Assessment of Interference due to 41Ar Releases from Operating Reactors at Site in Whole Body Radioactivity Measurements

41Ar released through the stacks of Cirus and Dhruva reactors at the Trombay site, disperses at times, towards the Whole-Body Monitoring Laboratory and causes interference in body radioactivity measurements. In order to investigate if a simple correction procedure based on its 1.29 MeV gamma rays photopeak intensity could be evolved, long-term studies were carried out with 'shadow shield bed' and 'shielded chair' whole-body monitors. It has been observed that for a particular type of system, the scattering contribution in the lower energy regions is always a constant fraction of the counts in the 1.29 MeV photopeak and is dependent mainly on the detector shield configuration and is practically independent of other parameters like shield material/thickness and concentration of 41Ar. The data presented here may be useful for such standard systems used elsewhere in similar situations or where whole-body monitoring has to be performed under accidental or planned releases of 41Ar. The contributions in the lower energy regions are found to be higher in the case of the shadow shield bed in comparison with the shielded chair monitor. This effect is attributed to the higher Compton scattering probability in the case of the former shield configuration through angles of 90 deg. or more. (author)