| dc.description.abstract | Granitoid is generally believed to be a good repository for the nuclear waste diposal. However, the heat release from decay of the nuclear waste could combine with the groundwater and cause physical and chemical changes in the mineral phases of the granitic body. These changes may result in occurrence of crack and increase the crack of the granitic body, which could raise the probability of leaking of nuclear species. The Tianpu granite located at East Kimen is an idea experimental material and was used in this study. Samples were soaked in different solutions separately under two temperatures of 60 ℃ and 90 ℃. For practical purposes, the solution with pH value of 3, 5, 9, 11 were used in the experiments. Additionally, the sea water and the RO water were also used. Specimens were removed from the hot water bath each time after 5, 10, 20, 40, 80, 120 days of immersion. The method to monitor the mineralogical and chemical transformation of the granite samples in this study included petrographical and fluorescent microscopy, XRD, SEM and ICP-AES. Beside, the changes of samples weight, pH value of solutions were investigated during the immersion period.
The results showed that solutions of pH5, RO water and pH9 were readily neutralized within 20 days after experiment began. Dissolution rate at 90 ℃ condition is higher than at 60 ℃ condition. Likewise, the acidity increase of solutions caused higher dissolution rate. The concentrations of Na, Ca and Si were mainly reflected the dissolution from plagioclase. The Fe, Mg, K and Si were released from biotite. The K and Si were derived from K-feldspar, and minor content of Si were dissolved from quartz. During the immersion test up to 10 days, the density of flowable crack in the granite samples immersed in the solution of pH3, pH11 and seawater were increased. Later, density of flowable crack decreased during immersion up to 120 days in the sea water and the solution of pH11. The results indicated that acid solution adverse to the safety of the nuclear waste repository. In the XRD result, no secondary mineral can be found. | en_US |