Radiation protection dosimetry最新文献

We established two types of site-specific DNA double strand breaks (DSB) induction systems to elucidate factors which affect the efficiency or quality of DSB repair. For mutation assays, a site specific DSB was generated by the transient expression of a zinc finger nuclease which targets the human HPRT1 gene. A cell line in which time and site specific DSBs can be generated in a HR reporter construct was used for homology-directed repair (HR) analysis. By using these two systems, we investigated the effects of PI3-kinase inhibitors on the efficiency and quality of DSB repair. Ataxia telangiectasia mutated (ATM) kinase inhibition resulted a decrease in mutant frequency and a slight increase in deletion-type mutations accompanied by microhomology. Furthermore, the HR frequency increased significantly when ATM kinase activity was inhibited. Thus, ATM kinase activity might be involved in the suppression of DSB end resection, and this may promote DSB repair through canonical non-homologous end joining.

The exchangeability of hydrogen atoms within organic molecules in vivo with ambient water hydrogen is uncertain. We assessed this by administrating the tracer deuterium to the fish. Flatfish were retained in deuterium-elevated seawater for 48 h, and the deuterium-to-hydrogen (D/H) ratios in the flesh samples were measured. Rapid in vivo equilibration between exchangeable organically bound hydrogen (Ex-OBH) and tissue-free water (TFW) hydrogen was indicated by the linear relationship between the D/H ratios of total organically bound hydrogen (t-OBH) and TFW. The estimated ratio of Ex-OBH to t-OBH (fe) in vivo was 7.2 ± 0.0%, while there was no in vivo production rate of non-exchangeable organically bound deuterium (Nx-OBD). In contrast to this estimation of no production of Nx-OBD in vivo, the D/H values of Nx-OBH measured by equilibration in vitro increased, consequently reducing the value of fe in vitro to some extent compared to that of fe in vivo. This indicated that a certain portion of Ex-OBH in vivo was not exchangeable during the equilibration in vitro.

The final disposal of the soils removed from the area affected by the Fukushima nuclear accident will be carried out by 2045. This study investigated how acceptance of final disposal differed between top-down, opinion-aggregative, and opinion-reflective approaches to the decision outcome, and what factors influenced these differences. In 2022, a survey of 3000 randomly selected participants living outside Fukushima Prefecture was conducted using the postal method, with responses obtained from 871 consenting participants. The proportions of respondents who agreed to accept the final disposal were 22.6, 37.6 and 56.9% for the top-down, opinion-aggregative, and opinion-reflective approaches, respectively. The preferences for both opinion-aggregative and opinion-reflective approaches showed significant positive associations with interest in final disposal and social benefits, and significant negative associations with intergenerational expectations and age. This study highlights the importance of procedural fairness in determining final disposal sites, and identifies factors that contribute to greater acceptance through this process.

For systematic monitoring of radioactive nuclides in marine products, this study aimed at streamlining and simplifying the analysis method for the prominent radioisotope, strontium-90 (90Sr). The DGA chelate solid-phase extraction technique was employed for enhanced efficiency. The study focused on optimizing the necessary pretreatment procedures while minimizing the steps involving HNO3 leaching. This protocol enabled the quantitative recovery of strontium, and it facilitated a rapid analysis without the need for a time-consuming evaporation step and without waiting for secular equilibrium between 90Sr and its progeny to be reached. The method incorporating the optimized pretreatment protocol was applied to three diverse marine fish species and the accurate quantification of 90Sr at background levels in surface seawater was achieved. The method obtained concentrations in bone samples from these species that ranged from 0.036 to 0.120 mBq per kg-dry, and chemical yield values were notably high, ranging from 87.7% to 92.5%.

In this study, we selected the Japanese red fox (Vulpes vulpes japonica) as a representative mid-size mammal from the forests near the spent nuclear fuel reprocessing plant at Rokkasho. A fox voxel phantom was constructed based on magnetic resonance imaging of a female red fox caught in Rokkasho. This phantom consisted of 264 × 321 × 383 voxels (each voxel size: 0.78 × 0.78 × 2 mm) with internal organs. The external radiation dose rate to the voxel phantom by beta and gamma rays from environmental radionuclides was estimated using a Monte Carlo code (EGS4 and UCPIXEL). We estimated the dose rates to the phantom on the ground and in an average fox burrow in the Rokkasho forest, which were 11 and 27 nGy h-1, respectively. Assuming that the animal on the ground was irradiated by cosmic rays of 27 nGy h-1, the total external dose rate was evaluated to be 38 nGy h-1. Based on the assumption that the fox lives on the ground for 12 h and in the burrow for 12 h, the dose rate was estimated to be 33 nGy h-1.

People generally wish to return home after being evacuated due to disaster situations. Evacuation orders have now been lifted in the Fukushima region following the nuclear accident in 2011, and the Japanese government is promoting a return policy. However, many residents who wish to return home remain unable to and continue living in evacuation sites or other areas. Sixteen residents of Katsurao village were interviewed after evacuation orders were lifted in 2016 who have not yet returned. Concerns were cited regarding radiation, prolonged evacuation, health problems, buying a house in the evacuation area and schooling. The problems identified were primarily due to the rapid ageing and decline of the regional population, reflecting similar issues throughout Japan. In particular, health problems and intention to return were thought to be closely related. Over 10 y have passed since the evacuation, and many residents have experienced familial separation and divided living situations.

Japan's first commercial nuclear fuel reprocessing plant is expected to release radioiodine into the atmosphere, and orchard grass plants grown in the vicinity of this plant may absorb this radioiodine. In this study, we investigated the mechanism underlying the absorption and volatilization of iodine in the leaves of orchard grass. Our findings suggest that iodine can be transferred from the leaves of this grass to the atmosphere via two routes: direct volatilization and absorption followed by volatilization. Previous studies on rice and oats also show that iodine can be absorbed by the roots and volatilized from the plant's body. Although orchard grass absorbs iodine via the leaves, the chemical form of volatilized iodine may differ from that absorbed via the roots. We applied a NaI solution to the leaves of orchard grass and analyzed the volatilized iodine. The experimental results showed that the iodine was volatilized as methyl iodide.

DNA mutations are one of the effects of radiation exposure. A large amount of radioactive materials was released into the environment from the Fukushima Daiichi Nuclear Power Plant after a major earthquake and tsunami. Wild animals and plants living in highly radiation-contaminated areas are constantly exposed to high doses of radiation, and concerns occur about its effects on their health and the next generations. As a pilot study, double-digest restriction site-associated DNA (ddRAD) sequencing was conducted to assess the incidence of mutations in wild large Japanese field mice collected from the evacuation area. The optimal combination of restriction enzymes, encompassing the functionally important coding regions, was selected using in silico analysis. These enzymes were used for ddRAD sequence analysis of females and their fetuses to evaluate mutation rates. The results indicated that no significant differences were observed in mutation rates between mothers and fetuses in the study areas.

The new electrolytic enrichment system with compact glass cell was designed. Three (Ni-Fe-Ni) electrodes are used, and electrolysis is carried out at a rate of 2.45 g per h with constant current density of 120 mA per cm2. This enrichment system allows the enrichment for small, limited sample volumes (e.g. Tritiated Water (HTO) recovered from air). With an initial water volume of 100 ml, the tritium enrichment factor of 7 within 2 days and a detection limit of 0.12 Bq per L can be obtained by Liquid Scintillation Counter (LSC) measurement for 1000 minutes, which is better than the direct measurement with 50 ml sample water using large vial. It is also possible to perform the high enrichment process. The initial sample volume of 700 ml enriched for 12 days by manual refilling yields a tritium enrichment factor of around 43 and detection limit of 0.02 Bq per L for 1000 minutes of LSC measurement.

Interventional radiology (IR) provides significant advancements in diagnostic and therapeutic procedures, yet concerns persist regarding radiological risks such as erythema, burns, and epilation. Direct dose measurements observed difficulties regarding the perturbation of the detector probe in X-ray images during fluoroscopy-guided procedures, high-cost expenses, and non-compliant patients. This study aims to develop a statistical-based model for estimating entrance skin dose (ESD) in body IR procedures using patient radiation-dose recording data. Models are categorized into vascular and non-vascular procedures. This study demonstrates that the simplified models are sufficient in estimating patient ESDs for both IR groups, with a 95% confidence interval. This user-friendly method enables radiologists to calculate doses without complex parameters such as the backscatter factor and mass-energy absorption coefficient, as required in conventional calculation methods. It not only does this support to radiologists in effectively refining treatment protocols, but also enables patients to monitor their received doses immediately after treatment ends.