Earticle

The development of spectroscopic gamma-ray detectors requires the optimization of several factors, such as the growth of a relatively thick (>1 mm), defect-free, and compositionally uniform radiation-sensitive medium, the extraction of radiation-induced carriers from the medium without loss, a good response linearity between the radiation energy and the number of collected carriers, and the long-term stability in an ambient environment. We review recent advances in the structural design of novel gamma detector systems based on nanoparticles (NPs), including nanocrystals (NCs). The use of NPs in gamma-ray detection has been attracting great attention recently, due to their enhanced optical properties, favorable carrier multiplication condition, low-cost fabrication, and improved chemical properties with stability. Many different fabrication approaches have been adopted for indirect and direct detectors. The indirect detector can be realized by both luminescent NCs and non-luminescent (or weakly luminescent) NPs with high atomic numbers. A proper polymerization process leads to a uniform and high loading of NPs in a large volume, which protects the NPs from oxidation. Furthermore, additional types of composites, including fluorescent dyes or cosolvent, may facilitate efficient charge carrier transfer to linearly convert the incident gamma-ray energy into the number of scintillation photons with negligible loss. The direct detector is implemented by interconnecting NCs with high packing density and mitigating crack formation to extract radiation-induced charge carriers to electrodes across millions of NCs and interfaces. In addition, controlling the NC size, ligand chain length, and NC dispersion state determines the leakage current level. To the best of our knowledge, several studies of NC-based gamma-ray detectors have recently demonstrated gamma spectroscopy capability in the last 10 years, showing improved energy resolution comparable to single-crystal gamma-ray detectors. This review will provide an in-depth overview of the current status and challenges in developing NP-based gamma detectors.

This review is based on articles published in the Japanese Journal of Health Physics on ‘Dosimetry and dose assessment’ related to Tokyo Electric Power Company Incorporated’s Fukushima Daiichi Nuclear Power Station accident. Here, we have considered five special articles, one original article, four technical data, four review articles, one report, three topics, and five cases of Japan to the World (J to W). The dosimetry data and dose assessment methods reported in these articles are valuable for monitoring radiation accidents in the future.

Background: Radon, a radioactive gas, is ubiquitous and commonly inhaled by individuals. It was originating from the Earth's crust. Radon can also be released by building materials, water, basement air, soil, and other environmental components. When radon gas decays, it produces radioactive particles that can be inhaled. These particles damage lung tissue, increasing the risk of lung cancer over time. Materials and Methods: Indoor and outdoor radon concentrations were determined in 24 houses in two cities in Al-Najaf province, Al-Najaf city and Al-Kufa city, using Airthings Corentium Digital Radon Detector. Results and Discussion: The arithmetic mean of indoor radon concentration was 18.09±9.41 Bq/m3, while the arithmetic mean of outdoor radon concentration was 4.50±2.96 Bq/m3. The arithmetic mean of ‘the annual effective dose’ received by home occupants by indoor radon was 0.46±0.24 mSv/yr. The arithmetic mean of the ‘effective dose to the lung’ was 1.09±0.57 mSv/yr. Conclusion: The total annual effective dose due to indoor and outdoor radon concentration was lower than the reference level of International Commission on Radiological Protection. The results of the radiological survey due to indoor and outdoor radon levels in studied dwellings suggest that the radionuclides and their radiological hazard indexes in all studied dwellings do not impose a health hazard.

Background: Ionizing radiation is widely used as a diagnostic and treatment tool in healthcare. Nurses play a significant role in healthcare environments, accompanying patients during examinations, including exposure to inward X-ray procedures, and requiring them to keep up with radiation safety protocols. This study aims to assess the radiation knowledge and understanding of the ionizing radiation physics, protection, and safety principles of the associated hazards among nurses. Enhancing safety culture and establishing standardized guidelines at both national and international levels are crucial for developing radiation protection measures for nurses. Materials and Methods: Using a cross-sectional design, a validated self-administered survey was conducted in person with 40 nurses at King Abdulaziz Medical City in Jeddah. The Healthcare Professional Knowledge of Radiation Protection (HPKRP) scale is distributed via an online platform using Google Forms. Data were analyzed using JMP Pro 14 software (SAS Institute Inc. ; 1989–2019). Structural equation modeling (SEM) was employed to evaluate associations related to the HPKRP scale. Results and Discussion: Nurses reported the highest knowledge level in safe ionizing radiation guidelines, with a mean of 6.26±2.74. The second highest is radiation protection with 5.97± 3.00, but low knowledge levels in radiation physics and radiation use principle have a mean of 4.15±2.60. The SEM explained significant direct pathways were knowledge/safety and knowledge/ protection (p<0.001), but also a significant indirect pathway to knowledge/principle (p=0.035). Conclusion: Previous research in Saudi Arabia has investigated nurses’ awareness of radiation; however, none have used the HPKRP scale, indicating a gap that warrants further investigation. This study highlighted the crucial role of radiation education for healthcare organizations to enhance the knowledge and training standards for all nurses who work with or are exposed to ionizing radiation.

Background: Nuclear material accountancy is essential for nuclear security and non-proliferation, requiring fast and accurate measurement methods. To overcome the limitations of conventional thermal neutron multiplicity counting, this study developed a fast neutron multiplicity counting (FNMC) system using organic scintillators. Materials and Methods: An FNMC system was constructed using a pixelated trans-stilbene array and a silicon photomultiplier (SiPM) array. Performance was evaluated through Monte Carlo N-Particle Extended (MCNPX)-PoliMi simulations and experiments at 50 keVee and 100 keVee energy thresholds, analyzing detection efficiency, crosstalk, and singles (S), doubles (D), and triples (T) rates. Results and Discussion: The FNMC system showed a linear relationship between S, D, and T values and mass, with mass estimation errors of 0.4% at 50 keVee and 2.2% at 100 keVee threshold. Lower energy thresholds provided higher detection efficiency and accuracy. The system effectively minimized crosstalk and pile-up errors. Conclusion: The FNMC system provides a precise and reliable method for rapid nuclear material verification. It demonstrates strong potential for non-destructive analysis and nuclear safeguards applications, offering improved efficiency and accuracy compared to conventional methods.

Background: Radon (222Rn) and thoron (220Rn) are naturally occurring radioactive gases with significant differences in half-life, influencing their indoor behavior. Radon has well-documented health risks and mitigation strategies, but thoron has received less attention. This study explores thoron behavior in relation to air flow dynamics and ventilation conditions used to mitigate radon levels. Materials and Methods: Controlled experiments were conducted from February to June 2021 in an empty basement room and a laboratory simulation. Radon and thoron activity concentrations were measured using Durridge RAD7 radon monitors. Forced air movement was achieved through a fan, and ventilation conditions were simulated in the laboratory using air pumps with inline flow control valves. The exhaust state varied between closed and open air systems. Results and Discussion: The experiments revealed that while radon concentrations were stable or decreased under both forced air movement and increased ventilation rates, thoron concentrations displayed an inverse relationship with forced air movement, irrespective of an open or closed air system. Additionally, thoron required much higher ventilation rates (>50 air changes per hour [ACPH]) to reduce concentration levels that radon achieved with much lower rates (1–10 ACPH). This suggests certain ventilation strategies might inadvertently elevate thoron levels despite reducing radon levels, indicating a nuanced interaction between thoron concentration and air flow dynamics. Conclusion: This study underscores the importance of considering thoron’s unique behavior when implementing ventilation strategies for indoor radioactive gas mitigation. It calls for a nuanced approach to managing air flow dynamics to effectively reduce both radon and thoron levels. Further research is needed to refine models for ventilation strategies in radiation hazard mitigation for radon and thoron.