Document: NRC Regulatory Guide
Document ID: 4d46a966-d280-43da-9b03-8b0abe7b29ce
Document Type: regulatory_guide
Title: Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2120/ML21204A065.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.183
CFR Part: 
CFR Title: 

Content:
d on a case-by-case basis with sufficient justification. The single valve limitation is based on the consideration that leakage in excess of 200 scfh may indicate a substantial valve defect. The total MSIV leakage limitation of 400 scfh is based on considerations of the relationship of MSIV leakage rate to the allowable containment leakage rate (La), as well as providing defense in depth related to the single valve limitation. Consistent with the BWROG TR, the following information related to the reliability of the pathway to the main condenser should be provided when holdup within the condenser is credited: a. the alternative drain pathway and the basis for its functional reliability, commensurate with its intended safety-related function; b. the maintenance and testing program for the active components (such as valves) in the alternative drain path, and a confirmation that the valves which are required to open the alternative drain path are included in the inservice testing program; c. how the alternative drain pathway addresses the single failure of active components to verify its availability to convey MSIV leakage to the condenser; d. a secondary path to the condenser; and e. emergency operating procedures that may be required to identify necessary operator actions to mitigate MSIV leakage consequences utilizing the alternative drain pathway if a highly reliable power source is available or to identify necessary operator actions to mitigate MSIV leakage consequences using the alternative drain pathway if a highly reliable power source is unavailable. DG-1389, Appendix A, Page A-8 A-5.5 Licensees that have already evaluated the seismic ruggedness of the steamlines, alternate drain paths, and the main condenser, and who have obtained prior staff approval, may credit the piping addressed in that approval. Also, licensees that have not previously applied for such approval may do so in accordance with the guidance in Reference A-13 or using the revised seismic