Photon spectra were measured inside and outside a house in Minami-Soma city by using a NaI(Tl) scintillation spectrometer. The photons were categorized into three groups according to their energy. The groups were (1) scattered photons, which include low energy photons, (2) direct photons from 134Cs and 137Cs sources and (3) the other photons. Then the ratios of the ambient dose equivalents H*(10) of the scattered photons to those of the direct photons from the 134Cs and 137Cs sources have been evaluated from the measured photon spectra. The ratios are high inside the house compared with those out of the house. It was found that the scattered photons contribute to the H*(10) by more than 50% inside the house. The ambient dose equivalent average energies of the scattered photons are around 0.25 MeV both inside and outside the house. These data is worthwhile to design the optimum shielding for the protection against the public radiation exposure.
With regard to the calibration of dosemeters in the 90Sr/90Y reference field, the influence of the difference of beta-ray irradiation systems on the calibration results has been investigated. Two different types of beta-ray irradiation systems installed at the Facility of Radiation Standards (FRS) in the Japan Atomic Energy Agency (JAEA) were chosen for the comparison. The 90Sr/90Y sources of each system showed different depth-dose profiles reflecting different energy spectra due to their source structure. The difference in depth-dose curves implied the calibration results would be affected in the case of a thick dosemeter. In order to confirm the influence of the difference of depth-dose curves, optically stimulated luminescence ring type dosemeters were irradiated with both systems. The results showed the calibration factors were slightly different as predicted from the depth-dose curves.
Management of radiation-induced risks in areas contaminated by a nuclear accident is characterized by three ethical issues: (i) risk trade-off, (ii) paternalistic intervention and (iii) individualization of responsibilities. To deal with these issues and to clarify requirements of justification of interventions for the purpose of reduction in radiation-induced risks, we explored the ethical basis of the radiological protection system of the International Commission on Radiological Protection (ICRP). The ICRP's radiological protection system is established based on three normative ethics, i.e. utilitarianism, deontology and virtue ethics. The three ethical issues can be resolved based on the decision-making framework which is constructed in combination with these ethical theories. In addition, the interventions for inhabitants have the possibility to be justified in accordance with two ways. Firstly, when the dangers are severe and far-reaching, interventions could be justified with a sufficient explanation about the nature of harmful effects (or beneficial consequences). Secondly, if autonomy of intervened-individuals can be promoted, those interventions could be justified.
This paper describes the background lifetime risk of mortality from non-cancer diseases, such as circulatory, respiratory, digestive, and blood diseases among the 47 prefectures of Japan. Calculations were conducted using publicly available vital statistical and national census data as of 2000, 2005, and 2010 disclosed by the Ministry of Health, Labour and Welfare and the Ministry of Internal Affairs. The annual trends and geographical characteristics of the background lifetime risk of non-cancer disease mortality as well as their variability are estimated. As an example result, the arithmetic mean and its relative standard deviation of the background lifetime risk for circulatory disease mortality in Japan were calculated to be 30.2% and 4.92%, respectively. These data are expected to be helpful when considering the future development of the system of radiological protection.