Natural radioactivity level in fly ash samples and radiological hazard at the landfill area of the coal-fired power plant complex, Vietnam

Truong Thi Hong Loan,Vu Ngoc Ba,Bui Ngoc Thien 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.4

In this study, natural radioactivity concentrations and dosimetric values of fly ash samples were evaluated for the landfill area of the coal-fired power plant (CFPP) complex at Binh Thuan, Vietnam. Theaverage activity concentrations of 238U, 226Ra, 232Th and 40K were 93, 77, 92 and 938 Bq kg 1, respectively. The average results for radon dose, indoor external, internal, and total effective dose equivalent (TEDE)were 5.27, 1.22, 0.16, and 6.65 mSv y 1, respectively. The average emanation fraction for fly ash were0.028. The excess lifetime cancer risks (ELCR) were recorded as 20.30 10 3, 4.26 10 3, 0.62 10 3, and25.61 10 3 for radon, indoor, outdoor exposures, and total ELCR, respectively. The results indicated thatthe cover of shielding materials above the landfill area significantly decreased the gamma radiation fromthe ash and slag in the ascending order: Zeolite < PVC < Soil < Concrete. Total dose of all radionuclides inthe landfill site reached its peak at 19.8 years. The obtained data are useful for evaluation of radiationsafety when fly ash is used for building material as well as the radiation risk and the overload of thelandfill area from operation of these plants for population and workers.

The Factors Affecting Corporate Income Tax Non-Compliance: A Case Study in Vietnam

NGUYEN, Loan Thi,NGUYEN, Anh Hong Viet,LE, Hac Dinh,LE, Anh Hoang,TRUONG, Tu Tuan Vu Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.8

In many countries, the Government enacts tax laws in order to manage tax collection and regulate the macro-economy. According to Noor, Jamaludin, Omar, and Aziz (2013), tax non-compliance is a growing concern because of its negative effects on the state budget. The main objectives of this article are to identify the factors affecting corporate income tax non-compliance of enterprises in Ho Chi Minh City in accordance with the current situation of Vietnamese tax administration. We use several research methods, including the exploitation of information and practical experiences from both taxpayers and tax authorities; with Probit regression model on a sample of 187 enterprises that have been inspected or examined by tax authorities in Vietnam during the period from 2013 to 2017.The article identified eight factors affecting corporate income tax (CIT) non-compliance: (1) working capital/total assets; (2) revenue/total assets; (3) total debt/total assets; (4) loss in the previous year; (5) receivables/revenue; (6) the size of enterprises; (7) tax administrative penalties/tax payable; and (8) business field. In particular, the tax non-compliance was studied as a violation of Vietnamese tax laws by enterprises declaring an insufficient amount of CIT payable to the State budget.

Calculation of Jaws-only IMRT (JO-IMRT) dose distributions based on the AAPM TG-119 test cases using Monte Carlo simulation and Prowess Panther treatment planning system

Luong Thi Oanh,Duong Thanh Tai,Truong Thi Hong Loan,James CL Chow 한국원자력학회 2021 Nuclear Engineering and Technology Vol.53 No.12

The aim of this study is to calculate the JO-IMRT dose distributions based on the AAPM TG-119 usingMonte Carlo (MC) simulation and Prowess Panther treatment planning system (TPS) (Panther, ProwessInc., Chico, CA). JO-IMRT dose distributions of AAPM TG-119 were calculated by the TPS and wererecalculated by MC simulation. The DVHs and 3D gamma index using global methods implemented inthe PTW-VeriSoft with 3%/3 mm were used for evaluation. JO-IMRT dose distributions calculated by TPSand MC were matched the TG-119 goals. The gamma index passing rates with 3%/3 mm were 98.7% formulti-target, 96.0% for mock prostate, 95.4% for mock head-and-neck, and 96.6% for C-shape. The dose inthe planning target volumes (PTV) for TPS was larger than that for the MC. The relative dose differencesin D99 between TPS and MC for multi-target are 1.52%, 0.17% and 1.40%, for the center, superior andinferior, respectively. The differences in D95 are 0.16% for C-shape; and 0.06% for mock prostate. Mockhead-and-neck difference is 0.40% in D99. In contrast, the organ curve for TPS tended to be smaller thanMC values. JO-IMRT dose distributions for the AAPM TG-119 calculated by the TPS agreed well with theMC.

Study on the Characteristics of X-ray Spectra in Imaging Diagnosis Using Monte Carlo Simulations

Khanh Ai Tran,Loan Thi Hong Truong,Nhon Van Mai,Phuong Nguyen Dang,Dung Thi Thuy Vo 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.69 No.7

X-rays are widely used in diagnostic imaging such as radiography and computed tomography. An understanding of the X-ray spectrum is essential for estimating the dose absorbed by the patient and for improving image quality. In this research, X-ray emission spectra were investigated by using two different approaches: a Monte Carlo method using the MCNP5 code and a semi-empirical calculation with SpekCalc software. The results were compared with each other to validate the Monte Carlo simulation of the X-ray spectra, so that the simulation model can be applied to estimating the dose rate distribution in X-ray imaging. The obtained results show good agreement between the two approaches, but some divergence is still observed in the characteristic X-ray peaks. In addition, the influence of X-ray tube parameters such as the peak voltage, filter, anode angle and target material on of the beam quality was investigated.

Effects of element composition in soil samples on the efficiencies of gamma energy peaks evaluated by the MCNP5 code

Ba, Vu Ngoc,Thien, Bui Ngoc,Loan, Truong Thi Hong Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.1

In this work, self-absorption correction factor related to the variation of the composition and the density of soil samples were evaluated using the p-type HPGe detector. The validated MCNP5 simulation model of this detector was used to evaluate its Full Energy Peak Efficiency (FEPE) under the variation of the composition and the density of the analysed samples. The results indicates that FEPE calculation of low gamma ray is affected by the composition and the density of soil samples. The self-absorption correction factors for different gamma-ray energies which was fitted as a function of FEPEs via density and energy and fitting parameters as polynomial function for the logarithm neper of gamma ray energy help to calculate quickly the detection efficiency of detector. Factor Analysis for the influence of the element composition in analysed samples on the FEPE indicates the FEPE distribution changes from non-metal to metal groups when the gamma ray energy increases from 92 keV to 238 keV. At energies above 238 keV, the FEPE primarily depends only on the metal elements and is significantly affected by aluminium and silicon composition in soil samples.

Accumulation and distribution of nutrients, radionuclides and metals by roots, stems and leaves of plants

Huynh Truc Phuong,Vu Ngoc Ba,Bui Ngoc Thien,Loan Truong Thi Hong Korean Nuclear Society 2023 Nuclear Engineering and Technology Vol.55 No.7

In the process of growth and development, plants not only absorb essential nutritional elements, but also absorb radioactive and non-essential elements from the environment, and their distribution varies in different parts of the plant. In this study, neutron activation analysis and gamma spectrometry were performed on stems, roots, and leaves of vegetables. The results indicate that the accumulation of radionuclides and multi-elements depends on the plant type and plant parts. Activity concentrations of ²²⁶Ra and ²³²Th in plants were accumulated in the following order: Roots > Stems > Leaves. The highest concentrations of ⁴⁰K and ²¹⁰Pb were observed in the stems and leaves of plants, respectively. Essential nutrient requirements of plants are in the following order: K > Ca > Mg > Fe > Zn > Mn. Among the nonessential metals, the concentration of Na in the vegetable sample was much greater than those of the other elements. The K/Na ratio in the plant depends on the type of plant and the translocation within the plant.