Radiation protection dosimetry最新文献

This study summarises the responses to information on thyroid cancer, which possibly provoked misunderstanding and unfounded rumour, described in a letter issued by five former Japanese Prime Ministers on 27 January, 2022. Fukushima Medical University (FMU) implemented countermeasures and follow-up in three phases in response to the letter. In Phase 1, FMU shared scientific facts on the relationship between radiation exposure and thyroid cancer, as well as the response of FMU towards those who read the letter and were concerned about the description. Furthermore, FMU organised lectures and workshops to facilitate peer support among medical and non-medical staff, which were publicised through a newspaper article. In Phase 2, the peer support programme targeting patients with thyroid cancer was launched. In Phase 3, FMU participated in a TV programme to explain the medical aspects of thyroid cancer and the importance of providing peer support to patients with cancer, featuring individuals with experiences as medical staff and survivors.

Long-term changes in particulate and dissolved 137Cs concentrations in rivers and dam reservoirs have been reconstructed using 137Cs depth distributions in bottom sediments near Chornobyl and Fukushima. However, few studies have applied this method to pond water. This study tested the applicability of this reconstruction method in ponds within the Fukushima evacuation zone. Bottom sediments in ponds were collected in November 2019. Our reconstruction of a shallow closed pond disagreed with our observations. Even in ponds where the reconstruction agreed well with observations, underestimations may have occurred because the time constant for the decrease in 137Cs concentration was lower than those previously reported. We conclude that the present reconstruction method may be applied to deeper Fukushima ponds with inflow and outflow, but underestimations of initial 137Cs concentrations in water may lead to uncertainties. For realistic reconstruction, attention should be paid to pond characteristics, catchment conditions, and sediment core selection.

Researchers have stressed that crops may absorb radioactive cesium (Cs) in the soil and translocate it to its edible parts. Therefore, a method was developed to suppress Cs absorption through high K fertilisation. However, this method is less effective for rice plants after ear emergence, thus demanding the application of a suppression method at this stage. In this study, we test whether immersion of ears in a Ca solution during its ripening period could suppress the translocation of Cs from roots to brown rice. The results show that the translocation of Cs absorbed from the hydroponic solution to brown rice is reduced based on the Ca concentration applied to the ears. In addition, differences in the inhibition of translocation were observed among the different Ca salts. In addition, the effect of immersion of ears in Ca solution on Cs translocation was effective at lower concentrations than that effective for K.

In applying fluorescent nuclear track detectors for heavy ion measurement, the fluorescence intensity directly influences linear energy transfer (LET) estimation. However, the conventional analysis highly depends on the analyzed depth and the reference frames from the optical readout. To improve the accuracy of measurements of heavy ions, the gradient of intensity and moving average fluorescence intensity were acquired and calculated to optimize the measurement conditions. The results indicate that the intensity gradient is an alternative quantity to discriminate ions with different LET, and the moving average fluorescence intensity is readily differentiated among individual ions without overlapping values in fluorescence intensity. The scanned range of 25-45 μm is suggested to be the most suitable depth for measurement. To exclude the impact of the variation in fluorescence intensity on evaluation, it is recommended to use the quantities calculated in moving averages with depth in the future.

Nuclear fuel reprocessing plant releases several kinds of radioactive nuclides, mainly 3H and 129I, into the oceans. Radio iodine causes thyroid dose. Iodine accumulates in several marine species such as wakame and abalone, which are food materials. Therefore, an analysis of iodine behavior in the marine environment is important to assess the impact of 129I. Iodine in seawater exists mainly in two chemical forms: iodide (I-) and iodate (IO3-). Their environmental behaviors are different. Thus, understanding these behaviors is important to assess the environmental behavior of total iodine. In this study, iodate and iodide transfer between seawater and abalone (Haliotis discus hannai) with 125I tracer was observed.

222Rn is recognized as a matter of international concern for human health risk. Because 220Rn as well as 222Rn coexist in the natural environment, thoron sometimes influences the experiment for radon measurement. It is important to measure radon and thoron separately to evaluate the risk of the exposure to 222Rn. As a discriminative measurement method for 222Rn and 220Rn, a simple technique with a single scintillation cell is well known. However, in recent years, the influence of atmospheric environment on the geometrical efficiency of the scintillation cell has not yet been investigated. In this study, environmental dependence of geometrical efficiency for the scintillation cell in 222Rn and 220Rn measurement was investigated using the Lucas type scintillation cell and Monte Carlo particle simulation. It was found that the influence of temperature and pressure on the geometrical efficiencies were larger than that of relative humidity.

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.