Health physics最新文献

Abstract: This study evaluates the influence of the method used to calculate the effective atomic number (Z eff ) on the estimate of secondary radiation yielded under kilovoltage x-ray beams by metal alloys with a wide range of biomedical applications. Two methods for calculating Z eff (referred to here as M 1 and M 2 ) are considered, and six metallic alloys are investigated: Ti-6Al-4 V, Co-Cr-Mo, Ni-Cr-Ti, Ni-Cr, Co-Cr-Mo-W, and Ag 3 Sn-Hg (amalgam). The results indicate significant differences in the estimates of fluorescence yield depending on the method used to estimate Z eff for each metallic alloy. Both the choice of the calculation method for Z eff and the energy ranges of the incident radiation are essential factors affecting the behavior of alloys in terms of fluorescence production. Our results may guide the selection of the best material for a biomedical application. The metallic alloys simulated here show equivalences and discrepancies that depend on the method used to estimate Z eff and the energy range of the incident photons. This finding allows for the creation of combinations of alloys and methods for calculating Z eff and the photon energy to maximize safety and minimize cost.

Abstract: The International Commission on Radiological Protection recommended that the representative person concept should be used in radiation dose assessment of the general public to specify exposed individuals. The objective of this study is to assess radiation doses of the residents around nuclear power plants (NPPs) in relation to the introduction of the representative person concept. Critical group candidates and representative agro-livestock product producing areas were selected around a NPP site by considering radioactive effluents and regional meteorological data, geographical information, etc. A total of five exposure scenarios, including adult (non-fishery, fishery, and commuter), 10-y-old, and 1-y-old groups, were selected for the dose assessment. Generally, radiation doses were higher for 1-y-old, 10-y-old, and adult groups, in that sequence. There was no significant difference among the radiation doses by occupation in adult groups. Radiation dose results calculated by applying the representative person concept and dose assessment method currently used in Korea were compared. Application of the representative person concept results in lower radiation dose by 68.2% due to consideration of actual residential and agro-livestock product producing areas for the radiation dose assessment, by 13.3% due to the application method of habit data for dose calculation, and by 33.3% due to representative value of the dose results. Finally, considering all the factors above, radiation dose calculated by the current dose assessment method was 8.16 × 10 -2 mSv y -1 , while that calculated using the representative person concept was 1.40 × 10 -2 mSv y - 1 (82.8% lower). The results of this study can be used as reference data when introducing the representative person concept to the regulatory systems in Korea.

Abstract: Radioactive materials and ionizing radiation have both medical value and disease risks, necessitating radiation dose measurement and risk reduction strategies. The International Commission on Radiological Protection (ICRP) lowered the lens of the eye exposure limit, leading to Japan's revised "Ionizing Radiation Ordinance." However, the effects on radiation exposure in medical settings and compliance feasibility remain unclear. To examine the impact of the revision to the "Ionizing Radiation Ordinance" and use it for measures to reduce exposure to radiation, a comprehensive analysis was conducted on data collected from Nagasaki University Hospital, Hiroshima University Hospital, and Fukushima Medical University Hospital in 2018, 2020, and April to September 2021. This included information on age, sex, occupation, department, and monthly radiation doses of workers, aiming to assess the impact of the revision to the "Ionizing Radiation Ordinance" on radiation exposure before and after its enforcement. Out of 9,076 cases studied, 7,963 (87.7%) had radiation doses below the measurable limit throughout the year. Only 292 cases (3.2%) exceeded 1 mSv y -1 , with 9 doctors and 2 radiological technologists surpassing 5 mSv y -1 . Radiological technologists showed significantly higher doses compared to doctors, dentists, and nurses (p < 0.01), while male subjects had significantly higher exposure doses than females (p < 0.01). No significant changes in radiation exposure were observed before and after the revision of the Ionizing Radiation Ordinance; however, variations in radiation exposure control were noted, particularly among nurses and radiological technologists, suggesting the impact of the revision and the need for tailored countermeasures to reduce radiation dose in each group.

Abstract: Steady efforts for recovery and reconstruction after the accident at the Fukushima Daiichi Nuclear Power Plant have been underway for 12.5 y. The present study reports on the world's first-ever efforts for a gradual and safe return to areas contaminated with radiation fallout and reconstruction support by providing an overview of the actual situation regarding the strategy for return, especially with the transition after the lifting of the evacuation order by the Japanese government. A stage-by-stage progression of the evacuation order and lifting strategy is summarized chronologically in the following three phases: the Emergency Phase in 2011, the Reconstruction Phase from 2013 to 2020, and the Challenging Phase for Lifting All the Evacuation Zones from 2023. Through the lifting strategy of the government, the number of evacuees decreased significantly, especially during the Reconstruction Phase, from 152,113 in May 2013 to 37,826 in May 2020. It is crucial to strengthen support for reconstruction and convey an unbiased and accurate understanding of Fukushima Prefecture by developing a concrete strategy for community development and increasing the size of the exchange population.