Cr_2O_3对高放核废料磷酸盐玻璃固化体的影响

Effect of Cr_2O_3 on the HLW Iron Phosphate Glass Wasteforms

在含高放核废料的玻璃固化体中添加了不同含量的Cr2O3,以考察其对玻璃固化体的结构和性质的影响.对添加Cr2O3的玻璃固化体进行了各种方法(溶出速率法,蒸汽水化侵蚀和试样坚固性法)的化学稳定性的测试.测试结果表明,Cr2O3的引入不会对玻璃固化体的化学稳定性产生不良的影响.与此相反,Cr2O3能抑制各种离子自玻璃固化体中沥析出来, 改善玻璃固化体的化学耐蚀性. XRD内标法测定,Cr2O3在铁磷酸盐玻璃中的溶解度可达4.1%,是其在硼硅酸盐玻璃的3倍. FTIR和DTA的结果表明,不同含量的Cr2O3的引入, 不会对玻璃固化体的网络结构造成显著的变化. Mossbauer谱表明,Fe2+/Fe3+的比值随着Cr2O3的含量的增加而增大,说明Cr离子和Fe离子在玻璃熔制过程中发生氧化还原反应, 形成的Cr+6有利于提高玻璃固化体的化学耐蚀性.

The chemical durability, and structure of iron phosphate glasses containing 70wt% of a simulated high level nuclear waste (HLW), doped with different amounts of Cr2O3 were investigated. All of these iron phosphate glassy and crystallized wasteforms possess an outstanding chemical durability as measured by their small dissolution rate (10(-9)g/(cm(2.)min)) in deionized water at 90 degrees C for 128 days, their low normalized mass release as determined by the Product Consistency Test (PCT) and a barely measurable corrosion rate of < 0.1 g/(m(2.)d) after 7 days at 200 degrees C by the Vapor Hydration Test (VHT) can meet all current DOE requirements for chemical durability. The PCT results show that the Cr2O3 doping into IP70W samples can suppress the element release from both the glassy and crystallized samples and improve the chemical durability. The solubility limit for Cr2O3 in the iron phosphate melts estimated at 4.1 wt %, is at least 3 times larger than that for borosilicate glasses. The results from FTIR and DTA show that the structure of IP glass wasteforms has no significant changes when Cr2O3 doped into IP70W samples. Mossbauer spectra show that there is a redox reaction between Fe and Cr ions during the melting process and that the ratio of Fe2+/Fe3+ increases with the increase of Cr2O3 amount in the compositions. These Cr6+ ions formed can improve the chemical durability of the glass wasteforms.