New Stack Effluent Monitoring System at the Risoe Hot Cell Plant

摘要

This report describes a new stack effluent monitoring system that has been installed at the Hot Cell facility. It is an integrating iodine/particulate system consisting of a gamma -shielded flow house in which a continous air sample from the ventilation channel is sucked through coal and glass filter papers. Activity is accumulated on the filter papers and a thin plastic scintillator detects the beta -radiation from the trapped iodine or particulate activity. The stack effluent monitoring system has a two-step regulating function as applied to the ventilation system, first switching it to a recirculating mode, and finally to building-seal after given releases of sup 131 I. The collection efficiency for iodine in form of elementary iodine (I sub 2 ) and methyliodide (CH sub 3 I) has been determined experimentally. The unwanted response from a noble gas release has also been determined from experiments. The noble gas response was determined from puff releases of the nuclide sup 41 Ar in the concrete cells. It is concluded that the iodine/particulate system is extremely sensitive and that it can easily detect iodine or particulate releases as low as a few MBq. A gamma monitor placed in connection with the iodine/particulate system detects Xe/Kr-releases as low as a few tens of MBq per second. (Atomindex citation 16:021092)