BẢN TIN KHOA HỌC

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 L−1 with a mean of 0.183 ± 0.034 Bq L−1, and the gross beta results in the water samples ranged from 0.027–0.632 Bq L−1 with a mean of 0.152 ± 0.015 Bq L−1. 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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Simultaneous correction of the coincidence summing and self‑absorption for radioactivity measurement in solid samples by MCNP‑CP code

Le Quang Vuong, Tran Thien Thanh, Phan Long Ho, Le Cong Hao, Chau Van Tao

Journal of Radioanalytical and Nuclear Chemistry

Abstract:

The present work of this study involves an advanced analytical procedure that allows direct and fast determining the specific activity of ²³⁸U and ²³⁵U using the gamma-rays of 63.3 keV and 185.7 keV after subtraction of the contribution of overlapping peaks. This procedure also included MCNP-CP code in order to calculate the coincidence summing and the self-absorption correction factor. Validation of the developed procedure was confirmed by the IAEA proficiency test to calculate the activities of radionuclides in various types of samples such as rich thorium, secular equilibrium, and disequilibrium of uranium. The final scores were received “acceptable” for all radionuclides.

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Sensitivity of secondary particle emission to hadronic physics models in GATE/Geant4 proton therapy simulations at 100 MeV

Pham Thi Cam Lai, Nguyen Tri Toan Phuc, Vo Hong Hai

Science & Technology Development Journal 2023, 26(3):2930-2936

Abstract:

Introduction: Proton therapy simulations rely on Monte Carlo techniques, such as the GATE code based on the Geant4 toolkit, to predict dose distribution and secondary particle production. The accuracy of these simulations is heavily influenced by the chosen physics models.

Methods: In this study, we analyzed three Geant4 hadronic physics models, BIC, BERT, and INCL++, by calculating the angular and energy distributions of secondary neutrons and gamma particles. We conducted GATE/Geant4 simulations on a water phantom irradiated with a 100 MeV proton beam.

Results: Our investigation revealed notable differences in the angular and energy distributions of emitted particles among the three models.

Conclusion: This study emphasizes the necessity of carefully selecting a hadronic physics model for GATE/Geant4 simulations in proton therapy.

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

Journal of Radioanalytical and Nuclear Chemistry

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 cosθ^ηp_lab < -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.