Gamma scanner for radiation hotspot imaging and nuclide identification

Presence of radiation hotspots in operating areas of a nuclear facility is of great concern to a Health Physicist as unidentified hotspots can lead to unexpected higher exposures of radiation workers. Effective dose management requires locating hotspots, nuclide identification and root cause analysis of its formation. This information is useful in deciding and implementing effective action plan and preventing hotspot reappearance. Surveys with existing portable survey instruments result in exposure of the surveyor and there are chances of skipping high radiation spots. Moreover, these do not have facility for nuclide analysis (except for few instruments such as NaI:Tl based Field Spec identifier which can identify certain radionuclides but has a poor resolution). Semiconductor based Cadmium Zinc Telluride (CZT) RoSCAN gamma imager which can be operated at room temperature was procured by Health Physics Division. It has a capability of locating radiation hotspots and identification of contributing radio nuclides. This instrument being first of its kind in our country, detailed performance evaluation of the instrument was carried out systematically using standard gamma radiation sources in laboratory conditions for arriving at its optimum settings for desired results. The instrument was also used in a few nuclear facilities. Systematic data collected has helped performance evaluation of the gamma imager over a wide gamma energy range of interest for hotspot identification and nuclide analysis has been carried out at Bhabha Atomic Research Centre. Field surveys conducted have helped in confirming optimum settings and minimum time of spectrum acquisition so as to implement ALARA during surveys. With the optimised settings, this instrument can be used in locating radiation hotspots in nuclear facilities and analysing radionuclide contents