Applied Radiation and Isotopes最新文献

This study serves as a proof of concept for a Bayesian variational framework enabling high-resolution 3D activity reconstruction in 220 liter waste drums using Angular Segmented Gamma Scanning (ASGS) data and transmission-derived attenuation maps. Our proposed inference and uncertainty quantification approach is demonstrated using virtual experiments that simulate typical waste characterization scenarios. Computations are made tractable by using stochastic variational inference (SVI) together with a multi-resolution spatial prior to infer the spatial activity distribution. Results show that the approach can recover the spatial activity distribution within the considered drum, while also providing more accurate total activity estimates than conventional methods, thereby enhancing the accuracy of radiological waste characterization.

A novel compact Rn-220 reference chamber with stable temperature and humidity control was successfully designed and developed to support radiation-related experimental studies. The device consists of a 200 L cylindrical sealed chamber made of 304 stainless-steel, providing excellent airtightness and corrosion resistance. Concentration levels inside the chamber were tested using both 36 and 9 thorium doped lantern mantles as radioactive sources. A tray containing iodine-free supersaturated salt solution was placed at the bottom to regulate humidity, while a fan positioned at the top ensured adequate air mixing at a circulation rate of 12 m³ min^-1. Experimental results indicated that the system could maintain a relative humidity of 73 ± 3%, while the temperature was stabilized at 31 ± 1 °C by an external air-conditioning system. Multi-point monitoring using a RAD7 radon detector indicated that the overall Rn-220 concentrations reached 166,700 ± 35,300 Bq m^-3 and 47,700 ± 12,400 Bq m^-3. The uncertainty of the 9 thorium doped lantern mantles configuration was 26.0%. Given the small vertical concentration difference across three heights with 9 thorium doped lantern mantles, this configuration was selected as the reference Rn-220 source. This compact Rn-220 reference chamber has potential applicability in instrument calibration and radiation-related studies.

We have theoretically studied the laser isotope separation of ¹⁶⁹Yb from irradiated natural Yb through three-step laser photoionization process. The optimal configuration of the laser isotope separation system for enriching ¹⁶⁹Yb has been determined by applying the density matrix formalism to the laser-atom interactions in a three-step photoionization process. It has been shown that it is possible to produce 63.1% enriched ¹⁶⁹Yb at a production rate of 4.2 μg/hour (or 100 μg/day) which corresponds to 2.4 Ci/day from the natural Yb irradiated in low flux reactors. Employing the derived configuration, it is possible to produce one to two orders higher activity of ¹⁶⁹Yb from natural Yb irradiated in medium or high flux reactors respectively. This is the first ever study on the laser isotope separation of ¹⁶⁹Yb.

This retrospective multicenter study aimed to establish local diagnostic reference levels (LDRLs) for digital mammography and assess radiation dose variability across five government hospitals in northern Saudi Arabia. A total of 1729 mammographic examinations performed between January and June 2024 were analyzed. Data included patient demographics, technical parameters (kVp, mAs, compression force, and compressed breast thickness), and dose metrics, average glandular dose (AGD) and entrance surface exposure (ESE), for standard craniocaudal (CC) and mediolateral oblique (MLO) views. Following the methodology outlined in ICRP Publication 135 (2017), LDRLs were derived as the 75th percentile of the median dose values from the participating facilities for examinations performed at a compressed breast thickness of 50 ± 5 mm. Statistical analysis employed the Kruskal-Wallis test for inter-center comparisons and Spearman correlations to examine relationships between dose and technical parameters across the dataset. Significant inter-center variability was observed (p < 0.001), indicating notable differences in clinical technique and dose optimization practices. The combined 75th-percentile AGD was 1.27 mGy, with MLO projections requiring higher doses than CC views (AGD = 2.47 mGy vs. 1.22 mGy). AGD demonstrated strong positive correlations with mAs (r = 0.781) and compressed breast thickness (r = 0.609), while compression force showed a weak negative correlation (r = -0.185), confirming the impact of both patient-related and technical factors on radiation dose outcomes. The established LDRL falls within previously reported Saudi values and remains lower than many international benchmarks, indicating that mammography practices in northern Saudi Arabia are well optimized and aligned with global standards, while highlighting the need for continued protocol standardization across centers.

Electron beam sterilization in medical and nuclear facilities creates ongoing challenges for protective glove integrity, with frequent failures imposing significant safety risks and operational costs. This study employed a comprehensive multi-technique molecular analysis approach using Electron Paramagnetic Resonance (EPR), Positron Annihilation Lifetime Spectroscopy (PALS), and Small-Angle X-ray Scattering (SAXS) to investigate the performance gap between nanofiber-reinforced woven (NFW) and surface-coated (SC) nitrile gloves subjected to clinically-relevant radiation doses (10-25 kGy). The main finding revealed that NFW gloves achieve 2.5-fold longer service life than SC alternatives through superior molecular-level protection mechanisms. EPR spectroscopy showed SC gloves developed 61 % higher radical concentration than NFW gloves at 25 kGy (8.7 × 10¹⁷ vs 5.4 × 10¹⁷ spins/g), with NFW exhibiting superior radical stability (62 % retention at 168h versus 43 % for SC gloves). PALS demonstrated NFW's significantly lower Void Expansion Coefficient (0.07 vs 0.41 ų/kGy), correlating with reduced oxygen diffusion rates (1.4 × 10^-9 vs 8.7 × 10^-9 cm²/s). SAXS analysis established superior Structural Preservation Quotient for woven architecture (0.81 vs 0.33), reflecting enhanced nanoscale organizational stability. NFW gloves retained 68 % of tensile strength at 25 kGy compared to only 42 % for SC gloves, demonstrating practical performance advantages. Integration of these molecular parameters into a comprehensive Molecular Protection Factor (5.7 vs 2.3) enabled accurate prediction of mechanical performance retention with 92 % correlation across the radiation spectrum. Three-dimensional woven integration provided extended Effective Protection Period of 42 months versus 17 months for surface-concentrated alternatives. The protection mechanism hierarchy demonstrated stress distribution effectiveness as the primary factor (41 % contribution), followed by radical isolation (27 %), void restriction (19 %), and network balance (13 %). Interface engineering and spatial distribution optimization offered superior enhancement potential (215 % calculated improvement) compared to traditional antioxidant approaches (maximum 65 % enhancement), establishing validated molecular-scale design principles for next-generation radiation-resistant protective equipment development.

Background: The handling of non-sealed radiopharmaceuticals poses significant risks of occupational exposure and radioactive contamination. With rapid growth in demand, an increasing number of workers are long-term exposed to various radiation hazards. However, the exposure characteristics and dosimetry basics remain poorly understood.

Methods: This study reconstructed 1189 personal dose equivalent data for 311 radiation workers from 2021 to 2023 in China to analyze exposure characteristics. Through on-site inspections of the radiation levels in 15 representative facilities, 1889 measurement points were assessed for radiation hazard distributions and dose contributions. Based on Biological Effects of Ionizing Radiation-VII (BEIR-VII) risk models, 120 exposure scenarios were considered to estimate excess lifetime risks of stochastic effects.

Results: The maximum annual effective dose reaches 5.29 mSv and presents a decreasing trend annually. Some occupational personnel, such as production technicians, should be given more attention regarding radiation exposure. Monitoring of nuclide operational quantities is conducive to avoiding overexposure. Gamma-rays are the largest dose source, contributing more than 75 % of the personal dose, with a maximum dose rate of 50 μSv/h. The dose contribution of neutrons cannot be ignored, particularly for cyclotron operators. The highest lifetime risks of thyroid cancer and leukemia caused by annual doses are 1.8 × 10^-5 and 1.03 × 10^-5, respectively. The radiological risk also increases with longer working years and higher doses.

Conclusions: It is necessary to strengthen radiation protection for some workers, especially production technicians and cyclotron operators, and conduct radiation monitoring in high-risk workplaces, including hot cells. The radiological risks caused by accumulated dose should not be ignored, particularly during the early career.

An appropriate target system is crucial for converting the incident proton beam from a cyclotron into a neutron beam, which drives a subcritical reactor in a small-scale accelerator-driven system (SS-ADS). The methodology for designing the target system was a combination of the Particle and Heavy Ion code Transport System (PHITS) simulation and the Response Surface Methodology (RSM) analysis. PHITS simulations applied the proton beam specifications from the DECY-13 cyclotron as the particle source model, and RSM incorporated the external neutron beam requirement of the SAMOP subcritical reactor into the optimization. Beryllium was chosen as the target material because it produces the highest neutron yield per incident proton, outperforming other candidates such as manganese, titanium, and vanadium. The heavy water moderated neutrons produced by the ⁹Be(p,n)⁹B reaction, while polyethylene functioned as a neutron reflector. The analysis result shows that the optimal target system consisted of the target material in a form of obstructed needle with radial thickness of 0.18 cm, cavity length of 2.56 cm, obstructed thickness and angle of 0.17 cm and 31.06 degree; the moderator in a shape of truncated cone with length of 3.26 cm, entrance and exit radius of 0.85 cm and 0.91 cm; and neutron reflector thickness 15.64 cm. Equipped with the target system, the DECY-13 cyclotron can deliver a thermal neutron flux of (2.7 ± 0.1)×10⁸ n/cm²s, sufficient to drive the SS-ADS subcritical reactor. An additional PHITS simulation with the optimal configuration validated the RSM prediction by producing a thermal neutron flux of (2.81 ± 0.02)×10⁸ n/cm²s. It indicates that RSM prediction is highly accurate in this case, with a deviation of 3.91 %.

Neutron detectors play a vital role in radiation applications, particularly in nuclear, high-energy physics experiments and fusion facilities, where accurate neutron spectrum measurements and flux monitoring are essential. In fusion research, detecting 2.45 MeV neutrons, produced via D-D fusion, is especially important, offering key information on the progress of the reaction. However, accurate neutron measurements at energies below 6 MeV remain challenging due to high background levels, low detector efficiencies, and the fact that many reaction channels are closed. Among the various detection technologies, semiconductor detectors based on diamond and silicon carbide (SiC) are highly favored thanks to their excellent energy resolution and ability to operate in harsh environmental conditions. A common approach in semiconductor neutron detection involves conversion layers (e.g., LiF or hydrogen) to enable detection via secondary charged particles such as tritons, alpha particles, or proton recoils. In this work, we investigate and compare the response functions of a diamond and a SiC detector to fast neutrons at 2.45 MeV, 2.95 MeV, 3.45 MeV, and 3.95 MeV, using direct detection through elastic scattering without the use of conversion layers. For this purpose, a 50 μm single-crystalline diamond and a 50 μm SiC detectors were exposed to quasi-monoenergetic neutron beams at NCSR "Demokritos" in Athens. The resulting experimental spectra were compared with Geant4 simulations to validate the measurements and to extract the detection efficiencies.