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Kien Cuong Nguyen, Ton Nghiem Huynh, Vinh Vinh Le, Ba Vien Luong
Published: 15 December 2013
Nuclear Science and Technology, Volume 3, pp 20-28; https://doi.org/10.53747/nst.v3i4.323

Abstract:
From evaluated data sources like ENDF, JENDL and JEFF, neutronics data libraries forMCNP computer code have been produced, including neutron scattering cross section library S (β,α) in thermal energy range, by using NJOY computer code. The evaluation and validation of these neutronics data libraries have been carried out through calculation of some parameters such as effective multiplication factor and reaction cross sections of benchmark problems, VVR-M2 fuel type as well as the critical configurations of the Dalat Nuclear Research Reactor loaded with low enriched Uranium fuel. After implementing about analysis and evaluation of the calculated results with abovementioned libraries, the library provides results that consistent with experimental data can be used in core and fuel management calculation for the Dalat Nuclear Research Reactor (DNRR).
Dac Dung Bui, Van Giap Trinh, Kovacs Tibor, Ngoc Toan Tran, Dinh Cuong Le, Khanh Minh Tran, Huu Quyet Nguyen, Van Khanh Nguyen
Published: 15 December 2013
Nuclear Science and Technology, Volume 3, pp 49-55; https://doi.org/10.53747/nst.v3i4.327

Abstract:
In this study, we have tested the possibility of parallel measurement of radon (222Rn) and thoron (220Rn or Tn) by alpha track detectors at the extraction and processing of black sands that contains high content of Zircon and Monazite minerals in a coastal area of the Ha Tinh province. A pair of cylindrical cups RADUET, designed to separately measure Rn and Tn with CR-39 detectors (Radosys Company Ltd – Hungary), were used for the test. The results showed that concentrations of indoor Rn and Tn in the black sand extraction area are not high (28 ± 6 Bq/m3 for Rn, 14 ± 5 Bq/m3 for Tn). The Rn and Tn concentrations in the indoor air of the titanium processing plant are 34 ± 6 Bq/m3 for Rn, 58 ± 11 Bq/m3 for Tn, and are higher than those concentrations in the residential houses outside the plant (20 ± 4 Bq/m3 for Rn, 16 ± 8 Bq/m3 for Tn) but still comparable to the average concentrations of indoor Rn and Tn reported by the UNSCEAR 2006. At Zircon processing plant, indoor Rn concentrations are similar to those in the titanium processing plant but Tn concentrations in the houses for separating Rutile and Zircon are very high. Indoor Tn concentration is especially high in the house for separating Zircon where it could reach 2931 Bq/m3, hundred times higher than that in the surrounding residential houses and that of the world average published by UNSCEAR 2006.
Hoai Nam Tran
Published: 15 December 2013
Nuclear Science and Technology, Volume 3, pp 1-11; https://doi.org/10.53747/nst.v3i4.321

Abstract:
The paper presents the development of a neutron noise simulator for fast reactors based on diffusion theory with multi-energy groups. The noise sources are modelled via small stationary fluctuations of macroscopic cross sections, and the induced first order noise is solved fully in the frequency domain. The tool is expected to be applicable for monitoring of fast reactor cores and also for other reactor types with hexagonal fuel assemblies. Some numerical calculations of the neutron noise induced by localized perturbations in a sodium-cooled fast reactor are demonstrated.
Chien Dong Nguyen, Hong Son Duong, Dinh Cong Bui, Huu Hieu Ho, Thi Hoang Linh Nguyen
Published: 15 December 2013
Nuclear Science and Technology, Volume 3, pp 40-48; https://doi.org/10.53747/nst.v3i4.326

Abstract:
After reviewing the trace metals (Sn, W, Mo)-bearing granitoid deposits in the world, theauthors recognized that some deposits in Sweden (e.g. Nozzboten, Vasterbotten, Hotagen, Bergslagen, Bohus, Gosthenburg, Gotemar, Blekinge) contain not only trace metals (Sn, W, Mo), but also F, Li, U,Th, etc… which are similar to the Phia Oac granitoids. The correlation chart with the T. Carlsson (1982)’s criteria helps to determine the uranium-bearing granitoids. Initially, we constructed some correlation charts of granitoid fields in Northern Vietnam and concluded that some granitoid fields certainly related to uranium are Phia Oac, Xom Giau, Phu Sa Phin, and some granitoid fields possibly related to uranium are Ye Yen Sun, Muong Lat, Ban Chieng, and Song Chay (based on data from the Geology of Vietnam, Part II, Magma Section). This issue needs to be further studied.
Thi Kim Lang Vo, Thuy Khanh Nguyen, Thi The Doan, Thi Tu Trinh Nguyen
Published: 15 December 2013
Nuclear Science and Technology, Volume 3, pp 29-32; https://doi.org/10.53747/nst.v3i4.324

Abstract:
Garlic powder was irradiated by gamma-rays from a Co-60 source to reduce microbialcontamination for prolong the storage and preservation time. Results showed that the initial microbial number of about 106CFU/g contaminated in garlic powder was exceeded for the set standard of TCVN 7809 – 2007 and ISO 5560 – 1997. The total aerobic bacteria and yeast mold cells of irradiated garlic powder were reduced from 106 CFU/g to 104, 6103 and 6102 CFU/g at doses of 0, 4, 8 and 12 kGy, respectively. The level of microbial contamination was significantly reduced by irradiation at 4 kGybut it is only appropriate for domestic acceptance. At the irradiation doses of 8 and 12 kGy, the level of microbial contamination was further reduced after storage for two months and it is appropriate to export. In addition, the irradiated garlic powder was in good quality with no change of moisture, oil content and sensory properties. Thus, gamma Co-60 irradiation is a very effective method for reducing the number of microbial contaminated in garlic powder.
The Nghia Nguyen, Thi Lan Nguyen, Ho Phong Vi, Van Loat Bui, The Anh Tran, Hong Khiem Le
Published: 30 September 2013
Nuclear Science and Technology, Volume 3, pp 50-55; https://doi.org/10.53747/nst.v3i3.269

Abstract:
Although electron accelerators are equipments which accelerate electron, in fact they are intense sources of bremsstrahlung photon and neutron beams. Therefore the study on spectroscopy of bremsstrahlung is of great importance. This work presents the results obtained by the authors about the energy distribution of bremsstrahlung spectra, the method for determination of bremsstrahlung photon flux as well as the possibilities for producing neutron and neutron rich radioactive ions beams for fundamental research and practical applications.
Quang Luan Le, Huynh Phuong Uyen Nguyen
Published: 30 September 2013
Nuclear Science and Technology, Volume 3, pp 41-49; https://doi.org/10.53747/nst.v3i3.268

Abstract:
The β-glucan extracted from the yeast cell wall was irradiated by gamma rays from a Co-60 source at doses from 100 to 300kGy in swelling condition of 10% (w/v) for degradation. The water soluble content of irradiated sample increased from 25.89 to 66.71% by the increasing of doses from 100 to 300kGy. While the molecular weight of water soluble β-glucan was found to be decreased from 48.13 (at 100kGy) to 10.77 kDa (at 300kGy). The UV-spectra of resultant water soluble β-glucan were appeared a new peak at 265nm with the intensity increased by the increase of the dose. The IR spectra of irradiated β-glucan samples were also recognized by an increase of peak intensity at 1731cm-1 assigned to C=O linkages and a decrease of peak intensity at 1156cm-1 assigned to C-O-C glycosidic linkages by the increasing of dose. In addition, the oligoβ-glucan with Mw about 18 kDa obtained at 250kGy-irradiated sample strongly promoted the growth of mustard green and lettuce. The oligoβ-glucan prepared by radiation techniques showed as a high effective plant growth promoter. This product is potentially promising for application in high-technological agriculture for production of clean vegetables and agro-products.
Xuan Du Dang, Phuoc Phuc Bui, Thi Thuy Tran, Anh Quoc Le, Van Phu Dang, Quoc Hien Nguyen
Published: 15 December 2013
Nuclear Science and Technology, Volume 3, pp 32-39; https://doi.org/10.53747/nst.v3i4.325

Abstract:
Degradation of chitosan in swollen state with hydrogen peroxide solution (5% w/v) by γ- irradiation was investigated. Molecular weight (Mw) of irradiated chitosan was determined by gel permeation chromatography (GPC). Fourier transform infrared (FT-IR) and ultraviolet-visible (UVvis) spectrawere analyzed to study the structure changes of degraded chitosan. The results showed that the chitosan of low Mw ~30-45 kDawas efficiently prepared by γ-irradiation of chitosan swollen in hydrogen peroxide solution at low dose less than 20kGy. The main structure as well as the degree of deacetylation of the degraded chitosan was almost no significant change. Furthermore, the radiation degradation yield (Gs) was remarkably enhanced by the presence of H2O2. The obtained low Mw chitosan revealed high antimicrobial activity for E. colithat can be used for food preservation and other purposes as well.
Thi Yeu Ly Ho, Mong Sinh Nguyen
Published: 15 December 2013
Nuclear Science and Technology, Volume 3, pp 12-19; https://doi.org/10.53747/nst.v3i4.322

Abstract:
The cross-linking chitosan modified by citric acid has been studied for sorption of U(VI) from aqueous solution in a bath system. The effects of parameters such as pH, initial U(VI) concentration, contact time and temperature on the sorption of U(VI) were analyzed using response surface methodology (RSM). The Minitab was used to conduct the regression analysis and the analysis of nvariance of the U(VI) adsorption by modified chitosan. The U(VI) concentration of 100 mg/L, pH 4.2, temperature of 313 K and contact time of 211 min were determined as optimum conditions for U(VI) adsorption by acid citric grafted chitosan (C-GCh). The maximum efficiency of U(VI) removal by CGCh was 97,35 % at the optimum sorption conditions. Thermodynamic parameters such as ΔG, ΔH, ΔS for U(VI) adsorption process in aqueous solution were also determined.
Quoc Duong Tran, Nhi Dien Nguyen, Kien Cuong Nguyen, Ton Nghiem Huynh, Ba Vien Luong, Minh Tuan Nguyen, Quang Huy Pham, Doan Hai Dang Vo, Minh Phong Do, Nguyen Thanh Vinh Ho
Published: 30 September 2021
Nuclear Science and Technology, Volume 11, pp 1-10; https://doi.org/10.53747/nst.v11i3.364

Abstract:
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.
Thi Thanh Nga Nguyen, Nhu Sieu Le, Dinh Tung Nguyen, Van Phu Nguyen, Dinh Khoa Tran, Thi Thu Hang Vuong, Trong Ngo Nguyen
Published: 30 September 2021
Nuclear Science and Technology, Volume 11, pp 19-26; https://doi.org/10.53747/nst.v11i3.368

Abstract:
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.
Anh Quoc Le, Dai Nghiep Ngo, Van Phu Dang, Ngoc Duy Nguyen, Chi Thuan Nguyen, Quoc Hien Nguyen
Published: 30 September 2021
Nuclear Science and Technology, Volume 11, pp 44-51; https://doi.org/10.53747/nst.v11i3.371

Abstract:
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.
Van Tai Vo, Van Kien Nguyen, Nhi Dien Nguyen, Dinh Hai Trinh, La Son Phan
Published: 30 September 2021
Nuclear Science and Technology, Volume 11, pp 11-18; https://doi.org/10.53747/nst.v11i3.367

Abstract:
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.
Thi Kim Lan Nguyen, Ngoc Duy Nguyen, Nhut Khanh Chu, Chi Thuan Nguyen, Thi Giang Huong Duong, Quoc Hien Nguyen
Published: 30 September 2021
Nuclear Science and Technology, Volume 11, pp 27-33; https://doi.org/10.53747/nst.v11i3.369

Abstract:
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.
Thi Ly Nguyen, Van Chung Cao, Nhut Khanh Chu, Thi Thu Hong Pham, Binh Doan, Quang Thanh Le, Anh Tuan Vo, Duy Ngoc Nguyen, Tuong Vy Ngo, Thi Thu Hien Phan, et al.
Published: 30 September 2021
Nuclear Science and Technology, Volume 11, pp 34-43; https://doi.org/10.53747/nst.v11i3.370

Abstract:
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.
Duc Thinh Le, Thi Kieu Oanh Ngo
Nuclear Science and Technology, Volume 11, pp 44-50; https://doi.org/10.53747/nst.v11i2.361

Abstract:
Alternating Current Field Measurement (ACFM) is a technique of the Electromagnetic method used to detect surface defects of metal materials. Currently, this technique is widely applied in the field of maintenance of Oil and Gas projects as an alternative to the Magnetic Particle Testing method. The establishment of ACFM training program according to Recommended Practice No. SNT-TC-1A of The American Society for Nondestructive Testing (ASNT) will increase the autonomy of the domestic testing human resources, especially advanced techniques. Based on documents and standards combined with the actual survey, training programs, training materials, question banks, examinations developed meet the requirements of international standards and in accordance with the conditions applied in Vietnam
Viet Cuong Phan, Thi Thao Ho, Tuan Anh Le, Duc Ton Nguyen, Dinh Khai Nguyen, Hong Ha Nguyen
Nuclear Science and Technology, Volume 11, pp 9-13; https://doi.org/10.53747/nst.v11i2.356

Abstract:
Monte Carlo-based scatter modeling in SPECT has demonstrated the ability on improving image quality and quantitative accuracy but high computational cost. In this study, we describe a deep learning method based on a convolutional neural network (CNN) to increase the image quality, decrease the computation time for SPECT/CT reconstruction. Monte Carlo (MC) simulation and true scatter data are used for training and validation phase and the CNN network is trained to match the MC scatter estimation. In the testing step with a liver subject, visual image quality by CNN was better than MC scatter estimation method. Besides, the CNN scatter estimate was generated over a much shorter period of time than MC model (about 15 seconds for CNN vs ~2 hours for MC). The short processing time with CNN while maintaining quality has high clinical significance for quantitative SPECT imaging.
Van Thai Nguyen, Ngoc Dat Nguyen
Nuclear Science and Technology, Volume 11, pp 14-22; https://doi.org/10.53747/nst.v11i2.357

Abstract:
This paper presents the feasibility study of potential application of multi-layer feed-forward Artificial Neural Networks (ANN) to predict local void fraction of subcooled boiling flows in vertical upward annular channel. A total of 638 experimental data points performed at KAERI and reported in literature was selected for training and testing ANN model. The seven basic parameters are chosen to be input variables and then the optimal structure of ANN which consist of two hidden layers with 131 neurons was determined based on traditional Trial-and-Error method after balancing the trade-off between the performance and training time. Results showed that the ANN model is capable to accurately predict the local void fraction with R2 value of 0.99931 for training data, R2 value of 0.99483 for testing data and R2 value of 0.99828 for all data. Also, it proved that the ANN training will be more effective with an extensive experimental database.
Van Khanh Hoang, Viet Phu Tran, Thi Dung Nguyen
Nuclear Science and Technology, Volume 11, pp 23-36; https://doi.org/10.53747/nst.v11i2.358

Abstract:
For the future of nuclear power, the design and development of an economical, accident tolerant fuel (ATF) for use in the current pressurized water reactors (PWRs) are highly desirable and essential. It is reported that the composite fuels are advantageous over the conventional UO2 fuel due to their higher thermal conductivities and higher uranium densities. Due to higher uranium densities of the composite fuels, the use of composite fuels would lead to the significant increase of discharged burnup, thereby enhancing fuel cycle economy compared to that of the UO2 fuel. The higher thermal conductivities of composite fuels will increase the fuel safety margins. For implementation of the accident tolerant fuel concept, this study also investigates on the replacement of the conventional Zircaloy-4 cladding with SiC to minimize the hydrogen production due to interaction of water with cladding at high temperatures. In the present work, neutronic investigation of the composite fuels for a PWR has been conducted in comparison with that of the conventional UO2 fuel. Numerical calculations have been performed based on a lattice model using the SRAC2006 system code and JENDL-4.0 data library. Various parameters have been surveyed for designing a fuel with the UO2 and composite fuels such as U-235 enrichment, fuel pin pitch. In order to reduce the excess reactivity, Erbium was selected as a burnable poison due to its good depletion performance. The temperature coefficients including fuel, coolant temperature reactivity coefficients, and both the small and large void reactivity coefficients are also investigated. It was found that it is possible to achieve sufficient criticality up to 100 GWd/t burnups without compromising the safety parameters including that four reactivity coefficients are considered those associated with the fuel temperature, coolant temperature, small (5%) void and large (90%) void. Further analysis of the performance of the UO2 and composite fuels in a full core model of a PWR is being conducted.
Van Khanh Nguyen, Van Thang Duong, Thi Oanh Nguyen, Thuy Hau Doan, Thi Hoa Le, Duc Viet Cao, Duc Thang Duong
Nuclear Science and Technology, Volume 11, pp 37-43; https://doi.org/10.53747/nst.v11i2.359

Abstract:
In this study, a method to estimate the baseline of ambient dose equivalent rate (ADER) of the Lang Son radioactive monitoring station was presented. The warning level is calculated from the arithmetic mean and standard deviation of the terrestrial background value. The terrestrial background value estimated from the Radon peak removal algorithm is 39.85 nSv/h with a standard deviation of 7.58 nSv/h. For comparison, the soil samples around the monitoring equipment were collected and analyzed the activity concentration of nuclides 226Ra, 232Th, 40K. The terrestrial background value estimated from these values of activity concentration is of 41.10 ± 2.96 nSv/h. There is a good agreement between the results evaluating ADER from Radon peak removal algorithm and from the activity concentration of nuclides 226Ra, 232Th, 40K.
Xuan Chung Le, Ho Phong Vi, Tuan Anh Le, Duc Ton Nguyen, Hoang Phuc Nguyen, Duy Linh Bui
Nuclear Science and Technology, Volume 11, pp 1-8; https://doi.org/10.53747/nst.v11i2.355

Abstract:
Neutrons and gamma-rays from a 152Cf source have been measured and separated based on the time of flight (TOF) technique. Their pulse shape characteristics measured by EJ-299-33 scintillator were used to train an artificial neural network (ANN) in a machine learning method. Afterward, the ANN was used to predict another set of pulse shape data to identify neutron and gamma-ray events. Comparing to the charge-comparison method, the ANN gave better identification. This result proves a potential application of machine learning method in the nuclear data analysis.
Dai Dien Le, Thi Hoa Bui, Thi Huong Vo
Published: 30 September 2014
Nuclear Science and Technology, Volume 4, pp 1-6; https://doi.org/10.53747/jnst.v4i3.230

Abstract:
In this study, MELCOR computer code is used to simulate the progression of a severe accident initiated from station blackout (SBO) accident for a Westinghouse 4-loop PWR. The hydraulic system is modeled using control volumes and flow paths. The reactor pressure vessel and internals, the primary loops with a pressurizer, steam generators, containment and accumulators are simulated for steady state in a good agreement with reference data. The two scenarios concerning SBO are investigated. The first scenario simulates RCP seal leakage during SBO and the other is SBLOCA to highlight an effectiveness of accumulators as well as to compare with the first simulation. All active safety systems which depend on AC power are assumed to be unavailable in this analysis. The main result of the study is an evaluation of RPV lower head integrity during severe accidents. This is preliminary work and expected to give the experience for further studies in the severe accident in nuclear power plants.
Dai Dien Le, Thi Hoa Bui, Thi Huong Vo
Published: 30 September 2014
Nuclear Science and Technology, Volume 4, pp 19-28; https://doi.org/10.53747/jnst.v4i3.232

Abstract:
In this study, MELCOR computer code is used to simulate the progression of a severe accident initiated from station blackout (SBO) accident for a Westinghouse 4-loop PWR. The hydraulic system is modeled using control volumes and flow paths. The reactor pressure vessel and internals, the primary loops with a pressurizer, steam generators, containment and accumulators are simulated for steady state in a good agreement with reference data. The two scenarios concerning SBO are investigated. The first scenario simulates RCP seal leakage during SBO and the other is SBLOCA to highlight an effectiveness of accumulators as well as to compare with the first simulation. All active safety systems which depend on AC power are assumed to be unavailable in this analysis. The main result of the study is an evaluation of RPV lower head integrity during severe accidents. This is preliminary work and expected to give the experience for further studies in the severe accident in nuclear power plants.
Thi Hong Loan Truong, Thi Thao My Dang, Phuc Long Hoa Cao
Published: 30 December 2014
Nuclear Science and Technology, Volume 4, pp 17-21; https://doi.org/10.53747/jnst.v4i4.239

Abstract:
In this work, the methodology of estimating the radioactivity of nuclides from point gamma source using method of full spectrum analysis combined with Gold unfolding algorithm are studied. The reference sources with known activities as Ba-133, Cd-109, Co-57, Co-60, Cs-137, Mn-54, Na-22 and Zn-65 are counted in front of the HPGe detector. The source which is mixed by these radioisotopes with known weighting factors C(i) are counted. Its spectra are unfolded to have the relative radioactivity of these isotopes from analyzed source, Cunf(i). The difference of less than 0.2% between calculated ratios of Cunf(i) from the unfolded spectra and known weighting factors of C(i) opens a possibility to improve the accuracy for the analysis method with low background HPGe detector.
Van Loat Bui, Van Quan Nguyen, Tuan Anh Le, Thi Hong Bui, Cong Tam Nguyen
Nuclear Science and Technology, Volume 4, pp 1-6; https://doi.org/10.53747/jnst.v4i2.220

Abstract:
In this work the non - destructive gamma spectroscopic method for determination of uranium enrichment is presented. In order to determine the uranium enrichment the activity ratios of 234U/235U and 238U/235Uwere measured. The activity ratios234U/235U and 238U/235U were determined by using intrinsic efficiency calibration. As a test of this method, low - enriched uranium standard was measured, the obtained result was in good agreement with the estimated value.
Ba Vien Luong, Vinh Vinh Le, Ton Nghiem Huynh, Kien Cuong Nguyen
Nuclear Science and Technology, Volume 4, pp 10-25; https://doi.org/10.53747/jnst.v4i1.209

Abstract:
The paper presents calculated results of neutronics, steady state thermal hydraulics and transient/accidents analyses for full core conversion from High Enriched Uranium (HEU) to Low Enriched Uranium (LEU) of the Dalat Nuclear Research Reactor (DNRR). In this work, the characteristics of working core using 92 LEU fuel assemblies and 12 beryllium rods were investigated by using many computer codes including MCNP, REBUS, VARI3D for neutronics, PLTEMP3.8 for steady state thermal hydraulics, RELAP/MOD3.2 for transient analyses and ORIGEN, MACCS2 for maximum hypothetical accident (MHA). Moreover, in neutronics calculation, neutron flux, power distribution, peaking factor, burn up distribution, feedback reactivity coefficients and kinetics parameters of the working core were calculated. In addition, cladding temperature, coolant temperature and ONB margin were estimated in steady state thermal hydraulics investigation. The working core was also analyzed under initiating events of uncontrolled withdrawal of a control rod, cooling pump failure, earthquake and MHA. Obtained results show that DNRR loaded with LEU fuel has all safety features as HEU and mixed HEU-LEU fuel cores and meets requirements in utilization as well.
Minh Quy Nguyen, Long Hoang, Thi Thu Huong Le, Van Huan Luong, Thi Tuong Hanh Vo
Nuclear Science and Technology, Volume 4, pp 32-41; https://doi.org/10.53747/jnst.v4i2.226

Abstract:
The objective of this study is to identify the sources of the formation water in the Southwest Su Tu Den (STD SW) basement reservoir. To achieve the objective, isotopic techniques along with geochemical analysis for chloride, bromide, strontium dissolved in the water were applied. The isotopic techniques used in this study were the determination of water stable isotopes signatures (δ2H and δ18O) and of the 87Sr/86Sr ratio of strontium in rock cutting sample and that dissolved in the formation water. The obtained results showed that the stable isotopes compositions of water in the Lower Miocene was -3‰ and -23‰ for δ18O and δ2H, respectively indicating the primeval nature of seawater in the reservoir. Meanwhile, the isotopic composition of water in the basement was clustered in a range of alternated freshwater with δ18O and δ2H being –(3-4)‰ and -(54-60)‰, respectively). The strontium isotopes ratio for water in the Lower Miocene reservoir was lower compared to that for water in the basement confirming the different natures of the water in the two reservoirs. The obtained results are assured for the techniques applicability, and it is recommended that studies on identification of the flow-path of the formation water in the STD SW basement reservoir should be continued.
Xuan Vinh Ha, Phan Thao Tien Doan, Chi Thang Nguyen
Published: 30 September 2014
Nuclear Science and Technology, Volume 4, pp 47-54; https://doi.org/10.53747/jnst.v4i3.236

Abstract:
K2YF5 and K2GdF5 doped with rare earth can be used as thermoluminescent (TL) dosimeters for gamma, beta radiations. In this study, the K2YF5 and K2GdF5 doped with Tb, Pr, Sm, and Dy with different concentrations were synthesized by solid state reaction method. These double fluoride dosimeters were irradiated with different radiations, namely beta and gamma. The study results showed that in general, the TL intensity of K2GdF5 is higher than that of K2YF5. The K2GdF5 crystals doped with Tb3+, Pr3+ have very high TL sensitivities. But the sensitivities of Sm3+, Dy3+ doped- are very low. The TL glow curve of K2YF5:Tb consists of three peaks at temperatures 132oC, 207oC and 240oC, and its intensities are approximately. The TL glow curve of K2GdF5:Tb has dosimetric peak at the temperature 196oC (heating rate 2oC/s), the temperature of this peak suitable for dosimetry application. The TL sensitivity of K2GdF5:Tb is higher than that of TLD-100 and TLD-900 dosimeters for the gamma and beta radiation. The dosimeters K2GdF5:Tb has high sensitivity and linearity for gamma, beta radiations. In addition, the thermal fading effect of TL intensity was very low. The study results showed that these materials can be used in nuclear radiation dosimeters.
Van Dong Duong, Ngoc Dien Pham, Van Cuong Bui, Phuoc Tho Mai, Thi Thu Nguyen, Cam Hoa Vo Thi
Nuclear Science and Technology, Volume 4, pp 46-56; https://doi.org/10.53747/jnst.v4i1.213

Abstract:
After reconstruction, the Dalat Nuclear Research Reactor (DNRR) was inaugurated on March 20th, 1984 with the nominal power of 500 kW. Since then the production of radioisotopes and labelled compounds for medical use was started. Up to now, DNRR is still the unique one in Vietnam. The reactor has been operated safely and effectively with the total of about 37,800 hrs (approximately 1,300 hours per year). More than 90% of its operation time and over 80% of its irradiation capacity have been exploited for research and production of radioisotopes. This paper gives an outline of the radioisotope production programme using the DNRR. The production laboratory and facilities including the nuclear reactor with its irradiation positions and characteristics, hot cells, production lines and equipment for the production of Kits for labelling with 99mTc and for quality control, as well as the production rate are mentioned. The methods used for production of 131I, 99mTc, 51Cr, 32P, etc. and the procedures for preparation of radiopharmaceuticals are described briefly. Status of utilization of domestic radioisotopes and radiopharmaceuticals in Vietnam is also reported.
Nhi Dien Nguyen, Ton Nghiem Huynh, Vinh Vinh Le, Hai Dang Vo Doan, Chulgyo Seo, Cheol Park, Hak Sung Kim
Nuclear Science and Technology, Volume 4, pp 26-35; https://doi.org/10.53747/jnst.v4i1.210

Abstract:
This paper presents some of studied results of a pre-feasibility project on a new research reactor for Vietnam. In this work, two conceptual nuclear designs of 20 MW multi-purpose research reactor have been done. The reference reactor is the light water cooled and heavy water reflected open-tank-in-pool type reactor. The reactor model is based on the experiences from the operation and utilization of the HANARO. Two fuel types, rod and flat plate, with dispersed U3Si2-Al fuel meat are used in this study for comparison purpose. Analyses for the nuclear design parameters such as the neutron flux, power distribution, reactivity coefficients, control rod worth, etc. have been done and the equilibrium cores have been established to meet the requirements of nuclear safety and performance.
Huu Tan Vuong, Ngoc Son Pham, Nhi Dien Nguyen, Tuan Anh Tran, Xuan Hai Nguyen
Nuclear Science and Technology, Volume 4, pp 62-69; https://doi.org/10.53747/jnst.v4i1.215

Abstract:
The neutron filter technique has been applied to create mono-energetic neutron beams with high intensity, at the horizontal channels No.2 and No.4 of the Dalat nuclear research reactor. The mono-energetic neutron beams that have been developed for researches and applications are thermal (0.025eV), 24keV, 54keV, 59keV, 133keV and 148keV. The relative intensities of main peak in filtered neutron energy spectra and the collimated neutron fluxes at the sample irradiation positions are 90 ¸ 96% and 2.8×105 ¸ 7.8×106 n/cm2.s, respectively. Monte Carlo simulations and transmission calculations were performed to each neutron energy beam for optimal design of geometrical structure and neutron filter materials. These filtered neutron beams have been applied efficiently for experimental researches on neutron total and capture cross sections measurements, and elemental analysis in various kinds of samples based on the prompt gamma neutron activation analysis method. This paper reviews the progress of filtered neutron beams development and its applications for past many years at the Dalat nuclear research reactor.
Nhi Dien Nguyen, Ba Vien Luong, Van Lam Pham, Vinh Vinh Le, Ton Nghiem Huynh, Kien Cuong Nguyen, Minh Tuan Nguyen, Manh Hung Nguyen, Quang Huy Pham, Quoc Duong Tran, et al.
Nuclear Science and Technology, Volume 4, pp 36-45; https://doi.org/10.53747/jnst.v4i1.212

Abstract:
After completion of design calculation of the Dalat Nuclear Research Reactor (DNRR) for conversion from high-enriched uranium fuel (HEU) to low-enriched uranium (LEU) fuel, the commissioning programme for DNRR with entire core loaded with LEU fuel was successfully carried out from 24 November 2011 to 13 January 2012. The experimental results obtained during the implementation of commissioning programme showed a good agreement with design calculations and affirmed that the DNRR with LEU core have met all safety and exploiting requirements.
Tuan Khai Nguyen, Dinh Cuong Le, Xuan Anh Do, Duc Thang Duong, Van Giap Trinh, Thu Ha Nguyen Thi, Quang Long Nguyen, Hao Quang Nguyen, Nam Giang Nguyen, Hong Hiep Le Thi, et al.
Nuclear Science and Technology, Volume 5, pp 1-7; https://doi.org/10.53747/jnst.v5i1.178

Abstract:
Based on guides RG 1.109, RG 1.111 published by United States Nuclear Regulatory Commission (USNRC) our research concentrates on assessing radiation doses caused by radioactive substances released from the Ninh Thuan 1 nuclear power plant (NPP) to the environment under scenario of an INES-level 6 nuclear accident caused by the Station Black Out (SBO) incident and the loss of coolant accident (LOCA) phenomenon using software RASCAL4.3 provided by the Emergency Operations Center of USNRC. The NinhThuan 1 plant is assumed to use the VVER-1200 technology with a total power of 2400 MWe. The input data for the model calculations is based on building the accident scenario, the technical parameters of VVER-1200 technology and the meteorology. In this work the meteorological data on dry and rainy seasons which are typical for the NinhThuan region was considered. The maximum dose values were calculated within an area of 40 km radius from the NPP site. The obtained calculation results showed that the dose distributions affected by meteorological conditions. In the rainy season the dose values near the plant are higher than those in the dry season, especially at the distances less than 10 kilometers from the plant the total effective dose equivalence (TEDE) values can be from about 3.5 to 15 times higher than the dose limit for publics. As a result, it is requested to follow the evolution of the accident in order to issue timely the appropriate response measures based on the guidance specified by the Circular 25/2014/TT-BKHCN.
Xuan Du Dang, Phuoc Phuc Bui, Thi Thuy Tran, Anh Quoc Le, Van Phu Dang, Quoc Hien Nguyen
Published: 30 December 2014
Nuclear Science and Technology, Volume 4, pp 1-8; https://doi.org/10.53747/jnst.v4i4.237

Abstract:
Degradation of chitosan in swollen state with hydrogen peroxide solution (5% w/v) by γ-irradiation was investigated. Molecular weight (Mw) of irradiated chitosan was determined by gel permeation chromatography (GPC). Fourier transform infrared (FT-IR) and ultraviolet-visible (UV-vis) spectrawere analyzed to study the structure changes of degraded chitosan. The results showed that the chitosan of low Mw ~30-45 kDawas efficiently prepared by γ-irradiation of chitosan swollen in hydrogen peroxide solution at low dose less than 20kGy. The main structure as well as the degree of deacetylation of the degraded chitosan was almost no significant change. Furthermore, the radiation degradation yield (Gs) was remarkably enhanced by the presence of H2O2. The obtained low Mw chitosan revealed high antimicrobial activity for E. colithat can be used for food preservation and other purposes as well.
Huu Toan Trinh, Kim Tuan Tran, Thuy Duong Tran, Duc Luong Cao
Nuclear Science and Technology, Volume 4, pp 7-14; https://doi.org/10.53747/jnst.v4i2.221

Abstract:
In this work, the main features of a nuclear pressurizedthermal hydraulic testing facility named BKTF (BK testing facility) are presented. The facility consists of major systems and components similar to the standard PWR prototype, and it is a volume and pressure scaled model with the total mass of primary coolant in order of hundreds of kilograms. The model is designed to work at normal temperature and pressure less than 160 0C and 10 bars respectively. In this part of research, preliminary results of cold test and hot test are presented. These results show that the system is qualified enough to work under designed pressure and temperature. It is seen that the similarity between temperature and pressure trend lines with these from a real power system during starting up process. In addition, natural circulation was appreciated and compared with forced circulation during the cooling down process and this may help us to have a better vision on passive safety and completely recognize about safety system of nuclear power plant.
Q. Thien T., D. Vu C., V. Doanh H., T. Sy N.
Nuclear Science and Technology, Volume 4, pp 76-83; https://doi.org/10.53747/jnst.v4i1.217

Abstract:
White rice is a main food for Asian people. In the framework of Forum for Nuclear Cooperation in Asia (FNCA), therefore, the eight Asian countries: China, Indonesia, Japan, Korea, Malaysia, the Philippines, Thailand and Vietnam selected white rice as a common target sample for a collaboration study since 2008. Accordingly, rice samples were purchased and prepared by following a protocol that had been proposed for this study. The groups of elements that were analyzed by using neutron activation analysis in the white rice samples were toxic elements and nutrient elements, including: Al, As, Br, Ca, Cl, Co, Cr, Cs, Fe, K, Mg, Mn, Na, Rb and Zn. The analytical results were compared between the different countries and evaluated by using the Tolerable Intake Level of World Health Organization (WHO) and Recommended Dietary Allowance or Adequate Intake (AI) of the U.S. Institute of Medicine (IOM) guideline values. These data will be very useful in the monitoring of the levels of food contamination and in the evaluation of the nutritional status for people living in Vietnam and other Asian countries.
D. Vu C., Q. Thien T., V. Doanh H., D. Quyet P., T. Anh T.T., N. Dien N.
Nuclear Science and Technology, Volume 4, pp 70-75; https://doi.org/10.53747/jnst.v4i1.216

Abstract:
In the framework of the program on Russian Research Reactor Fuel Return (RRRFR) and the program on Reduced Enrichment for Research and Test Reactor (RERTR), the full core conversion of the Dalat Nuclear Research Reactor (DNRR) to low enriched uranium (LEU, 19.75% 235U) fuel was performed from November 24, 2011 to January 13, 2012. The reactor is now operated with a working core consisting of 92 WWR-M2 LEU. After the full core conversion, the neutron spectrum parameters which are used in k0-NAA such as thermal neutron flux (fth), fast neutron flux (ffast), f factor, alpha factor (a), and neutron temperature (Tn) have been re-characterized at four different irradiated channels in the core. Based on the experimental results, it can be seen that the thermal neutron flux decreases by 6÷9% whereas fast neutron flux increases by 2÷6%. The neutron spectrum becomes‘harder’ at most of irradiated positions. The obtained neutron spectrum parameters from this research are used to re-establish the procedures for Neutron Activation Analysis (NAA) according to ISO/IEC 17025:2005 standard at NuclearResearch Institute.
Phuong Thao Hoang, Van Binh Nguyen, Bang Diep Tran, Dang Sang Hoang, Thuy Huong Trang Nguyen, Duy Duong Pham, Minh Quynh Tran
Nuclear Science and Technology, Volume 4, pp 27-31; https://doi.org/10.53747/jnst.v4i2.225

Abstract:
Herbal eyebright products and their raw materials have been irradiated with 1, 2, 3 and 5 kGy by Co-60 gamma radiation source at Hanoi Irradiation Center for decontamination. Initial bioburdens were under the limitation levels established for the traditional medicines according to the decree of 16/2011/TT-BYT issued by Vietnam Health Ministry. These values for both bacteria and fungus slightly increased during storage to three months, reach to about 103 and 102 CFU/g for bacteria and molds, respectively. However, there are no microbial colonies that could be observed in the samples irradiated with dose higher than 3 kGy. Results suggested that the dose of 3 kGy was enough for decontamination of eyebright raw powders and products. At dose of 5 kGy, the moisture and vitamin A content of the samples were insignificantly changed. These mean the radiation treatment with low dose did not influenced the quality of eyebright products, and radiation treatment can be applied to prolong the storage of not only eyebright, but also other traditional medicines.
Tan Man Nguyen, Hai Le, Huu Tu Le, Thu Hong Tran, Duy Hang Nguyen, Thi Le Ha Pham, Thi Thuy Tran, Trong Hoanh Phong Nguyen, Xuan Cuong Le
Published: 30 September 2014
Nuclear Science and Technology, Volume 4, pp 43-46; https://doi.org/10.53747/jnst.v4i3.235

Abstract:
Silver nanoparticles were prepared from (Ag+) aqueous solution by the method of γ-ray irradiation using chitosan as stabilizer. The saturated conversion dose (Ag+ à Ago) determined by UV-Vis spectroscopy was found to be about 16 kGy. The UV-Vis spectrum showed that an absorption peak at λmax = 400 nm due to surface plasma resonance. The image of transmission electron microscopy (TEM) showed that the silver nanoparticles were mostly spherical in shape and the average diameter was of about ~ 12 nm. The prepared colloidal silver nanoparticles solution was in good stability during storage time.
Minh Giang Hoang, Tan Hung Hoang, Phu Khanh Nguyen
Nuclear Science and Technology, Volume 5, pp 8-17; https://doi.org/10.53747/jnst.v5i1.179

Abstract:
Recently, CTF, a version of COBRA-TF code is reviewed to validate its simulation models by several experiments such as Castellana 4x4 rod bundle, EPRI 5x5 bundle tests, PSBT bundle tests and TPTF experiment. These above experiments provide enthalpy, mass flux (Castellana), temperature (EPRI) and void fraction (PSBT, TPTF) at exit channel only. In order to simulate PWR rod bundle flow behavior, it is necessary to review CTF with more experiment in high pressure condition and it is found that the ENTEK BM facility is suitable for this purpose. The ENTEK BM facility is used to simulate Russia RBMK and VVER rod bundle two phase flow with pressure at 3 and 7 MPa and it gives measured void fraction distribution along the channel. This study focus on two points: (a) accuracy assessment between CTF’s void fraction distribution predictions versus experiment void fraction distributions and (b) investigation of void fraction prediction uncertainty from propagation of input deviations caused by measured accuracy.
Van Duc Hoang, Ngoc Ha Tran, Thi Thuc Phuong Nguyen, Thanh Chung Nguyen
Nuclear Science and Technology, Volume 4, pp 50-59; https://doi.org/10.53747/jnst.v4i2.228

Abstract:
This work has investigated preparation of silver nano-particles using spinning disc reactor. The effects of technological factors and experimental conditions such as: concentrations of AgNO3, glucose, PVP K30 (polyvinylpyrrolidone), spinning speed... on quality of nano-silver particles have been studied. With experimental conditions: rotation speed of 2000 rpm, weight rate of mPVP:mAgNO3 = 1, AgNO3 concentration of 0.01 M, glucose concentration of 0.02 M, silver particles of about 12 nm were obtained and the nano-silver solution were stable for more than 42 days.
Xuan Anh Do, Dinh Cuong Le, Duc Thang Duong, Thu Bac Vuong, Thi Thu Ha Nguyen, Quang Long Nguyen, Van Giap Trinh, Hao Quang Nguyen, Tuan Khai Nguyen
Published: 30 December 2014
Nuclear Science and Technology, Volume 4, pp 9-16; https://doi.org/10.53747/jnst.v4i4.238

Abstract:
Based on guides RG 1.109, RG 1.111 published by United States Nuclear Regulatory Commission (USNRC) our research concentratesinassessing radiation doses caused by radioactive substances released from the nuclear power plant (NPP) Ninh Thuan 1 under the scenario of normal operation using software package NRCDose72 provided by the USNRC. The database including the released radioactive nuclides, meteorology, terrain, population and agricultural production activities have beencollectedand processed to build the input data for the model calculation. The wind rose distribution obtained from the meteorological data in a five-year period from 2009-2013 showed that the radioactive nuclides released to environment spread in two main wind directions which are North East and South West. The X/Q (s/m3) and D/Q (s/m2) qualities which are, respectively, the ratio of activity concentration to release rateand that of deposition density of radioactive nuclides to release rate were calculated within an area of 80 km radius from the NPP site using XOQDOQ. Population doses were calculated using GASPAR. The XOQDOQ and GASPAR are two specific softwares in NRCDose72 package.
Huu Tan Vuong, Dinh Khang Pham, Tuan Anh Tran, Nhi Dien Nguyen, Xuan Hai Nguyen, Huu Thang Ho, Ngoc Son Pham, Lumengano Mangengo
Nuclear Science and Technology, Volume 4, pp 57-61; https://doi.org/10.53747/jnst.v4i1.214

Abstract:
The event-event coincidence spectroscopy system was successfully established and operated on thermal neutron beam of channel N0. 3 at Dalat Nuclear Research Reactor (DNRR) with resolving time value of about 10 ns. The studies on level density, gamma strength function and decay scheme of intermediate-mass and heavy nuclei have been performed on this system. The achieved results are opening a new research of nuclear structure based on (n, 2ɣ) reaction.
V.T. Nguyen, H.T. Trinh
Published: 30 September 2014
Nuclear Science and Technology, Volume 4, pp 7-18; https://doi.org/10.53747/jnst.v4i3.231

Abstract:
The non-condensable gas effect is a primary concern in some passive systems used in advanced design concepts, such as the Passive Residual Heat Removal System (PRHRS) of AP1000, APR1400, AES-2006, the Passive Containment Cooling System (PCCS) of AP1000 design, and Isolation Condensation System (ICS) of ESBWR design. The accumulation of the non-condensable gas inside the condensing tubes can significantly reduce the level of heat transfer which affects the heat removal capacity in accident condition and impacts plant safety. The objective of the present work is to assess the analysis capability of two wall film condensation models of RELAP5/Mod3.2 with the presence of non-condensable gas in a vertical tube on condensation experiments performed at MIT, USA. The results of the simulations and experimental data show the similar tendencies that the heat transfer coefficients increase as the inlet steam-non condensable gas mixture flow rate increases, the inlet steam-non-condensable gas mass fraction decrease, and the inlet saturated steam temperature decrease
Van Doanh Ho, Quang Thien Tran, Thi Sy Nguyen, Nhi Dien Nguyen
Published: 30 September 2014
Nuclear Science and Technology, Volume 4, pp 36-42; https://doi.org/10.53747/jnst.v4i3.234

Abstract:
A rapid neutron activation analysis technique for determination of the concentration of selenium in biological materials using short-lived radionuclide 77mSe (half-life = 17.4 seconds) has been developed at Dalat Nuclear Research Institute (DNRI). The technique is very simple and rapid. It involves irradiation of a sample for 20 s, decay for 20 s and counting for 20 s. The accuracy of the method has been evaluated by analyzing a number of biological standard reference materials of varied selenium levels. An agreement between measured and certified values was acceptable in regarding to the deviation of the above mentioned two values within 8 percent. The result shows that the utilization of short-lived radionuclide 77mSe is more useful in comparison with long-lived radionuclide 75Se (half-life = 120 days). In addition, it is suggested that a further study for cyclic irradiations should be done in order to enhance the detection limit of the determination of the short-lived radionuclide 77mSe.
Nhi Dien Nguyen, Ba Vien Luong, Vinh Vinh Le, Van Dong Duong, Xuan Hai Nguyen, Ngoc Son Pham, Dong Vu Cao
Nuclear Science and Technology, Volume 4, pp 1-9; https://doi.org/10.53747/jnst.v4i1.208

Abstract:
The Dalat Nuclear Research Reactor (DNRR) with the nominal power of 500 kW was reconstructed and upgraded from the USA 250-kW TRIGA Mark-II reactor built in early 1960s. The renovated reactor was put into operation on 20th March 1984. It was designed for the purposes of radioisotope production (RI), neutron activation analysis (NAA), basic and applied researches, and nuclear education and training. During the last 30 years of operation, the DNRR was efficiently utilized for producing many kinds of radioisotopes and radiopharmaceuticals used in nuclear medicine centers and other users in industry, agriculture, hydrology and scientific research; developing a combination of nuclear analysis techniques (INAA, RNAA, PGNAA) and physic-chemical methods for quantitative analysis of about 70 elements and constituents in various samples; carrying out experiments on the reactor horizontal beam tubes for nuclear data measurement, neutron radiography and nuclear structure study; and establishing nuclear training and education programs for human resource development. This paper presents the results of operation and utilization of the DNRR. In addition, some main reactor renovation projects carried out during the last 10 years are also mentioned in the paper.
Zuyen Phu Luong, Huu Ha Nguyen
Published: 30 December 2014
Nuclear Science and Technology, Volume 4, pp 38-44; https://doi.org/10.53747/jnst.v4i4.242

Abstract:
The article presents the multipole expansion for the electron-nucleus scattering cross-section at high energies within framework of the unified electroweak theory. The electroweak currents of the nucleus is expanded into simple components with definite angular momentum, which are called the multipole form factors. The multipole expansion of the cross-section is a consequence of the above expansion. Besides the familiar electromagnetic form factors FxL , there are new form factors VLX and ALX related to weak interactions, corresponding to the vector and axial weak currents. The obtained general expressions are applied to the nucleus 36Li , where the partial form factors are computed in the multiparticle shell model.
Quang Vinh Trinh, Thi Hong Loan Truong, Van Nhon Mai, Truc Phuong Huynh
Published: 30 December 2014
Nuclear Science and Technology, Volume 4, pp 22-29; https://doi.org/10.53747/jnst.v4i4.240

Abstract:
Integrating the gamma spectrum auto-analysis program withelemental analysis software by k-zero method is the objective for many researchers. This work is the first stepin building an auto analysis program of gamma spectrum, which includes modules of reading spectrum, displaying spectrum, calibrating energy of peak, smoothing spectrum, calculating peak area and determining content of elements in sample. Then, the results fromthe measurments of standard samples by a low level spectrometer using HPGe detecotr are comparedto thoseof other gamma spectrum auto-analysis programs.
, D. Vu C., Q. Thien T., N. Son P., T. Sy N., Giang N., N. Dien N.
Nuclear Science and Technology, Volume 4, pp 84-90; https://doi.org/10.53747/jnst.v4i1.218

Abstract:
An auto-pneumatic transfer system has been installed at the Dalat research reactor for rapid instrument neutron activation analysis based on very short-lived nuclides. This system can be used to perform short irradiations in seconds either in the vertical channel 13-2 or in the horizontal thermal column of the reactor. The transferring time of sample from irradiation to measurement position is approximately 3.2 seconds. A loss-free counting system using HPGE detector has been also setup in compacting with the pneumatic transfer system for measurement of sample’s activity, automatically starting for data acquisition at irradiated sample’s arrival. This new facility was tested and shown to have high potential for the determination of short-lived nuclides with half-lives from 10 ¸ 100 seconds. This work presents the results of timing parameter measurements, characterization of irradiation facilities, and application of this system to determining Selenium concentration in several biological reference materials.
Dang Sang Hoang, Van Binh Nguyen, Bang Diep Tran, Thi Thom Nguyen, Phuong Thao Hoang, Duy Duong Pham, Minh Quynh Tran
Nuclear Science and Technology, Volume 5, pp 39-45; https://doi.org/10.53747/jnst.v5i1.184

Abstract:
Poly(N-isopropylacrylamide) (PNIPAM) based hydrogels with the lower critical solution temperature (LCST) near the human body-temperature have been obtained from 10% solutions of N-isopropylacrylamide (NIPA) and N,N’-dimethyl acrylamide(DMA) mixture of 90:10 and 85:15 (w/w) by radiation copolymerization and crosslinking using a gamma Co-60 source at a dose of 20 kGy. Water swelling behaviour of the resulting hydrogels was much dependent on the initial ratio of NIPA and DMA. The hydrogels of 85:15 NIPA/DMA was chosen for further investigation for the use as drug cariers.Two kinds of drug carriers were prepared by immerging the hydrogels in solutions containing dexamethasone and tegafur. Then the drug incorporation efficiencies and in-vitro release behaviors of the ingredient were analysed. Loading capacities of the hydrogels were about 48.6 and 95.7 mg per g of dried gel for dexamethasone and tegafur, respectively. The results also revealed that the presence of ions in simulated body fluid and solution temperature much affected to the release behaviors of hydrogels for both dexamethasone and tegafur. Release rates of the ingredients were quite fast for both drug models. These drug-loaded hydrogels were biocompatibility without skin irritation suggesting that they may be used as controlled release drug carriers.
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