In view of the rapid increase of nuclear energy facilities such as power plants, fuel-reprocessing plants and so forth, the safe control of the disposal of radioactive wastes into the sea has been and will be of great concern in the world. The present paper deals with the following matters; (1) historical background information of radioactive contamination of the sea due to the past military use of atomic energy, (2) natural and artificial radioactivity in the sea, (3) general features of the behaviour of radioactive nuclides in marine environment, (4) safe management of coastal discharge of radioactive liquid wastes, (5) disposal of solid radioactive wastes into deep sea bottom, and (6) problem on international control of radioactivity release in marine environment.
This study was carried out to investigate the percutaneous absorption of radioisotopes and the first aid procedure for skin contamination accidents. In the experiments of the percutaneous absorption, a small amount of carrier free 32P (pH 1) or 90Y (pH<1, =10) was pipetted on the normal and the injured skin of rats, and the absorption of these radionuclides was measured for about one hour using the outer counting method. Autoradiographs of the skin contaminated with 32P or radiocolloidal 198Au were made. Percentage of the absorption of 32P through the normal skin was 6.5% of the applied amount. With injury on the skin, the amounts absorbed ranged from 20 to 90%, depending on depth and bleeding state of the wound, but coagulated blood which covered the wound was found to be a good barrier against the absorption of the radioisotope just like as the normal skin. The absorption of 90Y was affected with the pH and radiocolloidal 90Y was difficult to be absorbed through the normal and the injured skin. To investigate the blocking means against the percutaneous absorption, the effects of washing and of administration of tannic acid and epirenamine-hydrochlor were examined. Epirenamine-hydrochlor was found to have, although for short time, strong blocking effect against the absorption into the body. From this result, the use of peripheral-angiotonics has been proposed as a first aid procedure for the skin contamination accident.
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.