Document: NUREG-0800
Document ID: 4e1c316a-99c2-4fd3-9d9b-323791bd85f8
Document Type: srp
Title: SHORT-TERM ATMOSPHERIC DISPERSION ESTIMATES FOR ACCIDENT
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0707/ML070730398.pdf
Revision Date: 2023-06
Chapter: 2
Section ID: 2.3.4
CFR Part: 
CFR Title: 

Content:
ghest χ/Q value which is exceeded 0.5% of the time in each of 16 compass directions from the plant. b. A direction-independent probabilistic approach which uses the χ/Q value which is exceeded 5% of the time independent of direction. These values are assumed to represent conditions for a 2-hour period. χ/Q values for time periods greater than two hours are estimated for the LPZ distance by assuming either a logarithmic relationship between the "2-hour" value and the annual average value or a “sliding window” approach using hourly meteorological data. As applied herein, the term “sliding window” refers to the calculation of running mean χ/Q values for time periods varying from 1 to 720 hours in duration, using an averaging method similar to that used for control room χ/Q values as calculated by the ARCON96 computer code referenced in Regulatory Guide 1.194. The methodology is described in Sections 3.6, 3.7, and 3.8 of NUREG/CR-6331, Rev.1, “Atmospheric Relative Concentrations in Building Wakes”. Any similar methodology that is applied to LPZ calculations should be made on a direction-dependent basis, analogous to that presented in Regulatory Guide 1.145. These values of χ/Q based on appropriate models for appropriate time intervals and distances are used in the analyses presented in SRP Chapter 15 for dose assessment of design basis accidents. ARCON96 is used to estimate the level of control room exposure during postulated accidents, as documented in Regulatory Guide 1.194. Interpretation of results from ARCON96 should take into account control room inflow from dual air intake valves as discussed in Regulatory Guide 1.194. 6. Review Procedures Specific to 10 CFR Part 52 Application Type a. Early Site Permit Reviews Subpart A to 10 CFR Part 52 specifies the requirements and procedures applicable to the Commission’s review of an ESP application for approval of a proposed site. Information required in an ESP application includes a description of the