4 U.S. NUCLEAR REGULATORY COMMISSION, STANDARD REVIEW PLAN X,< OFFICE OF NUCLEAR REACTOR REGULATION 6.2.5 COMBUSTIBLE GAS CONTROL IN CONTAINMENT REVIEW RESPONSIBILITIES Primary- Containment Systems Branch (CSB) Secondary- None

CSB reviews the information presented in the applicant's safety analysis report (SAR) concerning the control of combustible gases in the containment following a loss-of-coolant accident to assure conformance with the requirements of General Design Criteria 41, 42 and 43. Following a loss-of-coolant accident, hydrogen and oxygen may accumulate inside the containment. The major sources of hydrogen and oxygen are: a chemical reaction between the fuel rod cladding and steam, the cor-rosion of aluminium and other materials by an alkaline spray solution, and the radiolytic decomposition of the water in the reactor core and, the containment sump. If excessive hydrogen is generated it may combine with oxygen in the containment atmosphere. For inerted containments, the potential exists for hydrogen to combine with oxygen generated following the accident. The CSB review includes the following general areas: 1. The production and accumulation of combustible gases within the containment following a postulated loss-of-coolant accident. 2. The capability to mix the combustible gases with the containment atmosphere and prevent high concentrations of combustible gases in local areas. 3. The capability to monitor combustible gas concentrations within containment. 4. The capability to reduce combustible gas concentrations within containment by suitable means, such as recombination, dilution, or purging