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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

Tran ThienThanh, Le Hoang Minh, Nguyen Quoc Bao Cuong, Huynh Dinh Chuong, Nguyen Duy Thong, Vo Hoang Nguyen, Phan Long Ho, Chau Thanh Tai,  Chau Van Tao

NIM A Available online 23 April 2020, 163995

Abstract:

Experimental data of Rayleigh to Compton scattering ratios depending on the effective atomic number of the fifteen powder samples in the range 10 < Z < 30 obtained at an energy of 59.54 keV using six well-known methods are presented in this article. In this study, a Si(Li) detector is placed at a scattering angle of 150 degrees to detect emitting signals from the interaction of incident gamma rays and powder samples. A new fitting procedure with the least squares method was used to fit the Compton peak using a Voigt function and the Rayleigh peak using a Gaussian function by Root software. The ten calibrating samples provided results that were in good agreement with the fitting procedure for all methods using linear functions. The estimated values of the Rayleigh to Compton scattering ratio using the effective atomic numbers were compared to the theoretical calculation. Furthermore, the best solution for the interpolated effective atomic number of the six methods was found and confirmed with the maximum relative deviation lower than 4% for five analysed samples.

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

 Scientific Reports Volume 10, Article number: 4299 (2020)

Abstract:

This paper presents information on the gross alpha and gross beta activity concentrations of two hundred twenty-six groundwater samples collected by gas ow proportional counters in southern Vietnam. The gross alpha results in the water samples ranged from 0.024 to 0.748 Bq L1 with a mean of 0.183 ± 0.034 Bq L1, and the gross beta results in the water samples ranged from 0.027–0.632 Bq L1 with a mean of 0.152 ± 0.015 Bq L1. The values obtained in this work were compared with those previously published for various regions or countries. Next, untreated and treated groundwater samples were analyzed to assess their in uences on the treatment process. The results showed that there
were di erences in the minimum detection concentrations and the mean activity values between the untreated and treated groundwater samples (The p-value of the mean comparison tests is signi cant with p < 0.05). In both sample groups, there was a strong positive correlation of the gross alpha versus the gross beta results (r > 0.6). This means that among the radionuclides, the major sources of beta radiation are uranium and thorium decay series radionuclides. Finally, the annual e ective dose for adults (>17 years) was calculated based on the assumption that major radionuclides have the highest e ective dose conversion factors. In general, the results for Pb-210, Ra-226, and Ra-228 were observed to be lower than the recommended reference values established by the World Health organization and the International Atomic Energy Agency, except for the value of Po-210.

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 Ba Ngoc Vu, Thien Ngoc Bui, Phong Thu Nguyen Huynh, Hao Cong Le, Phuong Truc Huynh, Hong Loan Thi Truong

Abstract:

In this work, the radon exhalation, annual effective dose and excess lifetime cancer risks due to the exposure of radon released from raw building materials containing fly ash of different fractions were evaluated. The 226Ra and 222Rn concentrations were evaluated by the measurements on HPGe gamma spectrometer, RAD 7 radon detector combined with model calculation of radon exhalation for standard rooms. The results indicated that the emanation fraction for fly ash is lower than the corresponding value for soils and rocks. The surveyed building materials of containing fly ash can result in an indoor radon concentration up to 1.7 Bq m−3 which is below the recommended value of 100 Bq m−3 by WHO, the annual effective dose increases from 0.007 to 0.022 mSv year−1, the excess lifetime cancer risks ranges from 0.027 × 10–3 to 0.085 × 10–3 with the ratio of 3.2 for the additional fly ash content in cement up to 75%. In the meanwhile, it has a down trend and influences inconsiderably on these parameters for sand. The obtained mean annual effective doses are lower than the dose limitation of 10 mSv year−1 recommended for occupational workers.

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 N. Tomida, T.N.T.Ngan, et al.

Physical Review Letters 124, 202501 (2020)

Abstract:

We measured missing mass spectrum of the 12C(γ,p) reaction for the first time in coincidence with potential decay products from η' bound nuclei. We tagged an (η + p) pair associated with the η'N ηN process in a nucleus. After applying kinematical selections to reduce backgrounds, no signal events were observedinthebound-stateregion.An upper limit of the signal cross section in the opening angle cosθηplab < -0.9 was obtained to be 2.2 nb/sr at the 90% confidence level. It is compared with theoretical cross sections, whose normalization ambiguity is suppressed by measuring a quasifree η' production rate. Our results indicate a small branching fraction of the η'N ηN process and/or a shallow η'-nucleus potential.

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Author: Thu T.C.Nguyen, Binh T.Nguyen, Nhon V.Mai

Purpose

Under geometrical uncertainties, different plan evaluation methods have been suggested but the dose distribution at a specified confidence level being highly desirable is lacking. In this work, we used the DVPH (Dose Volume Population Histogram) tool to evaluate the dose distribution of CTVs and OARs (Organs at Risk) and validate the PTV concept at a certain confidence level.

Methods

The plans were evaluated using PTV DVH and the DVPH approach. The DVPH approach is based on statistical analyzing of multiple CTV DVHs under geometrical errors with corresponding occurring probabilities. The random and systematic geometrical errors, assumed to follow a Gaussian distribution, are simulated by shifting the CT images.

Results

For target doses, the results showed that the minimum dose to PTV does not represent the minimum dose to the CTV. For two prostate cases, the minimum doses reduced from 98% and 95% of prescribed dose from PTV DVH to 89% and 92% of prescribed dose from CTV 90% CL-DVPH (90% Confidence Level-DVPH). This reduction was also seen in head and neck cases, from 95% to 68% and 74% of prescribed dose. For OAR doses, OAR DVHs underestimated the OAR dose receiving.

Conclusions

With the DVPH tool, the results showed that the minimum dose to the PTV is not a representative of the minimum dose to the CTV in IMPT at the 90% confidence level. The OAR DVH does not match any OAR CL-DVPHs.

 

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Optimization of uranium separation using silica gel impregnated tri‐n‐butyl phosphate for alpha spectrometry analysis of soil samples

 Van Thang Nguyen, Xuan Son Vi, Nguyen Phong Thu Huynh, Cong Hao Le

Abstract:

Silica gel impregnated tri-n-butyl phosphate was used as a chromatography column for extraction of uranium radioisotopes from soil samples. Diluted HNO3 and H2SO4 were used as the mobile and striping phases, respectively. In these stages, concentrations of HNO3 and H2SO4 solutions for the uranium extraction yield were optimized. We found that 5 M HNO3 and 3 M H2SO4 were the best solutions for uranium separation. Effects of electrodeposition conditions on uranium deposition yield were considered. Results showed that current of 1.5 mA, deposition time of 75 min, pH 2 and electrode gap of 1.5 cm were optimal conditions for electrodeposition.

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