The Evalution of Gaseous Radioactive Materials in the Reactor Room and in the Exhaust from the Research Reactor

Abstract

The concentrations of several radionuclides released from the stack of the research reactor, Kyoto University (KUR) were examined according to the modified procedure of the regulatory guidance “The measurement of released radioactive substances from a light water moderated power reactor.”
It was found that the concentrations of all radionuclides detected such as tritium, iodine-131, -133 and strontium-90 etc. were sufficiently lower than the lower limit concentration in the air presented in the guidance except for the Ar-41. Then the radiation control system was established so that the average Ar-41 gas concentration for three months in the reactor room would not exceed the permissible concentration 4×10^-7μCi/cm3 regulated by the law, setting the reasonable alarm level 5×10^-6μCi/cm3 which is connected with the operational interval of KUR and the average Ar-41 concentration of the past twelve weeks.