Radiation protection dosimetry最新文献

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.

This study investigated the implementation and efficacy of trauma-focused psychotherapies at a psychiatric clinic in Minamisoma City, Fukushima, after the 2011 Great East Japan Earthquake and nuclear disaster. Analyzing medical records from April 2016 to March 2021, the authors identified a significant dropout rate of 43.2% among post-traumatic stress disorder (PTSD) patients within the first 5 years. These findings highlight the challenges and effectiveness of trauma-focused treatments like prolonged exposure therapy in disaster-stricken areas, where PTSD incidence is notably high. This study emphasizes the necessity to establish robust therapeutic frameworks capable of addressing PTSD in such contexts, considering the limited coverage of comprehensive psychotherapies by Japan's healthcare system.

As the integrated measurements of radon progeny are essential to its risk assessment, a new method based on the morphological analysis of tracks on CR-39 was established for the discrimination of alpha particles emitted from different progenies. The preliminary experiment confirmed its feasibility and revealed its potential for application in long-term surveys of indoor radon progeny. This new attempt was expected be benefit to the improvement of integrated measurements of radon progeny.

The National Metrology Institute of Japan plan to use an inner-through-type ionization chamber (IC) as a working standard to calibrate radon monitors. Novel methods to calibrate the IC were described, and the calibration factor, CF [Bq m -3 A-1], of the IC with its expanded uncertainty (k = 2) was evaluated to be (2.0 ± 0.2) × 1016 Bq m-3 A-1 in the order of 10-13 A in the IC output current. In this study, the CFs, evaluated under sampling conditions between continuous gas flowing and stationary gas filled inside the IC, were in agreement within the uncertainty.

Alanine dosemeters are widely used as solid dosemeters; however, evaluating doses in the mGy order of radiation is difficult because of their lower sensitivity for low doses. We applied the electron spin resonance dosimetry technique to investigate whether hydroxyapatite, the main component of teeth, is a suitable material for a new dosemeter to detect radiation from mGy to Gy. Commercially available synthetic hydroxyapatite possesses the essential characteristics required for a dosemeter material and has been demonstrated to accurately measure doses in the mGy to Gy range.

This study aimed to measure tritium (3H) concentrations in Thailand. Nationwide tap water samples were collected in July 2021. Rainwater samples were collected monthly during May-October 2020, April-October 2021, and February-March 2022 in Chonburi province and in Chiang Mai province during July-November 2021, January 2022, and March-June 2022. The measurements of 3H activity concentrations were conducted by Osaka Sangyo University (OSU) and were compared with measurements by the Thailand Institute of Nuclear Technology (TINT). The results from OSU and TINT showed that 3H concentrations in tap water were matched in the ranged from 0.08 ± 0.03 to 0.28 ± 0.04 Bq L-1, while those in rainwater samples collected from Chonburi province and Chiang Mai province are also matched in the ranged from 0.11 ± 0.02 to 0.21 ± 0.03 Bq L-1 and 0.19 ± 0.02 to 0.57 ± 0.04 Bq L-1, respectively. Our measured result suggests that 3H concentration in tap water and rainwater shows a similar relation depending on latitude.

This study aimed to determine the annual effective dose resulting from radon and thoron progeny inhalation. The levels of radon, thoron, and progeny were assessed in residences situated in the Doi Lo region of Chiang Mai, Thailand. Indoor radon and thoron concentrations were detected using passive discriminative detectors. Using a progeny deposition rate detector, this study evaluates radon and thoron progeny [equilibrium-equivalent radon concentration (EERC) for radon and equilibrium-equivalent thoron concentration (EETC) for thoron]. Data were collected from 44 dwellings between March and May 2020. The results found that indoor radon concentrations ranged from 17 to 118 Bq m-3, while thoron concentrations ranged from 12 to 72 Bq m-3. The radon progeny (EERC) ranged from 4 to 173 Bq m-3, whereas thoron progeny (EETC) ranged from 1 to 15 Bq m-3. The total annual effective dose received from radon and thoron progeny inhalation varied from 0.5 to 5 mSv y-1.