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What really happens to the “vanishing overpack”?

Published online by Cambridge University Press:  27 March 2012

I. G. McKinley
Affiliation:
MCM. Baden, Switzerland
F. B. Neall
Affiliation:
Neall Consulting, Kendal, UK
E. M. Scourse
Affiliation:
MCM. Baden, Switzerland
H. Kawamura
Affiliation:
Obayashi, Tokyo, Japan
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Abstract

Concepts for the disposal of high-level radioactive waste (HLW) and spent fuel (SF) in several countries include a massive steel overpack within a bentonite buffer. In past conservative safety assessments to demonstrate feasibility of geological disposal, overpacks are assumed to provide complete containment for a given lifetime, after which all fail simultaneously. After failure, they are ignored as physical barriers to radionuclide transport. In order to compare different repository designs for specific sites, however, a more realistic treatment of overpack failure and its subsequent behaviour is needed. In addition to arguing for much longer lifetimes before mechanical failure and a distribution of overpack failure times, such assessment indicates that the presence of the failed overpack greatly constrains radionuclide release from the waste matrix and subsequent migration through the engineered barrier system. It also emphasises the key role of the bentonite buffer and the need to be able to assure its performance over relevant timescales.

Type
Articles
Copyright
Copyright © Materials Research Society 2012

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