The purpose of the present study was to estimate a biological half-life of iodine in normal Japanese thyroid for the calculation of the thyroid dose from iodine-129 with a long physical half-life. The Japanese takes stable iodine through sea food in a more considerable amount than the Caucasian who is assumed to be the Reference Man recommended by ICRP. It can be shown by medical research in thyroidology that the iodine metabolism between the Japanese and the Caucasian is different owing to the amount of the ingested stable iodine. Furthermore, in the Japanese the thyroid releases inorganic iodine since it takes up iodine more than physiologically required to produce thyroid hormone. We calculated the biological half-life of iodine for both the Japanese and the Caucasian by using a five compartment model. The following results were delivered. The biological half-life in the Japanese was approximately 40 days, which was in agreement with the values reported before. On the other hand, that of the Caucasian was 130 days nearly equal to the Reference Man.
The influence of interstitial water velocity on the migration of Sr-85 and Cs-137 in an aerated sandy soil layer was studied at different feed water velocities and feed times. As well known, it was found that Sr-85 migrated with interstitial water, but Cs-137 little migrated with interstitial water. The apparent migration velocity for each fraction corresponding to three concentrations (2×10-2, 1×10-2 and 5×10-3μCi/g) of Sr-85 was further investigated. At constant interstitial water velocity (1cm/mm), different values were given for the apparent migration velocity of three fractions, and the fraction with thin concentration migrated faster. At constant feeding time (100hr), there was a linear relationship between apparent migration velocity of three fractions and interstitial water velocity, in the range of slow water velocity (<1cm/mim). However, there was no linear relationship between apparent migration velocity of two fractions (equal to the concentration of 1×10-2 and 5×10-3μCi/g) and interstitial water velocity, in the range of fast water velocity (>1cm/min).
Bulk-etch rate (VB) is one of the most fundamental characteristics in solid state nuclear track detector (SSNTD). For CR-39, a new important SSNTD, the VB was measured by changing the concentration of NaOH solution from 10 to 30% and the etching temperature from 50 to 70°C. The amount removed by etching was determined by measuring the thickness of detector before and after etching with a micrometer. The detector absorbed water and subsequently swelled. A way to remove the water was obtained, which raised the reliability in the measurements. The VB was found to be constant during etching and 1.18×1010 exp (0.122×C)·exp(-8.74×103.1/T) (μm/h), where C and T are the concentration (%) and the temperature (°K) of etchant respectively. The activation energy was calculated and found to be 0.75eV.
The toluene extraction-liquid scintillation counting method was used to measure the radon concentration in water samples of Taiwan, R. O. C. The experimental results showed that the counting efficiency for both α and β emitted from radon and its daughters could reach 100%. The separation of activity of 222Rn from 220Rn was performed according to Bunny method. Thirty sampling stations including water samples from wells and hot springs throughout Taiwan were analyzed. The measured data show that 220Rn has much higher concentration than 222Rn. The concentration for the former is in the order of 10-7Ci/l while that for the later is about 10-10Ci/l.
In order to evaluate the deposition rate of airborne radon daughters, the cellulose nitrate films Kodak LR115, type II had been put on the walls inside and outside of buildings. After having been exposed to airborne radon daughters for about one year, the films were collected and etched for 140min using 2.5N NaOH solution at 60°C. Then the track densities were counted under the microscope. From the track densities, the deposition rates of radon daughters (φA) were evaluated, the value of which showed fairly good correlation with 222Rn concentrations measured at each location. The deposition velocities were also estimated from φA using the concentration of free RaA atoms (RaA atoms unattached on aerosols) measured simultaneously with φA, and were found to be 0.7-1.0cm/s which agree fairly well with the values obtained by other researchers.
In order to clarify the safety of Ca-DTPA and Zn-DTPA recommended to use as drugs in the therapeutic removal of incorporated radionuclides from the human body, the teratological study on these two agents was carried out in rats as one of a series of the toxicological tests. The teratological effects of DTPA were observed because the fetus is highly susceptible to any drug. The pregnant females of Wistar rat were injected subcutaneously daily on days 9-13 of gestation with 1, 6, 12, 24 and 36 H. D. (H. D.=human dose, 1 H. D.=30μmol/kg body weight) of Ca-DTPA or Zn-DTPA, respectively. In the dams, no toxic effects were observed. In the fetuses, the decrease of the survival rate was observed in only the group injected daily with 36 H. D. of Ca-DTPA. Some cases of gross defects of fetuses: the exencephaly, microphthalmia, anophthalmia and fusion of ribs were observed in the groups injected daily with 12, 24 and 36 H. D. of Ca-DTPA. The results obtained show that Ca-DTPA should not be given to a pregnant woman. However, no toxic effects of either Ca-DTPA or Zn-DTPA observed in the dams and of Zn-DTPA even in the fetuses indicate that these agents can be used by a radiation worker who usually is an adult man.
Present report deals with a computer program which provides a method to calculates absorbed radiation dose of various organs from radionuclides internally distributed in the body. The program is based on the MIRD method and a transformation method which estimates absorbed doses for physiques different from the MIRD phantom, for example, those for Japanese people. Specific absorbed fractions for arm bones and leg bones were calculated in terms of the buildup method in order to estimate Japanese red bone marrow dose. Specific absorbed fraction for breast was estimated in the MIRD phantom by using the buildup method. The program list will be sent by request.
The world population has been exposed to fallout plutonium from nuclear tests. About 320kCi of 239+240Pu was deposited on the earth for the period from 1945 to 1973. In this work, the organ burden and the dose to man have been estimated by using the measured airborne 239+240Pu concentration from 1954 to 1980 in Tokyo and Ibaraki. The model for the respiratory system developed by the ICRP Task Group on Lung Dynamics and the “source-target method” were used to calculate the burden and the dose. The burden in the organs of the reference man exposed to airborne 239+240Pu was estimated to be 0.028pCi in lung, 0.16pCi in lymph node, 0.51pCi in liver, 0.58pCi in bone and 0.00049pCi in testes, respectively at the end of 1980 based on the assumption that the Activity Median Aerodynamic Diameter (AMAD) was 0.4μm and the solubility class was Y. On the same assumption, the cumulative dose from 1954 to 1980 was 18mrem to lung, 760mrem to lymph node, 8.5mrem to liver, 2.7mrem to red marrow, 38mrem to endosteal surface and 0.39mrem to testes, respectively, and the effective dose was 5.6mrem. The burden and the dose for other cases of the AMAD and the solubility class have also been estimated.