Nuclear Science and Technology
ISSN : 1810-5408
Published by: Vietnam Atomic Energy Institute (10.53747)
Total articles ≅ 210
Latest articles in this journal
Nuclear Science and Technology, Volume 11, pp 11-18; https://doi.org/10.53747/nst.v11i3.367
This paper presents a design of the neutron flux measurement channel that consists of a Boron-contained gamma-compensated ionization chamber (CIC) named KNK-3 and operates in current mode, a current to frequency (I to F) converter, and a neutron flux measurement and control module (FPGA-WR). The designed measuring channel allows to measure and control the neutron flux density from 1.0x106 to 1.2x1010 n/cm2.s corresponding to the range from 0.1 to 120% of the nominal power of 500 kW of the Dalat nuclear research reactor (DNRR). The measurement and control module uses FPGA Artix-7 and digital signal processing algorithms to measure and calculate the reactor power and period values and generate warning and emergency signals by the reactor power and period. The measurement channel was tested by using simulated signals and examining in the reactor to compare with the neutron flux measurement channel using the BPM-107R neutron flux controller of the existing complex ASUZ-14R for the DNRR control and protection system (CPS). The comparison results show that the measurement channel fully meets the requirements on the accuracy of the reactor power and period parameters as well as the ability to respond at once to the warning and emergency signals of the reactor power and period. Therefore, the measurement channel can be used for testing, research, and training. The FPGA-WR measurement and control module can replace the BPM-107R controller for the working range of the CPS.
Nuclear Science and Technology, Volume 11, pp 44-51; https://doi.org/10.53747/nst.v11i3.371
The Maillard reaction products of chitosan and glucosamine (CTS-GA MRPs) were formed by gamma Co-60-irradiation method and determined their minimum bactericidal concentrations (MBC). The mixed solutions of chitosan - glucosamine were irradiated with a dose range of 0-100 kGy to induce the Maillard reaction products (MRPs). The formations of MRPs were determined by spectrophotometric analyses and the contents of remaining glucosamine were evaluated by high performance liquid chromatography (HPLC). The antibacterial activities of CTS-GA MRPs were tested by agar well diffusion test and MBC determination test against both gram negative (Escherichia coli) and positive bacteria (Bacillus subtilis) at acidic and alkaline pH was also carried out. By agar well diffusion test, irradiated CTS-GA solutions were able to form inhibition growth zones on E. coli plate whereas on B. subtilis plate, only CTS-GA MRPs irradiated at 25 kGy expressed this ability. The results of the MBC determination test indicated that CTS-GA MRPs formed at 25 kGy exhibited highly antibacterial activity in pH 5 and even pH 7. Therefore, this CTS-GA MRPs could be used as a promising preservative agent applied for meat and meat-product preservation.
Nuclear Science and Technology, Volume 11, pp 19-26; https://doi.org/10.53747/nst.v11i3.368
In this work, activity of radioactive isotopes in some offshore seawater samples at vicinity areas of three islands has been investigated Phu Quy (Binh Thuan province), Phu Quoc (Kien Giang province), and Bach Long Vy (Hai Phong province). The ranges of radioactivity 226Ra, 238U, 137Cs, 90Sr, and 239,240Pu in seawater at three offshore islands are 2.09 ÷ 4.77 mBq/L, 2.33 ÷ 4.95 mBq/L, 0.98 ÷ 1.45 mBq/L, 1.22 ÷ 1.49 mBq/L, and 0.0045 ÷ 0.0066 mBq/L, respectively. These values show that the radioactivities of the above-mentioned radionuclides differ between monitoring periods and between three offshore islands of Vietnam, but which is equal to or lower than the corresponding value according to others seas in Vietnam and Asia – Pacific. The correlation between radioisotopes and properties of seawater (pH, conductance, and salinity) is also shown in this study to assess their impact on the fluctuations of the above radinuclides.
Nuclear Science and Technology, Volume 11, pp 34-43; https://doi.org/10.53747/nst.v11i3.370
Using electron beam (EB) irradiation as quarantine treatment for fresh fruits in particular and foods of plant origin in general is a growing trend of the world. Our preliminary results on EB irradiation impacts on Hoa Loc mangoes showed that EB irradiation could be a suitable quarantine treatment for the Hoa Loc mango fruits having weight from 407 to 552g and thickness from 7.3 to 8.0 cm to ensure the dose uniformity ratio (DUR) among irradiated products is within limitation (DUR ≤ 2.5). Main quality parameters of irradiated mangoes were insignificantly affected by exposure to EB with the dose ranging from 0.4 to 0.8 kGy, though their weight loss, the color indices L* (lightness), a* (redness to greenness), b* (yellowness to blueness) and firmness were slightly changed in compared with the control (non-irradiated). The results also revealed that vitamin C concentration of the fruits irradiated at 1 kGy much reduced and the hue angle significant increased by the end of storage. These results suggested that EB irradiation of Hoa Loc mangoes at the generic doses of 0.4 kGy is a feasible quarantine treatment that maintains the main the fruit quality.
Nuclear Science and Technology, Volume 11, pp 1-10; https://doi.org/10.53747/nst.v11i3.364
The estimation of radiological properties of activated structural components of a nuclear reactor due to irradiation of neutron produced by fission is a very important task for radiation safety and reasonable cost of dismantling and radioactive waste management in the decommissioning plan of the reactor. In this work, the calculation approach was carried out by using three-dimensional neutron transport model with the Monte Carlo code MCNP5 to evaluate neutron fluxes and reaction rates. The Bateman equation was solved with neutron absorption reactions (fission and capture) and disintegration by ORIGEN2 code to obtain the activity of materials in reactor structures. This paper presents the evaluation results of the neutron flux distribution and the radioactivity of long-lived key activation products such as 60Co, 55Fe, 59Ni, 63Ni, etc. isotopes in the structural components of the Dalat Nuclear Research Reactor (DNRR). The validation of calculation methodology of the two codes was implemented by comparing calculation results with measured neutron fluxes at irradiation positions in the reactor core as well as specific activities at the bottom part of the aluminum guiding tube at 13-2 channel, which has been removed from the reactor core about six years. The calculation results were in good agreement under 7% difference with the experimental neutron flux value of (6.05±0.52) × 1012 n/cm2.s, and under 33% difference with the experimental specific activities of 60Co isotope being 1.86×104, 9.99×104, and 1.28×105 Bq/g at the positions of -32.5, -17.5 and -2.1 cm (the centerline of the reactor core is at 0 cm), respectively, in the aluminum guiding tube of irradiation channel 13-2. The neutron flux distributions in other structural components such as the graphite reflector, thermal column, thermalizing column, concrete shielding, etc. of the reactor were also evaluated. The obtained calculation results and experimental data are very valuable for the development of a suitable decommissioning plan and a reasonable dismantling strategy for the DNRR.
Nuclear Science and Technology, Volume 11, pp 27-33; https://doi.org/10.53747/nst.v11i3.369
Environmental pollution, especially water pollution, is of great concern nowadays. Textile wastewater treatment by electron beam irradiation (EB) shows the advantage of not using toxic additives and not creating secondary sludge. In this study, textile wastewater was treated by electron beam irradiation in a low absorbed dose range of 0.5-2 kGy in combination with biological treatment. Besides, a study on combining EB irradiation and H2O2 oxidizing agent was also carried out to reduce the absorbed dose. The results show that after EB irradiation in the presence of oxidizing agents H2O2 combined with biological treatment, the color indicator of wastewater is within the allowed range according to column B of the national technical regulation on the effluent of the textile industry (QCVN 13–MT/2015/BTNMT), which is eligible for discharge into the environment. Research on the treatment of textile wastewater by EB irradiation combined with biological methods has shown that it increases the ability to effectively treat textile wastewater, contributing to reducing the environmental pollution.
Nuclear Science and Technology, Volume 9, pp 27-33; https://doi.org/10.53747/jnst.v9i4.138
The k0-based internal mono-standard (IM) method was first proposed for the concentration analysis of samples of non-standard geometry in the 2000s. The method has demonstrated several advantages such as the elimination of gamma-ray self-attenuation and geometrical effects. On the other hand, the accuracy of the method principally depends on the in situ relative detection efficiency, which requires to be obtained in each measurement. Therefore, the relative detection efficiency is always under consideration for the improvement of the analysis results. The present paper describes a simple and automatic procedure for the determination of the relative efficiency using one or more activation products emitting gamma rays over a considered range of the spectrum. The procedure can be applied for INAA and PGNAA analysis.
Nuclear Science and Technology, Volume 9, pp 1-8; https://doi.org/10.53747/jnst.v9i4.132
Grid spacers installed in subchannels of fuel assemblies for nuclear reactors can promote heat transfer. However, the fluid velocity and bubble behavior are greatly affected as the cross-sectional area of the flow passage changes. Therefore, the void fraction distribution behind the obstacle that simulates the grid spacer shape simply was measured by using a wire mesh sensor (WMS) system. Moreover, a two-phase flow analysis was performed to investigate the effect of the obstacle on the bubble behavior in a vertical duct.
Nuclear Science and Technology, Volume 9, pp 34-40; https://doi.org/10.53747/jnst.v9i4.135
Evaluating measurement uncertainty of a physical quantity is a mandatory requirement for laboratories within the recognition ISO/IEC 17025 certification to access reliability of measured results. In this work, the uncertainty of ionizing radiation measurements such as air-kerma, personal dose equivalent Hp(d) was evaluated based on GUM method and Monte Carlo method. An uncertainty propagation software has been developed for evaluation of the measurement uncertainty more convenient.
Nuclear Science and Technology, Volume 9, pp 9-15; https://doi.org/10.53747/jnst.v9i4.133
A severe accident-induced of a Steam Generator (SG) tube releases radioactivity from the Reactor Coolant System (RCS) into the SG secondary coolant system from where it may escape to the environment through the pressure relief valves and an environmental release in this manner is called “Containment Bypass”. This study aims to evaluate the potential for “Containment Bypass” in VVER/V320 reactor during extended Station Blackout (SBO) scenarios that challenge the tubes by primarily involving a natural circulation of superheated steam inside the piping loop and then induce creep rupture tube failure. Assessments are made of SCDAP/RELAP5 code capabilities for predicting the plant behavior during an SBO event and estimates are made of the uncertainties associated with the SCDAP/RELAP5 predictions for key fluid and components condition and for the SG tube failure margins.