staff objective of approximately 10-7 per year. Because of the difficulty of assigning accurate numerical values to the expected rate of unprecedented potential hazards generally considered in this SRP section, judgment must be used as to the acceptability of the overall risk presented. The probability of occurrence of the initiating events leading to potential consequences in excess of 10 CFR Part 100 exposure guidelines should be estimated using assumptions that are as representative of the specific site as is practi- cable. In addition, because of the low probabilities of the events under consideration, data are often not available to permit accurate calculation of probabilities. Accordingly, the expected rate of occurrence of potential exposures in excess of the 10 CFR Part 100 guidelines of approximately 10 6 per year is acceptable if, when combined with reasonable qualitative arguments, the realistic probability can be shown to be lower. The effects of design basis events have been adequately considered if analyses of the effects of those accidents on the safety-related features of the plant have been performed and measures have been taken (e.g., hardening, fire protec- tion) to mitigate the consequences of such events. III. REVIEW PROCEDURES In some cases it may be necessary to consult with'or obtain specific data from other branches, such as the Structural Engineering Branch (SEB) or 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