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KHOA VẬT LÝ - VẬT LÝ KỸ THUẬT

BỘ MÔN VẬT LÝ HẠT NHÂN - NGÀNH KỸ THUẬT HẠT NHÂN - NGÀNH VẬT LÝ Y KHOA

 Le Hong Khiem, Koichiro Sera, Takako Hosokawa, Le Dai Nam, Nguyen Huu Quyet, Marina Frontasyeva,  Trinh Thi Thu My, Nguyen Thi Bao My, Inga Zinicovscaia, Nguyen The Nghia, Trinh Dinh Trung, Khuat Thi Hong, Nguyen Ngoc Mai, Duong Van Thang, Nguyen An Son, Tran Thien Thanh, Sonexay Xayheungsy

 Journal of Radioanalytical and Nuclear Chemistry(2020)

Abstract:

For the rst time, the active moss biomonitoring technique has been used in Vietnam for investigation of atmospheric elemental contamination in the air of Hanoi region. The Sphagnum girgensohnii moss harvested in the clean area were used to produce the moss-bags.After 2 months of expose in 45 di erent sites in Hanoi area, the moss samples were prepared and the concentration of 27 heavy metal elements were determined by proton induced X-ray emission at Cyclotron Research Center of Iwate Medical University (Japan).The comparison of the obtained results with those in several cities in Europe shows that Hanoi’s air pollution of heavy metal is much more serious. Based on the values of contamination coe cient, it is shown that Hanoi’s air is extremely polluted by Co; seriously polluted by V and Se; moderately polluted by Cl, Cr, As, Br, Zr, Nb, Mo and Hg; slightly polluted by Mg, Al, Si, K, Ca, Ti, Fe, Cu, Zn, Ga, Rb, Sr, Mo, Ba, W and Pb Statistical analysis has been applied to the original concentration data of the detected elements to nd the possible pollution sources.

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Van Thang Nguyen, Nguyen Phong Thu Huynh, Cong Hao Le

Journal of Environmental Management 271 (2020) 111001

Abstract:

In topsoils, the activity concentrations of natural radionuclides (hereafter NRs) increase due to the addition of NRs from fertilizers, irrigation water, and air dust pollution. On the other hand, various physical-chemical and environmental processes such as radioactive decay, volatilization, leaching, erosion, and plant uptake were responsible for the decrease of the activity concentrations of NRs in the topsoils. In this study, behaviours of 40K, 210Pb, 226Ra, 238U, and 232Th in topsoils were modelled by the CEMC soil model and the HYDRUS-1D model. An exponential equation was proposed for estimating the accumulation rates of these radionuclides in the topsoils. Long-term accumulation of radionuclides was assessed for water spinach (Ipomoea Aquatica Forssk.) soil (here-after VES) and rice (Oryza sativa L.) soil (hereafter RIS). We found that the current agricultural practices caused the increase of 40K activity concentration in the water spinach soil, and 40K, 210Pb, 226Ra, and 232Th activity concentrations in the rice soil. The accumulation rates of radionuclides were in the order 238U <232Th <226Ra <210Pb <40K. 25 years of cultivation with water spinach can increase/decrease +(165 +/- 6) Bq of 40K, (8.2 +/-0.7) Bq of 210Pb, (4.3 +/-0.2) Bq of 226Ra, (7 0.3 +/-0.3) Bq of 238U, and (1.8 +/-0.1) Bq of 232Th in 1 kg soil. For rice cultivation, these values are +(1004 +/-39), +(3.3 +/-0.2), +(3.0 +/-0.2), (5.1 +/-0.3), (2.2 +/-0.1) Bq kg-1 for 40K, 210Pb, 226Ra, 238U, and 232Th, respectively.

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A simple approach for developing model OF Si(Li) detector in Monte Carlo simulation

Huynh Dinh Chuong, Nguyen Thi Truc Linh, Le Thi Ngoc Trang, Vo Hoang Nguyen, Le Hoang Minh , Chau Thanh Tai, Tran Thien Thanh

Abstract

In this paper, a simple approach for developing the model of a Si(Li) detector in Monte Carlo simulations is presented and validated. Experimental measurements using “point-like” standard radioactive sources including 133Ba, 137Cs, 152Eu, 154Eu, 241Am were performed for both configurations with and without collimator, respectively. The MCNP6 code was used for Monte Carlo simulation of photon transport inside the models constructed similar to these configurations. Firstly, an initial model of the Si(Li) detector was constructed based on the manufacturer's specifications, but the simulated efficiency shows a very high discrepancy from the experiment. Then, the critical geometric parameters of the model of Si(Li) detector were improved step-by-step to achieve the optimized model. For the optimized model, a good agreement was obtained between the experimental and simulated results. The relative deviations of experimental and simulated efficiencies are less than 4% with energies in the range of 12–60 keV for both configurations.

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

Applied Radiation and Isotopes, Available online 10 April 2020, 109179

Abstract:

In present work, the validity of the virtual point detector (VPD) model for the NaI(Tl) detectors is studied and confirmed in the photon energy range of 60-1408 keV. The full energy peak efficiency (FEPE) of two NaI(Tl) detectors, which have scintillation crystal dimensions of 5.08×5.08 cm and 7.62×7.62 cm respectively, is measured for “point-like” radioactive sources on the symmetry axis with source-to-detector distances in the range of 2-40 cm. It is found that the VPD model is valid to fit too well to the experimental FEPE for the two surveyed NaI(Tl) detectors. The dependence of the VPD position on the incident photon energy for the NaI(Tl) detectors with different scintillation crystal dimensions is shown based on experimental data. A semi-empirical equation involving incident photon energy and source-to-detector distance is proposed to calculate the FEPE for the NaI(Tl) detectors. The calculated results for the two surveyed NaI(Tl) detectors by this equation are in a good agreement with experimental results for photon energies in the range of 344-1408 keV. However, the difference between experimental and calculated results is quite significant for source-to-detector close geometries for photon energies lower than 344 keV.

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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 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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