Evaluation of the Response of Tritium-in-air Instrumentation to HT in Dry and Humid Conditions and to HTO Vapour
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Nuclear plant (power generation, decommissioning and reprocessing operations) have a legal requirement to monitor releases of tritium species for regulatory compliance and radiation protection purposes during normal operating conditions.
Tritium-in-air monitors are typically calibrated in dry conditions but in service may operate at elevated levels of relative humidity. The NPL radioactive gas-in-air calibration system has been used to study the effect of humidity on the response to tritium of two tritium-in-air ion chamber based monitors and one proportional counting system which uses a P10/air gas mixture.
In each case instrument responses were initially obtained for HT in dry conditions (RH ~2%), HT in 45% RH, and finally HTO at 45% RH.