Polonium is among the most radiotoxic naturally occurring radionuclides, yet soil solid-liquid distribution coefficient (Kd (Po)) data remain scarce. This scarcity largely reflects analytical challenges and the widespread reliance on alpha spectrometry, which, although highly sensitive, requires substantially longer sample preparation and counting times than liquid scintillation counting (LSC). In this study, measurement conditions for 210Po in soil extracts were systematically optimised using contrasting soils. An extract-to-scintillation cocktail ratio of 8:12 (v/v) was identified as the most appropriate, yielding detection efficiencies of 94–98%. Potential 210Po losses due to adsorption onto polypropylene (PP), polycarbonate (PC) and polytetrafluoroethylene (PTFE) centrifuge tubes were evaluated. In soil-free experiments, 70–80% of 210Po was retained on tube walls after 24 h for all materials, while no losses were observed onto nylon filters. However, under batch sorption conditions in the presence of soil, PP tube-wall retention accounted for up to 2% of the initial activity for high-sorbing soils and up to 10% for very low-sorbing soils, without statistically affecting calculated Kd (Po) values. Filtration through 5 μm nylon filters did not statistically affect Kd (Po) values across 12 soils, but it did reduce inter-replicate variability with a mean relative standard deviation (RSD) of 9.4% vs. 15.6% without filtration. This pore size therefore improves analytical uncertainty without artificially increasing Kd (Po) as often reported for the classical 0.45 μm filtration. The proposed workflow provides a robust and time-efficient approach for Kd (Po) determination in large soil collections with contrasting edaphic properties.
True coincidence summing (TCS) effects on a LaBr3(Ce) scintillation detector were systematically investigated using experimental measurements and Monte Carlo simulations with RayXpert and EFFTRAN software at source-to-detector distances of 2-10 cm. TCS correction factors showed agreement between RayXpert and EFFTRAN at 10 cm (<2.1% difference), with larger deviations ranging from −0.3%-10.2% were observed at 4 cm. After applying the correction factors to the experimental raw efficiency values, experimental efficiencies agreed with simulations within < 3% at 4 cm source-to-detector distance. TCS effects decreased systematically with distance, and depended strongly on decay scheme complexity, with the magnitude of the TCS corrections was most pronounced for 152Eu, with the correction factor reaching 1.039 ± 0.006 at 2 cm for the 244.7 keV photopeak, corresponding to a deviation of approximately 3.9% from unity. 137Cs and 241Am showed only smaller effects (<0.5% at all distances) compared with the other gamma energies of the other radionuclides used in this study. At distances ≥ 8 cm, TCS corrections for most photopeaks were below the experimental uncertainty. The results validate Monte Carlo-based TCS correction methodology and provide practical guidance for optimizing measurement geometries in gamma-ray spectrometry with medium resolution detectors.
Although low in fluence, high-LET secondary ions and nuclear fragments within spacecraft contribute non-negligibly to astronaut radiation exposure. CR-39 is used for personal dosimetry in space, where a calibrated relationship between the etch-rate ratio V and LET enables particle LET inference and subsequent dose assessment. For low-energy Li, B, and C ions, however, experimental data show that the local etch response is not uniquely determined by REL350 alone and can vary systematically with track position. Discrete beam data cannot cover the continuous energy and incidence-angle ranges encountered in space, while existing simulations mainly address alpha particles and protons. This study developed an experimentally constrained forward-simulation framework for low-energy light-ion tracks in CR-39. The framework takes particle species, initial energy, incidence angle, and removed-layer thickness as inputs. Geant4 calculates the depth-resolved restricted energy loss REL350(x) with a 350 eV cutoff. REL350(x) is coupled with the experimentally derived position-dependent response V(REL350, x) to obtain V(x), which drives a track-evolution model predicting surface-opening dimensions, track depth, and 2D/3D morphology. The framework was evaluated for Li ions against published data and extended to B and C ions. The model reproduced the surface-opening dimensions and main morphological features of Li tracks, while predicted track-depth trends agreed with experiments. The B- and C-ion results showed that the workflow can be extended across species, although quantitative accuracy requires further experimental validation. The framework establishes a forward-response basis for future track interpretation and LET analysis. Whether the framework can quantitatively improve LET-spectrum reconstruction or dose assessment remains to be demonstrated.
Background Robust dosimetric validation is essential for using any new radiation device for clinical purposes. Monte Carlo (MC) simulation techniques have emerged as a powerful tool for dosimetric validation. Recently, ophthalmic plaques embedded with Ruthenium-106 (Ru-106), developed by Bhabha Atomic Research Centre (BARC), Mumbai, India, have been made commercially available for manual brachytherapy. Therefore, dosimetric validation of the plaques at users’ end is needed for safe and optimal clinical application. Purpose For the first time, the BARC-make Ru-106 notched eye plaque was simulated with the MC technique in this study. The 3D dosimetry results obtained with the MC simulations were validated with film dosimetry and with the data provided by the manufacturer. Methods EGS_Brachy MC code and EBT3 radiochromic film were chosen to determine absolute dose, 2D and 3D dose distributions for the eye plaque. A customised water phantom was designed and fabricated in-house for film dosimetry. Results The MC simulation results were consistent with film dosimetry and with the manufacturer's stated values for absolute dose rate (at a clinical depth of 2.0 mm) and percentage depth dose (PDD), showing a deviation of less than 5.0%. The statistical uncertainty in the MC simulations was 0.2% for the dose calculated at a depth of 2.0 mm. Conclusion The 3D dosimetry of BARC-make Ru-106 notched eye plaque was performed using the EGS_Brachy MC code for the first time and validated with film measurements. Thus, it is believed that based on the technical details provided by the manufacturer (BARC), the eye plaques could be reliably simulated for clinical dosimetric planning purposes.
