低放射性廢棄物最終處置場混凝土工程障壁目的為阻絕低放廢棄物內核種外釋，使其與人類生活環境長期隔離。低放射性廢棄物中主要核種銫及鍶，其半衰期約30年，須經10個半衰期，廢棄物中核種的濃度才會降到可被忽略的程度，因此低放廢棄物工程障壁之服務壽命至少應在300年以上。由於混凝土工程障壁在處置場服務期間內可能遭受環境因素及接觸物質影響而產生劣化，降低其耐久性。因此，必須充分考量混凝土在最終處置環境中可能發生的各種劣化機制。本研究利用實驗室實驗模擬取得各種劣化機制作用於混凝土的影響程度，依各種劣化作用建立各單一劣化之預估模式，同時依據美國國家標準署(NIST)所發展之混凝土劣化預測模式進行深入模擬研究，並根據對單一劣化機制的掌握與瞭解，將NIST所發展的預測模式加以修正，成為適合臺灣地區環境特性之工程障壁劣化預估模式，供未來低放射性廢棄物最終處置場混凝土工程障壁設計及安全評估之依據。 Engineering barrier for the final disposal of low-level radioactive wastes serves to isolate the wastes from human biosphere for a very long design life. Concrete has been widely accepted as engineering barrier material due to its longevity, which provides good structural integrity for prolonged service life. The half life of 137Cs and 90Sr, the 2 major radio nuclides in low-level wastes, is about 30 years. It is estimated that the radioactivity of these nuclides would decay to a level that is comparable to the background. Hence, concrete material is expected to serve at least 300 years in the final disposal site. However, the adverse environmental conditions at the disposal site could attack concrete barrier material and results in degradation of the material. It is necessary to investigate the possible degradation mechanisms that would occur to the concrete barrier at the disposal site, such that an analytical model capable of evaluating the synergism effects be developed. The degradation process of concrete material under simple adverse environment has been studied by many researches so far. Study on the synergism effects resulting from multi-degradation processes is the focus of this research project. Based on the service life prediction model developed by National Institute of Standards and Technology (NIST), this study aims to develop a prediction model for the safety evaluation of concrete barrier material for applications to final disposal of low-level radwastes. Modifications will be made on the NIST prediction model, such that the model can be adapted to the environmental characteristics in Taiwan. The prediction model developed will be used in the review processes of barrier design for the low-level radwastes disposal site. 研究期間 : 9801 ~ 9812
