To use residual blood of blood examinations in radiation workers for chromosome examination, a culture method of EDTA-treated human peripheral lymphocytes by adding 3 metal rations (Ca, Zn, Fe) was developed. EDTA-2K, an anticoagulant to be added to blood for blood examinations, is an effective inhibitor of PHA-induced lymphocyte transformation, whereas several metal cations have been reported to be effective in reversing EDTA inhibition of PHA-induced transformation. In the experiment, the solutions of 3 metal cations (Ca, Zn, Fe) in several concentrations were added to EDTA-treated blood for culture. It was found that when mol-concentrations of Ca, Zn, Fe ions were 3, 0.4, 0.25 times respectively as much as the concentration of EDTA in blood, a maximum number of mitotic cells could be observed. In 50hr incubation, the number of mitotic cells observed, using the EDTA-2K method, was approximately 36% of that observed in PHA-stimulated culture of blood without EDTA using the conventional method. However, over a period of 74hr incubation, the results by the two methods became very similar.
The concept of effective dose equivalent was introduced as a primary limit in the ICRP 26. It was proposed that deep dose equivalent index could be evaluated as a secondary limit for external dose limitation system. A thermoluminescent dosimeter (TLD badge) using Li2B4O7(Cu) elements has been developed to measure deep dose equivalent index for photon depending on this dose limitation system. Radiation characteristics were studied using this TLD badge and a phantom. The results were obtained as follows, 1) Deep dose equivalent index was able to be measured with the accuracy of 20% by 7Li211B4O7(Cu) element under 1, 000mg/cm2 filter. 2) In the condition of anterior irradiation, the ratios of effective dose equivalent to deep dose equivalent index were 0.65, 0.76 and 0.85 for photon energy of 60, 100, 662keV respectively.
Iodine-129 will be accumulated in the environment owing to its long half-life. In order to estimate its impact on man, it is necessary to obtain the information about its accumulation and movement in the environment over the long period. In this paper, the sorption and desorption of iodide (I-) on sandy soils were examined by using column and batch experiments. The results obtained were as follows: 1) Every breakthrough curves of I- showed plateau, before the ratio of concentration (C/C0) were reached 1.0. The ratio C/C0 on plateau in the effluent was affected by the kind of soil and NaI concentration in the inflow solution. 2) Iodine once sorbed on soil would be scarcely removed with 5.0×10-4mol/l CaCl2 solution. 3) Chemical form of iodine in the effluent was identified, showing that, more than 90% was recovered as I-. 4) In batch experiment, the equilibrium period on the sorption of I- by anion exchange resin and soil was examined. The equilibrum period on the sorption by anion exchange resin was within 3hr, but the period by soil was more than 15 days. This means that the sorption phenomenon of I- to soil is not always based on an ion exchange reaction on the surface of soil particle. 5) A new theory should be examined for evaluating the movement of I- in a soil.
Comparison of tritiated water leak rate into air and water from hydrates of calcined plaster or molecular sieve which used as fixation materials for waste storage was made. The results were as follows; (1) The leak ratio of tritiated water varied with square root of time when the specimen were in water, but it varied linearly with time when they were in air. (2) The tritiated water leak rate into air was smaller than that into water; for example, 1/100 in hydrates of calcined plaster or 1/6, 000 in molecular sieve adsorbent, comparing the time to reach at 50% of leaked tritium fraction. (3) The fixation materials which show good containment of tritiated water in water leak test were also good in air leak test. (4) The leak rate was reduced by use of the coating of adsorbent with methylmethacrylate polymer or in low humidified air. Furthermore, we discussed the difference of mechanism between leakages into water and air, and finally the amount of tritiated water leaked from a hydrates of 200 litre drum can size for extended period was estimated.
We investigated a practical method for assessing effective dose equivalent, one-cm-depth dose equivalent and mid-line dose equivalent by using personal dosimeters. Film badge, CaSO4-TLD and pocket dosimeter were used as the personal dosimeters. All these dosimeters were put on the chest surface of a Mix-DP phantom. BeO-TLDs were set in the phantom in order to measure depth-dose distributions. The phantom was irradiated to unidirectional or isotropic radiations from 137Cs, 226Ra and 241Am. From the view point of radiation protection practice, we calculated the factors for converting the reading values of dosimeters to effective dose equivalent, one-cm-depth dose equivalent and mid-line dose equivalent. The conversion factors to these dose equivalents were proposed 0.9, 2.0 and 1.1, respectively, from the present experiment. We considered that mid-line dose equivalent was the most appropriate value for external radiation, since it was close to effective dose equivalent and simple to estimate.
Effective dose equivalents in practical use were estimated in outdoor fields and in a reactor room of the Kyoto University Reactor on the basis of the energy distributions of the external photons. Gy to Sv (R to rem) conversion factors for respective organ or tissue of Japanese reference man were determined referring to the results by T. MARUYAMA et al., T. D. JONES et al., R. KRAMER and G. DREXLER in the energy region from 0 to 10MeV. Differences between the anterior and the posterior exposures of workers were evaluated in the natural environment and in the controlled area of workplace using thermoluminescence dosimeter. The ratios of the effective dose equivalent to the exposure was almost constant in the various natural environmental conditions, with the exception of the sky shine gamma-ray field, while its ratio changed by almost 5 percents depending on the energy spectrum of the measuring point in the reactor room. It also became clear that the effective dose equivalent varied remarkably with the direction of incident photons on a human body when they were dominantly composed of the low energy photons below 0.4MeV in the reactor room.
A household dehumidifier was used to collect the moisture from air without the need of air pump and desiccants. The continuously collected water samples were enriched by alkaline electrolytic method and the concentration of tritium was measured by a liquid scintillation counting system. The minimum detectable concentration of this method was 30pCi/l·water (0.48pCi/m3·air) which is much lower than the enriched tritium concentration of the environmental air samples. To observe the influence of the 25th nuclear denotation of mainland China on the atmospheric tritium concentration of Taiwan, 73 samples were continuously collected and measured in Kaohsiung. Data showed that the variation of tritium concentrations in the atmosphere were in good agreement with the variation of meteorological conditions. This showed that the developed method was available and reliable for the measurement of tritium concentration in the atmospheric water vapor.