硅酸盐学报

以在美国Washington州Hanford市存放的17类不同组成的高放射性核废料(highlevelradioactivenuclearwaste,HLW)为研究对象,设计了含Cr2O3为4%(质量分数,下同)的模拟HLW。采用25%～35%磷酸盐与含Cr2O3的65%～75%的HLW模拟组成相混合,经1150～1250℃加热处理数小时,能熔化成为均质玻璃体,然后冷却成固化体。用试样坚固法(productconsistencytest,PCT)测试包容70%和75%HLW的2种玻璃固化体的各元素,在90℃放置7d,元素沥析量总和分别为小于1.5g/m2和2.0g/m2。用蒸汽水化侵蚀法(vaporhydrationtest,VHT)对此2种试样在200℃的水蒸汽中进行水化侵蚀,经7d处理,平均被侵蚀的速率分别小于0.2g/(m2·d)和3.5g/(m2·d)。晶化处理后的此2种试样的PCT和VHT测试结果与晶化前基本相近。对HLW不同包容量的玻璃固化体的红外光谱分析表明:在较高的HLW包容量的玻璃固化体的结构中,容易被水化的(PO3)-结构转化为分离的(P2O7)4-或(PO4)3-。X射线衍射分析表明:玻璃固化体中分离的(P2O7)4-和(PO4)3-阴离子团被金属离子Al3+,Fe3+,Cr3+和Zr4+等所连接,形成O—Me—O—P键,不仅提高了玻璃的抗析晶的能力,而且也大大地提高了其化学稳定性。样品O/(Si+P)的摩尔比为3.7～4.1,从结构上也表明核废料包容量高达70%～75%的玻璃固化体有优良的

A simulated high level radioactive nuclear waste (HLW) containing 4% (in mass, the same below) chrome oxide, which represents 17 clusters of the high chrome oxide waste stored at Hanford Washington, USA, was designed. The homogeneous phosphate glass was obtained by melting the mixture of 65%—75% of the simulated HLW with 25%―35% of iron phosphate(IP) . The batches can be melted into homogeneous phosphate glass at the temperature of 1 150—1 250 ℃ for a few hours and cooled to form the glass westeforms.. The glass wasteforms have excellent chemical durability. The total elemental mass releases at 90 ℃ within the 7 d determined by product consistency test (PCT) for two glassy wasteforms that contained 70% and 75% of simulated HLW, are less than 1.5, 2.0 g/m², respectively. The average corrosion rates within 7 d at 200 ℃, for these two glassy wasteforms are less than 0.2, 3.5 g/(m²·d), respectively determined by vapor hydration test(VHT). The PCT and VHT values for two samples are not changed significantly by crystalline treatment. The glass structure of wasteforms was analyzed by FTIR, and the results show that the structure unit is changed from (PO₃)~- groups of P—O—P bond, which is easy to be hydrated, into isolated (P₂O₇)^4- or (PO₄)^3- groups with the increase of HLW waste loading in IP glass. XRD reveals that the ions such as Al³⁺, Fe³⁺, Cr³⁺ and Zr⁴⁺ in the intermediate metal oxide can be connected with the isolated (P₂O₇)^4- or (PO₄)^3- groups to form the O—Me—O—P bonds, which improved the resistant ability of crystallization and enhanced the chemical durability. The molar ratio of O/(Si+P) between 3.7 to 4.1 of the samples also proofs the excellent chemical durability of the glass wasteforms with high HLW waste loading of 70%—75% from the structure aspect.