Barium Sulfate Shielding Report

1. Introduction
Barium is a dense alkaline earth metal in Group IIA of the periodic table that occurs in nature as a divalent cation in combination with other elements. Gamma radiation is best absorbed by dense materials consisting of heavy atoms such as lead and barium [1]. Two commonly found forms of barium are barium sulfate and barium carbonate, often found as underground ore deposits. Shielding aprons manufactured from environmentally-friendly barium sulfate as a potential substitute for the lead aprons. Barium sulfate shielding can be processed easily to any type, with the same shielding ability as lead. Barium sulfate has long been utilized for in-vivo tests by employing the difference in density between soft tissues in radiology, and

[9] proposed a new expression for the prediction of the continuum intensity (Ik) to take into account the self absorption of Bremsstrahlung for the accurate description of the Bremsstrahlung process ------ (1)
Here, ---------- (2)
In the present work, it has been evaluated Zmod using Markowicz’s equation (2). The estimated Zmod for BaCl2, BaCO3, BaTiO3, Ba(NO3)2 and BaSO4 are 41.267, 39.116, 37.373, 36.447and 35.077 respectively.
The EB cross section for these compounds is evaluated using Lagrange’s interpolation technique, Seltzer-Berger’s [10] theoretical EB cross section data given for elements and the evaluated results of Zmod using the following expression ------- (3)
Where lower case z is the atomic number of the element of known EB cross section z adjacent to the modified atomic number (Zmod) of the compound whose EB cross section is desired and upper case Z are atomic numbers of other elements of known EB cross section adjacent to Zmod. Seltzer-Berger’s [10] theoretical EB cross section data is based on Tseng-Pratt theory[11].
The number of EB photons of energy k when all of the incident electron energy T completely absorbed in thick target is given by Bethe and Heitler [12]

Here IB and BG are internal Bremsstrahlung and background respectively. The Perspex was then placed below the target compound and the spectrum IB+BG was recorded for the same time. The difference in the two spectra gives Raw EB spectrum. Data were accumulated each time for 12 hours. From several sets of data recorded, the average of the six sets of data in the energy region 200keV to 2000keV was used for the final analysis. Liden-Starfelt procedure [13] is followed to unfold the measured into true photon spectrum S(k) which gives No. of photons per moc2 per beta,. Observed pulse height distribution were corrected for background, Dead time of analyzer, resolving power, Compton distribution, K x-ray escape gamma detection efficiency and absorption in target compound, air, aluminum can. The major error in the present measurement were statistical error; error in determining intrinsic and geometric efficiencies, Photo fraction, energy resolution of the detector, EB absorption in target compound, air, aluminum can etc,. And beta source strength. In determining these errors we have followed the methods adopted by Liden-Starfelt [13] and Shivaramu [14]. Overall error estimated to be varies between 4% to 12% from low to high energy end of the spectrum.
To determine the attenuation of EB in BaCl2, BaCO3, BaTiO3,