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[en] Highlights: • A methylthymol blue–polyvinyl alcohol–glutaraldehyde dosimeter has been studied by nuclear magnetic resonance analysis. • The MTB-PVA-GTA dosimeter has a reproducible linear dose response up to 40 Gy. • No significant dose rate and photon energy effects were observed. - Abstract: A new formulation of hydrogel dosimeter consisting of ferrous–methylthymol blue (MTB)–polyvinyl alcohol (PVA) cross-linked chemically with glutaraldehyde (GTA) was studied and evaluated by nuclear magnetic resonance analysis by means of the R2 spin-spin relaxation rate. Previous optical studies of this transparent solid chemically cross-linked gel showed important dosimetric features in terms of sensitivity, auto-oxidation rate, and diffusion. This study shows that the MTB-PVA-GTA dosimeter has a reproducible linear dose response up to 40 Gy. For the optimum formulation of 0.1 mM MTB, 2.5% PVA, and 26.6 mM GTA, the measured R2 sensitivity was higher than that of traditional natural matrix–containing gels (MTB-gelatin) and all other reported PVA gel–based radiochromic dosimeters with MTB, xylenol orange (XO), or GTA (MTB-PVA, XO-PVA, XO-PVA-GTA). Additionally, the auto-oxidation rate was approximately ten times lower than that of the Fricke-MTB-gelatin system, which is consistent with the spectrophotometry results. The results of the independent experimental spectrophotometry and nuclear magnetic resonance analyses indicate that the transparent cross-linked dosimeter has good and consistent dosimetric features.
[en] Highlights: • Primary standardisation of 44Sc and 89Zr performed. • Reported dial settings for radionuclide calibrators in clinically relevant geometries. • New dial settings identified for calibrators and clinically relevant geometries. • Results provide data that did not previously exist in the literature. - Abstract: Radionuclide activity meters depend on “calibration setting numbers” that are specific for a certain combination of radionuclide, volume and geometry. This work describes their determination for two PET emerging nuclides (44Sc and 89Zr), three commercial activity meters (CAPINTEC CRC15 BETA, ATOMLAB BIODEX 500 and VEENSTRA VDC 405) and two geometries: 1 mL plastic syringes and 5 mL glass vials. For 44Sc, only values for the dial setting for 5 mL ampoules were reported previously and its use for the assayed geometries would lead to significant differences. For 89Zr more data were available in the literature, and results are provided for new geometries. All results rely on the absolute standardisation in activity of solutions of both radionuclides.
[en] Highlights: • Polonium-210 analytical method needed for air filter samples following a radiological emergency. • Polonium-210 can be difficult to measure due to its volatility during sample digestion. • New oxidizing fusion method digests organic filters and solid particulates while minimizing Po volatility. • Employs rapid, rigorous digestion, preconcentration steps, and extraction chromatography. • Polonium-210 was measured using alpha spectrometry, after purification and microprecipitation. - Abstract: A rapid method for the determination of polonium-210 in air filters has been developed for use following a radiological event and for routine environmental monitoring. Air filter samples, including cellulose and glass fiber, are fused with a sodium or potassium nitrate/sodium hydroxide flux material. The alkaline matrix minimizes polonium volatility during sample digestion steps, while efficiently dissolving the air filter and inorganic matter implanted on the filter. The addition of nitrate to the flux destroys organic material which can decrease Polonium recovery during precipitation, extraction and source preparation steps. Polonium is concentrated and separated from the sample matrix using an iron hydroxide precipitation and extraction chromatography with DGA Resin. Polonium-210 is subsequently measured by alpha spectrometry following rapid microprecipitation with bismuth phosphate. The new method employs extraction chromatographic purification to remove alpha emitting interferences and sample matrix constituents which can interfere with 210Po measurements using alpha spectrometry. The novel blend of sodium hydroxide and alkali metal nitrate digests the air filters quickly and effectively.
[en] Highlights: • The MDA of the portable internal contamination monitor had been test by a Solid BOMAN Phantom for China Reference Adult Men and reached excellent detection limits for Cs-137. • The monitor with compact structure and low cost can be applied in the rapid test for large-scale screening, especially in the high population density areas. - Abstract: In the case of a radiological incident, large numbers of affected people should get rapid internal contamination screening, so a portable internal contamination monitor for large-scale application has been developed. It comprises dual detectors, a digital gamma spectrometer, and analysis software. Experiments carried out with a Chinese adult man model. Because of the inadequate shielding and poor detector resolution, the monitor is not sensitive to the lower energy emitters. However, it shows the excellent performance for the emitters above 661 keV. MDA for Cs-137, Y-88, and Co-60 reached 320Bq, 300Bq, and 530Bq in 5-min measurement. Due to the strong mobility, considerable detection limit, and low cost, the monitor can be applied to the rapid internal contamination screening in a radiological incident.
[en] Highlights: • This study aims to evaluate the annual effective dose from a sleeping mattress containing NORM. • The dose rate was measured using two different types of portable radiation detectors. • The equivalent dose was evaluated via Monte Carlo (MC) simulation and using the computational human phantom. • The annual effective dose calculated in this study is less than the annual effective dose limit for the general public (1 mSv/y). - Abstract: This study aims to evaluate the annual effective dose from a sleeping mattress containing naturally occurring radioactive material (NORM). In this study, the dose rate was measured using two different portable radiation detectors, namely the Geiger Müller (GM) tube and portable high-purity germanium (HPGe) detector; the annual effective dose was calculated using annualized usage of the products, and the equivalent does was evaluated via Monte Carlo (MC) simulation and using the model of the human body, which is known as a computational human phantom. The dose rate of the product, excluding background radiation at the shielded room, was measured as 0.22 and 0.13 μSv/h in the GM-tube and portable HPGe, respectively. Assuming that the sleeping mattress was used for an average sleeping of 8 h/day, the annual effective dose was calculated as 0.64 and 0.38 mSv/y using the GM-tube and portable HPGe detectors, respectively. Also, the annual effective dose calculated using MC simulation and radioactivity values from the nuclides analysis was 0.13 mSv/y. The annual effective dose calculated using the two different portable detectors and MC simulation is less than the annual effective dose limit for the general public, which is set at 1 mSv/y. This technique could be used not only for the safety regulation for products containing NORM but also for the accurate evaluation of the effective dose for radiation workers in the diverse radiation field.
[en] Highlights: • Buildup factors with standard formulations for lead, iron, concrete, and tungsten. • Exposure buildup factors for 1 MeV gamma rays in lead, iron, and concrete above 40 mfp. • Exposure buildup factors for tungsten above 40 mfp at gamma ray energies from 15 keV to 15 MeV. - Abstract: In this study, gamma ray buildup factors were investigated for conventional shielding materials such as lead, iron, concrete, and tungsten based on standard formulations in order to understand the variations between different formulations. The exposure buildup factors for 1 MeV gamma rays in lead, iron, and concrete for thicknesses beyond 40 mean free paths were computed using the modified geometric progression fitting formula and compared with previously reported data. For the first time, the exposure buildup factors were computed for tungsten at gamma ray energies from 15 keV to 15 MeV and for a penetration depth beyond 40 mean free paths.
[en] The cross-sections for 86Sr (n, 2n)85Sr reaction are measured at neutron energies 19.44 ± 1.02 MeV and 16.81 ± 0.85 MeV wherein there is scarcity of data. The standard neutron activation analysis technique and offline gamma ray spectroscopy have been employed for measurement and analysis of the data. The results are compared with experimental data available in EXFOR database, JEFF-3.3, JENDL-4.0, TENDL-2017 and ENDF/B-VIII.0 evaluated data. The theoretical prediction was incorporated using nuclear modular codes TALYS 1.8 and EMPIRE 3.2.2. A detailed comparative study of experimental results with the theoretical models and various major evaluations has been presented.
[en] Highlights: • Efficiency calibrations for geometries of a point source and a surface plane source were performed using the MCNP code. • Based on natural background spectra simulations, MDAs were calculated for selected acquisition times and geometries. • MDAs of a point source lie in a range of several MBq to a few GBq for the detector heights 1–30 m above the ground. • In the case of a surface plane source, MDAs are in the order of hundreds of kBq m−2 (for the sampling time 5 s).
[en] Highlights: • The minimum detectable activity (MDAs) in singles mode were higher by a factor of 8–36 than for coincidence mode measurements. • The activity concentration of 238U and 232Th series radionuclides were determined using a gamma-gamma coincidence method despite us not having any traditional background shielding. • The activity concentration of 238U and 232Th series radionuclides in the IAEA-375 reference soil material were below the MDA for singles mode measurements. - Abstract: Traditionally, activity concentrations of naturally occurring radioactive materials (NORMs) are measured using a gamma-ray spectrometer with a single detector shielded with lead. In this measurement, a gamma-ray spectrometer comprising an array of four LaBr3:Ce detectors without shielding was used. This spectrometer allowed for measurement in singles and coincidence (gamma-gamma) modes. In addition to using the coincidence method, a novel method of background reduction by using the photon time-of-flight was utilized. Activity concentration of 238U and 232Th series radionuclides in soil reference (IAEA-375) and beach-sand (Bs) were measured in singles and coincidence modes. In coincidence mode, the minimum detectable activities (MDAs) were lower by a factor of 8–36 than for singles mode. Activity concentration of 238U and 232Th series in soil material (IAEA-375) were determined in coincidence mode while it was below MDA in singles mode. The results correlate with the certified values to within the uncertainty although the uncertainties were high because of low statistics.
[en] Highlights: • TL and IRSL of limestone (CaCO3) have been studied. • Sample shows three composite TL glow peaks at 92 °C (P1), 165 °C (P2) and 239 °C (P3). • Sample has continuum trap distribution with E between 0.40 and 1.12 eV. • Dose response is linear for P1 (10‒1000 Gy) and P3 (10–100 Gy & 100–1000 Gy). • IRSL dose response is linear in two separate ranges within 10–100 Gy & 100–1000 Gy. - Abstract: Thermoluminescence (TL) and infrared light stimulated luminescence (IRSL) of limestone (CaCO3) collected from the Mawsmai Cave, India is reported. Structural and compositional analyses show that the sample has a rhombohedral crystal structure and contains 33.45% of CaO. TL measured at 1 °C/s from a sample irradiated to 600 Gy produces three composite glow peaks P1, P2 and P3 at 92, 165 and 239 °C respectively. The nature of the glow peaks is suggestive of the presence of a continuum trap distribution with activation energy between 0.40 eV and 1.12 eV. As regards to dose response, the TL intensity of P1 increases at a uniform rate with dose between 10 and 1000 Gy. Interestingly, the intensity of P3 increases with dose through two uniform regions, one within 10–100 Gy and the other between 100 and 1000 Gy. The IRSL measurement produces ill-shaped decay curves. The IRSL intensity also increases with dose at two different uniform rates within 10–100 Gy and 100–1000 Gy. Residual TL recorded after each IRSL measurement shows similar dose response as that under the conventional TL. Regarding fading, P1 fades by 88% and P3 by 14% within 12 h of irradiation.