Journal of Radiological Protection最新文献

To mitigate exposure of the public during an accidental atmospheric release of radioactive material, protective actions may be implemented. Sheltering can have a protective effect against both external and inhalation exposure pathways. This paper seeks to quantify the radiological protection offered from sheltering inside the types of buildings where individuals spend most of their time. Findings from other studies by way of a literature review are combined with modelling performed by the authors to assess the radiological protection offered were an individual to shelter inside a residential building. Housing stock and environmental conditions typical of the UK are considered. For the effectiveness of sheltering against external gamma irradiation from deposited material and material in the plume, best estimate location factors of 0.15 are recommended. For the effectiveness of sheltering against exposure from inhalation of the plume, a best estimate dose reduction factor (DRF) of 0.6 is recommended. These recommended values supersede previous recommendations on the effectiveness of sheltering as a protective action in the UK. The quantification of the effectiveness of sheltering, by way of location factors and a DRF, will better inform the process of determining urgent protective actions as part of the emergency planning required under the Radiation (Emergency Preparedness and Public Information) Regulations 2019 and will be of value when undertaking emergency response assessments.

Over the last 60 years epidemiologic radiation studies have largely shifted from identifying the range of detriments from high radiation exposures to quantifying the magnitude and uncertainties of risks in the low-dose range. Similarly, my efforts began with relatively high-dose studies of cohorts from bygone eras: follow-up of children who were treated with x-ray for scalp ringworm, infants whose thymus glands were shrunk by radiation, and women who received x-ray therapy for breast infections. A follow-up study was conducted to estimate cataract risk among clean-up workers after the 1986 Chernobyl nuclear accident. At the Radiation Effects Research Foundation my goals in supervising research on the lifespan study (LSS) of atomic bombing survivors were to stimulate new research initiatives and to provide guidance on methodology and analyses. These included dose-response studies of circulatory diseases and cataract in survivors, and of metabolic and cardiovascular outcomes amongin uterosurvivors and F₁offspring. A challenging NCRP committee task was to evaluate the degree of epidemiologic support for a linear nonthreshold model of radiation risk for solid cancer. A public health assessment for UNSCEAR concluded there was little likelihood of future detectable cancer risks from the Fukushima nuclear plant disaster in 2011. A recent ICRP effort has been to develop epidemiologic estimates of the dose rate effectiveness Factor by comparing cancer risk estimates from occupational and environmental radiation studies with mostly low cumulative photon radiation doses and/or low dose-rates (LDLDR) to those derived from the LSS. Continued observation of the Million Person Study and other cohorts exposed to LDLDR radiation has the potential to further improve estimates of potential risks from radiation exposure and should be pursued.

The objective of this study is to quantitatively estimate the annual population exposure to terrestrial gamma radiation in South Korea by conducting a high-resolution car-borne survey across the entire country. From 2013 to 2017, a total of 723 052 gamma-ray measurements were collected using a vehicle-mounted NaI(Tl) scintillation detector. The measured count rates were converted into the activity concentrations of radionuclides (²²⁶Ra,²³²Th, and⁴⁰K), and subsequently into absorbed dose rates in air (nGy h^-1) using Beck's formula. The spatial distribution of dose rates was visualized using both inverse distance weighting and kriging interpolation methods. Based on the 2020 population census data, population-weighted averages were calculated at both administrative and national levels. Annual effective doses were subsequently estimated by applying dose conversion coefficient and occupancy factors. The national population-weighted outdoor absorbed dose rate in air was 108 ± 19.5 nGy h^-1, which is approximately 1.8 times higher than the global average of 59 nGy h^-1reported by UNSCEAR, and about 16% higher than the previous national survey result (93 nGy h^-1). The corresponding annual effective dose was estimated to be 0.87 mSv, with approximately 85% attributable to indoor exposure. Among the radionuclides,²³²Th showed the highest contribution to the total dose, and a strong positive correlation was observed between²³²Th and⁴⁰K (r= 0.6530). In contrast, a weak but significant positive correlation was found between outdoor terrestrial gamma dose rates and indoor radon concentrations (r= 0.2063), suggesting that indoor radon levels are influenced by various environmental factors beyond gamma radiation, which should be considered when evaluating or predicting indoor radon exposure. This study presents the most comprehensive and representative estimates of terrestrial gamma radiation exposure in South Korea, based on the largest nationwide dataset of terrestrial gamma dose rates to date. These results can serve as a scientific basis for developing and optimizing radiation protection strategies under existing exposure situations.

This study analysed computed tomography (CT) radiation dose trends in Switzerland from 2018 and 2023 with the aim to update the CT dose estimation for the 2023 national survey on radiation exposure of the Swiss population. Data from eight major healthcare providers, including all five Swiss university hospitals, were collected for nine key anatomical regions. The analysis showed large variability in dose length product changes, ranging from -55% to +30.2% across anatomical regions and providers. Most regions exhibited dose reductions, with the largest decreases in thehip(-15.4%) andpelvis(-11.4%), whereas thespineshowed the greatest dose increase (+6.6%). The statistical analysis revealed no significant differences between university hospitals and other healthcare providers.

Large-scale decommissioning or partial refurbishment of process equipment in nuclear facilities can pose considerable challenges for controlling radiation exposure. While there is substantial literature on external exposure control during decommissioning activity, the works on internal exposure control are limited. Moreover, unlike external exposure, which can be planned and budgeted through extensive radiological mapping, internal exposures can escalate rapidly during decommissioning activities and can lead to severe exposures. This paper presents a case study on replacing six heat exchangers in thermosyphon evaporators at a spent nuclear fuel reprocessing facility, with radiological challenges analogous to small-scale decommissioning in both scope and complexity. By carrying out root cause analysis (RCA) of historical internal exposure events, we identified four categories of causes for internal exposure: radiological environment, respiratory equipment, monitoring & measurements, and safety culture. Within the facility's established radiation-protection programme, we implemented a set of RCA-derived measures that included localized ventilation systems for increased air exchanges, newly designed airline respirator manifolds with real-time flow alarms, validated in-cell air-monitoring protocols, personal air sampling in the breathing zone of workers, and intent-based training for personnel. The implementation of the methods delineated in the paper, resulted in an achievement of zero internal exposure cases, for a work that spanned for 3 years and involved more than 2000 man-hours spent inside active process cells.

Clearance monitors (CMs) are used at the Paul Scherrer Institute to characterise radioactive waste, including thoriated tungsten (W-Th) welding electrodes, which contain thorium oxide (ThO2). The decay of²³²Th and its progeny poses challenges to the accurate determination of the CM detection efficiency due to a potential disequilibrium. In this work, a methodology developed for estimating the detection efficiency of CMs for²³²Th not in secular equilibrium with its progeny is presented. A Monte Carlo model of the CM was implemented using FLUKA to determine stand-alone efficiencies for all gamma emitting nuclides in the thorium decay chain. The model accounts for the time evolution of progeny build-up, and a legal figure of merit was used to determine the most conservative efficiency scenario. The methodology successfully estimates the detection efficiency by considering the evolving decay chain of²³²Th with time. Additionally, it enables a conservative assessment of activity in the copper holders of the W-Th electrodes by selecting the nuclide vector relevant at the time of the measurement. The approach improves clearance measurements for materials containing long-lived radionuclides, enhancing regulatory compliance and radiation safety. It can be extended to other radionuclides with complex decay chains and applied to different counter detectors.

In radiological and nuclear emergencies, military personnel and first responders are at elevated risk of internal contamination via inhalation of airborne radionuclides. Rapidin-vivoassessments are required for efficient triage, regulatory compliance, and medical intervention. This study investigates the impact of chest wall thickness (CWT) on lung counting efficiency using military-specific mesh-type human computational phantoms that represent the current standards and anthropomorphic parameters of U.S. members of the military. A 2″ × 2″ NaI(Tl) scintillation detector with digital base was modeled and benchmarked against experimental measurements using polymethyl methacrylate slab phantoms to assess attenuation effects. Monte Carlo simulations in Particle and Heavy Ion Transport code System were employed to characterize lung deposition of radionuclides, with variations in CWT examined across different anthropometric models. Results demonstrated an inverse exponential relationship between CWT and detector peak counting efficiency, with minor deviations in female phantoms due to geometric constraints. These results support improved calibration approaches forin-vivoradiation detection systems and enable more consistent internal contamination assessments across a range of body types during emergency response operations.

This study systematically analyses the concrete activation problem and associated radiation risk caused by long-term operation of medical cyclotron. The research shows that medium energy (10-30 MeV) medical cyclotrons under high current operating conditions can induce concrete activation with penetration depths of 100-120 cm, mainly producing long-lived radionuclides such as Eu-152 and Co-60 with activity concentrations up to 600 Bq g^-1and 250 Bq g^-1, respectively. Under operation at maximum design parameters, the peak ambient dose equivalent rate around the target chamber reaches 961μSv h^-1at the end of operation and remains above 500μSv h^-1even after two years of cooling, posing significant radiation risks to personnel. China's current radiation safety management system faces the twin challenges of a lack of standards and insufficient radioactive waste management capacity. Based on international practices such as IAEA, recommendations are proposed to improve the management system in three dimensions: revision of regulations and standards, financial safeguards, and technological innovation.

Radiation protection for workers in diverse environments, exposed to varying radiation fields, is a critical aspect of occupational health and safety. To address the challenges in personnel dosimetry, this study introduces excel for kerma-to-dose equivalent conversion (EKDEC), a user-friendly, Excel-based analytical tool designed to calculate the kerma-to-dose equivalent average conversion coefficients for a wide range of photon radiation spectra. EKDEC supports the calculation of dose equivalents for the traditional International Commission on Radiological Protection quantities (H_p(10),H_p(3),H_p(0.07)) as well as the newly recommended ICRU 95 dose equivalents, including personal dose (H_p), local skin dose (D_{p,local skin}), and absorbed dose to the eye lens (D_p,lens). The tool is capable of handling photon beams such as those defined in International Organization for Standardization 4037-1, diagnostic x-rays, therapy beams, unfiltered x-rays, and custom photon spectra. Through rigorous validation, EKDEC demonstrates excellent agreement with previously published results, showing relative differences typically within ±5% for most cases. By offering high accuracy, flexibility, and ease of use, EKDEC empowers radiation safety professionals, health physicists, and dosimetry laboratories to perform precise dosimetric measurements. This tool provides a comprehensive solution for enhancing the safety of radiation workers, supporting both standard and custom dosimetry needs with precision and simplicity.