For the adsorbents used in radioiodine monitoring in nuclear reactor accidents, high retention efficiencies for radioiodine species and low retention efficiencies for noble gases are required under various conditions such as relative humidity, sampling time and bed depth. To find the suitable adsorbents for air monitoring, retention efficiencies for methyl iodide and xenon were examined for Ag-zeolite, Ag-silicagel, Ag-alumina and TEDA-charcoal.
In Ag-alumina and Ag-silicagel-A, the retention efficiencies for methyl iodide were more than 97%, and the retention ratios, defined as the ratio of the retention efficiency for methyl iodide to that for xenon, were more than 10
5 under the conditions of face velocity 19cm/sec, relative humidity ≤20-90%, loading time 5-60min and bed depth 2cm. For other two adsorbents, with lower retention ratios, the retention ratio could be raised by means of post-test ventilation of the adsorbent by clean air.
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