Document: NRC Regulatory Guide
Document ID: de79d411-4fc9-456e-a5a0-f4a910ca4c9a
Document Type: regulatory_guide
Title: Assumptions Used for Evaluating a Control Rod Ejection Accident for Pressurized Water Reactors (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2111/ML21119A157.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.77
CFR Part: 
CFR Title: 

Content:
from the isolation dampers, then credit will be allowed for the travel time between the detectors and the dampers. The isolation system and its components, the recirculating filter system, and the air conditioning system should meet Institute of Electrical and Electronics Engineers (IEEE) Standard 603-2018, “IEEE Standard Criteria for Safety Systems for Nuclear Power Generating Stations” (Ref. 23), since these systems are needed to maintain a habitable environment in the CR during a design-basis accident. For plants that isolate CRs, steps should be taken to ensure that the isolated exchange rate is not inadvertently increased by design or operating error. Ventilation equipment for the CR and for the adjacent zones should be reviewed to ensure that enhanced air exchange between the isolated CR and the outside will not occur. All doors leading to the CR should be kept closed when not in use. DG-1387, Page 13 4.3 Protection System If the evaluation of possible accidents for any hazardous chemical indicates that the applicable toxicity limits may be exceeded in the CR, measures should be in place to provide adequate protection to CR operators. The evaluation should consider the use of full-face, self-contained, pressure-demand-type breathing apparatus (or the equivalent) and protective clothing. Adequate air capacity for the breathing apparatus (at least 6 hours) should be readily available on site to ensure that at least 6 hours is available to transport additional bottled air from offsite locations. This offsite supply should be capable of delivering several hundred hours of bottled air. The units of breathing apparatus should be enough for the emergency crew or staff working in the CR. Storage provisions for breathing apparatus and procedures for their use should be such that operators can begin using the apparatus within 2 minutes after detection of a hazardous release. Breathing apparatus, air supply equipment, and protective clothing should meet the criterion