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:
)(b) ACH 0.015(c) ACH 0.06 ACH 1.2 0.3 (0.5) to 0.5 (0.8) 4.1(d) 1.0 0.050 0.5 (0.8) to 0.7 (1.1) 16 4.0 0.20 0.7 (1.1) to 1.0 (1.6) 55 14 0.68 1 (1.6) to 2 (3.2) 123 31 1.5 2 (3.2) to 3 (4.8) 590 150 7.4 3 (4.8) to 4 (6.5) 1,680 420 21 4 (6.5) to 5 (8.0) 4,000 1,000 50 (a) The table is adapted from RG 1.78, Rev. 1 (2001) and added with SI units. (b) Values in parenthesis are in unit kilometer (km). (c) An ACH of 0.015 (i.e., 0.015 of the control room air by volume is replaced by atmospheric ambient air in one hour) is considered representative of a “tight” CR that has very low-leakage construction features and automatic isolation capabilities. ACH of 0.06 is considered representative of a CR that has normal leakage construction features and automatic isolation capabilities, whereas an ACH of 1.2 is considered representative of the CR with construction features that are not as efficient for leakage control and without automatic isolation capabilities. (d) Storage weights, in unit of metric ton (i.e., 2,205 lb) are obtained based on a 50 mg/m3 concentration and Category F Pasquill Stability Class. The evaluation of CR habitability should consider estimates of the frequencies for shipments that are within 8 km radius of a nuclear power plant. The NRC considers shipments to be frequent if there are 10 total shipments per year for truck traffic, 30 total shipments per year for rail traffic, or 50 total shipments per year for barge traffic. These frequencies are based on transportation accident statistics, conditional spill probability given an accident, and a limiting criterion for the number of spills from DG-1387, Page 9 NUREG/CR-6624. Therefore, the technical basis for Table 2 in this RG is the same as that of RG 1.87, Revision 1. Therefore, mobile sources need not be considered further if the total shipment frequency for all hazardous chemicals (i.e., all hazardous chemicals considered as a singular cargo category without further distinction of the nature of