The Impact of Increased Waste Loading on Vitrified HLW Quality and Durability

Abstract

The Sellafield Waste Vitrification Plant (WVP) immobilises highly active liquid waste (HAL) arising from the reprocessing of spent nuclear fuel in the UK. In order to optimise WVP operations a full scale working replica of a WVP processing line, the Vitrification Test Rig (VTR), was constructed to processes non-active HAL simulants. Recently the VTR has been used to determine an operational envelope for the vitrification of HAL from Magnox reprocessing at a waste oxide incorporation rate in glass of up to 35wt% (compared to a “standard” incorporation rate of 25wt%). This paper discusses the differences in operating conditions necessary to achieve acceptable waste throughput at the increased incorporation rate. The chemical durability of the resulting vitrified product is also discussed, along with the formation of secondary phases, and a comparison is drawn between 35wt% incorporation glasses and products made at the standard 25wt% incorporation.

Uranium Retention in Silica-Rich Natural Glasses: Nuclear Waste Disposal Aspect

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Radioactive waste (RAW) conditioning, immobilization, and encapsulation processes and technologies: overview and advances

“…Joule heated melters are relatively intolerant of crystal growth in the melt which causes slag formation. [161] Recently, Sellafield has shown the ability to go to 38 wt% waste loading [162] from 25 wt% waste loading [163] by allowing spinel formation in the melt but the Sellafield melter is induction heated not a JHM design. However, 1-2% crystallization of spinels is planned for Hanford's HLW AJHM and it is anticipated that the spinel crystals will stay buoyant from the melt pool agitation afforded by the bubblers.…”

Glassy Wasteforms for Nuclear Waste Immobilization

“…Encapsulation is carried out either by deliberate dispersion of insoluble compounds into the glass melt, immiscible phase separation on cooling, or by sintering [36] £10 for fission products and minor actinide oxides.…”