5.1 Activated carbons used in containment systems for nuclear reactors must be capable of functioning under both normal operating conditions and those conditions which may exist following a design basis accident (DBA). Adsorbent beds that are part of recirculatory systems inside containment may be exposed to the peak pressure, temperature, and steam content of a post-DBA condition.
5.2 Carbon beds outside containment will be protected by fast-acting shutoff valves from the sudden rise in pressure, temperature, and humidity of the containment atmosphere which would exist following a DBA. However, some rise in temperature and humidity will be experienced even by beds outside containment if they are reconnected to containment after the initial pressure rise (due to escape of steam into the containment volume) has been reduced by containment coolers. The amount of radioactivity that can reach either type of adsorption system is conceivably quite high; hence, there is a possibility of a bed temperature rise due to decay heating. The gaseous radioactive contaminants of most interest are organic iodides. In this test, CH3I is used to typify the performance of the carbon on organic iodine compounds in general. The test described here provide a reasonable picture of the effectiveness of an activated carbon for organic iodides under normal and post-DBA conditions. The equipment and methods described can be used, with discretion, for similar tests at different gas flow conditions and, to some extent, on different gaseous radioactive contaminants and other adsorbents.
