Using steel slag and two types of (soft and hard) iron slags, ten samples were prepared. Different gamma radiation interaction parameters were computed theoretically and measured experimentally at different energies: 60 keV, 136 keV, 662 keV, 1173 keV and 1332 keV in low and medium energy range using narrow transmission geometry. It has been observed that shielding effectiveness of a sample is inversely proportional to Half Value Layer (HVL). The obtained results were compared with Pure Flyash and it was observed that slag is better aggregate than flyash in shielding radiation as well as in construction applications. The results have been presented in the form of tables and graphs with more useful conclusions.
Gamma radiation interaction is the most accurate, convenient and a non destructive method of determining the various characteristics of the material. With increasing the use of radioactive isotopes and applications of radiations in many fields such as industry, agriculture, medicine, technology and research, there seems a need to study in depth gamma ray analysis of every material. Gamma ray interaction depends on the extent of absorption or scattering, incident energy, nature of the target material and also on the geometrical conditions. The knowledge of gamma ray interaction parameters [
Effective atomic number (Zeff) is another useful important parameter for a composite material. It measures the effect of chemical composition, atomic number as well as abundance of each element in the sample. Therefore, effective atomic number [
Electron density (electron/g) and half value layer (HVL) are two other useful parameters for understanding the interaction of gamma ray. The degradation or attenuation of gamma rays are directly related with electron density [
On the basis of these computed and measured interaction parameters, an attempt has been made and it is proposed to use iron and steel slags for the shielding of nuclear radiation in preference to flyash.
A parallel beam of monochromatic radiation is attenuated in matter, its intensity decreases from I0 to I according to Lambert-Beer law
where ρ is density and x is thickness of the material. μ (cm−1) is linear attenuation coefficient. Equation (1), can be written as,
where
For a composite material,
where
This is another important parameter for the interpretation of attenuation of radiation by composite materials. As atomic number is not constant for different interaction processes in different energy regions, the various atomic numbers of elements present in the sample have to be weighted differently. The effective atomic number, (Zeff), can be defined through the following relations;
The total molecular cross-section
where
The total atomic cross-section
The total electronic cross-section
where
where
Electron density is defined as number of electrons per gram in the material. It can be determined from the following relations;
where
The atomic cross section and mass attenuation coefficient (
In an attenuating medium, half value layer (or half thickness) is defined as the thickness of any material which can reduce the intensity of incident gamma ray beam to one half of its original value.
HVL is related to the linear attenuation coefficient μ (cm−1) by the following relation
It is measured in units of length.
Both Steel slag and Iron slags materials are by product of steel and iron industries respectively. Steel slag is taken from Modern Steel plant, situated at Mandi Gobindgarh whereas Iron slags (soft and hard type) have been collected from factories situated in local industrial area of Patiala. Large production and cheap availability of these materials pose a serious threat to our environment. That is why present work is undertaken and an attempt has been made to study the intensity of gamma radiation with the mixture of Steel slag (SS) and Iron slag with an intent to investigate the possibility of their utilization and disposal [
The test specimens were prepared according to specifications Bureau of Indian Standards. First, these materials were crushed and grinded separately so as to get powdered form. Both types of iron slags (soft and hard) are mixed together in equal proportions to get what may be called Mixed Iron Slag (MIS). Then steel slag is replaced by 0%, 10% 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% in Mixed Iron Slag content by weight. The materials were weighed accurately and mixed properly. Cube moulds were filled with these mixtures and kept for 48 h in a casting room at a temperature of 25˚C after which they were demoulded. The prepared ten samples were named as IS0, IS1, IS2, IS3, IS4, IS5, IS6, IS7, IS8 and IS9. A Pure flyash sample is also prepared for comparing results.
The chemical composition of Steel slag and MIS was determined by Energy dispersive X ray analysis (EDX) available at Thapar University, Patiala. The weight percentage of different elements present in Steel slag-Iron mixtures are shown in
Narrow beam y-ray transmission geometry was used for the attenuation measurements of prepared specimens. The experimental setup of geometry is shown in
WEIGHT PERCENTAGE | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|
ELEMENT | IS0 | IS1 | IS2 | IS3 | IS4 | IS5 | IS6 | IS7 | IS8 | IS9 |
CARBON | 10.59 | 9.53 | 8.47 | 7.42 | 6.35 | 5.30 | 4.24 | 3.18 | 2.12 | 1.06 |
OXYGEN | 44.69 | 43.77 | 42.84 | 41.92 | 40.99 | 40.07 | 39.15 | 38.22 | 37.30 | 36.37 |
MAGNESIUM | 0 | 3.68 | 0.82 | 1.23 | 1.64 | 2.05 | 2.45 | 2.86 | 3.27 | 3.68 |
ALUMINIUM | 0.77 | 1.35 | 2.10 | 2.76 | 3.42 | 4.08 | 4.75 | 5.41 | 6.07 | 6.74 |
SILICON | 3.76 | 4.42 | 5.07 | 5.73 | 6.38 | 7.07 | 7.69 | 8.35 | 9.00 | 9.66 |
CALCIUM | 0 | 1.81 | 3.61 | 5.42 | 7.23 | 9.04 | 10.84 | 12.65 | 14.46 | 16.26 |
CHROMIUM | 0 | 0.09 | 0.19 | 0.28 | 0.37 | 0.47 | 0.56 | 0.65 | 0.744 | 0.84 |
MANGANESE | 0.76 | 2.69 | 1.05 | 1.20 | 1.35 | 1.50 | 1.64 | 1.79 | 1.94 | 2.08 |
IRON | 39.44 | 37.58 | 35.73 | 33.87 | 31.95 | 30.16 | 28.35 | 26.44 | 24.58 | 22.73 |
ZINC | 0 | 0.59 | 0.13 | 0.20 | 0.26 | 0.33 | 0.39 | 0.46 | 0.52 | 0.56 |
ELEMENTS | OXYGEN | ALUMINIUM | SILICON | POTASSIUM | CALCIUM | IRON | COPPER | ZINC |
---|---|---|---|---|---|---|---|---|
WEIGHT%AGE | 46.3 | 13.79 | 26.74 | 1.33 | 1.00 | 5.71 | 2.46 | 2.67 |
collimator was 40 mm. The prepared samples were cubes of each side 5 cm. Samples were positioned on specimen holder at a distance of 290 mm from the source. The distance between source and detector was held at 585 mm. The detector was surrounded with proper lead shielding so as to prevent the scattered radiations from nearby objects reaching the detector. The total scatter acceptance angle (θsc) [
The model 802 scintillation detector of 3 × 3 NaI(Tl) type was used in the study. It was enclosed in a hermetically sealed assembly which includes a high resolution NaI(TI) crystal, a PMT with a pre-amplifier, an internal magnetic/ light shield, an aluminium housing and a 14-pin connector. The reliability and stability of the geometrical setup was tested using aluminium as a reference absorber at 662 keV. The spectrum was recorded for sufficient long time so as to reduce statistical error in counts less than 0.3%. The best resolution 7.5% was obtained for the 662 keV gamma ray from Cs-137 source. The background counts recorded for the same time were subtracted from each spectrum. To stop the fluorescence X-rays of lead entering in the detector, the lead shield was lined on the inside and with brass and aluminium sheets outside. The experiment was conducted at constant low temperature to avoid shifting of spectrum peak.
The incident (Io) and transmitted (I) y-ray intensities have been measured for experimentally determining the values of mass attenuation coefficients of specimens. The experimental values of mass attenuation coefficient obtained using Equation (1) are enlisted in
SAMPLE | 60 KeV | 136 KeV | 662 KeV | 1173 KeV | 1332 KeV | |||||
---|---|---|---|---|---|---|---|---|---|---|
Exp. | Theo. | Exp. | Theo. | Exp. | Theo. | Exp. | Theo. | Exp. | Theo. | |
IS0 | 0.600 | 0.601 | 0.176 | 0.174 | 0.0758 | 0.0757 | 0.0584 | 0.0574 | 0.0547 | 0.0538 |
IS1 | 0.598 | 0.599 | 0.176 | 0.174 | 0.0758 | 0.0757 | 0.0586 | 0.0574 | 0.0550 | 0.0538 |
IS2 | 0.589 | 0.590 | 0.171 | 0.173 | 0.0759 | 0.0758 | 0.0579 | 0.0574 | 0.0541 | 0.0538 |
IS3 | 0.584 | 0.585 | 0.174 | 0.173 | 0.0759 | 0.0758 | 0.0576 | 0.0575 | 0.0533 | 0.0539 |
IS4 | 0.582 | 0.579 | 0.171 | 0.172 | 0.0758 | 0.0759 | 0.0578 | 0.0575 | 0.0535 | 0.0539 |
IS5 | 0.577 | 0.574 | 0.171 | 0.172 | 0.0760 | 0.0759 | 0.0565 | 0.0576 | 0.0537 | 0.0539 |
IS6 | 0.564 | 0.569 | 0.172 | 0.171 | 0.0761 | 0.0760 | 0.0565 | 0.0576 | 0.0531 | 0.0540 |
IS7 | 0.558 | 0.563 | 0.170 | 0.171 | 0.0761 | 0.0760 | 0.0563 | 0.0576 | 0.0528 | 0.0540 |
IS8 | 0.556 | 0.557 | 0.172 | 0.171 | 0.0762 | 0.0761 | 0.0566 | 0.0577 | 0.0530 | 0.0541 |
IS9 | 0.551 | 0.552 | 0.169 | 0.170 | 0.0762 | 0.0761 | 0.0567 | 0.0577 | 0.0530 | 0.0541 |
where t is the sample thickness in centimetres, and are the errors in the intensities Io, I, density and thickness t of the sample respectively. It was found that the estimated error in experimental measurements was less than 3.7%. The experimental results are in good agreement with the theoretical results within estimated errors.
The linear attenuation coefficient μ (cm−1) is shown graphically as a function of given photon energies in
For the (MIS + SS) specimens, effective atomic numbers have been determined from the mass attenuation coefficients. The obtained values of effective atomic numbers are shown graphically in
SAMPLE | 60 KeV | 136 KeV | 662 KeV | 1173 KeV | 1332 KeV | |||||
---|---|---|---|---|---|---|---|---|---|---|
Exp. | Theo. | Exp. | Theo. | Exp. | Theo. | Exp. | Theo. | Exp. | Theo. | |
IS0 | 4.24 | 4.17 | 3.26 | 3.28 | 2.93 | 2.94 | 2.93 | 2.98 | 2.93 | 2.97 |
IS1 | 4.24 | 4.24 | 3.25 | 3.27 | 2.96 | 2.95 | 2.95 | 3.02 | 2.95 | 2.99 |
IS2 | 4.23 | 4.22 | 3.24 | 3.26 | 2.95 | 2.94 | 2.95 | 2.96 | 2.95 | 2.97 |
IS3 | 4.21 | 4.14 | 3.23 | 3.25 | 2.96 | 2.95 | 2.95 | 2.96 | 2.93 | 2.92 |
IS4 | 4.20 | 4.21 | 3.24 | 3.22 | 2.96 | 2.95 | 2.95 | 2.98 | 2.95 | 2.94 |
IS5 | 4.19 | 4.03 | 3.24 | 3.23 | 2.96 | 2.98 | 2.95 | 2.91 | 2.94 | 2.93 |
IS6 | 4.18 | 4.06 | 3.26 | 3.27 | 2.97 | 2.99 | 2.96 | 2.93 | 2.95 | 2.92 |
IS7 | 4.17 | 4.02 | 3.28 | 3.26 | 2.97 | 2.98 | 2.96 | 2.92 | 2.96 | 2.91 |
IS8 | 4.15 | 4.08 | 3.30 | 3.31 | 2.96 | 2.96 | 2.95 | 2.91 | 2.95 | 2.90 |
IS9 | 4.14 | 4.14 | 3.23 | 3.21 | 2.96 | 2.97 | 2.95 | 2.90 | 2.95 | 2.91 |
of Zeff with variation in steel slag content at given energies (60, 136, 662, 1173, 1332 KeV) is same as that of μm or μ (cm−1). With the increase in steel slag content, effective atomic numbers of specimens do not change much. The present results are in line with the results of Lingam et al. (1984), Parthasaradhi (1968) and Modi et al. (1991) in the covered energy region. In the energy region of 662 to 1332 KeV, the values of effective atomic number are almost constant which is also in line with the viewpoint of El-Kateb and Abdul Hamid.
The computed electron density values using Equation (4) are shown in
The values of half value layer (HVL) of the prepared specimens were computed using Equation (5) and are shown graphically in
From the obtained results, it is observed that, half value layer increases with increase in energy and with decrease in steel slag content. To assess the shielding ability [
Both slags are environmentally hazardous materials and are being produced in huge amounts every day. So, their utilization and disposal is a matter of serious concern. Taking into consideration their attenuation abilities, these materials can be used for radiation shielding if properly compacted or admixed with concrete. Slag mixed concretes are most suitable especially where huge structures are required e.g., Nuclear reactors, Underground bunkers for protection against Nuclear experiments or testing Nuclear weapons etc. These structures become
more durable, economical as well as eco-friendly when slags are used in concretes. The reason is that concrete develop micro-cracks due to higher level of hydration and porosity. Also, variation in composition and large water content leads to decrease of density and structure strength of concretes. As slags contain silica, which converts free lime present in concretes into insoluble calcium silicate hydrates that decreases heat of hydration, thereby reducing cracks in concretes. It also provides strength to concretes at later ages.
The performance of a concrete radiation shield with slags is improved effectively. Though, flyash is also used as an aggregate in making radiation shields its density is far less than slag. Thus, effective attenuation ability of slag is more than that of flyash. The comparison of gamma ray shielding properties of steel slag + iron slag mixtures with Pure Flyash at various gamma ray energies shows that the mixtures are more suitable than Pure Flyash in shielding gamma radiations. Keeping in view these facts and their utilization, steel slag + iron slag mixture is more appropriate for making shields as well as in other construction activities.
Singh, R., Singh, S., Singh, G. and Thind, K.S. (2017) Gamma Radiation Shielding Properties of Steel and Iron Slags. New Journal of Glass and Ceramics, 7, 1-11. http://dx.doi.org/10.4236/njgc.2017.71001