低放射性廢棄物最終處置將使用混凝土障壁，因營運時間長，故須針對可能遭遇不良環境探討其使用年限，本研究針對兩種障壁混凝土受到氯離子入侵可能情形進行服務年限的推算。 本研究針對可能用於製作盛裝容器(含蓋子) 配比C、封蓋之填縫材料配比M，依據ASTM C1556規範製作標準試體，於養治齡期28天、90天、183天時，將試體浸泡氯化鈉溶液36天，再以ASTM C1152量測不同齡期之混凝土濃度剖面，藉由費克第二定律衍生式，計算出表面氯離子濃度與瞬時擴散係數。並以實驗數據計算瞬時擴散係數隨時間增加而降低之速率，求取時間因子m 值，據以推算不同齡期瞬時擴散係數的變化。 研究團隊先前完成之配比HIC-C與配比HIC-M依據AASHTO T259規範製作之試體，浸泡於3%氯化鈉水溶液中，再依據AASHTO T260量測不同齡期之混凝土濃度剖面，藉由費克第二定律衍生式，計算表面氯離子濃度與擴散係數。混凝土表面氯離子濃度隨浸泡時間增加而增加，依據表面氯離子濃度與時間的自然對數關係，求出關係式推算不同歷時表面氯離子濃度，已完成四年之數據，並將結果與ASTM法所得加以比較。 依據ACI所發表程式Life-365，針對鋼筋混凝土受氯離子入侵之服務年限推估方法，發展一套計算程序，可用於推估未來處置設施其使用年限，並藉由此計算程序推估配比HIC-C與配比HIC-M濃度剖面，與四年氯離子濃度實驗數據比較，其結果相近，故此計算程序具有一定可信度，而藉由此計算程序推估盛裝容器桶壁35mm處氯離子濃度到達0.05%之時間為使用年限，所得使用年限皆超過500年。 ;The final disposal of low-level radioactive wastes will be using concrete barriers. Due to the long service time, it is likely to encounter adverse environments and thus the service life of the concrete barrier needs be explored. In this study, two concrete mixes possibly used for fabricating highly integrated containers, namely mixes C and M, were tested by ASTM C1556 standard procedures to determine their diffusion coefficient under the attack of chloride irons. The profile of chloride concentration at various depths was determined for concrete specimens at 28, 90, and 183 days of age after immersing in NaCl solution for 36 days. Then, Fick’s second law was used to obtain chloride diffusion coefficient and surface chloride content using non-linear regression technique. And the experimental data were used to estimate the change in diffusion coefficient with time for the two concrete mixes. Also, based on AASHTO T259 test method, concrete specimens immersed in NaCl solution for about 4 years were determined for their apparent diffusion coefficient. And the results obtained from the two methods were compared in the study. Finally, a computation scheme was developed to calculate the time required for chloride irons to penetrate 35 mm (approximately one-half of the thickness of containers) of the concrete barrier and reaching a concentration level of 0.05% by weight of concrete. The calculated results were compared and verified with those derived from Program Life-365, and found to be very similar. By using the computation scheme, the service life, in terms of resistance to chloride attack, of the two concrete mixes are both found to be more than 500 years.
