Detection of fission product noble gases by in-vivo monitoring systems

The whole body counting laboratory at RSD, Indira Gandhi Centre for Atomic Research (IGCAR) houses shielded chair whole body counting system and a phoswich based lung monitoring systems as part of in vivo monitoring service. Following a fuel clad failure incident that had occurred at the Fast Breeder Test Reactor (FBTR) there was increase in the levels of fission product noble gas activity in some areas of the plant. Immediately, following the incident all the occupational workers who have entered the RCB for carrying out a planned job, have reported for in vivo monitoring under special monitoring procedures. The workers were subjected to both whole body counting and lung monitoring. The measurement has given us confidence that the combination of phoswich detector and whole body counting system can efficiently detect radio-xenons in the absence of HPGe-based monitoring systems. The monitoring has to be carried out as immediately as possible for efficient detection and estimation. If one could have repeated measurements on the first day, it could have provided additional information about biokinetic behaviour of radio-xenons in the subjects. The experience indicates the requirement to establish a procedure for radio-xenon dose estimation