Radiation protection dosimetry最新文献

To overcome the time-resolution limitation inherent in the airflow-through scintillation cell method for radon measurement, this study introduces a compartmental model elucidating the behaviors of radon and its progeny within such cells. The computed results of the normalized equilibrium functions derived from the compartmental model, provide quantitative insights into the equilibrium progression of 222Rn and its progeny over time, substantiating the identified time-resolution limitation of 2-3 hours. Laboratory experiments confirm the efficacy of the proposed correction algorithm, showcasing its ability to surmount the time-resolution limitation and achieve a rapid response in radon measurement using airflow-through scintillation cells.

In the progress of nuclear fusion development, environmental radiation monitoring in the vicinity of the facility would be an important issue. At the National Institute of Fusion Science (NIFS), the deuterium plasma experiment, which produces tritium and neutrons using d-d fusion reactions, was conducted from 2017 to 2022. Environmental radiation and tritium in environmental water were monitored before and during the deuterium plasma experiment for public acceptance. As a result, there was no significant change in the observed dose rate and tritium concentration in the rainwater, and no statistically significant difference was identified in the statistical analysis of the data observed before and during the deuterium plasma experiment. Therefore, the environmental impact of the deuterium plasma experiments at NIFS is considered to be negligible.

Institute for Radiological Science (NIRS), National Institutes for Quantum Science and Technology (QST), and Institute for Environmental Sciences (IES) have conducted large-scale animal experiments for radiation risk analyses in terms of life shortening and cancer prevalence. It is important to store data and biological samples from these large-scale experiments for sharing and future use since the economic and practical limitations, as well as the ethical considerations, make it difficult. QST/NIRS established an archive called the Japan Storehouse of Animal Radiobiology Experiments (J-SHARE) for the purpose of storing and sharing these historic collections. We plan to integrate the data and tissue specimen images obtained at the IES into J-SHARE by standardizing the archive format, with the aim of maximizing the results of radiation biology research. This integration is expected to contribute to the generation of new knowledge for radiation risk assessment and the provision of scientifically based information on radiation protection.

This study measured the atmospheric concentration and deposition flux of radiocesium in Koriyama City, Fukushima Prefecture, Japan, from November 2011 to October 2014. The results show synchronous seasonal change in atmospheric concentration and deposition flux of radiocesium, which is high during winter to early spring and low during summer to autumn. These seasonal variations are similar to those observed in Fukushima City but differ from those in Namie Town, Fukushima Prefecture, comprising a larger contaminated forest area. The evaluation of the relationship between atmospheric 137Cs concentration or 137Cs specific activity in atmospheric particulate matter (PM) and deposition density of 137Cs in PM source area suggest that stronger winds blowing from areas with relatively large 137Cs deposition (west of Koriyama City) toward the study site affect the site's atmospheric 137Cs concentrations.

The lifetime attributable risk (LAR) of cancer caused by radiation exposure is crucial when deciding on radiological protection measures or protective actions for nuclear emergency preparedness and response. Although a model for estimating LAR among the Japanese population has been developed based on epidemiological data from A-bomb survivors, a flexible projection code implementing this model must be developed. This study investigated existing codes to contribute to the development of a projection code. Based on these investigations, we compared their LAR calculation results and explored the causes of their differences.

Lead aprons are used to reduce radiation dose to patients. As the distance between the lead apron and the edge of the scan range increases, organ dose is expected to decrease, but with increasing scattered radiation dose in the body. By simulation, this work aims at estimate whether the organ dose increases due to the scattered radiation in the body with lead apron. A standard-sized male and a female phantom is used to simulate organ doses of chest scans in various lead apron shielding situations. Simulations in this work considered different distance between the edge of the 0.35-mm lead apron and the edge of the scan range. For the female phantom, the dose to the gonads was significantly reduced (56% on average), but not as much as men (78% on average). However, the amount of dose reduction is small for male and female phantoms (0.0082 mGy/100 mAs and 0.0160 mGy/100 mAs).

This paper summarises key findings of United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 2020/2021 Report on the evaluations of medical and occupational exposures to ionising radiation. Medical exposure remains by far the largest human-made source of radiation exposure of the population. In the period 2009-18, about 4.2 billion medical radiological examinations were performed annually, resulting in an effective dose per caput of 0.57 mSv. The worldwide annual number of workers exposed to natural and human-made sources of ionising radiation is estimated to be ~24 million in the period 2010-14. About 52% of those were employed in the sectors that involve exposure to natural sources of radiation. The annual effective dose was estimated to be around 2.0 mSv for workers exposed to natural sources (excluding radon exposure in workplaces other than mines) and 0.5 mSv for workers exposed to human-made sources. It is important to motivate United Nations Member States to fully participate in UNSCEAR's global surveys on radiation exposure. Future surveys will be relevant and useful and adapted to changing data sources and uses of radiation across the world.

To assess the biological effects of low-dose and low-dose-rate radiation, we established a sensitive assay system for detecting somatic mutations in hypoxanthine-phosphoribosyltransferase 1 (HPRT1) gene. In this study, we investigated the dose-rate effects of mutagenesis by gamma irradiation at dose-rates of 6.6, 20 and 200 mGy d-1. We identified a potential inflection point in the gamma-induced mutant frequency, which ranged between 6.6 and 20 mGy d-1. In addition, the mutant spectrum was not different from that of the non-irradiated control at all dose-rates. Compared with previous studies with low-concentration HTO exposure, mutant frequencies were similar, but mutant spectrum showed different trends, especially at high-dose-rates (200 mGy d-1). These observations indicate the presence of potential mechanistic differences in mutagenic events between tritium beta and gamma-rays.

The purpose of the study was to determine whether environmental enrichments (EE) can mitigate the adverse effects of chronic low-dose-rate radiation exposure in mice. Female B6C3F1 mice were continuously exposed to 20 mGy d-1 gamma-rays under specific-pathogen-free conditions since 8 weeks of age for 400 d. After completion of the radiation exposure, OV3121 cells, derived from an ovarian granulosa cell tumor, were inoculated subcutaneously alongside age-matched non-irradiated control mice. Irradiated mice were shown to have a significantly reduced ability to eliminate inoculated tumors. The results indicate that EE may be able to mitigate the adverse effects of low-dose-rate radiation exposure, but the effects vary greatly and are complex depending on the type of EE.

This study investigated the effects of chronic low-dose-rate radiation exposure on gene expression related to immunological defense mechanisms and epigenetic regulation in the testis of male mice. The study found that radiation exposure (4.5 mGy/hr until 4000 mGy) led to a significant decrease in the expression of genes involved in epigenetic regulation and a significant increase in the expression of several genes linked to innate and acquired immunity, suggesting a noticeable effect on the immune response. In addition, there was a significant increase in the expression of SRY-box transcription factor 9, which plays a crucial role in testicular development, indicating a response to irradiation. These findings provide insights into the biological effects of chronic low-dose-rate radiation exposure on innate immunity and epigenetic regulation in the testis.