In this paper we described an experimental study on the first aid for the accidental intake of radionuclides. Following experiments on first aid were made: (1) Sodium Alignate or prussian blue was respectively given orally to the mice immediately after administration of 85Sr or 134Cs. (2) Isotonic saline intraperitoneal treatment as a type of water supply or DTPA oral treatment was made to the mice immediately after intravenous injection of 58Co or 54Mn. The whole body retention in mice was measured with a 5cm NaI(Tl) scintillation detector up to 28hr after administration. Sodium alginate or prussian blue reduced intestinal absorption of radiostrontium or radiocesium. DTPA and isotonic saline increased excretion of radiocobalt and radiomanganese in urine. DTPA oral treatment reduced the whole body retention of 58Co to 66% and 54Mn to 89% of the control. It was worked out from the dose estimation that the intraperitoneal injection of 10ml isotonic saline or DTPA oral administration immediately after 58Co injection decreased the internal radiation dose by approximately 22% or 14%, respectively.
Upon the indoor concentrations of radon short-lived decay products, the influence of the air-exchange has been studied. On the basis of a simple model, the degree of radioactive disequilibrium between radon short-lived decay products has been calculated. These calculations were performed taking into account of: (1) the collection efficiency of ventilation equipment at the side of air supply, (2) the removal of radioactivity by ventilation and wall deposition, (3) the degree of radioactive disequilibrium of radon decay products to radon in outdoor air, and (4) the ratio of radon concentration between indoors and outdoors. The result estimated agrees fairly well with that observed in room air.
As a method for analysing epidemiological observations from populations occupationaly exposed to radiation, the proportional hazard model was applied to the simulated observations on the mortality assuming 40 years follow-up. The risk factor of cancer death for compiling the simulation is based on the value proposed by ICRP. The applicability of this method is discussed. Using the proportional hazard model, the estimated least population size for detecting the excess cancer deaths is 50 to 150 thousand. Two alternative conditions are also investigated using simulated observations, i. e., the risk factor is assumed 10 times greater, and the length of follow-up study period is shortened to 30 years. This method was compared to the multiple logistic model applied to deceased samples. The former method was more adoptive from the viewpoint of reducing the effects from time trend factors. Therefore, the proportional hazard model is applicable to assess the risk level of cancer death from radiation exposures based on the follow-up studies of human populations.
Reverse osmosis is a simple process and has relatively high decontamination factor comparing to other processes used for the treatment of radioactive liquid waste. Furthermore the quantity of secondary waste of this process is small. In this study, test solution containing nine elements such as cesium, strontium, cobalt etc. in chloride forms are treated by reverse osmosis. Permeate rate decreases as the increase of osmotic pressure of feed solution and is expressed by linear equation. Decontamination factor of cations of univalency is more than ten, and about one tenth of that of bivalency. Decontamination factors of all the elements used in this experiment are approximately estimated using the solution-diffusion model.
The collection efficiency, f-value, of a parallel-plate ionization chamber exposed to diagnostic X-rays has been numerically obtained. The results of calculations show that the f-value deviates from the well-known Boag's formula when the pulse duration becomes of the same order of the ion transit time between the electrodes. Furthermore, the effects of the pulse shape on the f-value and the output currents have been clarified. The output currents and the saturation curves have been measured in fields generated by an X-ray tube for medical diagnosis. There found a good agreement between experimental and calculated results. The true f-value has been determined by the saturation curve method previously reported. It was concluded from the experimental confirmation of the inverse square law of the exposure that the method was useful for diagnostic X-rays.
The present study was designed to investigate the decontamination procedures in first aid for wounds contaminated with radionuclides. Abrasion of mouse skin was contaminated with 58CoCl2. Irrigation by decontamination fluids began at 2min after administration of the radionuclide and continued for 14min. Tap water, 0.5% Hyamine solution or 10% Ca-DTPA solution were used as the decontamination fluids. Radioactivities of whole body, wounded skin surface and washed solution were measured with an animal counter with 5cm NaI (Tl) and a well-type auto-gamma-counter. Decontamination effectiveness were expressed as follows: (1) absorption rate of radionuclide through the wound and (2) residual rate of radionuclide on the wound. More than 20% of the radionuclide applied on the wounded skin was absorbed in 15min after contamination. The absorption rate decreased to 2% by the decontamination procedures. The Ca-DTPA solution reduced the residual rate of radionuclide on the wounds. The results suggested that the decontamination for the contaminated wounds should begin as soon as possible. Irrigation with 0.5% Hyamine solution has been advocated for the decontamination in the first aid.
In plutonium facilities, false countings have been experienced frequently in monitoring plutonium contaminations on clothes, gloves, vinyl sheets and arches of shoes. Electric fields, alpha contaminations and Rn concentrations were measured in the rooms of the facilities, and the conditions and the mechanisms of the false countings were studied through the measurements. It was found that the false countings are caused by the negative electrification of the surface of the objects and/or high Rn concentrations in the room air due to inflow of underground air.