International Journal of Chemical and Physical Sciences, ISSN:2319-6602
IJCPS Vol. 5 Special Issue - 7 FESEM – 2016
www.ijcps.org
Measurement of Cross Section of (n,γ) Nuclear Reactions for Chlorine and
Bromine Induced by Thermal Neutrons
*
1
G. R. PANSARE1, M.A.KOLHE2, M. S. TANPURE3, V. K. MULIK4
Department of Physics, Haribhai V. Desai College, Pune, Maharashtra, India.
E-mail: [email protected]
_________________________________________________________________________
__
Abstract
The Cross-section values of nuclear reactions 37Cl(n,γ)38Cl, and 81Br (n,)82Br induced by
thermal neutrons of energy 0.025eV have measured using the NaI(Tl) gamma ray
spectrometer coupled to the 8K Multichannel Analyzer and Computer software. The
thermal neutron flux was measured using the nuclear reactions. 55Mn(n,)56Mn and
75
As(n,)76As. The induced gamma ray activities of radioisotopes 37Cl (E=1600KeV), 82Br
(E=780KeV), 56Mn (E=840KeV) and 76As (E=559KeV) were measured from the
respective gamma ray spectra counted using NaI(Tl) detector and M.C.A. Measured
values of thermal neutron cross-section of Chlorine and Bromine isotopes are found to be
0.46 barns and 2.39 barns respectively. The results are in good agreement with literature
values.
Keywords: Thermal neutrons, Nuclear Reactions, Cross-section, NaI(Tl) gamma ray
detector, 8K M.C.A., Neutron flux.
.__________________________________________________________________________________
Introduction
Elements such as Chlorine and Bromine have potential applications in many fields such as
Medical, Industrial, Environmental pollution and basics researches [ 1,2,3,4 ]. Chlorine-36 is used in fuel
arises from the activation of 35Cl. Chlorine is used to kill bacteria in drinking water and swimming pools.
It is also used in disinfectants and bleach for the same reason. Chlorine is very effective against e coli
bacteria. It is more regularly used by terrorist groups. Chlorine is used to make plastics. Chlorine
compounds are widely used as cleaning and disinfecting agents in medical facilities all over the world,
especially for disinfecting the machines and equipment used in these facilities. Bromine is used in many
areas such as agricultural chemicals, dyestuffs, insecticides, pharmaceuticals and chemical intermediates.
Bromine compounds can be used as flame retardants. They are added to furniture foam, plastic casings for
electronics and textiles to make them less flammable. Silver bromide is a chemical used in film
photography. Interaction of thermal neutrons with Chlorine and Bromine can be understood in terms of
capture cross-section. Many workers have measured the cross-section of (n,γ) nuclear reactions for these
element at thermal neutron energy[5,6,7]. Literature serve indicate that large variations exist in the
measured values of nuclear reaction cross-section at thermal neutron energy. It is essential to update the
present data of cross-section values. At present, precise nuclear data, advance data acquisition systems
and computer software are available which will help to improve the accuracy in the measurement of
cross-section values. In view of this, cross-section of 37Cl(n,γ)38Cl, and 81Br (n,)82Br nuclear reaction
have measurement at thermal neutron energy of 0.025eV.
Measurement of Cross Section of (n,γ) Nuclear Reactions
for Chlorine and Bromine Induced by Thermal Neutrons
*G.
R. PANSARE1, M.A.KOLHE2,
M. S. TANPURE3, V. K. MULIK4
- 59 -
International Journal of Chemical and Physical Sciences, ISSN:2319-6602
IJCPS Vol. 5 Special Issue - 7 FESEM – 2016
www.ijcps.org
Experimental Details
In the present work, thermal neutron source, Cf-252 available in the Savitribai Phule Pune
University was used. The induced gamma-ray activities of the thermal neutron irradiated samples were
measured with the help of NaI(Tl) scintillation spectrometer. The gamma-ray spectrometer was coupled
to the computer based 8K M.C.A. NaI(Tl) detector was calibrated using standard gamma ray sources. The
measured gamma ray spectrum was analyzed using the computer software.
Sample preparation and neutron irradiation
The samples are prepared from pure powders of Sodium Chloride (99.9 %), Potassium Bromide
(99.9%) , Manganese (99.9%) and Arsenic (99.9%). Three samples of each element are prepared. Each
sample was made by packing known weight in range of 500mg to 800mg in polyethylene bag. Along with
each Chlorine sample , Manganese powder of known weight was packed in separate polyethylene bag to
calculate the thermal neutron flux as standard. Similarly, along with each Bromine sample , known weight
of Arsenic powder was packed in separate polyethylene bag to calculate the thermal neutron flux as
standard. Each sample along with standard sample was irradiated with thermal neutron flux ~ 10 2 – 103
n/cm2sec and neutron of energy 0.025 eV from the Cf-252 neutron source for different time periods
.Gamma ray activity of each irradiated sample and monitor was counted using the NaI(Tl) gamma ray
detector available in the Department of Physics, of H. V. Desai College, Pune. The induced gamma ray
activities of Chlorine 38Cl (Eγ=1600 KeV), Bromine 82 Br (Eγ = 780 KeV) , Manganese 56Mn (Eγ = 840
KeV) and Arsenic 76As (Eγ= 550 KeV) were counted separately .Table 1 shows the experimental
activation parameters, irradiation time t1,cooling time t2 and counting time t3 .
Name of
Element
Nuclear
Reaction
Chlorine
Bromine
Manganese
Arsenic
Cl(n,γ)38Cl
81
Br(n,)Br82
55
Mn(n,)Mn56
75
As(n,)As76
Irradiation time
t1
(h)
0.61
40.58
12.28
40.58
37
Cooling time
t2
(h)
1.11
1.20
1.59
4.41
Counting time
t3
(h)
1.0
3.0
1.0
3.0
Table 1: Details of nuclear reactions and nuclear data used, irradiation time, cooling time and counting time.
Name
Element
of Nuclear
Reaction
Chlorine
Bromine
Manganese*
Arsenic*
Cl(n,γ)38Cl
81
Br(n,)Br82
55
Mn(n,)Mn56
75
As(n,)As76
37
Abundance
(%)
24.47
49.31
100
100
Half life
T
(h)
0.61
35.34
2.58
24.60
Gamma Energy
(KeV)
1600
780
840
559
Disintegration
probability
Fd (%)
33.30
83.40
98.85
45.00
Table 2 : Details of neutron activation experimental parameters
*Elements used for flux measurements as a standard or monitor.
Measurement of Cross Section of (n,γ) Nuclear Reactions
for Chlorine and Bromine Induced by Thermal Neutrons
*G.
R. PANSARE1, M.A.KOLHE2,
M. S. TANPURE3, V. K. MULIK4
- 60 -
International Journal of Chemical and Physical Sciences, ISSN:2319-6602
IJCPS Vol. 5 Special Issue - 7 FESEM – 2016
www.ijcps.org
Calculations of neutron flux and cross section
From the induced gamma ray activity of 56Mn, Eγ = 840 KeV, and 76As, E γ =559KeV, thermal
neutron flux of Cf – 252 source was calculated using the following activation relation [ 8].
φ=Aλ/Nfdε(1-e-λt1 ) (e-λt2) (1-e-λt3)
……..(1)
σ is cross section for (n, γ) reaction, Ф is neutron flux, A is total count under photo peak, λ is
decay constant, fd is number of disintegration/gamma quanta, N is number of target atoms, Є is detector
efficiency for gamma ray, t1 is irradiation time, t2 is cooling time (time between end of irradiation and start
of counting), t3 is counting time. The induced gamma ray activities of the reaction products, 38Cl, 82 Br ,56
Mn and 76As were calculated from the gamma ray spectra of respective radio nuclide. Using these values
of gamma ray photon activities the thermal neutron flux received by the respective samples were
calculated using the above relation [1]. The thermal neutron flux was calculated using the values of
cross-section of nuclear reactions 55Mn(n,)Mn56 and 75As(n,)As76 ,13.03 barn and 4.28 barn
respectively. Experimental values of the cross sections of nuclear reactions under study were calculated
using the relation [8].
σ = Aλ/ФNε fd (1-e-λt1 ) (e-λt2) (1-e-λt3)
……….(2)
The parameters involved were for respective nuclear reaction. The details of the nuclear data,
which includes gamma ray energies, branching ratio of gamma photons (f d), half life of generated
radioisotopes were taken from the literature[9]. The Table 2 shows different nuclear parameters used for
calculation of thermal neutron flux and cross-section values . The measured values of cross-section are
given in Table 3. Figure 1,2,3 and 4 shows gamma ray spectra of thermal neutron irradiated samples of
Chlorine, Bromine, Manganese and Arsenic respectively.
B
1000
1200
800
1000
( 1)= 40.96Hrs.
Irradiation Time t
( 2)= 1.03Hrs.
Cooling Time t
( 3 )=
Counting Time t
3 Hrs.
800
B
counts
600
400
1600KeV
200
600
780KeV
400
200
0
0
0
200
400
600
800
0
200
channel no
Figure 1: Gamma ray spectrum of 38Cl
Measurement of Cross Section of (n,γ) Nuclear Reactions
for Chlorine and Bromine Induced by Thermal Neutrons
400
600
800
1000
1200
Channel No.
Figure 2: Gamma ray spectrum of 82Br
*G.
R. PANSARE1, M.A.KOLHE2,
M. S. TANPURE3, V. K. MULIK4
- 61 -
International Journal of Chemical and Physical Sciences, ISSN:2319-6602
IJCPS Vol. 5 Special Issue - 7 FESEM – 2016
www.ijcps.org
1200
1200
Irradiation time(t1)=40.96hrs.
( 1)= 43.46Hrs.
Cooling time(t2)=4.68hrs.
(t2)= 1.98Hrs.
counting time(t3)=3 hrs
Irradiation Time t
1000
840KeV.
Cooling Time
Counting Time
( t3 ) =
1 Hrs.
800
Counts
Counts
800
600
400
(559KeV)
400
200
0
0
0
200
400
600
800
1000
1200
0
200
Channel No.
400
600
800
1000
1200
Chnnel No.
Figure 3: Gamma ray spectrum of 56Mn
Figure 4: Gamma ray spectrum of 76As
Results and Discussion
Gamma ray spectra of thermal neutrons irradiated samples of Chlorine, Bromine, Manganese
and Arsenic shown in figures1, 2, 3 and 4 indicate that thermal neutrons produced the sufficient
measurable gamma ray activities of 38Cl, 82Br, 56Mn and 76As in the samples. Therefore thermal neutron
activation technique can be used effectively for the analysis of these elements in any sample .The
measured values of cross-section of neuclear reactions 37Cl(n,γ)38Cl and 81Br(n,)Br82 are given in
Table 3. The results are in good agreement with reported literature values [5,6,7].
Name of Element
Nuclear Reaction
Cl(n,γ)38Cl
81
Br(n,)Br82
37
Chlorine
Bromine
Measured cross-section
values (barn)
0.46
2.39
Literature
reported values (barns)
0.41
2.6, 4.1, 2.25
Table 3: The measured values of cross-section of neuclear reactions.
Conclusion
The experimentally measured cross -section for the formation of 38Cl and 82Br at thermal
neutrons energies formed through the nuclear reaction 37Cl(n,γ)38Cl and 81Br (n,)82Br are respectively
0.46 barn and 2.39 barn. These experimental measured values of cross-section in the present work are in
good agreement with literature values reported earlier [5,6,7]. The Manganese and Arsenic elements can
be used as standards for the measurements of thermal neutron flux and can be used for the measurements
of cross-section of nuclear reactions for different elements of interest.
Acknowledgements
Authors are thankful to the Head, Department of Chemistry, Savitribai Phule Pune University for
permission of using the thermal neutron source. Authors are also thankful to BCUD, Savitribai Phule
Pune University and P.K.G, Mandal for financial assistance.
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Measurement of Cross Section of (n,γ) Nuclear Reactions
for Chlorine and Bromine Induced by Thermal Neutrons
*G.
R. PANSARE1, M.A.KOLHE2,
M. S. TANPURE3, V. K. MULIK4
- 62 -
International Journal of Chemical and Physical Sciences, ISSN:2319-6602
IJCPS Vol. 5 Special Issue - 7 FESEM – 2016
www.ijcps.org
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Measurement of Cross Section of (n,γ) Nuclear Reactions
for Chlorine and Bromine Induced by Thermal Neutrons
*G.
R. PANSARE1, M.A.KOLHE2,
M. S. TANPURE3, V. K. MULIK4
- 63 -