[en] The Dalat Nuclear Research Institute (DNRI) of Vietnam has become an important R and D centre in the country for researches and applications of nuclear analytical techniques (NATs). The DNRI is in cooperation with various organizations, having growing needs for NATs, geological departments, mineral exploration companies, national environment agency, province's departments of science and technology, medical-nutritional-occupational health sectors and agricultural research institutes and centers, etc. Recently, the NATs at DNRI are challenged by a strong competition from non-nuclear analytical techniques (e.g. AAS, GC, IC, ICP-MS, etc.). Therefore, in order to develop a strategy for sustainable operation, the improvements in aspects of method equipment and in particular of the implementation of quality system for NATs laboratories have been carried out. By these improvements, the annual analysis capability reaching to several thousands samples with tens thousands constituents analysed, the reliability of results ensured, thereof the customers are being expanded to also private and joint venture companies for mineral exploration in the country as well. The status of analytical services as provided to customer by the NATs at DNRI are presented and discussed. (author)

[en] The proceedings contains 130 papers of scientists from institutes, universities, enterprises nation-wide in Vietnam. Its subjects include: nuclear physics, theoretical physics, science and technology of nuclear reactor, application of nuclear techniques in industry, agriculture, biology, medicine, geo-hydrology, environmental protection, nuclear equipment, radiation technology, material technology, waste management, ect

[en] An air radioactivity monitoring study carried out in Dalat, Vietnam since 1986 has revealed distinct peaks of caesium isotope concentrations in air and fallout during December-January, when the monthly average air temperature was lowest and dry fallout dominated. These peaks provide evidence of the intrusion of more radioactive cold air masses from temperate northern latitudes during the development of large-scale anti cyclones, frequently observed in the most active winter monsoon period. High dry fallout velocity (about 10 cm/s) determined from the measured concentrations, clearly demonstrates one of the most relevant features of cold air masses: behind the cold front, vertical air motion is descending. The role of other processes, such as injection of radioactive air from stratosphere and local resuspension of soil dust, has been shown to be insignificant. The interpretation of the experimental results was based on the analysis of environmental -meteorological factors as well as the behaviour of other naturally-occurring radionuclides. (author). 7 refs, 2 figs

[en] The main applications of the nuclear and supplementary analytical techniques (N and SATs) in the Dalat Nuclear Research Institute (DNRI) and the facilities for the techniques are presented. The NATs in DNRI include the neutron activation analysis (NAA) with instrumental, radiochemical and prompt gamma methods (INAA, RNAA, PGNAA), the X-ray fluorescence analysis (XRFA) and the low-level counting and spectrometry. The sample irradiation sites for NAA, the automatic and manual pneumatic transfer systems, were installed at channels 7-1 and 13-2 and rotary rack on the Dalat research reactor. An ORTEC automatic sample changer (model ASC2) for γ-ray counting was equipped. A computer software for NAA based on the k₀-standardization method for calculation of elemental concentration was developed. The low-level counting and spectrometry techniques have been setup. The devices required for sampling, sample preparation and data processing have also been equipped. The applications of N and SATs for determination of elemental composition, particularly important in providing data so-called trace elements, radionuclides and multi-element have been enlarged for objects of geology, archaeology, bio-agriculture, health-nutrition and environment. The implementation a quality system for N and SATs has been planned and initiated. (author)

[en] Monthly records of Cs-137 and Cs-134 concentrations in air and fallout at Dalat for the period 1986-1991 are presented and discussed. The concentration variations exhibit distinct maxima during December-January, when dry fallout dominated. These peaks are explained by the intrusion of more radioactive cold air masses from temperate northern latitudes during the development of large-scale anticyclones frequently observed in the most active winter monsoon period. High dry fallout velocities (about 10 cm/s) determined from this data clearly demonstrate one of the most relevant characteristics of cold air masses: behind the cold front, vertical air motion is descending

[en] Photocatalysis has been applied to decompose the waste and toxic materials produced in daily life and in the global environment. Pure TiO₂ (Zn-TiO₂-0) and Zn-doped TiO₂ (Zn-TiO₂-x, x = 3-10 mol %) samples were synthesized using a novel sol-gel and ammonia-evaporation method. The Zn-doped TiO₂ samples showed high photocatalytic activity for the degradation of methylene blue (MB). The physicochemical properties of the samples were investigated using XRD, SEM, ICP, DLS and BET methods. In addition, the most important measurement of photocatalytic ability was investigated by a UV-vis spectrophotometer. The effects of the mol % of zinc ion doping in TiO₂ on photocatalytic activity were studied. Among the mol % Zn ions investigated, the Zn-TiO₂-9 sample showed the highest photoreactivity. This sample removed 91.4% of the MB after 4 h, while the pure TiO₂ only removed 46.4% of the MB

[en] The proposal and establishment of the environmental radioactivity monitoring network in Ho Chi Minh City aimed to update the database periodically and assess the changes in the status of environmental radioactivity on the region should be based on calculated results of contaminant materials released from industrial and/or radiation facilities located in the city and the surrounding area. This report presents the results of calculating separately the relative atmospheric dispersion factor (χ/Q) of three groups of contaminants (group of gaseous, volatile particulate matters, and aerosols) released from more than 150 mainly industrial and/or radiation facilities located in Ho Chi Minh City and six neighboring provinces by XOQDOQ and PAVAN computer codes. The obtained results show that a minimum of three air/fallout monitoring points in Ho Chi Minh City (a district in the central area, Cu Chi district and Can Gio district) should be established in order to detect the anomaly of environmental radioactivity. (author)

[en] This report presents the results of determining naturally occurring radioactive materials by using low background level gamma-ray spectrometry such as Ra-226, Th-232 and K-40 radionuclides in approximately of 30 building materials samples used commonly at Lam Dong province. The specific radioactivities of natural radionuclides in these building materials samples varied in 11.76 - 205.66, 4.49 - 196.23 and 131.97 - 1286.90 Bq/kg with the average values of 62.68, 59.09 and 600.04 Bq/kg for Ra-226, Th-232, and K-40, respectively. The activity concentration index (I), and the annual effective dose were also evaluated to assess the potential radiological hazard associated with these building materials. The results of activity concentration indexes of collected building materials varied from 0.14 to 2.08 show that there are some values of activity concentration indexes exceeding the limit value based on the dose criterion. The results of annual effective dose due to gamma radiation from building materials based on their contribution to the building structure for a reference room exceeding 1 mSv show that the ability not meet the dose criterion by using local building materials in Lam Dong is not possible. (author)

[en] Monthly records of ¹³⁷Cs and ¹³⁴Cs concentrations in air and fallout at Dalat for the period 1986-91 are presented and discussed. The concentration variations exhibit distinct maxima during December-January, when dry fallout dominates. These peaks are explained by the intrusion of more radioactive cold air masses from temperate northern latitudes during the development of large-scale anticyclones frequently observed in the most active winter monsoon period. High dry fallout velocities (about 10 cm/s) determined from these data clearly demonstrate one of the most relevant characteristics of cold air masses: behind the cold front, vertical air motion is descending. (author)

[en] Monthly records of ¹³⁷Cs and ¹³⁴Cs concentrations in air and fallout at Dalat for the period 1986-91 are presented and discussed. The concentration variations exhibit distinct maxima during December-January, when dry fallout dominated. These peaks are explained by the intrusion of more radioactive cold air masses from temperature northern latitudes during the development of large-scale anticyclones frequently observed in the most active winter monsoon period. High dry fallout velocities (about 10 cm/s) determined from these data clearly demonstrate one of the most relevant characteristics of cold air masses: behind the cold front, vertical air motion is descending. (Author)