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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

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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Nguyen Anh TUAN and Chau Van TAO

Nuclear Technology & Radiation Protection: Year 2020, Vol. 35, No. 1, pp. 36-41

Abstract:

An electron beam from the UELR-10-15S2 accelerator (average energy of 9.92 ± 0.48 MeV) was applied to irradiate food and medical items at the Research and Development Center for Radiation Technology, Vietnam Atomic Energy Institute, Vietnam. The materials are under an electron beam window, such as irradiation products, conveyor, magnet and shielding mate- rial for the magnet coil, bombarded by electrons and generated X-ray (bremsstrahlung effect). In this article, X-ray conversion efficiency from polypropylene, aluminum, iron, and lead bombarded by an electron beam from the UELR-10-15S2 accelerator is measured by the film dosimeter and simulated by the MCNP4c2 code, and there is good agreement between the calculation and measurement results. The results show that X-ray conversion efficiency is the highest from lead (4.3 %), so the gamma - neutron reaction (Q-value of –6.74 MeV for 207Pb) has to be studied in food and medical items irradiated by a 10 MeV eelectron beam.

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 Yuki Fujii, Yu Nakazawa, Ewen Lawson Gillies, Eitaro Hamada, Masahiro Ikeno, MyeongJae Lee, Satoshi Mihara, Yuta Miyazaki, Masayoshi Shoji, Chau Thanh Tai, Tomohisa Uchida and Kazuki Ueno for COMET Collaboration

 
Abstract:
A COMET Experiment Phase-I is designed to search for a muon to an electron conversion with a 100 times better sensitivity than the current upper limit on its branching ratio in order to investigate the new physics beyond the standard model. To achieve such an unprecedented sensitivity, a high intensity muon beam is mandatory. In consequence, an extremely high hit rate is predicted and it can cause a high trigger rate more than tens of kHz dominated by the background events. Then the high trigger rate would lead to the severe dead-time in the data acquisition. Therefore it is essential for a success of the experiment to reduce the trigger rate down to a few kHz within a processing time shorter than 5 μs while maintaining the signal efficiency high enough. We are developing an event classification algorithm utilising a CDC hit information and a dedicated fast online trigger system to accomplish this aim. The event classification based on a boosted decision tree shows 3.8 kHz of trigger rate, which almost satisfies the rate requirement, with a good compatibility to the trigger electronics. The total processing time to generate the trigger decision is estimated to be ~3 μs which also fulfils the timing requirement.
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Bui Ngoc Thien, Vu Ngoc Ba, Nguyen Thi Thao Vy, Truong Thi Hong Loan

Chemosphere Volume 259, November 2020, 127432

Abstract:

In this study, soil-to-plant transfer factor and annual organ equivalent dose due to ingestion of natural radionuclides in 13 popular food crop samples in Ho Chi Minh city, Vietnam were estimated. The obtained data show that the radioactive elements transported from soil to plants play an essential role as indicators for the nutritional needs of plant and the ability to accumulate radioisotopes and heavy metal elements for environmental decontamination. It is found that B. alba and C. gigantean is useful for decontamination of high content potassium in soil, otherwise, P. fruticosa and C. gigantean may be used for soil with high concentration of 210Pb and 226Ra. In addition, biological effects of the plant ingestion in human body were assessed. The doses due to ingestion of food crop samples varied from organ to organ, depending on the organotrophic properties of the radionuclides. For examples, equivalent dose for 40K in large intestine is higher than other organs. In contrast, equivalent dose for 238U, 226Ra, 210Pb and 232Th were mostly at bone surface. In general, the obtained dose values of lower than the average value recommended by UNSCEAR for food crop ingestion pose no threat to the public’s health. However, close investigations are needed in the near future.

 
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 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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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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