Radiation protection dosimetry最新文献

With the increase in the distribution of sources of electromagnetic fields in the environment, public exposure to non-ionizing radiation emitted from these sources will increase and change with time. This work aims at the evaluation of public exposure to radiofrequency electromagnetic fields in the West Bank and compares this exposure with previous studies with a time interval difference of 11 years. Measurements of exposure were conducted in the outdoor environment in 149 locations using tri-axial E-field frequency-selective personal exposure meter EME SPY 140 enabling measurements of electric field strength in 14 predefined frequency bands in the range from 80 to 6 GHz. The average field strength from all sources in all investigated locations was 1.4 Vm-1. The maximum exposure measured at any location in the country was 7.43 Vm-1 and was found in Ramallah City center. The exposure quotient corresponding to this value was about 19 times below unity. The total exposure quotient for all locations was 0.001 with FM broadcasting being the main contributor by about 36%, UMTS2100 downlink by 24%, GSM 900 downlink contributing by 17%, WiFi 5GHz by 9% GSM 1800 downlink by 5%. Seven other RF sources contributed together by only 9% including WiMax, TV, WiFi 2 GHz, and others. More than 90% of the electric field strength values were below the level of 3 Vm-1. Within 11 years the average total exposure coefficient increased by a factor of about 2.

Activity concentration of 238 U and 232Th and their decay products are assessed in soil at three hydrocarbon zones to determine the baseline before further fracking studies. The range of activity concentration for the three zones was 238U (from 9.2 ± 0.5 to 115.8 ± 7.5) Bq kg-1, 228Ra (from 8.3 ± 2.0 to 50.0 ± 4.4) Bq kg-1 and 226Ra (from 24.1 ± 2.3 to 86.8 ± 4.7) Bq kg-1; which are comparable to the global average values reported by UNSCEAR in soil. Similar activity-concentration patterns for 238U decay series and 232Th decay series for the three zones indicate no previous industrial action. This baseline is useful to assess a possible enrichment of Naturally Occurring Radioactive Materials if industrial activities take place in the future.

The UKHSA radon detectors with polyallyldiglycol carbonate sensing material produced from 2010 onward were used to confirm that they are purely radon detectors only with negligible interference from thoron presence. The statistical analysis of results, after following standard detector processing procedures, showed that such devices can only detect 2.4% ± 0.3% of the total thoron activity concentration compared to the calibrated reference device. It was also demonstrated that thoron, unlike radon, can only travel a very short distance from the source to be effectively measured. Based on the above, it has been concluded that interference of thoron in radon measurement is negligible (within the statistical measurement error), and hence can be ignored in standard indoor and outdoor measurements.

This paper presents a new method for correcting the contribution of scattered radiation to the measurement of 99mTc internal activity in nuclear medicine patients using gamma cameras. So, this study aims to derive scattering correction factors by Monte Carlo simulation for anterior and posterior count rates (${I}_{mathrm{A}}$ and ${I}_{mathrm{P}}$) in the conjugate view method, enabling more precise estimation of activity A(t) compared to traditional trapezoidal and triangular approximations. The new approach eliminates the need to use photopeak for determining the fraction of scattered photons. Our results showed differences of <3% with respect to the real activity and 11% for the trapezoidal and triangular approaches.

Environmental measurements of Radon and its progeny were carried out in a gold mining area in the department of Antioquia, Colombia. Radon concentration measurements were carried out during 2 y in seven different measurement points in three types of geological zones, by using EPERM electret chambers and DOSEman Pro detectors at each point. Radon concentration values between 858 ± 59 Bq m-3 and 2469 ± 158 Bq m-3 and an equilibrium factor between 0.15 and 0.27 were found. The annual effective dose, taking into account the radon concentration, was determined under two calculation methodologies ([1] and International Commission of Radiological Protection 137), obtaining values of up to 7.7 mSv, and 13.5 mSv, respectively, for 2000 annual working hours, which shows the importance of the dosimetric data and epidemiological studies carried out year after year to reduce the uncertainties regarding estimates of radon exposure and the need to carry out individual monitoring of miners.

Introduction: Bitewing examinations are used to examine the pediatric dental status. The aim of this study was to compare the image quality and radiation dose between two different X-ray systems used for pediatric bitewing imaging.

Materials and methods: Data were obtained from both pediatric in vivo bitewing studies and phantom studies. Two X-ray systems were used: Trophy CCX digital (TCCX) (Trophy Irix 70, Marne-la-Vallee, France) and Planmeca Pro X (PPX) (Planmeca, Helsinki, Finland). An Unfors dosimeter (Unfors EDD-30, Billdal, Sweden) was used to measure the skin dose. Image quality was evaluated blindly by three experienced dentists using a Likert scale of 1-5 based on the visual representation of the anatomical structures with emphasis on caries.

Results: The highest scoring in vivo bitewing images were obtained with TCCX, but the skin dose was 36% higher (mean 3029 ± 613 μGy) and 113% higher (mean 1364 ± 276 μGy) with standard settings than with compared to PPX. The evaluation of image quality revealed a higher median value for all ratings of TCCX compared to PPX for both the patient and phantom studies, meaning that the images of TCCX were rated as higher quality than the images from PPX. No correlation was found between the median score and the skin dose or between the median score and the exposure times.

Conclusion: A significant difference in radiation dose and image quality was found between TCCX and PPX in bitewing imaging. TCCX generally produced higher doses and better graded images, although all images were suitable for diagnosis.

Surface contamination monitors are used intensively in many facilities, like in the nuclear medicine departments for clearance measurements and decontamination and in decommissioning of nuclear installations. For a reliable use, all surface contamination monitors should have a valid calibration with traceability to the international standards. A comparison exercise for calibrations in terms of efficiency in 2π steradian for surface contamination monitors was organized between five dosimetry calibration laboratories, members of EURAMET (The European Association of National Metrology Institutes). Four β-beta radionuclide sources, Sr-90, Cl-36, Cs-137, Co-60, and one α-alpha source, Am-241, were used for calibrations during this exercise. Two transfer surface contamination monitors, one Canberra SABG 100 and one Berthold LB 124 with 100 cm2 and 343 cm2 effective area, respectively, were used. The monitors were circulated between the partners and were periodically returned to the pilot laboratory for stability checks. The efficiencies in 2π steradian measured by the participants do not fully agree for all sources and both detectors despite the fact that all laboratories used similar types of surface contamination sources and had proper traceability to primary standards for surface emission rate measurements. As no evident difference in measurements of surface emission rates is expected between the primary standard laboratories that calibrated the sources, it is very probable that the observed differences are mainly due to the calibration procedures used by each laboratory and that the measurement uncertainties of efficiency in 2π steradian are underestimated. This report presents the results of this pilot comparison for calibration of surface contamination monitors and stresses the need to organize similar generalized exercises. This report also identifies some gaps in procedures for calibration of surface contamination monitors.

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.

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.