The time variations of 222Rn were calculated using a local three-dimensional atmospheric dispersion model. The contribution of 222Rn emanated from at area near the measuring site to diurnal variations was estimated. The effects of a complex terrain were considered in this model. Some numerical analysis conducted in this study indicated that 222Rn emanated within a 40-kilometer circle around the objective point mainly contributes to diurnal variation of concentrations at the point. Simulated results considering the horizontal distribution of exhalation rate showed better coincidence with the observed results, compared with the results assuming a homogeneous exhalation rate. Model results were compared with three series of observed data of 222Rn concentrations at a height of 1m above the ground at Nagoya University. The variations of calculated and observed 222Rn concentrations were in good agreement.
This paper is intended to introduce the new recommendations of ICRP and IAEA to the practice of emergency preparedness and response. It estimates tentatively intervention levels for Japan as a case study with a human capital approach, describes a decision-making procedure with emphasis on decision-making in the early phase of an accident, and finally the authors' venture on the responsibilities of national and local competent authorities as well as the management of nuclear power plants for decision-making in nuclear emergency preparedness and response.
Transfer factors (TFs) of stable elements from soil to potato were determined for 26 pairs of samples which were collected at different sites in Aomori prefecture, Japan. The concentrations of 31 elements in both soil and potato samples were determined by neutron activation analysis. Several of these elements were divided into two groups, each having different TF characteristics. In the first group of elements, such as Cl, K, Ca, etc., an inverse correlation was seen between the TFs for each element and their concentrations in the soil. The relatively constant concentrations of these elements in potato were independent of the concentrations of the same elements in soil. However, in the second group, the TFs for other elements, such as Sc, Co and so on, in potato were independent of their concentrations in the soil. The fluctuation of TF observed in this study was smaller than that previously reported. It may be attributed to the fact that the experiment was done in a relatively narrow geographic area. In addition, the TFs for stable elements in this study were generally one to three orders of magnitude lower than those compiled for radioactive isotopes in IAEA publications. These differences should be precisely examined hereafter.
The radioactivities of eight main foodstuffs were investigated during 1985-1994 to evaluate the annual intake from the ingestion of 137Cs and 90Sr for the residents of Taiwan. The evaluation of annual intake was based on the results of radiochemical analysis of 90Sr and gamma-ray spectrometry of 137Cs as well as annual consumption rates of those foodstuffs in Taiwan. The annual intake of 90Sr and 137Cs per capita is 13 and 60Bq, respectively. Among the eight foodstuffs, fruit contributed the most to the annual intake of 90Sr, vegetable second, rice the third and egg the least. For 137Cs, rice contributed the most, then fruit, meat the third and flour the least. Based on the new conversion factors from ICRP 60, the annual committed effective doses of Taiwanese due to the ingestion of radionuclides 90Sr and 137Cs were estimated to be 3.7×10-7 and 7.8×10-7Sv, respectively.
The International Commission on Radiological Protection has recently recommended a new dosimetric model of the human respiratory tract, which was issued as ICRP Publication 66. This model permits us to calculate the deposition of inhaled particles for the subjects with different values of anatomical and physiological parameters in the respiratory tract. Using this model, we studied the variation of doses of 239Pu observed for varying body sizes, levels of physical exertion and breathing habits. The results are as follows. 1) The ratio of doses between the subjects with different body sizes does not exceed the reciprocal of the ratio of their body weights, because the deposition in the thoracic region decreases with decreasing body size, which partly compensates for the increase in the SAF (specific absorbed fraction) of α-particle energy in the smaller body size. 2) The effective dose per unit intake of 239Pu via nose breathing decreases with increasing level of physical exertion. 3) It is notable that breathing through the mouth enhances markedly the effective dose.