Indigenous design, development and calibration of an online ¹³¹I monitor

Reprocessing of spent fuels result in release of radioactive gases, vapours and volatile fission products. Monitoring of the gaseous effluents in the stack is mandatory to ensure compliance with the discharge limits specified by the regulatory agency. Though the fuel that is being reprocessed at COmpact Reprocessing of Advanced Lead cells (CORAL) at Kalpakkam are sufficiently cooled resulting in significant decay of all the iodine ¹²⁹I, any other major event could result in release of ¹³¹I. In CORAL, as a matter of abundant caution and due to the possibility of processing highburn up, short cooled fuels, discharge limits are specified for Iodine also. Previously, monitoring of iodine was done offline using charcoal cartridges but present paper highlights the indigenous design, development and calibration of an online ¹³¹I monitor for stack. The estimated activity in one litre bottle was 4.396 nCi/ml. Assuming the same activity is dispensed in the sampling head, the efficiency for the sampling head was estimated to be 0.029 counts/Bq. Integrity of the sampling head was established by analysing the data obtained from repeated counting of the sampling head at fixed intervals. The online iodine monitor is presently installed in the existing stack sampling system with data logging facility and is connected to the Radiation Data Acquisition System at CORAL