Development of innovative high-energy neutron and gamma-ray shielding material based on high density cement and crumb rubber

Abstract

The incorporation of carbon and hydrogen-rich material into radiation shielding material can improve its shielding performance. High-density cement mixed with crumb rubber was studied to be a gamma ray and neutron shielding material. Shielding materials were designed using high-density cement mixed with 5 – 25 vol% of crumb rubber. Monte Carlo N-Particle code was employed to simulate radiation shielding performances of the composed materials. The utilized neutron and photon sources were Am-241/Be and Co-60, respectively. These shielding designs were fabricated and experimentally evaluated on the radiation shielding properties. The cracking mechanism of high-density cement mixed with lead (HDCRL) was also investigated. The quantitative X-ray diffraction technique (QXRD) was used to determine the crystalline phases as well as elemental compositions of HDCRL. Buildup factors from gamma ray scattering, prompt and secondary gamma ray emissions from the neutron capture interaction were also evaluated. The prompt and secondary gamma ray emissions were determined using Prompt Gamma Neutron Activation Analysis (PGNAA). In addition, the mechanical properties of samples were evaluated using the Compressive Testing Machine (CTM). The high-density cement mixed with 5 vol% crumb rubber and 5 vol% lead powder demonstrated the highest neutron and gamma ray shielding performances. The neutron and photon attenuations were 64% and 68%, respectively, better than ordinary concrete. Analysis of the cracking mechanism of HDCRL revealed six crystalline phases: barite, portlandite, quartz, calcite, lead and PbO2. The weak adhesion of lead powder to high-density cement was the main cause of cracking. For photon interaction, the gamma interaction with high-density cement mixed with crumb rubber increased the buildup factor; however, the value was close to unity leading to the conclusion that the secondary gamma ray and prompt gamma ray were not present. For neutron interaction, no prompt or secondary gamma ray emission was detected using PGNAA technique. The average compressive strength indicated that the high-density cement mixed with 5 vol% crumb rubber exhibited higher strength than other specimens and that increasing the crumb rubber content decreased the mechanical property. This innovative composite radiation shielding material not only benefits nuclear science and engineering applications, but also helps solve the environmental issue of waste rubber.