Document: NRC Regulatory Guide
Document ID: 7bdfde6b-2c09-49db-8a3f-863eab24747e
Document Type: regulatory_guide
Title: Control of Combustible Gas Concentrations in Containment + HISTORY - HISTORY 08/2002 – DG-1117 , Proposed Revision 3 Prior to the issuance of DG-1117, RG 1.7 was entitled "Control of Combustible Gas Concentrations in Containment Following a Loss-of-Coolant Accident," to reflect its narrower original scope
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0222/ML022210067.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.7
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CFR Title: 

Content:
impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection. 2 B. DISCUSSION The Proposed Section 50.44 provides requirements for the mitigation of combustible gas generated by a beyond-design-basis accident. In an accident more severe than the design-basis loss-of-coolant accident (LOCA), combustible gas is predominately generated within the containment as a result of: 1. Fuel clad-coolant reaction between the fuel cladding and the reactor coolant, and 2. Molten core-concrete interaction in a severe core melt sequence with a failed reactor vessel. If a sufficient amount of hydrogen is generated, it may react with oxygen present in the containment at a rate rapid enough to lead to the breaching of the containment or a leakage rate in excess of technical specification limits. Additionally, damage to systems and components essential to continued control of the post-accident conditions could occur. In SECY-00-0198, “Status Report on Study of Risk-Informed Changes to the Technical Requirements of 10 CFR Part 50 (Option 3) And Recommendations on Risk- informed Changes to 10 CFR 50.44 (Combustible Gas Control),” dated September 14, 2000 (Ref. 1), the NRC staff recommended changes to 10 CFR 50.44 that reflect the position that only combustible gas generated by a beyond-design-basis accident is a risk- significant threat to containment integrity. Based on those recommendations, the proposed revision to 10 CFR 50.44 eliminates requirements that pertain to only design- basis LOCAs. Attachment 2 to SECY-00-198 (Ref. 1) used the framework described in Attachment 1 to the paper with risk insights from NUREG-1150 (Ref. 2) and the integrated plant evaluation programs to evaluate the proposed requirements in 10 CFR 50.44. It was noted in Attachment 2 that containment types that rely on pressure suppression concepts (i.e., ice baskets or water