Results of Operation and Utilization of the Dalat Nuclear Research Reactor

actor with a yearly average of 2000 
samples. It can be estimated that those make 
up 60% of geological samples, 10% of 
biological samples, 20% of environmental 
samples, 5% of soil and agriculture materials, 
3% of industrial materials. 
In order to determine the elements 
having short-lived radionuclides, the method of 
cyclic INAA with the alternation of irradiation 
and measurement was implemented by using 
the thermal column and vertical irradiation 
channel. An auto-pneumatic transfer system 
installed in 2012 at the DNRR can transfer a 
sample from irradiation position to measuring 
detector about 3 seconds. 
The k-zero method for INAA has been 
also developed to analyse airborne particulate 
samples for investigation of air pollution; crude 
oil samples and base rock samples for oil field 
study. Based on developed k-zero-INAA 
method, a multi-elements analysis procedures 
have been applied to simultaneously determine 
concentration for about 31 elements including 
Al, As, Ba, Br, Ca, Cl, Cr, Cu, Dy, Eu, Fe, Ga, 
Hf, Ho, K, La, Lu, Mg, Mn, Na, Sb, Sc, Sm, 
Sr, Th, Ti, V, Yb, Zn. 
C. Neutron beam utilization 
The reactor has four horizontal beam 
ports, which provide beams of neutron and 
gamma radiation for a variety of experiments. 
They also provide irradiation facilities for 
large specimens in a region close to the 
reactor core. Besides, the reactor also has a 
large thermal column with outside dimensions 
of 1.2m by 1.2m in cross section and 1.6m in 
length (Fig. 5). 
Up to now, only three beam ports (No.2, 
No.3 and No.4) and the thermal column have 
been used for reseaches and applications. At 
the beam port No.2, a BGO-HPGe gamma-rays 
Compton suppression spectrometer has been 
recently installed for PGNAA and 
experimental researches on neutron capture 
reactions. The filtered thermal neutron beams 
extracted from the tangential beam port No.3 
are used for nuclear structure studies, 
especially for experimental determination of 
nuclear energy levels and level density in 
regions below neutron binding energy. The 
filtered neutron beams at the piercing beam 
port No.4 with quasi-monoenergies of 24keV, 
54keV, 59keV, 133keV and 148keV are used 
RESULTS OF OPERATION AND UTILIZATION OF THE DALAT NUCLEAR RESEARCH REACTOR 
 6 
for the mesurements of neutron total and 
capture cross sections. In addition, these 
neutron beams are also applied for practical 
study on radiation shielding design. Typical 
research activities using neutron beam of the 
DNRR are listed below. 
Beam port # 1
Beam port # 2 Beam port # 3
Beam port # 4
Core
Therm alizing column (closed)
Therm al
Column
Pool tank w all
Spent fuel s torage tank
Concrete
shielding
Graphite reflector
door
Column
Bellow s
assem bly
Stainless steel
Aluminum
Fig. 5. Horizontal section view of the DNRR. 
Neutron physics and nuclear data measurement 
In the keV energy region, filtered 
neutron beams are the most intense sources, 
which can be used to obtain neutron data for 
reactors and other applications. The following 
experiments have been carried out at the 
DNRR including: 
- Total neutron cross section measurement 
for 
238
U, Fe, Al, Pb on filtered neutron beams 
at 144 keV, 55 keV, 25 keV and evaluation of 
average neutron resonance parameters from 
experimental data; 
- Gamma ray spectra measurement from 
neutron capture reaction of some reactor 
materials (Al, Fe, Be, etc.) on filtered neutron 
beam at 55 keV and 144 keV; 
- Measurement of average neutron 
radioactive capture cross section of 
238
U, 
98
Mo, 
151
Eu, 
153
Eu on the 55 keV and 144 keV 
neutron beams; 
- Measurement of isomeric ratio created 
in the reaction 
81
Br(n, )82Br on the 55 keV and 
144 keV neutron beams; 
- And other investigations, such as 
average resonance capture measurements, 
using the - coincidence spectrometer for 
study on the (n, 2) reaction, etc. 
Application of neutron capture gamma ray 
spectroscopy 
- Development of PGNAA technique using 
the filtered thermal neutron beam in 
combination with the Compton-suppressed 
spectrometer for analyzing Fe, Co, Ni, C in 
steel samples; Si, Ca, Fe, Al in cement 
samples; Gd, Sm, Nd in uranium ores, Sm, Gd 
in rare earth ores; etc.; 
- Utilization of the PGNAA method for 
investigating the correlation between boron 
and tin concentrations in geological samples as 
a geochemical indication in exploration and 
assessment of natural mineral resources; 
analyzing boron in sediment and sand samples 
No. 2: Gamma spectrometry 
system with BGO detector for 
PGNAA and neutron capture 
reactions study 
This port is closed 
No. 3: Nuclear 
structure study 
No. 4: Nuclear data 
measurement 
Thermal column 
NGUYEN NHI DIEN et al. 
 7 
to complement reference data for such samples 
from rivers; 
- Development of the spectrometer of 
summation of amplitudes of coinciding pulses 
for (n, 2) reaction research and for measuring 
activity of activated elements with high 
possibility of cascade transitions. 
D. Eduacation and training activities 
Training Center at Dalat Nuclear 
Research Institute which was established in 
1999 is responsible for organizing training 
courses and training in reactor engineering, 
nuclear and radiation safety, application of 
nuclear techniques and radioisotopes in 
industry, agriculture, biology and environment, 
etc. Training courses on non-destructive 
evaluation (NDE) including radiographic 
testing, ultrasonic testing as well as on security 
of nuclear facilities and radiation sources have 
also been done. The center also is the training 
facility for expertise students from local 
universities and foreign postgraduate students. 
Thereby, the human resource development is 
conducted annually so that it can deal with 
scientific works of higher and higher quality 
and meet a huge demand in the field of nuclear 
science and technology in Vietnam in the 
future. Thanks to the bilateral co-operation 
with the Japan Atomic Energy Agency, US 
Department of Energy, Bhabha Atomic 
Research Center of India, and Korea Atomic 
Energy Research Institute, we have conducted 
a variety of training courses in the four 
following key areas: 
- Reactor engineering for nuclear power 
programme; 
- Research and development activities; 
- State management in the field; 
- And University lecturer training program. 
Besides, the DNRR has been used as a 
main tool for practical training, a set of 
equipment was supported under IAEA TC 
project, bilateral projects with the Japan 
Atomic Energy Agency and Bhabha Atomic 
Research Center of India. The measuring 
systems for practices at the Training Center 
can meet the fast increasing demand and is 
expected to move forward to the regional 
standard in the field of nuclear training. 
E. Other applications 
Research on sediment using radiotracer 
techniques was carried out to investigate bed 
load layers displacement at estuaries 
navigation channel region and to explain the 
sediment deposition phenomenon causing 
frequent dredging activities. 
Research on radio-biology consists of 
using gamma radiation associated with other 
factors for improving agricultural seeds and 
applying radioactive tracers for studying 
biological metabolism, especially nutrition 
problems. These studies are to investigate 
phosphorus absorption and other nutritional 
problems during the growing processes of rice 
and other plants. Irradiation effects on some 
plants to gain higher yield or environment 
adapted varieties were also studied. 
Gemstone colorizing experiments of 
topaz and sapphire in the reactor core, in the 
rotary rack as well as in horizontal channels 
has been done. 
As research purpose, silicon mono-
crystals have been irradiated at the central 
neutron trap of the reactor. Irradiated products 
of good quality, appropriate for fabrication of 
power diodes and thyristors have been created 
thanks to proper neutron distribution in this 
irradiation facility and suitable cadmium ratio. 
RESULTS OF OPERATION AND UTILIZATION OF THE DALAT NUCLEAR RESEARCH REACTOR 
 8 
IV. SOME MAIN REACTOR RENOVATION 
PROJECTS PERFORMED 
A. Reactor conversion from HEU to LEU fuels 
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 DNRR core was partly 
converted from HEU to LEU in September 
2007. 
After this success, the full core 
conversion study from HEU to LEU of the 
DNRR was also carried out during years 2008 
- 2010. The results of neutronics, thermal 
hydraulics and safety analysis showed that a 
LEU core loaded with 92 fuel assemblies and 
12 beryllium rods around the neutron trap 
satisfies the safety requirements while 
maintaining the utilization possibility similar 
to that of the previous HEU and recent mixed 
fuel cores. 
Physics and energy start-up of the 
DNRR for full core conversion to low 
enriched uranium (LEU) fuel were performed 
from November 24
th
, 2011 until January 13
th
, 
2012 according to a planned program that 
was approved by Vietnam Atomic Energy 
Institute (VINATOM). At 15:35 on 
November, 30
th
, 2011 the reactor reached 
criticality with core configuration including 
72 LEU FAs and neutron trap in center. Then 
the fuel loading for working core and power 
ascension test were also carried out from 
December, 6
th
, 2011 to January, 13
th
, 2012. 
Experimental results of physical and thermal 
hydraulics parameters of the reactor during 
start up stages and long operation cycles at 
nominal power showed very good agreement 
with calculated results and met the safety 
requirements. 
B. Reactor control and instrumentation system 
modification 
The Control and Instrumentation System 
(C&I) of the DNRR was designed and 
manufactured by the former Soviet Union and 
put into operation in November 1983. Due to 
the spare part procurement problem was 
suspected and using technology of the 1970’s 
with discrete and low-level integrated 
electronic components, the system technology 
was somewhat obsolete and un-adapted to 
tropical climate. 
The first renovation work was 
implemented during 1992-1993 period and the 
renovated C&I system was commissioned at 
the end of 1993. The most important 
renovation task was to redesign and construct a 
number of electronic systems/blocks, which 
play the key role in enhancing the reliability of 
the system. This renovation work was focused 
mainly on the process and instrumentation 
system, but not on the neutron measurement 
and data processing parts. Because of that, it 
was necessary to fulfill the second renovation 
and modernization during the years of 2005-
2007 to replace neutron measurement and 
signal processing parts of the existing C&I 
system by the digital system named ASUZ-
14R. The main items replaced under the 
second modification are neutron detector 
channels; neutron flux control system 
(NFCS), reactor protection system, control 
console and control panels, reactor protocol 
and diagnostic system, etc. 
The commissioning of the new I&C 
system was finished in August 2007 and 
operating license was approved in October 
2007. 
NGUYEN NHI DIEN et al. 
 9 
V. CONCLUSIONS 
The DNRR has been safely operated and 
effectively utilized for 30 years. To achieve 
that, maintaining and upgrading the reactor 
technological facilities have been done with a 
high quality. The reactor physics and thermal 
hydraulics studies have also provided the 
important bases for safety evaluation and in-
core fuel management to ensure its safe 
operation and effective exploitation. The 
safety and security for the reactor are one of 
the main issues that national and local 
authorities are particularly interested in and 
strongly support up. 
During 30 years of operation, the DNRR 
has been playing an important role in the use 
of atomic energy for peaceful purpose in 
Vietnam. The reactor has been used for 
radioisotope production for medicine and 
industry purposes, NAA of geological, crude 
oil and environment samples, performance of 
fundamental and applied researches on 
nuclear and reactor physics, as well as 
creation of a large amount of human resource 
with high skills and experiences on 
application of nuclear techniques in the 
country. A strategic plan and long-term 
working plan for the DNRR has been set up in 
order to continue its safe operation and 
effective utilization at least to 2025. 
It should be mentioned that a project for 
establishment of a new nuclear science and 
technology center with a high power research 
reactor expected to put into operation between 
2020-2022 is now under preparation and 
consideration. Therefore, the DNRR will be 
necessary and keep playing an important role 
in scientific research, applications and human 
resource development for Vietnam in the 
coming time. 
REFERENCES 
[1] Nguyen Nhi Dien, Dalat Nuclear Research 
Reactor - Twenty five years of safe operation 
and efficient exploitation, Dalat, (March 2009). 
[2] Duong Van Dong, Status of Radioisotope 
Production and Application in Vietnam, Dalat 
Sym. RR-PI-09, Dalat, (2009). 
[3] V. V. Le, T. N. Huynh, B. V. Luong, V. L. 
Pham, J. R. Liaw, J. Matos, Comparative 
Analyses for Loading LEU Instead of HEU 
Fuel Assemblies in the DNRR, RERTR Int’l 
Meeting, Boston, (2005). 
[4] P.V. Lam, N.N. Dien, T.D. Hai, L.B. Vien, 
L.V. Vinh, H.T. Nghiem, N.M. Tuan and N.K. 
Cuong, Results of the reactor control system 
replacement and reactor core conversion at the 
Dalat nuclear research reactor, The 12th Annual 
Topical Meeting on Research Reactor Fuel 
Management, Hamburg, Germany, (2008). 
[5] P.V. Lam, N.N. Dien, L.V. Vinh, H.T. 
Nghiem, L.B. Vien and N.K. Cuong, 
Neutronics and thermal hydraulics calculation 
for full core conversion from HEU to LEU fuel 
of the Dalat nuclear research reactor, RERTR 
Int’l Meeting, Lisbon, Portugal, (2010). 
[6] L.B. Vien, L.V. Vinh, H.T. Nghiem and N.K. 
Cuong, Transient/ accident analyses for full 
core conversion from HEU to LEU fuel of the 
Dalat nuclear research reactor, RERTR Int’l 
Meeting, Lisbon, Portugal, (2010). 
[7] C.D. Vu, Study on application of k0-IAEA at 
Dalat research reactor, Project report (code 
CS/09/01-01), (2010). 
[8] N.N. Dien, L.B. Vien, P.V. Lam, L.V. Vinh, 
H.T. Nghiem, N.K. Cuong, N.M. Tuan, N.M. 
Hung, P.Q. Huy, T. Q. Duong, V.D.H. Dang, 
T.C. Su, T.T. Vien, Some main results of 
commissioning of the Dalat Nuclear Research 
Reactor with low enriched fuel, Nuclear 
Research Institute, (2012). 
[9] Safety Analysis Report (SAR) for the Dalat 
Research Reactor, Dalat, (2012).