The present study was conducted to investigate the decontamination procedure for the skin contaminated with radioactive materials; those were cobalt-58 (58CoCl2), mangan-54 (54MnCl2) and radioactive CRUD (Chalk River Unidentified Deposit) and the skins of pigs were used. The procedures and materials used for decontamination were as follows: (1) 0.5% Hyamin solution, (2) brushing, (3) acid soap, (4) stripping cream, (5) cosmetic cleansing cream, (6) potassium permanganate and sodium thiosulfate solutions, (7) titanium oxide paste, and (8) their combination. Each procedure was performed for 2min, and repeated twice or 4 times at 15 or 60min after contamination. The residual radioactivity after decontamination procedure was measured with a 2×2 inch NaI (Tl) scintillation detector or a solid state detector. The following sequential procedure was most effective: washing with 0.5% Hyamin solution for 2min, brushing with acid soap, rubbing cosmetic cleansing cream and washing for 2min with tap water. Since this procedure is simple and not irritable, it is appropriate for human skin. The residual activities on the skin after this decontamination were about 20, 20 and 10% for cobalt, mangan and CRUD, respectively. When the decontamination with 0.5% Hyamin solution began within 15min after contanimation, the residual radioactivity was 3% of administered activity, but 60% in the case 60min after contamination. Thus, a noteworthy point for decontamination is to begin as soon as possible.
Thorotrast, a colloidal solution of thorium dioxide was injected to wounded soldiers, for angiography from 1930 to 1945. The patients who received Thorotrast are interesting objects for finding a biological effect due to the internal irradiation by 232Th. To determine a distribution and body burden of 232Th, forty-one Thorotrast patients were measured their gamma-rays with a pair of NaI (Tl) scintillation detectors coaxially positioned above and below the coach in the whole body counter of Nagasaki University. The comparison between the usual method using constant values and the method using individual values depend on the organ positions determined with CT (Computed Tomography) scanner for patients was performed to estimate the errors due to the individual differences in the detection efficiency of 232Th. From the results, the estimates by the whole body counter of the amounts of 232Th deposits in abdominal region were obtained within the uncertainties of 16%. And the absorbed dose in the liver and the spleen was also estimated from the amounts of 232Th.
Assessment is made on the yearly trend of change in the age-specific accidental fatality rates due to occupational work in seven categories of industries in Japan during the period from 1973 to 1983. Data base utilized were (1) Annual Report of Workmen's Accident Compensation Insurance Council (Ministry of Labour) and (2) The Population Census (Statistics Bureau), on which accidental fatality rates were calculated for the occupation of forestry, fisheries, mining, construction, manufacturing, transportation and communication, and electricity, gas, water, steam and hot water supply. Accidental deaths in occupational workers showed a rather wide distribution ranging from 1000-1500 per million per year in mining to tens per million per year in manufacturing or electricity and others supply, all of which indicated tendency of decrease by year. Mean ages of workers were found greater by a few to several years than those of the deceased in all occupations except for fisheries. Agespecific fatality rates showed a trend of increase with the age in all occupations except for fisheries. Comparison was made on these results with those of other countries which were shown in ICRP Publications 27 and 45 in terms of number of accidental deaths per million per year, specifically, with the values in U. S. A. for the years of 1969 and 1972 as given in ICRP Pub. 27 and with those in Canada for the years from 1975 to 1981 as given in ICRP Pub. 45, respectively. In conclusion, fatality rates from occupational accidents in various industries in Japan are within the same order of levels which were observed in other countries as cited in ICRP Reports.
Each soil sample of more than 10kg (dry weight) was collected on three sites in southern part of Seta in Shiga prefecture and was separated into seven particle sizes. Each sieved soil sample was analyzed for the mineral compositions by means of X-ray diffraction and the concentrations of 238U, 226Ra, 228Ra and 40K by means of γ-ray spectrometry with Ge (Li) detectors. There were trends for the contents of anorthite (calcium-rich feldspar) decrease rapidly and those of albite (sodium-rich feldspar) and quartz to decrease slowly as particle size decreased. It is found that the concentrations of 238U, 226Ra, 210Pb and 228Ra increase with decreasing particle size and that of 40K decreases with decreasing particle size. It is concluded that for the soil weathered from a mother's rock the concentrations of 238U, 226Ra, 210Pb and 228Ra decrease with increasing the concentrations of 40K.
Experiments on direct probe measurements and smear tests were performed on various surface materials contaminated with alpha emitters, with a view to make clear the relations between the measurement effectiveness and the nature of surface. Uranium and 241Am were used for low and high specific activity contaminants, respectively. Main observations for direct measurements are: 1. For low specific activity alpha emitters, alpha probe measurements are unsuitable. Beta-gamma probes should be used, since the response is fairly constant on surfaces and compares well with that obtained from a thin alpha calibration source. 2. For high specific activity alpha emitters, the sensitivity of alpha probe measurements confirms the level of the derived limit of alpha surface contamination for controlled areas (3.7Bq/cm2), although the response varies with the nature of surface by factors less than 5. Per cent activity transferred to smear from surfaces are presented for low and high specific activity nuclides.
We performed an attempt for application of a radon daughter monitor which enabled the measurements of individual activity concentrations of short lived radon daughters in a natural environment. The monitor was fundamentally based on a filter method with gross counting, which was refered to as Tsivoglou-Thomas method; the radon daughters in the air were sampled on a membrane filter and α rays from RaA and RaC' in the collected daughters were counted over three time intervals. By comparing these counting values with theoretical decay characteristics, the activity concentration of each of three nuclides (RaA, RaB, RaC) was obtained. The precision of the assessment of activity concentration in this method depends on several parameters related to the measuring conditions. Therefore, to enable the most precise assessment of the activity, the values of these parameters were determined, based on the calculation of error propagation. The calculation showed that the most sensitive parameters to the assessment were a flow rate (L) of sampling air, a total counting time interval (t1+t2+t3) and a waiting time (t0) which is a time interval from the end of the sampling period to the start of count. Based on the results, we determined the values of these parameters as follows: sampling time=10min, t0=10sec, first counting time interval=4min, and second and third counting interval=27min. In order to confirm the validity of the monitor, the preliminary measurements were carried out indoor and outdoor. The result offered the possibility of using the monitor to automatically assess the activity concentration of short lived radon daughters.