Document: NRC Regulatory Guide
Document ID: ceaeb6d7-d85a-46d3-a1b6-70059a498965
Document Type: regulatory_guide
Title: 12/2001 (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0131/ML013100014.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.78
CFR Part: 
CFR Title: 

Content:
perature) 8. Fraction of chemical flashed and rate of boiloff when spilling occurs 9. Distance of source from control room 10. Meteorological data CONTROL ROOM 1. Volume of the control room, including the volume of all other areas supplied by the control room emergency ventilation system 2. Normal flow rates in cubic feet per minute for - unfiltered inleakage or makeup air - filtereda makeup air - filtered recirculated air 3. Emergency flow rates for the above 4. Time required to isolate the control room a "Filtered air" refers to the air filtered through filters that have an established removal capability for the particular chemical being considered.  For both types of accidents, release of contents during an earthquake, tornado, or flood should be considered for chemical container facilities that are not designed to withstand these natural events. In the evaluation of control room habitability, it may also be appropriate to consider hazardous chemical releases coincident with the radiological consequences (e.g., of a design basis loss-of-coolant accident for plants that are vulnerable to both events simultaneously) and demonstrate that such coincident events do not produce an unacceptable level of risk. For chemicals that are not gases at 100F and normal atmospheric pressure but are liquids with vapor pressures in excess of 10 torr, consideration should be given to the rate of flashing and boiloff to determine the rate of release to the atmosphere and the appropriate time duration of the 1.78-9 release. For lighter-than-air gases, the buoyancy effect should be considered in determining the dispersion characteristics. 3.3 Atmospheric Dispersion The atmospheric transport of a released hazardous chemical should be calculated using a dispersion or diffusion model that permits temporal as well as spatial variations in release terms and