Fission fragments mark scars on such an insulator as glass or mica, when fissions take place on the surface of or inside the insulator material. Very small scars on the surface of the insulator material caused by the fission fragments can be etched by the suitable chemical treatment to form etch-pits visible under the ordinary microscope. Therefore the combination of the fissionable material and the insulator material can be used for neutron detection or neutron dosimetry. We used thin film of uranium or thorium electrodeposited on gold foil as the fissionable material and the glass or mica as the detector material of the fission fragments. The thin film of the fissionable material was kept in contact with the surface of the glass or mica. The effect of the different etching condition and the stability of the scars have been studied. It has been shown by the fission film-glass or mica combination that a good agreement exists between the expected number of fissions and the number of etch-pits. Distribution of thermal neutron flux in the reactor (UTR-B) was estimated with this system. The results of the etch-pit counting were in good agreement with those estimated with the activation method. A wide range of thermal neutron dose 10 mrem to 1000 rem may be measured with a single detector of this type with reasonable accuracy.
Putting on the base of previously reported data on life-span shortening in irradiated mammals, life-span shortenings were estimated in man exposed with the dose rate of 5 R/year calculated from the present maximum permissible dose during 18 to 60 years old and with the dose rate of 0.2 R/day during 20 to 60 years old. The calculated values of life-span shortening were nil to 4, 070 day at 60 years old in man exposed with 0.2 R/day and nil to 1, 690 days in man exposed with 5 R/year. The possibility of life-span shortening in man exposed with the present maximum permssible dose could not be denied by the present estimation. The calculated results that radio-sensitivity responsible to life-span shortening was depending on the age, suggested that the age to start radiation works had better to be limited more than 25 years old under the condition to end radiation works at 60 years old.
The decontamination of cloth by means of commercial detergent and EDTA with suitable concentration has been carefully examined. Emphasis is laid on the temperature involved during the decontamination process. the effect of the interval of depositing the contaminated cloth, and the pretreatment with starch or with a mixture of starch and EDTA before the cloth being contaminated. A conclusion is reached that the contaminated cloth can be treated more easily if it was pretreated with 0.3% EDTA and 1.5% starch solution.
The present status of radioactive waste management on Taiwan is described. Emphasis is concentrated on the facilities, methods of waste treatment, and the quantities of waste disposed during 1962-1966. Some particular experiments related to the improvement of waste disposal are given. Future development and the description of a prospective waste management center on Taiwan are also included.
Telluric acid can be recovered from iodine-131 production liquid waste. The waste was alkalized with ammonia water and precipitated with alcohol. The crude ammonium tellurate precipitate can be turned to telluric acid by recrystallizing from nitric acid. Spectrophotometric and chemical analysis of telluric acid showed that the purity of recovered telluric acid was satisfactory. The recovered telluric acid was reused, and showed the yield of iodine-131 from recovered telluric acid was the same as from original Cica C.P. grade telluric acid.