LOW-RISK WASTE FORMS TO LOCK UP HIGH-LEVEL NUCLEAR WASTE

摘要

The highest cost component of DOE's clean up challenge centers on high-level waste (HLW) and consequently the greatest opportunity for cost and schedule savings lies with optimizing the approach to HLW cleanup. Synroc synrocANSTO’s ANSTO’s low-risk tailored alternative waste forms offer overall cost and processing schedule savings worth billions of dollars via: ? higher waste loadings (fewer disposal canisters); ? enhanced chemical durability (lower environmental risk); ? greater processing flexibility; ? lower off-gas emissions. The waste form is the key component of the immobilization process. To achieve maximum cost savings and optimum performance the selection of the waste form should be driven by the characteristics of nuclear waste to be immobilized rather than adopting a single baseline approach. The use of tailored, high-performance, alternative waste forms that include ceramics and glass-ceramics, coupled with alternative mature process technologies, such as hot-isostatic pressing, sintering and cold-crucible induction melting, offer significant performance improvements and efficiency savings to the cleanup program for wastes difficult to incorporate in glass. It is the waste form that determines how well the waste is locked up (chemical durability), and the number of disposal canisters required (waste loading efficiency). The use of tailored waste forms for problematic wastes also lowers the overall risk of the DOE’s accelerated cleanup challenge by providing high performance HLW treatment alternatives. The benefits tailored ceramic and glass-ceramic waste forms bring to the accelerated HLW cleanup program will be briefly reviewed with reference to the following three examples; INL sodium bearing waste (SBW) and HLW calcines, actinide-rich waste streams and niche wastes containing technetium, cesium and strontium. Benefits include glass ceramic matrices for the majority of INL HLW calcine that offer waste loadings of at least 90%, volume reductions of 45%, whilst maintaining chemical durability better than environmental assessment (EA) glass.