The organization of health physics and safety in U.K.A.E.A. were surveyed during the visit of the author to A.E.R.E., Harwell. At A.E.R.E., Harwell, the number of operational health physicists expressed as a percentage of all staff employed is said to be the smallest, as well as Los Alamos Laboratory, U.S.A., among the establishments in the world and also the great deal of effort is made in the basic research of health physics. In this report, the organization of health physics and safety in U.K.A.E.A., especially at large reactors, compared with JAERI is described.
Since there was no precedent in the management of radiation control in Japan from the standpoint of commercial power station, we were obliged to grope in the dark in establishing a policy at our station at first. Not being expert by nature it was necessary for us to deal with problems open-heartedly as unique matters which would crop up one after another in the course of practical business at site. Anyhow we were able to set our business in the right direction at present by conducting to suit the circumstances of our station though we were forced to make rules in various respects in attaining normal operation. An interesting experience gained at Tokai station has been compiled in this manuscript on the actual conditions of radiation control and the problems we had in mind during the period from the initial stage of operation to normal operation of the station based on the article introduced at the third research presentation meeting and we would like to present it to you all for a new trial.
In order to measure the particle size distribution of α-emitting dusts, the autoradiography method has been studied. Dusts involving 10% enriched Uranium oxide and Pu nitrate have been measured by the method after being sampled on the millpore filter AA. MMD of about 2.8μ in the UO2 case and that of about 1.7μ in the Pu case were obtained. The results are compared with those measured by conventional microscopic method. Several points to be exposed to careful consideration are discussed, in which (1) transfer rate of dusts from filter to photo-film, (2) Distribution pattern of dusts on the film for measuring of the alpha track, (3) geometrical efficiency of α-emittion in the film emulsion, (4) exposing time for radiography, and (5) determination of real gravity of dusts, are supposed to be of importance. The authers think the method is rather simple and economical and easy for the treatment, compared with those conventionally used for particle size measurement, and particularly worth while for applying to that of α-emitting dusts.
Metallurgical tests on irradiated natural uranium fuels of the JAPCO's Tokai reactor were carried out at the Hot Laboratory, JAERI. During cutting the fuel, fission products in the fuel were dispersed inside the cave in the form of airborne material, and were released to the stack. The concentration of airborne fission products in the cave, in the exhaust ducts and in the stack were assessed by the air sampling. Dispersion factor, removal efficiency of the exhaust air filtering system and release fraction from the stack for fission products were obtained from the result of air sampling. Dispersion factor depends on the volatility of each fission product, for example, 4.4×10-3 and 2.0×10-3 for I-131 and Cs-137 respectively, and varies with cutting procedures. Removal efficiency of the exhaust air filtering system was found to be 80% for I-131 and about 97% for other fission products. Distribution of airborne fission products collected in three types of sampling medium i. e. cellulose-asbestos filter paper (HE-40), charcoal-impregnated filter paper (CP-20B) and charcoal cartridge are also described.
A method is described for the analysis of plutonium in human urine. The urine sample is wet-ashed with nitric acid and the residue dissolved in hydrochloric acid. Plutonium (IV) is coprecipitated with iron cupferride from this solution and extracted with chloroform. After removal of the iron by liquid extraction, the plutonium is electrodeposited onto a stainless-steel disc with a circular area of deposition of 254 mm2 from M in NH4Cl and 0.01M in oxalic acid electrolyte and alpha counted. The quantitative electrodeposition of plutonium and removal of the iron by extraction with di-isopropyl ether is discussed. The recovery of 1 to 100 dpm of plutonium from 1.5 1 of urine is 80.7±9% and the analysis time 4 to 5 hours.