本研究針對放射性廢棄物深層處置場近場障壁工程中，探討近場環境中可能影響緩衝材料回脹性質的各種因素，包含當處置場封閉後初期地下水尚未入侵，緩衝材料無水狀態下遭受高溫作用之土壤粉末乾燥加熱、地下水入侵後形成水熱環境系統、高放射性廢棄物輻射照射造成緩衝材料劣化之粉末輻射照射處理、深層地下水入侵造成含鹽水溶液系統、膨潤土與混凝土反應使pH值提升及試體的尺寸效應等。 本研究試驗材料為台東樟原的日興土，試驗結果顯示(1) 100℃乾燥加熱對回脹行為沒有影響，200℃以內乾燥加熱的試體回脹應變量大幅下降，300℃~400℃乾燥加熱的試體回脹行為呈不規則變化趨勢；(2)日興土回脹應變量隨水熱溫度提昇而降低；(3)經輻射照射後日興土之回脹應變量略為降低；(4)含鹽溶液回脹應變量隨著濃度增加而降低；而在NaCl溶液中日興土最大回脹應變量皆高於CaCl2溶液中；(5)日興土的回脹應變量受溶液系統pH值影響，在pH=13時，日興土回脹應變量大幅提昇。 Compacted bentonites are attracting greater attention as buffer material for deep geological repository of high-level radioactive waste. Swelling behavior is a significant property of buffer material in achieving the self-healing function. The swelling behavior of buffer material will be affected by near-field environment, including decay heat, radiation, groundwater intrusion, and pH evolution, etc. To find out the impact on swelling behavior, several scenarios expected in the near-field were considered in this research work, including heat treatment, hydrothermal temperature, radiation, saline solution, and pH effect. The buffer material used was Zhisin clay produced from the eastern coast of Taiwan. Experimental results show that: (1) swelling behavior is not affected by thermal treatment temperature under 100℃, but the swelling strain decreases as Zhisin clay was heated up to 200℃, while the swelling strain varied irregularly at heating temperature greater than 300℃; (2) the swelling strain of Zhisin clay decreases with increasing hydrothermal temperature; (3) radiation causes reduction in swelling strain of Zhisin clay; (4) the swelling strain decreases with increasing electrolyte concentration, and the swelling strain of Zhisin clay in NaCl solution is higher than that in CaCl2 solution; (5) the swelling strain of Zhisin clay is affected by pH of the inundating solution, at pH=13, the swelling strain of Zhisin clay increases markedly.
