Plate-out distribution of iodine in a high temperature gas cooling in-pile loop facility

The information of fission products (FPs) deposition and re-entrainment behavior in the primary coolant system is important for design and safety analysis of the high temperature cooled gas reactor. In the department of JMTR project, the distribution of FPs plated-out on inner surface of the primary coolant circuit of OGL-1 has been measured during reactor operating and after shut-down. The OGL-1 is a high temperature gas cooling loop facility used for irradiation tests of the high temperature engineering test reactor (HTTR) fuels. The measurement data of FP distribution in the primary circuit of the OGL-1 showed the temperature effect on iodine plate-out. The iodine plate-out activity decreased exponentially with temperature increasing, and about 60% of total iodine was plated-out in the two heat exchangers where the surface was cooled. The data of iodine concentration in primary coolant showed that iodine release rate from irradiation fuels increase with fuel temperature increasing. The iodine release rate at 1500degC was 100 times of the release rate at 1300degC. And this paper shows the change of iodine distribution by plate-out and re-entrainment behavior of iodine in a high temperature gas cooling loop irradiation facility according to reactor operation. (author)