Progress of filtered neutron beams development and applications at the horizontal channels No.2 and No.4 of Dalat nuclear research reactor
Nuclear Science and Technology, Vol. 4, No. 1 (2014), pp. 62-69
Progress of Filtered Neutron Beams Development and Applications
at the Horizontal Channels No.2 and No.4 of Dalat Nuclear
Research Reactor
Vuong Huu Tan1, Pham Ngoc Son2*, Nguyen Nhi Dien2, Tran Tuan Anh2, Nguyen Xuan Hai2
1Vietnam Agency for Radiation and Nuclear Safety, 113-Tran Duy Hung, Hanoi
2Nuclear Research Institute, 01 Nguyen Tu Luc, Dalat
*E-mail: [email protected]
(Received 5 March 2014, accepted 12 March 2014)
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.
Keywords: Filtered neutron beam, nuclear data measurement, Dalat nuclear research reactor
I. INTRODUCTION
neutron induces nuclear reaction data
measurements since 1991 [2]. For efficient and
extensive uses of the neutron channel, the
neutron filter technique has been also applied
to create high intensity neutron beams with
quasi-monoenergies of 24keV, 59keV and
133keV at the channel No.4 in 2008 [3].
The Dalat nuclear research reactor
(DNRR), located in campus of the Nuclear
Research Institute, VINATOM, was originally
a TRIGA MARK II reactor with a nominal
power of 250kW completed construction and
reached critical state in 1963. The reactor then
has been upgraded to nominal power of 500
kW since 1984. There are three radial and one
tangential beam ports at DNRR, each of which
penetrates the concrete shield structure and the
reactor water to provide external beams of
neutron originated from reactor core [1]. The
cross section view of horizontal channels of
DNRR is shown in Fig.1. The radial beam port
No.4 has been used to develop mono-energetic
neutron beams of thermal, 54keV and 148keV
(previous reported as 55 and 144keV) by the
neutron filter technique for basic research on
Fig. 1. Structure of horizontal neutron channels of
the Dalat nuclear research reactor
©2014 Vietnam Atomic Energy Society and Vietnam Atomic Energy Institute
VUONG HUU TAN, PHAM NGOC SON, NGUYEN NHI DIEN, TRAN TUAN ANH, NGUYEN XUAN HAI
In order to enhance the utilizations of
DNRR for neutron capture experiments and
prompt gamma-rays neutron activation
analysis (PGNAA) applications, the beam port
No.2 of the reactor have been opened in
advance since 2010 [4] for development of a
II. FILTERED NEUTRON BEAMS
The optimal design structure for
insertion of filters into the horizontal channel,
beam collimators and radiation shielding
chamber at the Dalat nuclear research reactor is
shown in Fig.2 [4]. The neutron energy spectra
after filtered through a suitable composition
materials used as filters can be calculated as the
following expression:
modern
prompt
gamma-ray
Compton
suppression facility used a high efficient
HPGe-BGO detectors system. In the works of
neutron filters development, the Monte-Carlo
simulation used MCNP5 code, and
transmission calculation by CFNB code [5]
have been performed for each neutron beam
for optimal design of geometrical structure,
neutron filter materials and radiation
shielding.
, (1)
(E) (E)*exp( d (E))
0
k
k
t,k
k
where
,
are energy
0 (E)
(E)
distributions of the neutron spectra before and
after transmitted through the filters; k, dk and
t,k(E) are the mass density, length of filter and
total cross section of kth filter material,
respectively. The filter information and
physical parameter of each energy beam is
presented in the following sub-sections.
The applications of these filtered
neutron beams were mainly focus on nuclear
data measurements and PGNAA elemental
analysis, although these beam lines have
possibility for many other researches and
applications such as nuclear level density and
isomer ratio determination, Boron neutron
capture therapy (BNCT) research, neutron
dosimeter calibrations,... On the nuclear data
measurements respects, the channels provide
essential neutron beams for precise
experimental reaction data of neutron total and
capture reaction cross sections. On the
PGNAA application subject, the assessment of
analytical sensitivity for elements of B, H, Hg,
Si, Ca, C, S, Al, Fe, Cl, Ti,... has been carried
out, and shown that the new PGNAA
spectroscopy installed at the channel No.2 is a
good facility supplemented to the neutron
activation analysis (NAA) method at the Dalat
nuclear research reactor. The detail
characteristics of filtered neutron beams
development and results of its applications are
presented in the next sections.
Fig. 2. The design structure of filtered neutron beam
facility at the channel No. 2 of DNRR
The thermal neutron beams:
The thermal neutron beam at the channel
No.4 was developed in 1991 [2]. The material
compositions of filters are 98cm Si, 1cm Ti and
35g/cm2 S. The measured thermal neutron flux
is 1.7106 n/cm2.s, and Cadmium ratio Rcd(Au)
= 112 [3]. In order to enhance the utilizations
of the Dalat research reactor for researches and
applications based on the neutron capture
63
PROGRESS OF FILTERED NEUTRON BEAMS DEVELOPMENT AND APPLICATIONS AT …
reactions, the well thermal neutron beam at the
channel No. 2 has been developed and serviced
since 2011 [4]. The neutron filters for this
0.0253eV neutron beam line are single crystals
of 80cm Si and 6cm Bi. The measured thermal
neutron flux at outer position of the beam line
is 1.6106 n/cm2.s, and the value of Cadmium
ratio Rcd(Au) is 420.
nuclear research reactor from 1990s [2, 3].
Firstly, the two neutron beams with mono-
energies of 54keV and 184keV were created at
the channel No.4, and provided a good
experimental station for basis researches on
reactions of neutron with material in keV
energy region. The filter information and
physical parameters of these neutron beam
lines are introduced in Table I [3], and the
corresponding neutron spectra are shown in
Figs. 3-4.
The neutron beams of 54keV and 148keV:
The neutron filter technique has been
applied at the horizontal channels of Dalat
Table I. Physical parameters of the 54keV and 148keV neutron beams at the channel No.4
Parameters
54keV
6.7x105
1.5
148keV
3.9x106
14.8
Neutron flux (n/cm2.s)
Energy resolution (keV)
Peak relative intensity (%)
Beam collimated diameter
78.05
95.78
3 cm
3 cm
B 0.2g/cm2
Si 98cm
S 35g/cm2
B 0.2g/cm2
Si 98cm
Ti 1cm
Filter compositions
4000
3000
2000
1000
0
200
180
160
140
120
100
80
Exp. data
Fitted line
Intensity
Unfolding spectrum
Transport calculation
14000
12000
10000
8000
6000
60
4000
40
2000
20
0
8.0E+04
0
0
1.2E+05
1.6E+05
2.0E+05
200
400
600
800
1000
Channel
1200
Neutron energy (eV)
Fig. 3. Energy spectrum of the 148keV neutron beam at
the channel No.4 of DNRR
Fig. 4. Measured energy spectrum of the 54keV neutron
beam at the channel No. 4 of DNRR
64
VUONG HUU TAN, PHAM NGOC SON, NGUYEN NHI DIEN, TRAN TUAN ANH, NGUYEN XUAN HAI
The neutron beams of 24keV, 59keV and 133keV:
[3] based on the neutron source from the
channel No. 4 of DRR. The characteristics of
these neutron beam lines are introduced in
the references [6, 7], and summarized in
Table II. The calculated and measured energy
spectra of these neutron beam lines are
shown in Figs. 5-7.
As progressive necessary of reactor
based mono-energetic neutron beam lines for
experimental
researches
on
neutron
interaction with mater, the new three filtered
neutron beam of 24keV, 59keV and 133keV
have been developed and applied from 2008
Fig. 5. Measured neutron spectrum for 24keV beam by
proton recoil proportional counter
Fig. 6. Calculated neutron spectrum for the 59keV
filtered neutron beam
Table II. Characteristics of the 24keV, 59keV and 133keV neutron beams at the channel No.4
Parameters
24keV
6.1x105
1.8
59keV
5.3x105
2.7
133keV
3.2x105
3.0
Neutron flux (n/cm2.s)
Energy resolution (keV)
Peak relative intensity (%)
Beam collimated diameter (cm)
96.72
92.28
92.89
3
3
3
B 0.2g/cm2
Fe 20cm
B 0.2g/cm2
Ni 10cm
V 15cm
Al 5cm
B 0.2g/cm2
Cr 50g/cm2
Ni 10cm
Composition of Filters
Al 30cm
S 35g/cm2
Si 60cm
S 35g/cm2
1.0x103
8.0x102
6.0x102
4.0x102
2.0x102
CFNB
MCNP
0.0
5.0x10-2
1.0x10-1
1.5x10-1
En (MeV)
2.0x10-1
Fig. 7. Calculated neutron spectrum for the 133keV filtered neutron beam
65
PROGRESS OF FILTERED NEUTRON BEAMS DEVELOPMENT AND APPLICATIONS AT …
III. NUCLEAR DATA MESUREMENTS
Neutron capture cross section measurements:
193Ir [9]; 185Re and 187Re [10, 11]. In addition,
the horizontal thermal Column of DNRR, a
well thermalized neutron channel, has been
also used for measurement of thermal neutron
capture cross section and resonance integral of
69Ga and 71Ga [12]. A typical result of our
measurements in comparison with data from
other laboratories is shown in Fig. 7 [10].
The measurements of neutron capture
cross sections for a number of nuclides have
been performed on the filtered neutron beams
with mono-energies of 24, 54, 59, 133 and 148
keV, at the Dalat nuclear research reactor. The
measured neutron capture cross sections data
were obtained relative to the standard capture
cross sections of the 197Au(n,)198Au reaction
by the activation method. An abridged
description of data analysis procedure is
presented as follows:
10
ENDF/BVII
185Re(n,γ)186Re
YU.N.TROFIMOV
M.LINDNER
S.J.FRIESENHAHN
A.K.CHAUBEY
R.P.ANAND
A.A.BERGMAN
This w ork
1
The average capture cross sections,
<a>x, for nuclide x at average neutron
spectrum <> can be determined relative to
that of 197Au standard by the following
relations:
0.1
1.E+04
6.E+04
1.E+05
2.E+05
Neutron energy (eV)
Cx f (,t)x fcxIAuAuNAu a Au
Fig. 7. Neutron capture cross section of 185Re [10]
Measurements of neutron total cross sections:
(2)
;
a
CAu f (,t)Au fcAuIxxNx
The total neutron cross section
measurements are being carried out by the
transmission method for natural elements of U,
C, Fe and Al, at the filtered neutron energies of
24keV, 54keV, 59keV, 133keV and 148keV.
The experimental value of neutron total cross
section, t, can be exactly determined from the
following expression:
,
t3
(3)
f (,t)
t2
(1et )e (1e
)
1
where the superscript „x‟ denotes sample
nucleus, and „Au‟ denotes the reference
nucleus 197Au. „C‟ stands for net counts of
the corresponding gamma peak. „t1‟, „t2‟ and
„t3‟ are irradiating, cooling and measuring
times, respectively. „λ‟ is decay constant of the
product nucleus; „εγ‟ is the detection efficiency
of detector; „Iγ‟ is the intensity of interesting γ-
ray, and „fc‟ is the correction factor for self-
shielding multiple scattering effects that can be
exactly calculated by the Monte Carlo method.
1
1
1
0
,
(4)
t
ln
ln
d
T
d
where „T‟ is transmission coefficient of
the collimated neutron beam that transmitted
through a purity sample with thickness d
(cm); „‟ denotes density of the sample
(Atom/cm3). „0‟ and „‟ are measured
neutron fluxes at before and after positions of
In recent years, we have conducted a
series of cross section measurements for
neutron capture (n, ) reactions in different
nuclides, and reported in scientific papers such
as: 109Ag, 186W, 158Gd [8]; 139La, 152Sm, 191Ir,
the irradiating sample, respectively.
A
measurement of the transmission spectrum for
66
VUONG HUU TAN, PHAM NGOC SON, NGUYEN NHI DIEN, TRAN TUAN ANH, NGUYEN XUAN HAI
54keV neutron beam at the channel No.4 of
DNRR is shown in Fig.8.
of BGO-HPGe detectors was completely
developed and installed at the experimental
space of this beam port, from 2012. A
preliminary study on calibration and analytical
sensitivity for several domination elements has
been conducted.
A
prompt gamma-ray
spectrum of geometrical sample measured in
single and Compton-suppression modes is
shown in Fig.9. The results in this study allows
us to estimate that the new PGNAA facility
installed at the channel No.2 of DNRR is
qualified to participate in analytical services at
the Institute. A calibration curve for Boron
analysis is presented in Fig.10, and the results
of comparison analysis used standard soil
sample (NIST-2711a) is given in Table III.
Fig. 8. Measured neutron spectrum of 54keV
neutron beam transmitted through different
thickness of C sample.
IV. PGNAA APLICATIONS
From 1998, the 148keV filtered neutron
beam at the channel No.4 has been applied for
possibility studies the method of in-vivo
prompt gamma neutron activation analysis
(IVPGNAA) that involves the exposure of the
living human organs to a small dose of
neutrons. At that time, IVPGNAA is a new
technique for directly determination of toxic
elements accommodated in a specific living
human organ such as concentrations of Hg in
kidney and Cd in liver. The research was
carried out on a physical phantom installed at
the channel No.4 [13]. The results given from
this investigation introduced a high effective
new experiment with 148keV neutron beam
instead of thermal neutrons [13].
Fig. 9. Prompt gamma-rays spectrum measured at
the thermal neutron beam No.2 for soil sample, in
single and Compton-suppression modes.
Line
Model
Exp data
Linear fitting
y =
A + B*x
Equation
25
20
15
10
5
0
Reduced
Chi-Sqr
1
Adj. R-Square
Value Standard Error
A
B
-2.799
0.520
0.158620
cps
cps
0.00544162
The low background and well thermal
filtered neutron beam from the channel No.2
[4] of Dalat nuclear research reactor is an
advantage neutron source for prompt gamma-
ray neutron activation analysis (PGNAA).
Accordingly, a modern Compton suppression
PGNAA spectroscopy used a compact system
0
10
20
30
40
50
g B
Fig. 10. The calibration curve for Boron analysis by
using the PGNAA facility at the channel No.2
67
PROGRESS OF FILTERED NEUTRON BEAMS DEVELOPMENT AND APPLICATIONS AT …
Table III. The results of comparison analysis used the standard soil sample (NIST-2711a), by using the
PGNAA facility at the channel No.2
NIST-2711a
Sample
(Standard sample: Montana soil)
Elements
B (g/g)
Measured values
Reference values
50.5 ± 2.9
7.59 ± 3.34
6.96 ± 1.07
2.43 ± 0.59
7.1 ± 0.3
50
Gd (g/g)
Sm (g/g)
Ca (%)
Al (%)
5
5.93 ± 0.28
2.42 ± 0.06
6.72 ± 0.06
31.4 ± 0.7
2.53 ± 0.10
0.32 ± 0.01
1.20 ± 0.01
2.82 ± 0.04
Si (%)
31.66 ± 3.93
2.39 ± 0.28
0.29 ± 0.06
2.02 ± 0.48
3.01 ± 0.35
K (%)
Ti (%)
Na (%)
Fe (%)
V. CONCLUSIONS
supplementation to the neutron activation
analysis (NAA) method at the Dalat research
reactor.
The accomplishment of research
activities on the topics of filtered neutron
beams development and it‟s applications based
on the neutron sources from the horizontal
channel No.2 and No.4 of Dalat nuclear
research reactor is reviewed in this report. The
neutron filter technique has been effectively
applied to provide mono-energetic neutron
beam lines with qualified characteristics for
related applications at the Nuclear Research
Institute, VINATOM. The basis researches on
experimental neutron induce nuclear reaction
cross sections conducted by using these
neutron beams have been performed with
interesting results, and this research activity is
proposed to be continued, in order to
participate in providing of precise experimental
nuclear reaction data and educational
experiments. The new PGNAA facility
installed coupling with the well thermal
neutron beam at the channel No.2 plays as an
important application of this channel for
studies on neutron capture experiments and
elemental analysis. This will be an important
The new development of neutron beam
with possible mono-energy of 2keV, and
extension of application studies such as Boron
neutron capture therapy (BNCT) and neutron
dosimeter calibration are proposed.
ACKNOWLEDGEMENTS
This research is partly funded by
Vietnam National Foundation for Science
and
Technology
Development
(NAFOSTED) under grant number “103.04-
2012.59”. The authors are immensely
grateful to Mr. Luong Ba Vien, Deputy
Director of the Nuclear Research Institute,
VINATOM, for his great encouragement
and critical reading of the manuscript.
68
VUONG HUU TAN, PHAM NGOC SON, NGUYEN NHI DIEN, TRAN TUAN ANH, NGUYEN XUAN HAI
[8] Vuong Huu Tan, Pham Ngoc Son, et al.
Neutron Capture Cross Section Measurements
of 109Ag, 186W and 158Gd on Filtered Neutron
Beams of 55keV and 144keV. Nuclear Science
and Technology, Vol.3 No.1, pp.1-7; IAEA,
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