Gamma and neutron attenuation properties of alkali-activated cement mortars

Abstract

Radiation-shielding properties of alkali-activated cement (AAC) mortar mixtures prepared using different precursors such as ground granulated blast furnace slag (GGBFS), fly ash (FA), metakaolin (MK) and waste clay material containing boron (WCB) were investigated comparatively with Ordinary Portland Cement (OPC) mixture. The gamma linear attenuation coefficients of the mixtures were determined both experimentally and theoretically. The experimental coefficients of the mixtures were measured with NaI(Tl) detection system for gamma energies of Cs-137 (662 keV) and Co-60 (1173 and 1332 keV) and the gamma transmission parameters (half-value layer, HVL; tenth-value layer, TVL and mean free path, MFP) were determined using these coefficient values. The theoretical coefficients of the mixtures were calculated using XCOM software for the energy range of 10-3000 keV. In addition, neutron attenuation coefficients of the mortar mixtures were theoretically calculated with the NCNR computation software for thermal (0.025-1 eV), slow (1-10 eV), resonance (10-300 eV), intermediate (300 eV-1 MeV) and the fast neutrons (1 MeV-20 MeV). Test results indicated that GGBFS and FA based alkali-activated cement mortars had similar gamma attenuation properties to the OPC mortar while the WCB and MK-incorporating AAC mixtures had slightly worse properties in this respect. In terms of thermal and slow neutron shielding properties only AAC mixtures containing WCB showed significantly better behaviour compared to OPC. For neutrons having higher energy levels than slow neutrons, all AAC and OPC mortar mixtures showed comparable properties.