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In order to obtain data useful for the design of an air cleaning system at iodine-131 production facilities, the model 7FE charcoal filter (manufactured by Barnebey-Cheney Co., U.S.A.) installed in the exhaust air cleaning system at the lodine-131 Test Production Plant, JAERI was examined for performance for the removal of airborne radioiodine by using the airborne iodine-131 discharged into the exhaust system during the processing, the concentration of which ranges from 10-5to 10-8μCi/cc.The results obtained are summerized as follows:(1) Removal efficiency over a short period of 30 min at any time after the start of processing decreases with time, due to the increasing desorption of iodine; i. e. it maintains 97% on the average from the start to the first 2 hr independently of the relative humidity of the exhaust air, whereas from 8 hr after the start it decreases from about 95% to about 5% as the relative humidity is increased.(2) Removal efficiency as determined for long periods more than 5 hr after the start of processing depends greatly on the relative humidity; i. e. at relative humidity of less than 50% the removal efficiency over 24 hr after the start exceeds 90%, whereas at relative humidity of more, than 70% it decreases to 85%.(3) By installing the model 7FE charcoal filter in place of an absolute filter, an amount of iodine 131 discharged from the stack reduces to 1/20 on the average.(4) No appreciable deterioration of the performance for the removal of airborne iodine-131 is found through one year of continuous exposure to exhaust ventilation air from the Iodine-131 Test Production Plant.

Two types of cartridges to be attached to full face Gass masks, which are commercially available and have been in use for the purpose of preventing inhalation hazard due to airborne radioactive materials for a few years at JAERI, were examined for the performance of removing airborne radioiodine in order to obtain data necessary for establishing a guide of the radiation protection in wearing them.The airborne radioiodine-131 discharged ieto the exhaust system during the processing of iodine-131 at the radioisotope production plant was used for the tests, the concentrations of which ranged from 10-5 μCi/cc to 10-8 μCi/cc. The tests were carried out at the flow rate of 20 1/min (moderate work) and 40 1/min (medium hard work), respectively, in conditions of ralative humidities being over the range from 50% to 70%.This paper describes the experimental results on the penetration of airborne radioiodine two types of cartridges as a function of the period of air flow and discusses the relationship between the concentration and the service time, considering the leakage at seal between the mask and face.

Contamination limits on the skin surface employed as a guide of the radiation protection for occupationally exposed individuals are derived by taking into account the external exposure dose to the skin and the internal exposure dose recieved by the inhalation, ingestion and skin penetration of the contaminants.The adequacy of the derived limits is discussed in relation to the detection probability of a hand-foot monitor for the hand contamination.The contamination limits for the skin, which have been adopted in other establishments, are also reviewed together with the general basis of the derivation.

The Fuel Reprocessing Test Plant at JAERI was operated during the period of 1968-1969 to gain experiences of the fuel reprocessing.Fuel elements reprocessed were irradiated in the JRR-3 reactor up to about 700MWD/ton and cooled for 87-300 days.The purpose of this paper is to discribe the measured results of airborne radioiodine released in each stage of chemical processing and discuss collection efficiency of the charcoal impregnated filter paper for radioiodine in the presence of process off gas such as NO, NO2, NH3, HNO3 and solvent encountered during the fuel reprocessing.

The Fuel Reprocessing Test Plant at JAERI was operated during the period of 1968-1969 to gain experiences of the fuel reprocessing.Fuel elements reprocessed were irradiated in the JRR-3 reactor up to about 700MWD/ton and cooled for 87-300 days. Therefore, krypton-85 is the most dominant radionuclide in the long lived gaseous fission products and the major part of krypton-85 in the fuel is discharged from the stack to atmosphere in the process of uranium dissolution.The purpouse of the paper is to describe the measured results of gaseous krypton-85 released in each chemical processing and also to discuss the performance of krypton-85 gas monitor, in particular the relationship of counting rate and the inner pressure of the krypton-85 sampler. The measured activity of krypton-85 released was in fairly good agreement with the calculated inventory.

The Fuel Reprocessing Test Plant in JAERI was operated during the period of 1968-1969 to gain experiences of the fuel reprocessing. The fuel elements reprocessed were irradiated in the JRR-3 up to about 700MWD/ton and cooled for 87-300 days.Tritium is produced by ternary fission and is one of the important nuclides to be monitored during the reprocessing of the highly irradiated fuels, because it is easily released into the off-gas line and difficult to be trapped before discharging to the atmosphere.In this paper, the results of tritium monitoring at the stack are described. It was found that tritium discharged from the stack during the reprocessing was about 1% of the total inventory and its concentration in air was about 1×10-8μCi/cm3.