Radiation protection dosimetry最新文献

Tokyo Electric Power Company, TEPCO, has started tritiated water release into the Pacific Ocean. In order to reduce unreasonable rumor caused by tritium release, flounder, abalone, and sarggasum were exposed to tritium enriched seawater, and time dependent Tissues Free Water Tritium (TFWT) concentration was measured. Estimating the concentration of Organically Bound Tritium (OBT) is important to assess tritium impact because it has a longer biological half-life than TFWT. Current models estimate OBT concentrations using TFWT concentration. Understanding equilibration time is critical for making accurate TFWT concentration predictions. TFWT intake rate was analysed by the compartment model.

To precisely evaluate the concentration of iodine-129 (129I) in soil samples, changes in this concentration after thermal drying under several temperature conditions were investigated. The soil sample used in this study was collected from a site located near a nuclear fuel reprocessing plant, which atmospherically released 129I in a test operation in 2006-2008, resulting in the soil sample containing higher 129I concentrations than their natural levels. Thermal drying was conducted from 60°C to 110°C and compared with lyophilization result, showing that the 129I concentration in the soil sample was statistically comparable among all the drying treatments.

Elementary processing techniques such as cutting or grinding of foodstuffs are deemed adequate, particularly in the context of post-nuclear accidental situations, ensuring expeditious and effective testing for the gamma-ray spectrometry. Nevertheless, it is worth acknowledging that this straightforward procedure may predispose itself to appreciable variances in the detection efficiency of gamma-ray spectrometry, primarily attributable to the heterogeneity of the radioactivity distribution within the sample container, thereby incurring unexpected discrepancies or uncertainties. To investigate this impact, the precision of the actual sample measurements was scrutinised through statistical analysis.

Surface collection efficiency (SCE) of a cellulose membrane filter (CMF) and a cellulose-glass fiber filter used in environmental monitoring for alpha-emitting radionuclides from nuclear facilities and natural radioactivity sources was evaluated for particles in the size range of 0.03-0.1 μm at different levels of face velocity. The SCE of the CMF was higher than that of the cellulose-glass fiber filter, and only the membrane filter showed the dependence of SCE on the particle size at higher face velocity. The use of the CMF at higher face velocity in environmental radioactivity monitoring leads to measurements of the background alpha spectrum with more degradation under the changing particle size condition in the atmosphere. Consequently, that fact needs to be taken into account, along with the expected particle size distribution and concentration of the airborne radioactivity being sampled, when selecting a face velocity to achieve the best possible detection limit.

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).