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:
igned 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 fail in closed position). ii. For systems using recombiners, if the downstream hydrogen and/or oxygen concentration exceeds 4 percent (as appropriate), acceptable control features include automatic switching to an alternate recombiner train. iii. Injection of diluents to reduce concentrations below the limits specified herein. Systems designed to operate below 4 percent hydrogen and below 4 percent oxygen may be analyzed for either hydrogen or oxygen; systems designed to operate below 4 percent hydrogen only (no oxygen restrictions) should be analyzed for hydrogen; and systems designed to operate above 4 percent hydrogen should be analyzed for oxygen. For BWR systems with steam dilution upstream of the recombiners, analysis for hydrogen (oxygen analysis is not an acceptable alternative) should be downstream of the recombiners and upstream of the delay portions of the system. Analysis upstream of the recombiners is not expected if the system is designed to assure the availability of dilution steam during operation. For PWR systems using recombiners, analysis for hydrogen and/or oxygen should be downstream of the recombiners. In addition, unless the system design features preclude explosive gas mixtures of hydrogen and oxygen upstream of the recombiners, analysis for hydrogen and/or oxygen (as appropriate) should be upstream of the recombiners as well. The number of gas analyzers and control features at each location should follow the guidance of this SRP section. One gas analyzer upstream and one gas analyzer downstream of the recombiners should not be construed as dual gas analyzers. For systems involving pressurized storage tanks (excluding surge tanks), at least one gas analyzer should be provided between the compressor and the storage tanks. Dual gas analyzers set