Bentonite in a High-temperature Environment - Bentonite Erosion
This contractor report to RWM sets out a review of bentonite erosion.
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Disposal of higher-activity radioactive wastes in a Geological Disposal Facility (GDF) is the preferred way forward for many national waste management organisations. Implementation of the UK GDF is the responsibility of Radioactive Waste Management (RWM). RWM’s generic illustrative disposal concepts for high level waste, spent fuel, highly enriched uranium and plutonium in higher strength rock and lower strength sedimentary rock are currently assumed to use bentonite clay as a buffer material, to fulfil required safety functions.
Understanding processes that could affect bentonite clay, and their potential significance, warrant further research studies – could such processes affect the bentonite’s long-term stability?
This report considers the processes of erosion and piping, and their significance. Two types of erosion processes can occur, mechanical erosion and chemical erosion. In scenarios considered in this report, mechanical erosion may occur in partially saturated bentonite pellets if a build-up of water pressure forces the water through the pellets, resulting in the formation of ‘pipes’. Bentonite particles can then be transported by the water, leading to erosion. Chemical erosion refers to the loss of bentonite due to interaction with dilute groundwater.
This report establishes the current state of the art on mechanical and chemical erosion processes in bentonite clay, identifies the relevance of these processes to the UK programme, and identifies knowledge gaps for future research.
Authors: Lennart Börgesson, Magnus Hedström, David Holton, Richard Metcalfe and Torbjörn Sandén
Report No. 208955-TA01