BẢN TIN KHOA HỌC

A refined technique for extracting strontium from water samples and quantifying strontium radioisotopes using a gas flow proportional counter

Phan Long Ho, Vu Tuan Minh, Le Dinh Hung, Le Hoang Minh, Tran Thien Thanh, Dang Van Chinh, Chau Van Tao

Progress in Nuclear Energy 187 (2025) 105856

Abstract:

This study focuses on developing an improved analytical method for determining strontium radioactivity (Sr-89 and Sr-90) in water samples. While the original procedure used high concentrations of acid, requiring more sample processing time and reducing safety and analytical performance, the proposed procedure addresses all the drawbacks of the old method. The new method optimizations include using 65 % HNO₃ instead of 90 % HNO₃ for safety, reducing separation steps from forty-three to twenty-six to save time and costs, and shortening the century equilibration between Sr-90 and Y-90 to under two weeks. Method validation on sixty-one samples shows the detection limit is 0.035 Bq.L^-1, meeting EPA requirements of 0.074 Bq.L^-1. Strong linearity (r = 0.999) between spiked and measured activity concentrations was observed in the working range of 0.046–23.371 Bq.L^-1 encompasses WHO’s 10 Bq.L^-1 limit for Sr-90 in drinking water. Interlaboratory testing of three IAEA samples over 2021–2023 further verifies accuracy. The results indicated that the new method has improved efficiency and safety. That reduced costs and analysis time, demonstrating the method’s suitability for various radioanalytical applications, particularly emergency nuclear scenarios demanding rapid Sr-90 isotope quantification.

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A novel method for calculating number buildup factor in gamma-ray transmission measurements using narrow beam geometry

Huynh Dinh CHUONG , Le Thi Ngoc TRANG, Nguyen Thi Truc LINH, Vo Hoang NGUYEN and Tran Thien THANH

Nuclear Technology and Radiation Protection 2024 Volume 39, Issue 3, Pages: 185-198

Abstract:

In this article, we present a novel method to calculate the number buildup factor for arbitrary materials in gamma-ray transmission measurements using a narrow beam geometry. The MCNP6 code was used to simulate photon transport within a collimated transmission configuration, which included a NaI(Tl) scintillation detector paired with a ¹³⁷Cs or ⁶⁰Co radioactive source. From these simulations, the number buildup factor values were computed forvarious materials at gamma-ray energies of 661.7 keV, 1173.2 keV, and 1332.5 keV, with sample thicknesses ranging from 0.1-7.0 cm. At each specific gamma-ray energy and material, the number buildup factor values exhibited a strong linear relationship with the sample thickness. Furthermore, the slope of these linear relationships can be expressed as a product of mass density and a cubic polynomial function of the atomic number. Based on these findings, we developed a fitting formula to calculate the number buildup factor using the input variables of sample thickness, mass density, and atomic number. The accuracy of the fitting formula was evaluated by comparing its results with number buildup factor values computed by MCNP6 code. The comparison showed relative deviations below 1% for all the investigated cases, demonstrating the high accuracy and reliability of the fitting formula.

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Huynh Dinh Chuong, Le Thi Ngoc Trang, Hoang Duc Tam, Vo Hoang Nguyen, Tran Thien Thanh

NDT & E International Available online 4 May 2020, 102281

Abstract:

This study proposes a new approach to determine the thickness of the material plate. This approach uses Monte Carlo simulation to construct the calibration curve of the ratio R versus the thickness of the material plate (R is the ratio of area under a scattering peak for a given thickness to that for a saturation thickness). Using this calibration curve, the unknown thickness of a material plate is determined by experimentally measuring the ratio R. To validate the proposed approach, we performed 39 measurements for 13 aluminum samples with thicknesses in the range of 7.00 mm–35.20 mm. The results showed that except for two measurements with relative deviations of 5.45% and 6.17%, the relative deviation for the remaining measurements is less than 5%. Besides, the method for estimating the maximum measurable thickness with the desired deviation was presented, which shows good agreement between theoretical calculation and experimental value. The obtained results are the basis for completing the thickness measurement system using semi-empirical methods in further studies.

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A Geant4 procedure for precise simulation of PGNAA prompt gamma‑ray spectrum in a wide energy range up to 8 MeV

Thanh Tai Chau, Ngoc Son Pham, Thien Thanh Tran, Cong Phat Vo, Van Tao Chau

Journal of Radioanalytical and Nuclear Chemistry

Abstract:

In reality, after subtracting the beam background from the prompt g-ray spectrum induced by the irradiated sample with the same time measurement, it still exists the remaining g-ray background induced by the nuclei capturing the thermal neutrons scattered by the sample. This makes it difficult to validate the accuracy of the PGNAA detector response between the simulation and the experiment in the wide energy range. In this study, a simple method to construct the remaining g-ray background in the simulation prompt g-ray spectrum of ³⁵Cl(n,g)³⁶Cl reaction is proposed. Then the simulation prompt g-ray spectrum with the remaining g-ray background is compared to the experimental spectrum to validate the simulation PGNAA detector response in the energy range from 0.1 MeV to about 9 MeV.

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A benchmark for Monte Carlo simulations in gamma-ray spectrometry Part II: True coincidence summing correction factors

M.-C. Lépy, C. Thiam, M. Anagnostakis, C. Cosar, A. de Blas, H. Dikmen, M.A. Duch, R. Galea, M.L. Ganea, S. Hurtado, K. Karfopoulos, A. Luca, G. Lutter, I. Mitsios, H. Persson, C. Potiriadis, S. Röttger, N. Salpadimos, M.I. Savva, O. Sima, T.T. Thanh, R.W. Townson, A. Vargas, T. Vasilopoulou, L. Verheyen, T. Vidmar

Applied Radiation and Isotopes, 2023

Abstract:

The goal of this study is to provide a benchmark for the use of Monte Carlo simulation when applied to coincidence summing corrections. The examples are based on simple geometries: two types of germanium detectors and four kinds of sources, to mimic eight typical measurement conditions. The coincidence corrective factors are computed for four radionuclides. The exercise input files and calculation results with practical recommendations are made available for new users on a dedicated webpage.

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A benchmark for Monte Carlo simulation in gamma-ray spectrometry

M.C. Lépy, C. Thiam, M. Anagnostakis, R. Galea, D. Gurau, S. Hurtado, K. Karfopoulos, J. Liang, H. Liu, A. Luca, I. Mitsios, C. Potiriadis, M.I. Savva, T.T. Thanh, V. Thomas, R.W. Townson, T. Vasilopoulou, M. Zhang

Abstract:

Monte Carlo (MC) simulation is widely used in gamma-ray spectrometry, however, its implementation is not always easy and can provide erroneous results. The present action provides a benchmark for several MC software for selected cases. The examples are based on simple geometries, two types of germanium detectors and four kinds of sources, to mimic eight typical measurement conditions. The action outputs (input files and efficiency calculation results, including practical recommendations for new users) are made available on a dedicated webpage.

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