Advanced Fuel Cycle Development, Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong-gu, Daejeon 305-353, Korea.
Environ Sci Technol. 2011 Mar 1;45(5):1932-9. doi: 10.1021/es1029975. Epub 2011 Feb 2.
In the radioactive waste management, metal chloride wastes from a pyrochemical process is one of problematic wastes not directly applicable to a conventional solidification process. Different from a use of minerals or a specific phosphate glass for immobilizing radioactive waste salts, our research group applied an inorganic composite, SAP (SiO(2)-Al(2)O(3)-P(2)O(5)), to stabilize them by dechlorination. From this method, a unique wasteform composing of phosphate and silicate could be fabricated. This study described the characteristic of the wasteform on the morphology, chemical durability, and some physical properties. The wasteform has a unique "domain-matrix" structure which would be attributed to the incompatibility between silicate and phosphate glass. At higher amounts of chemical binder, "P-rich phase encapsulated by Si-rich phase" was a dominant morphology, but it was changed to be Si-rich phase encapsulated by P-rich phase at a lower amount of binder. The domain and subdomain size in the wasteform was about 0.5-2 μm and hundreds of nm, respectively. The chemical durability of wasteform was confirmed by various leaching test methods (PCT-A, ISO dynamic leaching test, and MCC-1). From the leaching tests, it was found that the P-rich phase had ten times lower leach-resistance than the Si-rich phase. The leach rates of Cs and Sr in the wasteform were about 10(-3)g/m(2)· day, and the leached fractions of them were about 0.04% and 0.06% at 357 days, respectively. Using this method, we could stabilize and solidify the waste salt to form a monolithic wasteform with good leach-resistance. Also, the decrease of waste volume by the dechlorination approach would be beneficial in the final disposal cost, compared with the present immobilization methods for waste salt.
在放射性废物管理中，高温冶金法产生的金属氯化物废物是一种难以直接应用传统固化方法处理的问题废物。与利用矿物或特定磷酸盐玻璃固化放射性废物盐不同，我们的研究小组应用无机复合材料 SAP（SiO2-Al2O3-P2O5）通过脱氯来稳定它们。通过这种方法，可以制备出一种由磷酸盐和硅酸盐组成的独特废物。本研究描述了废物形态、化学耐久性和一些物理性质的特征。废物具有独特的“域-基质”结构，这归因于硅酸盐和磷酸盐玻璃之间的不兼容性。在较高量的化学结合剂下，“富硅相包裹富磷相”是主要形态，但在较低量的结合剂下，其形态变为富磷相包裹富硅相。废物中的域和亚域尺寸分别约为 0.5-2 μm 和数百纳米。通过各种浸出试验方法（PCT-A、ISO 动态浸出试验和 MCC-1）确认了废物的化学耐久性。从浸出试验中可以发现，富磷相的浸出阻力比富硅相低十倍。废物中 Cs 和 Sr 的浸出率约为 10(-3)g/m(2)·day，在 357 天分别约为 0.04%和 0.06%。通过这种方法，我们可以稳定和固化废物盐，形成具有良好浸出阻力的整体废物。此外，与目前的废物盐固化方法相比，脱氯方法减少废物体积有助于降低最终处置成本。
