Testing Iodine Filters for Nuclear Installations

The removal efficiency of iodine filters for nuclear installations has been tested The test method in use includes laboratory tests of the adsorber material (under MCA conditions for temperature, relative humidity, pressure, loading, stay time and bed depth) and in-place tests at the site of the installation. For removal of methyl iodide under high relative humidity Kl-impregnated charcoal is widely used. Most of the data for charcoal removal efficiency available today result from experiments with tracer amounts of CH3131I mixed with CH3127I. Considering MCA conditions, the validity of those data should be confirmed for specific activities on charcoal 103 - 106 times higher. Experimental data are given for realistic loadings with CH3131I up to 10 Ci/g charcoal under 100% relative humidity. For standard laboratory adsorber tests a method is discussed for humidification and control of gas streams up to 100% relative humidity at elevated temperatures. The apparatus used is described. Experimental data are given for the removal efficiency and the adsorption of water in charcoal samples from long-time tests under 100% relative humidity. The overall test period was up to 98 h, simulating the phase of elevated pressure and, therefore, high iodine release from the reactor containment. The reproducibility of long-time tests under extremely high relative humidity is shown and discussed. A description of the hardware for in-place tests is included and results are given. (author)