Consistent with the guidelines of Regulatory Guide 1.7,[1] the prevention of local hydrogen concentrations in excess of 4% by volume after a LOCA requires mixing of the containment atmosphere. Preliminary calculations indicate that lower flammability limits will not be exceeded in the drywell of MARK III containments. However, additional evaluation and the development of a generalized calculational model applicable to all plants and conditions is needed. This item is documented in NUREG-0471.[2]
This item is covered in USI A-48, "Hydrogen Control Measures and Effects of Hydrogen Burns on Safety Equipment."
[1] Regulatory Guide 1.7, "Control of Combustible Gas Concentrations in Containment Following a Loss- of-Coolant Accident," U.S. Nuclear Regulatory Commission, November 1978. [7812270049]
[2] NUREG-0471, "Generic Task Problem Descriptions (Categories B, C, and D)," U.S. Nuclear Regulatory Commission, June 1978.
Page Last Reviewed/Updated 06/24/2025