Paul Scherrer Institute, Laboratory for Waste Management, 5232 Villigen PSI, Switzerland.
University of Bern, Department of Chemistry, Biochemistry and Pharmaceutical Sciences & Oeschger Centre for Climate Change Research, 3012 Berne, Switzerland.
Sci Total Environ. 2022 Apr 15;817:152596. doi: 10.1016/j.scitotenv.2021.152596. Epub 2021 Dec 25.
Carbon-14 is a key radionuclide in the safety assessment of deep geological repositories (DGR) for low- and intermediate-level radioactive waste (L/ILW). Irradiated metallic wastes generated during the decommissioning of nuclear power plants are an important source of C after their disposal in a DGR. The chemical form of C released from the irradiated metallic wastes determines the pathway of migration from the DGR into the environment. In a long-term corrosion experiment with irradiated steel simulating the hyper-alkaline, anoxic conditions of a cement-based DGR, total inorganic (TIC) and organic C contents (TOC) in the liquid and gas phases (TGC), as well as individual C-bearing carbon compounds by compound-specific radiocarbon analysis (CSRA), were quantified using accelerator mass spectrometry (AMS). The AMS-based quantification allows the determination of C in the pico- to femtomolar concentration range. An initial increase in TOC was observed, which could be attributed partially to the release of C-bearing oxygenated carbon compounds. In the long term, TOC and the TIC remain constant, while TGC increases over time according to a corrosion rate of steel of 1 nm/yr. In solution, C-bearing carboxylic acids (CAs) contribute 40% to TOC, and they are the main C carriers along with C-bearing carbonate (CO). The remaining fraction of TOC ( 60%) is likely due to the presence of as yet non-identified polymeric or colloidal organic material. In the gas phase, CH accounts for more than 80% of the TGC, while only trace amounts of CO, and other small C-bearing hydrocarbons have been detected. In a DGR, the release of C will be mainly in gaseous form and migrate via the gas pathway from the repository near field to the surrounding host rock and eventually to the environment.
碳-14 是低中放废物深地质处置库（DGR）安全评估的关键放射性核素。在核电站退役过程中产生的辐照金属废物在 DGR 处置后是 C 的重要来源。从辐照金属废物中释放的 C 的化学形态决定了从 DGR 向环境迁移的途径。在一项模拟水泥基 DGR 超碱性、缺氧条件的辐照钢长期腐蚀实验中，使用加速器质谱（AMS）对液相和气相中的总无机（TIC）和有机 C 含量（TOC）以及通过化合物特异性放射性碳分析（CSRA）的单个含 C 碳化合物进行了定量。基于 AMS 的定量可以测定皮克至飞摩尔浓度范围内的 C。TOC 最初呈增加趋势，这部分归因于含 C 的氧化态碳化合物的释放。从长远来看，TOC 和 TIC 保持不变，而 TGC 随时间推移根据钢的腐蚀速率 1nm/yr 而增加。在溶液中，含 C 的羧酸（CA）占 TOC 的40%，它们是与含 C 的碳酸盐（CO）一起的主要 C 载体。TOC 的剩余部分（60%）可能是由于存在尚未识别的聚合或胶体有机物质。在 DGR 中，C 的释放将主要以气态形式存在，并通过气体途径从储存库近场迁移到周围的主岩，最终迁移到环境中。
