Radiation protection dosimetry最新文献

This study assesses the activity concentrations of the radionuclides 238U, 232Th, and 40K in soil samples collected from Wolaita Sodo town, located in the Southern Nations, Nationalities, and Peoples' (SNNP) Region, Ethiopia. A gamma-ray spectrometer equipped with a NaI(Tl) detector was used for the measurements. The concentrations of 238U, 232Th, and 40K varied from 3.25 ± 1.5 to 13.84 ± 2.2 Bq.kg-1, 0.4 ± 0.9 to 85.12 ± 3.4 Bq.kg-1, and 34.43 ± 2.7 to 748.07 ± 5.9 Bq.kg-1, respectively. The average activity concentrations were 7.83 ± 1.9 Bq.kg-1, 40.74 ± 2.7 Bq.kg-1, and 161.63 ± 3.9 Bq.kg-1 for 238U, 232Th, and 40K, respectively. The average radium equivalent activity was 192.25 Bq.kg-1, well below the recommended safety limit of 370 Bq.kg-1. The average gamma dose rate, and annual effective dose rate were 35.68 nGy.h-1, and 0.18 mSv.y-1, respectively. The internal and external indexes are below the recommended limit set by UNSCEAR and ICRP. However, the estimated excess lifetime cancer risk and indoor radon concentrations are slightly higher. Despite this, the overall radiological impact on the environment and public health in the study area remains negligible. This study provides valuable baseline data for radiation protection and informs urban and environmental policy in the region.

The present work is the first and foremost radiological study of soil samples collected from industrial estates in Tamil Nadu. The magnetic susceptibility measurement revealed that 74.19% of the samples have medium %χFD, which denotes a commixture of coarser grains or the SP grains with a size of <0.005 μm. The range of measured activities of 210Po and 210Pb were 3 ± 0.3-38 ± 2.6 Bq kg-1 and 16 ± 1.5-48 ± 2.9 Bq kg-1. The mean activity concentrations of 238U (33 Bq kg-1) and 40K (467 Bq kg-1) marginally exceeded the Indian recommended values of 28.67 and 400 Bq kg-1, respectively, whereas 232Th (47 Bq kg-1) did not exceed 63.83 Bq kg-1. The 238U and 232Th are the significant contributors to the production of radiogenic heat in the study area. Pearson correlation analysis confirmed the prime role of 232Th in radiation hazards and the insignificant relation between magnetic minerals and natural radioactivity.

Radioactivity concentration in soil was analyzed around the capital city of Indonesia, Jakarta along with the adjoining provinces of West Java and Banten, representing one of the most densely populated in Indonesia. Nestled within this area is a nuclear research reactor. The analysis of natural and artificial radioactivity concentrations using a HPGe gamma spectrometry to measure 226Ra, 232Th, 40K, and 137Cs in surface soil samples. The results indicate that the average activity concentrations of 226Ra, 232Th, and 40K ranged from 18 to 49, 24 to 74, and 18 to 249 Bq/kg, respectively. The calculated value for the total average absorbed dose rate in the air in Banten and West Java is 38 ± 4 and 34 ± 4 nGy/h. Nonetheless, the calculated value of the external hazard index indicates that the soils in that region are deemed suitable for use in construction materials, and the area is safe for habitation. The activity concentrations of 137Cs in several districts of Banten and West Java ranged from <0.09 to 0.73 Bq/kg. Even a minor introduction of artificial radioactivity into the environment constitutes a form of pollution that must be closely monitored as a potential environmental threat.

This study assesses radiation doses in cone beam computed tomography (CBCT) procedures in Sri Lanka, with the goal of establishing initial diagnostic reference levels (DRLs). Data from 1162 retrospective scans across four institutions were analyzed, and the medians of the pooled dose distribution for seven clinical indication categories were presented as the DRL values. The proposed DRLs based on clinical indications are 1013 mGy·cm2 for pathological conditions including cysts, tumors, and lesions, 1307 mGy·cm2 for implant planning, 1266 mGy·cm2 for presurgery assessment, and 1585 mGy·cm2 for evaluation of sinus and nasal pathology, temporomandibular disorder, and facial trauma. Considerable variability in doses across facilities was observed, driven by differences in equipment and imaging practices. Therefore, this study recommends adopting suggested DRL values as benchmarks, standardizing protocols to reduce dose variability, and implementing a national framework for regular updates of DRL values.

As the International Commission on Radiological Protection lowers the equivalent dose limit for lens of the eye of radiation workers, the importance of radiation protection for the lens of the eye has been increased. In the case of poor working condition, such as high temperatures and humid environments at nuclear power plants, wearing an eye dosemeter near the worker's eye may interfere with work. In addition, it would not be reasonable for all workers to wear an eye dosemeter to evaluate the lens equivalent dose even in areas with an expected low exposure dose in the NPPs. Therefore, it is necessary to develop an indirect assessment method for lens equivalent dose. The purpose of this study is to develop an indirect assessment method for a lens equivalent dose using correlation factors between whole-body dose and eye. The correlation factors are calculated by MCNP simulation results.

This article analyzes the external occupational radiation exposure distribution and trends among radiation workers in Jiangsu Province. The results show that the total annual collective effective dose for radiation workers in Jiangsu Province from 2019 to 2022 was 24.82 person·Sv, with an average annual effective dose of 0.34 mSv over the 4-y period. The average annual effective dose exhibited an initial increase followed by a subsequent decrease, with statistically significant differences (P < .001) between different years. In the medical uses, nuclear medicine and interventional radiology had higher average annual effective doses compared to other categories, at 0.42 and 0.38 mSv, respectively (P < .05). In industrial applications, accelerator operation and industrial testing workers had higher average annual effective doses compared to others, at 0.32 and 0.31 mSv, respectively (P < .001). Among different levels of medical institutions, secondary hospitals had the highest average annual effective dose (0.38 mSv, P < .001). Overall, the average annual effective dose for radiation workers in Jiangsu Province remained relatively low from 2019 to 2022, meeting national standards. However, special attention should still be given to radiation workers in nuclear medicine, interventional radiology, industrial testing, and accelerator operation.

Radon and thoron exhalation rates from samples are estimated by the standard closed-loop technique using online radon monitors. Conventionally, the mass balance equation is formulated by considering the closed air volume of the sample chamber and the detector chamber put together. This model serves the purpose of estimating the radon/thoron exhalation rates for the prescribed pump flow rate of 1 L min-1 using RAD7 online monitor. The flow rate requirement is crucial for thoron measurement due to its short half-life. In the present work, an alternate model is proposed which simulates the dynamics of radon/thoron concentration dictated by the air entry and exit rate and brings out the effect of pump flow rate. This model is more of academic interest, where sample chamber and detector chamber are considered as two separate entities since they are separated by tubing. The mass balance equation is reformulated considering the air entry and exit in and out the individual chambers. The radon buildup in the sample chamber and detector chamber were treated separately by two coupled differential equations. The equations were numerically solved. The model reiterated the fact that the lower flow rates do not affect the buildup profile of relatively long-lived 222Rn (half-life 3.8 d) and its steady-state concentration attained in the closed air volume. However, experiments carried out for flow rates 0.3 and 0.5 L min-1 with RAD7 monitor using powdered granite sample with higher 226Ra and 232Th concentrations gave contradicting results. The radon effective removal rate was found to decrease with increase in flow rate from 0.3 to 1 L min-1. This issue was investigated, and it was speculated that the thoron interference problem might not be properly addressed for flow rates <1 L min-1. This was ascertained by observing the effective radon removal rate in the absence of thoron by conducting radon decay experiments with different flow rates. For the case of short-lived thoron (half-life 55 s), the model described the dynamics of thoron concentration in the closed loop and the steady-state concentrations attained in the detector and sample chamber. As expected, the model showed that due to decay losses during transit of thoron between the chambers, the steady-state concentrations attained in the chambers considerably differ from each other even for 1 L min-1 flow rate.

Radiation protection in dental radiography can be achieved by adjusting the image field size, exposure, and filtration parameters, and using protective lead shields. The aim of this study is to assess the radiation dose delivered to the thyroid in a phantom irradiated by an orthopantomogram (OPG) system using Geant4 simulation toolkit. Recently, researchers have been trying to find an alternative material to the lead thyroid shield so that the OPG image has minimal metal artifacts. In this study, several materials were introduced as alternatives to lead thyroid shields. The results showed that Pb, Bi, Bi2O3, stainless steel, polyurethane-Bi2O3 (50%-50% mixture), and polyurethane-W (50%-50% mixture) shields provide a thyroid dose reduction of up to 12.0%, 12.3%, 12.0%, 11.6%, 11.8%, and 12.0%, respectively. For the truncated thyroid shields, these values are up to 10.5%, 10.3%, 10.3%, 9.80%, 10.0%, and 10.1%, respectively. Therefore, Bi and Bi2O3 can be suitable alternatives to lead thyroid shields.

In recent decades, technological advances have been made in the field of radiotherapy and with it the emergence of new dosimetric systems for their calibration and commissioning, among other uses. Such is the case of the measurement in the build-up region, where there is no charged-particle equilibrium, which is reflected in the increase in surface dose for patient treatments and potential skin toxicities as a secondary effect. This study utilizes optically stimulated dosemeters (nanoDot) and the radiochromic film (EBT3) to measure skin doses in patients with head and neck cancer who received radiotherapy. Accurately depicting 15 patients with different diagnoses from 3 linear accelerators using 3D, intensity modulated radiation therapy, or volumetric arc therapy/RapidArc technology, these results were compared with those calculated in the treatment planning system (TPS) and obtaining a percentage of variation for the EBT3 ranged from 0.30% to 6.15%, while that observed for the nanoDot was from 0.51% to 4.88%. This difference may be attributed to the reproducibility of placement in patients. Therefore, for clinical use, nanoDot dosemeters are a viable alternative for in vivo dosimetry where rapid validation of planning system results is required.

We investigated the neutron dose estimation for the triage of personnel involved in criticality accidents by conducting 24Na measurements via the whole-body measurement method. For a case study, we examined the September 1999 Japan Nuclear Fuel Conversion Co. criticality accident (internationally known as "the Tokaimura accident"). We investigated the neutron-induced radionuclides produced in worker C's body due to the irradiation of the primary pulse. A total of 87 radionuclides were identified, with activities ranging from 1.3 × 10-19 Bq to 6.9 × 106 Bq for worker C by Monte Carlo simulations. The radionuclide with the highest activity was revealed by calculation results: 28Al (t1/2 = 2.2 min) 6.9 × 106 Bq. The specific activity of 38Cl reached a level that was three times that of 24Na. These radionuclides would severely affect the 24Na measurement in the whole-body measurements performed in the immediate post-accident period. Spectrometry would be preferable for determining 24Na specific activities by whole-body measurements at accident sites.