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TitleCementitious grouts for disposal of nuclear wasteforms in deep boreholes
Publication TypeConference Paper
Year of Publication2015
AuthorsCollier, N.C., Travis K.P., Gibb F.G.F., and Milestone N.B.
Conference Name15th International High-Level Radioactive Waste Management Conference 2015, IHLRWM 2015
Date Published2015
KeywordsBoreholes, Cements, Fluidity, Geothermal wells, Grouting, Hardened cement paste, High level nuclear wastes, High temperature and pressure, Mortar, Oil well cementing, Oil wells, Polycarboxylate admixture, Polycarboxylates, Radioactive waste disposal, Radioactive wastes, Radioactivity, Spent nuclear fuels, Superplasticisers, Waste disposal, Waste management, Well technology
AbstractSealing spent nuclear fuel and high level nuclear waste in boreholes drilled several kilometers into basement rock using the Deep Borehole Disposal (DBD) process is seen as a viable alternative to emplacement in (comparatively shallow) geological repositories. Based on existing oil and geothermal well technologies, we report developments in the use of cementitious grouts as sealing/support matrices (SSMs) in the DBD process where temperatures at the waste package surface do not exceed ∼190°C. Grouts based on Class G oil well cement partially replaced with silica flour are being developed, and the use of retarding admixtures investigated. Two superplasticisers have been investigated as retarders of grout thickening. A polycarboxylate admixture appears to provide sufficient retardation to be considered for use in this application and provides an increase in grout fluidity. The quantity of polycarboxylate product required to ensure fluidity for 4 hours at 90, 120 and 140 °C is 0.75, 1.0 and 2.0 % by weight of cement respectively. A sulphonated admixture only appears to provide desirable retardation at 90°C. The presence of either superplasticiser does not affect composition of hardened cement paste over 14 days; the phases formed are durable under conditions of high temperature and pressure.

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