[en] Full text: The Dalat Nuclear Research Reactor (DNRR) was reconstructed during 1982 - 1984 period from the previous 250 kW TRIGA MARK II reactor installed in 1963. The reconstruction had been completed at the end of 1983. The reactor core, the control and instrumentation system, the primary and secondary cooling systems as well as other associated systems were newly designed and installed. The PTS was improved for two irradiation channels in reactor. The first channel, namely 13-2 channel is received a neutron flux about 10¹² n cm^-2 s^-1 at the irradiation site and the second channel, namely thermal channel is received a neutron flux about 10¹⁰ n cm^-2 s^-1 at the irradiation site. The renovated reactor reached its criticality in November 1983 and obtained its nominal power of 500 kW in March 1984. Since then DNRR has been operated safely. It is mainly used for research, radioisotope production, neutron activation analysis and training. Since its improving from the previous system, the Pneumatic Transfer System (PTS) of the Dalat Nuclear Research Reactor (DNRR) has been playing an important role in the field of Instrumental Neutron Activation Analysis (INAA). However due to using discrete and low-level integrated electronic components, the system's technology was somewhat obsolete. After ten years of operation, the system's reliability was degraded because of ageing effects on equipment and electronic components. Furthermore, this system is unable to perform the cyclic INAA (CINAA) technique. Renovation of the PTS is imperative not only for increasing its reliability but also for expansion in functioning and convenience in operating. Following this spirit, the PTS has been renovated in the framework of the Vietnam Atomic Energy Committee (VAEC) Project, named 'Renovation of the Pneumatic Transfer System of the Dalat Nuclear Research Reactor'. Renovation and modernization tasks were implemented from March 2000 to February 2002. The main results are redesign and construction of the PTS's control system which based-on PC and construction of the measurement system on the spot based on gamma-ray spectrum system using semiconductor detector Ge for research on the CINAA technique with short-lived radioisotopes. The Main technological specifications of the renovated PTS are: (1) Simple and safety in operation with two mode: Manually and automatically (2) The length of the rabbit pipelines from the measuring - taking specimen capsule box to the irradiation site are about 15m with the 13-2 channel and 4m with the thermal channel. (3) The transfer time of rabbit from the specimen capsule loading box to the irradiation site and return is 2s - 2.2s with the 13-2 channel and 1s - 1.1s with the thermal channel. (4) The system enables the user to irradiate rabbits one by one continuously with predetermined length of irradiation times for every one of them. (5) Permitting to irradiate a rabbit with cycle of irradiation - measuring - irradiation with a predetermined number of cycles. (6) The process of irradiation - transfer - measuring - taking with one or more of irradiation capsules is carried out automatically. (7) The distance between detector block and measurement site, which contained irradiated capsule, enables to chance from 2cm to 20cm on the horizontal direction by a 'rail-car' with the moving speed is 2.8cm/min. This 'rail-car' is controlled by the user from control cabin. (8) The software program of the RPTS was written in Turbo C and Assembler languages. It is user-friendly and the most of information on the PTS such as transfer time, irradiation time, measurement time, number of cycles, position of rabbit, etc., are displayed on the screen under digital or graphic type and saved in hard disk for the task of operation management. (9) The control and measurement center is installed in a cabin which is located in the reactor hall. The renovation and modernization of the PTS were carried out by staff members of the Nuclear Research Institute. The RPTS was checked, commissioned by the VAEC and put into operation since February 2002. Until now, the system is working with high reliability, convenience for users and easy for repairing and maintenance works. In the implement process, a lot of technological problems such as how to detect exactly rabbit's position before into or out from the core and measuring-taking box, how to design and construction of the rabbit pipeline with short length and suitable style for rabbit's moving smoothly, how to brake softly the irradiation capsule in to measurement site, etc. are solved strictly. The radiation background in the measuring-taking box is increased by the radiation dusts discharged from the rabbit pipeline during operation process. In order to reduce their influence, the rabbit pipeline must be cleaned in periodic. (author)

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[en] The paper presents main safety related characteristics of the Dalat Nuclear Research Reactor (DNRR), which was reconstructed in 1982 at the site of the former TRIGA Mark II, while retaining some of its structures. Experience acquired from reactor operation is analysed. The programme of investigations aimed at better ensuring nuclear safety of the reactor, together with some of its results are presented. Finally some propositions to improve the present situation are suggested. (Authors). (2 Tables, 2 fig.)

[en] This paper presents a model development of the Dalat Nuclear Research Reactor (DNRR) loaded with low enriched uranium (LEU) fuel using the Serpent 2 Monte Carlo code. The purpose is to prepare the DNRR Serpent 2 model for performing fuel burnup calculations of the DNRR as well as for generating multi-group neutron cross sections to be further used in the kinetics calculations of the DNRR with a 3D reactor kinetics code. The DNRR Serpent 2 model was verified through comparing with the MCNP6 criticality calculations under different reactor conditions. The parameters to be compared include the effective neutron multiplication factor, radial and axial power distributions, and thermal neutron flux distributions. The comparative results generally show a good agreement between Serpent 2 and MCNP6 and thus indicate that the DNRR Serpent 2 model can be used for further calculations of the DNRR. (author)

[en] The Dalat Nuclear Research Reactor (DNRR) with the nominal power of 500 kWt is today the unique one in Vietnam. It was designed for the purposes of radioisotope production, neutron activation analysis, basic and applied researches, and nuclear education and training. With the rising demand in development of human resources for utilization of atomic energy in the country, the DNRR has been playing an important role in the nuclear education and training for students from universities and professionals who are interested in reactor engineering. At present, the Dalat Nuclear Research Institute (DNRI) offers two types of training course utilizing the research reactor: an one-week practical training course is applied for undergraduate students and a two-week training course on reactor engineering is applied for the professionals. This paper presents the reactor facility and experiments performed at the DNRR for education and training purposes. In addition, the co-operation between the DNRI with national and international educational organizations for nuclear human resource development for national and regional demands is also mentioned in the paper. (author)

[en] The paper presents the calculation results in re-design of neutron trap of the Dalat Nuclear Research Reactor (DNRR) for I-131 radioisotope production using TeO₂ target. The new design permits for loading more TeO₂ capsules from 9 to 12, 15 and 18 in the neutron trap. The enhancement of radioisotope production was implemented by re-arrangement of the neutron trap without changing the dimension or geometry of irradiation capsules. By using neutronics computer code as MCNP6, the obtained calculation results of I-131 activity in 6 investigated cases showed that the new design by the re-arrangement of the neutron trap can be used effectively for radioisotope production with thermal neutron flux in average range from 5.3×10¹² to 1×10¹³ n/cm².s and the total activity of I-131 isotope was increased from about 19.2% to 38.8% comparing with the original design using 9 capsules. The negative reactivity insertion was from 0.60 β_eff to 0.96 β_eff when loading capsules that also met the safety requirements of operational conditions of the DNRR. (author)

[en] The document informs about the suspension of the application of safeguards to the Da Lat research reactor from 6 April 1991, when the final report was submitted

[en] The combination and optimization of the cyclic modes in neutron activation analysis (NAA) at the Dalat research reactor were performed to determine short-lived nuclides. This work focused on determination of selenium in biological materials using "7"7"mSe (T_1_/_2 = 17.4 s) as a case in point. The detection limit was significantly improved by a factor of 3-4 times in comparison with the conventional NAA. The precision was typically within the range of 4-6 % at the third or fourth cycle. It is a reliable technique for determination of selenium in biological materials at sub-ppm concentration levels. (author)

[en] A modified method has been developed for the α determination in the 1/E^1+α epithermal neutron spectrum of reactor. It is based on the Cd-covered and without Cd-covered irradiations of two monitors. This method was applied to determine the α value in the channels of Dalat reactor and the results were compared with those obtained by the other methods. It appeared that the results of the modified method were in quite good agreement with those of other methods. It also showed that the modified method was simple in practical uses and a good application in the experiment of α determination in the reactor irradiation channels. (author)

[en] The studies for application of the Ko-NAA method have been carried out in order to aim at creating a concrete procedure of the method, which is able to apply for practical samples. The results of the calibration of neutron spectrum parameters at cell 7-1, 13-2 and rotary rack on Dalat reactor, the calibration of detection efficiency of gamma spectrometers, the application and development of computer software for processing of gamma-ray spectra and for calculating of related problems (i.e. detector efficiency, neutron spectrum parameters, elemental concentration, etc.) and the quality control/assessment (QC/QA) with the analysis of the reference material IAEA-Soil7 have been presented as well as the application of the ko-NAA for practical samples in geological, archaeological, bio-medical and environmental objects has also been shown. (author)