Study on source of radioactive material in primary coolant of HTTR

In the primary cooling system of the High-Temperature Engineering Test Reactor, the highest dose rate was observed at the Helium Gas Circulator filter areas. To find the origin of the radioactive material, the radiation dose rates, and γ – ray spectrums were measured. From these results, it is clear that the main radioactive nuclide at the filter is 60Co after 6 years reactor shutdown, and the incore materials are a low possibility as the candidates of radioactive materials. It is also clear that the mixtures of materials, the contained low-level impurities and other new candidate materials must be considered. (author)