Airborne radioactivity concentration measurement in CORAL reprocessing facility during off ventilation condition

Compact Reprocessing of Advanced fuels in Lead cells (CORAL) is situated in Kalpakkam and reprocesses the spent fuels discharged from the Fast Breeder Test Reactor (FBTR). The effluents from the facility are released at 116000 m³/h through a 75 m stack. The continuous air monitors (CAM) and Alpha spectrometry CAM readings are vigilantly monitored. At 0645 hrs, a baseline air sample (AS) is collected in the OPA and after that, AS are collected periodically in the OPA with suitable protective gears. Finally, an AS is collected approximately after 1 hr after restoring the ventilation systems. All the AS and CAM samples are counted at different counting intervals of > 8 h, > 24 h and > 200 h to measure the long-lived radionuclide concentration. The stack flow meter showed 40000 m3/h after switching off the exhaust. The standard two-count method is applied to measure the long-lived activity. It is observed that the residual activity in the filter papers during the second counting interval is within the statistical fluctuation of the expected activity in the filter paper calculated using the first count. All the CAM, ASCAM and spot air samples showed below detectable level of activities (MDA=0.098 DACh) when counted > 200 hrs of delay. One important observation from this study is that the draft due to the stack effect is enough to maintain the containment's integrity during off ventilation condition. Further, the trend of ²¹²Bi concentration demonstrates that the ventilation systems can provide a protection factor of 100