Experimental investigations on the thermal properties of Jalore granitic rocks for nuclear waste repository

Abstract

The main objective of this study is to analyze the thermo-physical properties of the potential host rock (golden, red, white and black Jalore granitoid) for the construction of a nuclear waste repository in India. The thermal properties of Jalore granitic rocks were determined using the transient plane source (TPS) technique in the temperature range from 25 °C to 250 °C. The dilatometric tests for thermal expansion and the thermal strain were carried out. The results indicate that the thermal conductivity, thermal diffusivity, mass loss and elastic wave velocity of Jalore granite decreases gradually as the temperature increases from 25 °C to 250 °C. The thermal expansion increases with the increasing temperature, and there is a good exponential growth relation between temperature and thermal strain. Additional laboratory tests including thermogravimetric (TG) and differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscope (SEM) have also been conducted to investigate the temperature evolution inside the rock specimens. The results show that the feldspars have a low and isotropic thermal expansion that do not affect the molecular structure as much in red and white granite, while on the other hand, thermal stresses are confined in quartz crystal, resulting in intense intragranular cracking for golden and black granite. This research in terms of measurement of thermal parameters subjected to below damage threshold temperature (≥ 250 °C) as well as the method of analyzing the results are novel for primary importance for the construction of nuclear waste repository applications in Jalore granitoid.