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TRƯỜNG ĐẠI HỌC KHOA HỌC TỰ NHIÊN, ĐẠI HỌC QUỐC GIA THÀNH PHỐ HỒ CHÍ MINH

KHOA VẬT LÝ - VẬT LÝ KỸ THUẬT

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

Vu Ngoc Ba,  Le Thi Ha Giang, Bui Ngoc Thien, Truong Thi Hong Loan, Ngo Quang Huy

Applied Radiation and Isotopes 163 (2020) 109229

Abstract:

In this work, the physical dimensions and the actual position of germanium crystal within a detector housing, the homogeneity of the crystal surface and outer dead layer thickness for a p-type HPGe detector were con rmed by the scan method using the collimated low energy photon beams combined with Monte Carlo simulation. The length and the diameter of the crystal were found to match with the values supplied by the manufacturer in discrepancy of about 3%. Only one mounting strap (Typical) for holding the crystal inside the mounting cup instead of two which is indicated in the detector drawing supplied by manufacturer was revealed by scanning along the lateral face of detector. Scanning on the front surface and around the lateral face of detector by the collimated 59.5 keV photon beam veri ed the outer dead layer thicknesses at the front surface and lateral face of the crystal averagely increases about 6.5% and 12% respectively. Adjusting the detector parameters for MCNP simulation by these veri ed values, the simulated peak ef ciencies for different photon energies become being in accordance with the experimental peak ef ciencies.

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Uranium isotopes in groundwater in Ho Chi Minh City and related issues:

Health risks, environmental effects, and mitigation methods

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

Journal of Contaminant Hydrology 245 (2022) 103941

Abstract:

Groundwater is regularly used for many purposes, such as drinking and agricultural irrigation systems. Still, it contains high levels of radionuclides (e.g., 238U, 232Th, and 226Ra) that are potentially hazardous to humans and the environment. In this study, activity concentrations of uranium isotopes were analyzed in 15 groundwater samples taken from 15 bored wells in Thu Duc district, Ho Chi Minh City, Vietnam. Environmental effects of the irrigation system with groundwater on agricultural soil in the study area were assessed by models. It was found that the activity concentrations of 238U and 234U in groundwater samples were in the ranges of (13.5–268.7) mBq l− 1 and (20.2–438.3) mBq l− 1, respectively. The ratio 234U/238U values were ranged from 1.12 to 2, with an average value of 1.44. Based on the model prediction, 25 years irrigation with the groundwater can inject 94.8 Bq both uranium isotopes in 1 kg topsoil. For investigated groundwater samples, the proposed removal method using K2FeO4 removed 74.28% and 81.04% for 234U and 238U, respectively.

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Van‐Chung Cao, Thi Ly Nguyen, Thi Thu Hong Pham, Thi The Doan, Han‐Tuong Luc, Nhut‐Huan Phan, Giang T. T. Phan,  Trung H. Duong,  Hoai‐Nam Tran

Journal of Radioanalytical and Nuclear Chemistry

Abstract:

A treatment of dose nonuniformity inside Lo Ren and purple star apples irradiated by 10 MeV electron beam accelerator has been proposed by using medium density berboards (MDF). The dose uniformity ratios (DURs) inside the Lo Ren and purple star apples were estimated as 2.47–2.48 and 2.18–2.22, respectively. To reduce the DURs, the arrangement and the thickness of the MDF boards were determined by Monte Carlo simulations. Measurements of the absorbed doses have been conducted to compare with the simulations. The DURs were reduced to 1.36–1.39 and 1.44–1.46 for the Lo Ren and purple star apples, respectively.

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Nguyen Tri Toan Phuc, Kazuki Yoshida, Kazuyuki Ogatta,

Phys.Rev. C100,064604 - Published 6 December 2019

ABSTRACT:

Background: Proton-induced nucleon knockout (p,pN) reactions have been successfully used to study the single-particle nature of stable nuclei in normal kinematics with the distorted-wave impulse approximation (DWIA) framework. Recently, these reactions have been applied to rare-isotope beams at intermediate energies in inverse kinematics to study the quenching of spectroscopic factors.

Purpose: Our goal is to investigate the effects of various corrections and uncertainties within the standard DWIA formalism on the (p, pN) cross sections. The consistency of the extracted reduction factors between DWIA and other methods is also evaluated.
Method: We analyze the ( p, 2 p) and ( p, pn) reaction data measured at the R3 B-LAND setup at GSI for carbon, nitrogen, and oxygen isotopes in the incident energy range of 300–450 MeV/u. Cross sections and reduction factors are calculated by using the DWIA method. The transverse momentum distribution of the 12C(p,2p)11B reaction is also investigated.

Results: We have found that including the nonlocality corrections and the Møller factor affects the cross sections considerably. The proton-neutron asymmetry dependence of reduction factors extracted by the DWIA calculation is very weak and consistent with those given by other reaction methods and ab initio structure calculations.

Conclusions: The results found in this work provide a detailed investigation of the DWIA method for ( p, pN ) reactions at intermediate energies. They also suggest that some higher-order effects, which is essential for an accurate cross-section description at large recoil momentum, is missing in the current DWIA and other reaction models.

DOI: 10.1103/PhysRevC.100.064604

Thickness determination of material plates by gamma-ray transmission technique using calibration curves constructed from Monte Carlo simulation

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

Radiation Physics and Chemistry(2021)

Abstract:

This paper presents a new approach for determining the thickness of material plates by gamma-ray transmission technique using calibration curves obtained from simulated spectra through the Monte Carlo algorithm. The narrow transmitted gamma-ray beam from a collimated source of 137Cs (with the energy of 661.7 keV) for different thicknesses of the metal plates (aluminum, copper, and steel) was recorded by a NaI(Tl) detector. Besides, the Monte Carlo simulations of radiation transport in a model with the same geometry, source, and detector characteristics as in the real experiment were performed to obtain the transmission spectra. A good agreement between the experimental and simulated spectra was observed. The linear calibration curves of the value of ln(R) versus the thickness of material plates were constructed using Monte Carlo simulated data (R is the ratio of the area under a transmitted peak for measurement with sample relative to that for measurement without sample). The unknown thickness of a sample was determined by substituting the experimental value of ln(R) into the linear calibration curve corresponding to such sample. Besides, the range of measurable thickness with the desired accuracy was estimated for each material based on simulated data. The obtained results showed excellent quantitative values even without using any standard plate with known thickness for the calibration.

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

Journal of Environmental Radioactivity 216 (2020) 106189

Abstract:

The effects of moisture content, grain size, temperature, major elemental composition, and the pH of soils on the radon emanation and diffusion coefficients were evaluated in this study. The emanation and diffusion coefficients are strongly influenced by moisture content and grain size. The radon emanation coefficient increased and the diffusion coefficient decreased with decreasing particle size. However, for soils with large particle sizes, the radon emanation and diffusion coefficient remain almost unchanged with variation in grain size. Comparing five different sized soil particles, the emanation coefficient increased and the diffusion coefficient decreased with moisture content. The radon emanation coefficient reached a constant value with different moisture contents depending on the range of grain sizes. The saturation emanation coefficient for less than 0.1, 0.1–0.2, 0.2–0.3, 0.3–0.5, and more than 0.5 mm sized soil grain ranges are 0.47, 0.42, 0.35, 0.26 and 0.23, respectively, with saturation moisture contents of 16%, 14%, 10%, 6% and 4%, respectively. A drastic increase in radon emanation is found at smaller grain sizes with increasing moisture content. Based on the content of major elements and pH of the soils, the multiple regression indicates that the radon emanation coefficient appears to be significantly dependent on iron content and pH. Effective diffusion coefficient values calculated in our study agree with the results calculated by a previous model. Experimental values show that the temperature dependence of the radon diffusion coefficient follows Arrhenius behavior.

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