Optimization of the heavy metal (Bi–W–Gd–Sb) concentrations in the elastomeric shields for computer tomography (CT)

Abstract

Eight elastomeric composites (NRU, GR1-GR4, NRBG08-NRBG24) containing mixtures of different proportions of heavy metal additives (Bi, W, Gd and Sb) have been synthesized and examined as protective shields. The NRU sample was a pure rubber matrix and served as a reference sample for heavy metal modified composites. Experimental procedure used for evaluation of the composite shields and their attenuation properties was based on the utilization of HPGe spectrometry and analysis of X-ray fluorescence radiation intensity of the heavy metal additives in the following energy ranges for: Sb (20-35 keV), Gd (35-55 keV), W (55-70 keV) and Bi (70-90 keV). The main contributor to the induced X-ray fluorescence radiation within the shield is Bi additive and the intensity of the X-ray radiation generated within the energy range of 70-90 keV strongly depends on its concentration. It was found that decreasing concentration of the Bi fraction from 0.35 (GR samples) to 0.15 (NRBG samples) results in significant lowering Bi X-ray fluorescence radiation within the 70-90 keV energy range. Secondary effect of decreasing Bi concentration was efficient diminishing excitation processes for lower Z heavy metal additives (W, Gd and Sb, GR vs. NRBG samples). As the final quality parameter of the shielding properties for the examined elastomers, dose reduction factor (DRF) coefficients were calculated for each shield. It was found, that the best shielding properties are observed for composites with lower Bi concentration (0.15 vs. 0.35 Bi mass fraction) with only slight further improvement of their parameters (DRF) with increasing of Gd concentration (Gd mass fraction 0.08, 0.16 and 0.24). The most efficient dose reduction composite was found to be NRBG24 elastomer with DRF value 0.47 (53 % dose reduction) for ca. 2 mm and 0.44 g/cm 2 layer thickness.

Effect of Tungsten concentration on the thermal properties of Ethylene Propylene Diene Monomer (EPDM) composite

“…In this regard, the preparation of flexible and light materials that efficiently protects radiation workers and the environment become a research effort [15]. E. Kusiak prepared the EPDM composites filled with selected fillers as radiation shielding substance [16]. Jaewoo K. offered a kind of polymer composites which were prepared by dispersing Tungsten nanoadditives into ethylene-propylene-based polymer combination using melt mixing and the attenuation of gammas for the composites was enhanced up to 75 % for Ba-133 (0.3 MeV) [17,18].…”

Klein Nishina Differential Equation for the Selection of Radiation Shielding Material (C, AL, Fe, and Zn) on the Basis of Attenuation and Cross sectional Area

“…Therefore, researchers and scientists are working to replace lead with bismuth, tungsten, barium, tin, cerium, and antimony. This is due to process the material into a thin film, a base material with excellent flexibility is preferred [11][12][13][14][15]. The energy of photons like X-rays and gamma rays is shield with the lower the atomic number with minimal thickness.…”

Analysis of the Correlation between Shielding Material Blending Characteristics and Porosity for Radiation Shielding Films

“…Currently, researchers are developing medical radiation shielding products using new materials that can substitute lead, which is heavy, causes human poisoning, and requires the processing of hazardous waste [1][2][3]. Bismuth, tungsten, barium, tin, cerium, and antimony are mainly used as shielding materials instead of lead [4]. Because it is desirable to process the material into a thin film, a base material with excellent flexibility is preferred.…”