SOP TRANSACTIONS ON APPLIED PHYSICS
Volume 1, Number 1, February 2014
Gamma Ray and Neutron Shielding Properties of
Bismuth Phosphate Glass Containing Iron and Barium
H. A. Saud*
Physics Department, Faculty of Science, Al-Azhar University, Girls Branch, Nasr City, Cairo, Egypt
*Corresponding author: heba [email protected]
Abstract
Glass system with chemical formula: xBaO-(30 x)Fe2 O3 -10Li2 O-30Bi2 O3 -30P2 O5 mole% is prepared to be used as radiation shield.
The mass attenuation coefficient, half value layer, the total atomic cross-section (σtot ) and the effective atomic number (Ze f f ) of the
glass system to gamma rays have been measured experimentally and compared with those determined from theoretical calculations
using the mixture rule of WinXCom program. A database of effective mass removal cross-sections for fast neutrons is also introduced
in this work. These results indicate that glasses in the present study can be used as radiation shielding materials, the glass system
with 15 mol% BaO is found to be superior gamma-ray and neutron shielding. The measurements are carried out to explore the
advantages of that glass samples in different radiation shielding applications.
Keywords
Absorption, Attenuation Coefficient, Effective Atomic Number
1. Introduction
2. Experimental Work
Phosphate glasses have unique properties which make them useful
for a wide range of technical applications. However, these glasses
have a relatively poor chemical durability [1] that often limits
their usefulness. Several studies have shown that the chemical
durability of phosphate glasses can be improved by the addition
of various oxides such as Bi2 O3 and, especially, Fe2 O3 [2, 3]. It
has been suggested that the addition of one or both of Bi2 O3 and
Fe2 O3 results in the formation of P–O–Bi and P–O–Fe bonds
which improves the chemical durability and the attenuation of
fast neutron [2–4]. Addition of Fe2 O3 to the phosphate network
leads to breakdown of the P=O bonds and the P–O–P bonds are
replaced by P–O–Fe bonds [1]. Bi2 O3 is known to play a dual
role in many oxide glasses, as both a network modifier and a
network former [2, 5, 6]. In Bi2 O3 – P2 O5 glasses it is found
that [2] BiO6 ions occupy a position between P–O–P layers.
Analytically, pure grade chemicals are used to prepare the following glass samples according to the formula: xBaO–(30 x)
Fe2 O3 –10Li2 O-30Bi2 O3 –30P2 O5 mole% where x= 0, 5, 10, 15,
20, 25 and 30.The batch mixtures are melted in porcelain crucibles
at1100 for two hours until homogeneous glasses are obtained
and then annealed in a separate annealing furnace at 250°Cand
then slowly cooled to the room temperature to remove any internal stresses. Samples have been obtained in circular shape
of 2cm.Glass density measurements are measured at room temperature using the standard Archimedes method, with toluene as
the immersion fluid of stable density (0.866g/cm3 ). Attenuation
coefficients of the proposed glass system are measured in narrow
beam transmission geometry by using NaI (TI) crystal detector
with energy resolution of 12.5% at 662 keV in conjunction with
multi-channel analyzer (MCA). Radioactive sources 60 Co and
137 Cs each is used for different photon energies. Incident and
transmitted intensities of photons are measured on MCA for fixed
preset time for each sample by selecting a narrow region symmetrical with respect to the centroid of the photo peak. Counting time
is chosen such that 103–105 counts, which are recorded under
each photo peak. The glassy structure of our samples is examined
by a standard X-ray method. Dry ground glass powders are investigated by using an X-ray Debye Scherrer camera. Photographs
of all samples show the diffuse bands characteristic of the X-ray
diffraction patterns of amorphous materials; no sharp line spectra
are observed confirming the glass formation.
Mass attenuation and energy absorption coefficients are widely
used in the study of interaction of γ-rays with matter. By measuring the values of the mass attenuation coefficient and the half
value layer, compare them with the calculated values that are
obtained using the WinXCom program based on the mixture rule,
where the mixture rule gives the attenuation coefficient of any
substance as the sum of the weighted contributions from the individual atoms in the mixture [2], and also by the development of
accurate data base for effective fast neutron removal cross-section
of different elements, compounds and substances. For simplicity,
fast neutron removal cross-section,∑ R−1 , is the probability that a
fast or fission- energy neutron undergoes a first collision, which
removes it from the group of penetrating and uncollided neutrons. The removal cross-section ∑ R of a given material behaves
formally as a cross- section in determining neutron attenuation.
3. Results and Discussion
2
SOP TRANSACTIONS ON APPLIED PHYSICS
Figure 1. Dependence of the Density and the Molar Volume of on the Percentage of BaO Content.
Figure 2. Mass Attenuation Coefficients of Glass Samples for Different Energies
3.1 Density (ρ) and molar volume
The density is a powerful tool capable of exploring the changes in
the structure of glasses. The density is affected by the structural
softening/ compactness [7], change in geometrical configuration,
coordination number, cross-link density and dimension of interstitial spaces of the glass. In the studied glasses, it is noted that Fig.
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Gamma Ray and Neutron Shielding Properties of Bismuth Phosphate Glass Containing Iron and Barium
3
1, the density increases with increasing BaO content in the glass
due to the replacement of the oxide (BaO) by oxide (Fe2 O3 ). So
addition of BaO to network causes some type of structural rearrangement of the atoms. There is a possibility for the alteration
of the geometrical configuration upon substitution of BaO into
the glass network. Molar volume is also an important physical
property, it is noted that, the density increases, congruent with a
decrease in the molar volume as the BaO content as shown in Fig.
1.
3.2 Mass attenuation coefficientMATH
The mass attenuation coefficients are estimated from the measured incident and transmitted gamma-ray intensities, as well as
the thickness and density of each sample of the system. Theoretical curves are calculated by the WinXCom program [8]. Fig.
2 shows the experimental and theoretical results of the mass attenuation coefficients of glass samples for different energies as
a function of BaO concentration. The behavior of the mass attenuation coefficient with composition generally increases with
increasing mole fraction of barium in glass on the expense of
Fe2 O3 Fig.2. This indicates that the addition of some BaO on
the expense of Fe2 O3 reduces the effect of the secondary γ-rays
produced from the in elastic scattering of neutrons by Fe [2, 8].
The behavior of the mass attenuation coefficients (cm2 /g)of the
present glass indicates the possibility of using these glass samples
as a substitute for lead in order to improve radiation-shielding
properties of glasses.
3.3 The half value layer (HVL)
HVL is the thickness of a material required to reduce the intensity of the emergent radiation to half. It is used to describe the
effectiveness of γ-ray shielding [9]. Fig. 3 shows the behavior
of the HVL for glasses with different amounts of BaO and different γ-energies. This figure indicates that the half value layer
(HVL) decreases with increasing mole fractions of BaO in this
glass system. This is due to the higher values of mass attenuation
coefficients and densities for glass samples.
Figure 4. The Total Atomic Cross-section (σtot ) of Glass Samples for
Different Energies
3.5 The Effective Atomic Number
The effective atomic number (Ze f f ) of the compound through the
relation [11]. A comparison is made between experimental and
theoretical values of σtot and Ze f f and it can be concluded that
the theoretical and experimental values are in good agreement
with each other within the experimental errors. The plots of
theoretical and experimental values of σtot and Ze f f are shown in
Fig.4, Fig.5.
3.6 Fast Neutron Removal Cross Section
The removal cross-section (∑ R)C of neutron fast neutron’s calculated for homogeneous mixtures [2, 12]. Fig. 6 shows the mass
removal cross-sections ∑ R as a function of BaO concentration.
The calculated values form removal cross-sections ∑ R/ρ show
that the sample contained 15BaO–15Fe2 O3 has the largest removal cross-section and the sample containing no Fe2 O3 has the
lowest one as shown in Fig. 6. Therefore, the addition of BaO
improves the removal cross section values of these glasses.
Figure 3. HVL of Glass Samples for Different Energies.
3.4 Total atomic cross-section (σtot )
The total atomic cross-section (σtot ) for glasshas been obtained
using relation [10]. The experimental and theoretical values of
σtot are compared and it is found that they are in good agreement
with each other.
Figure 5. The Effective Atomic Number (Ze f f ) of Glass Samples for
Different Energies.
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4
SOP TRANSACTIONS ON APPLIED PHYSICS
[2] N. S. H. A. Saudi, A.G.Mostafa and H.A.Sallam, Physica
B: Physics of Condensed Matter406. 2011.
[3] H. A. Saudy, S. El Mosallamy, S. U. El Kameesy, N. Sheta,
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Figure 6. Mass Removal Cross-sections ΣR/ρ (cm2 /g) for Glass
Samples.
4. Conclusions
[6] D. Corbridge and E. Lowe, “The infra-red spectra of some
inorganic phosphorus compounds,” Journal of the Chemical
Society (Resumed), pp. 493–502, 1954.
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pp. 653–654, 2004.
It can be concluded that the photon interaction of bismuth phosphate glass containing BaO, Li2 O and Fe2 O3 depends on the
photon energy, and the materials density is the main contribution in the photon attenuation coefficients which is important for
radiation shielding. The total mass attenuation of the glasses is increased with the increasing of BaO, concentration as the result of
increasing photoelectric absorption. The parameter Ze f f and σtot
are energy dependent and varies from a higher value at lower energies. The composition with15 mole% BaO is the most efficient
one for absorbing fast neutrons. I suggest that this sample with15
mole% BaO - and v is a good substitute for radiation shielding
glasses, and BaO is a good choice of candidate materials.
[10] W. Da-Chun, L. Ping-An, and Y. Hua, “Measurement of
the mass attenuation coefficients for sih¡ sub¿ 4¡/sub¿ and
si,” Nuclear Instruments and Methods in Physics Research
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References
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p. 535, 1996.
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[9] Definition of Half-value thickness from the European Nuclear Society. http://www.euronuclear.org/info /encyclopedia/h /half-value-thickness.
[12] A. S. Samuel, G., Nuclear Reactor Engineering, fourth
ed.vol. 1. 2004.
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