Document: NUREG-0800
Document ID: e1c5261f-4ef6-4478-8cf0-015611057574
Document Type: srp
Title: and 9.3.2, “Process and Post-accident Sampling Systems.”  The review addresses
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1502/ML15029A039.pdf
Revision Date: 2023-06
Chapter: 11
Section ID: 11.5
CFR Part: 
CFR Title: 

Content:
tion or buildup of explosive gas mixtures. The GRS is normally the only portion of the system that is vulnerable to potential hydrogen explosion. A. For a system designed to withstand the effects of a hydrogen explosion, the design pressure of the system should be approximately 20 times the operating absolute pressure (including the intermediate stage condenser for BWR offgas systems). B. Small allowances should be made to conform to standard design pressures for off-the-shelf components (e.g., if the system operating pressure is nominally 103 kPa (15 psia) but could approach 138 kPa (20 psia) by design, piping could be designed to 2413 kPa (350 psia), since the next higher standard pressure rating is 4137 kPa (600 psia)). C. The process gas stream should be analyzed for potentially explosive gas mixtures and annunciated both locally and in the control room. D. For systems not designed to withstand a hydrogen explosion, dual gas analyzers with automatic control functions should preclude the formation or buildup of 11.3-15 Revision 4 – January 2016 explosive hydrogen/oxygen mixtures. In this context, “dual gas analyzers” is defined as two independent gas analyzers continuously operating and providing two independent measurements verifying that hydrogen and/or oxygen are not present in potentially explosive concentrations. Gas analyzers should annunciate alarms both locally and in the control room. Analyzer “high alarm” setpoints should be set at approximately 2 percent and “high-high alarm” setpoints should be set at a maximum of 4 percent hydrogen or oxygen. Control features to reduce the potential for explosion should be automatically initiated at the “high-high alarm” setting. The automatic control features should be as follows: i. For systems designed to preclude explosions by maintaining either hydrogen or oxygen below 4 percent, the source of hydrogen or oxygen (as appropriate) should be automatically isolated from the system (valves should