Studies on Performance Characteristics of Hydrogen Loaded Concrete Mixes

Abstract

In many nuclear installations like particle accelerators and medical cyclotrons, concrete has been used as a radiation shield due to its gamma and neutron radiation shielding capabilities. The gamma radiation shielding properties of concrete mixes are found to be enhanced by using high density ingredients. It has been professed that the neutron radiation shielding properties can be enhanced by use of ingredients containing higher amounts of lighter elements like hydrogen and boron. In the present work, attempts are made to use alternative materials as additional hydrogen sources within the concrete mixes and evaluate their effectiveness in enhancing the neutron radiation shielding properties. In the first phase, commercially available Styrene Butadiene Rubber (SBR) latex was used to produce latex modified concrete mixes and their neutron shielding capabilities were evaluated. It is observed that the latex modified mixes showed enhanced neutron shielding capabilities reflected in terms of lower dose transmission values vis- à-vis a control concrete mix. In the second phase, pulverized high density polyethylene (HDPE) was used as a partial replacement (replacement in the range of 30-50% by volume) to the fine aggregate fraction of the concrete mix. It was necessary to proportion these mixes as a class of self compacting concrete mixes so as to restrict the segregation behavior of the polymeric particles, in such Polymer Incorporated Self Compacting Concretes (PISCC) mixes. The segregation characteristics of PISCC mixes are found to be within allowable limits, their fresh properties and the mechanical strength properties are satisfactory. It is found that such PISCC mixes have significantly improved neutron shielding performances. Though there are improvements in the attenuation of neutron flux, the PISCC mixes are in particular, more effective in reducing the neutron dose rates. In the final phase, efforts were made to incorporate high density aggregates (both fine and coarse) so as to enhance the shielding properties and produce highly flowing concrete mixes. The maximum polymer replacement was retained; high density fine and coarse aggregates and a small amount of borax were added. Based on the detailed experimental investigations, recommendations are made to design such class of mixes so as to have good slump flows (> 400mm) and better segregation resistance characteristics. The studies on neutron radiation shielding characteristics indicated greater improvements in the shielding properties with a maximum of 12.7% reduction in half value layer (HVL) thickness for neutron radiation. The gamma radiation shielding studies of these mixes have also indicated significant improvements with a maximum of 13.7% reduction in HVL thickness.