Effect of Stainless Steel Can/Glass-ceramic Interaction Layer on Aqueous Durability
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0985-NN04-07
Effect of Stainless Steel Can/Glass-ceramic Interaction Layer on Aqueous Durability Peter J. McGlinn, Yingjie Zhang, Huijun Li, and Timothy E. Payne Australian Nuclear Science & Technology Organisation, New Illawarra Road, Lucas Heights, Australia
ABSTRACT Calcined high-level radioactive waste (HLW) stored at the Idaho National Laboratory (INL) will eventually be immobilised in a suitable wasteform before disposal. A tailored glass-ceramic wasteform, produced by hot isostatic pressing (HIPing) in stainless steel (SS) cans, has been developed at the Australian Nuclear Science & Technology Organisation (ANSTO) as a costsaving alternative to glass which would improve waste loading and density, and reduce waste volume. We have studied the SS/wasteform interactions under HIPing conditions to understand whether such interactions would have any detrimental effect on long-term wasteform stability. This has been demonstrated by carrying out aqueous durability tests, under near-neutral and alkaline conditions, on the wasteform at the interaction layer, and on the wasteform distal to this reaction edge. Reaction during HIPing resulted in verifiable Cr diffusion from the can wall into the wasteform, yet without any detectable detrimental impact on the HIP can or the aqueous durability of the wasteform. INTRODUCTION About 4400 m3 of calcined high-level radioactive waste (HLW) is currently stored at the Idaho National Laboratory (INL) in the USA. This waste was generated at the Idaho Chemical Processing Plant from the reprocessing of irradiated defence nuclear fuel. The calcine composition varies considerably, but the majority consists primarily of CaF2 (50 wt%) and oxides of Al, Zr and B (50 wt%). The radionuclide content is generally less that 1 wt% and consists of typical 235U fission products [1]. The calcined waste will eventually be immobilised in a suitable wasteform before being sent to a Federal repository. Typical glass wasteforms would result in large volumes of immobilised waste due to their relatively low waste loadings (~30 wt%) for the calcined waste. A tailored glass-ceramic wasteform was therefore developed at ANSTO as a cost-saving alternative which would increase the waste loading to ~80 wt%, achieving ~25% greater density and ~65% less immobilised waste volume than a glass wasteform [2,3]. Hot Isostatic Pressing was selected by ANSTO for the production of the glass-ceramic because of its flexible processing environment and extremely low off-gas emissions due to the calcine and precursor components being sealed in SS cans prior to consolidation. We have studied the SS/glass interactions under HIPing conditions to understand whether such metal/glass interactions would have any detrimental effect on long-term wasteform stability. In this paper we report on the characterisation of the SS/glass interaction layer and whether the leaching properties of this layer differ from samples distal to this layer i.e. away from the reaction edge. For the purposes of this paper the specimens representing the inte
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