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Consequence modelling of hypothetical post-closure criticality events for spent fuel disposal

Published online by Cambridge University Press:  02 January 2018

R. M. Mason ,
J. K. Martin ,
P. N. Smith  and
R. J. Winsley
R. M. Mason*
Affiliation:
Amec Foster Wheeler, Kings Point House, Queen Mother Square, Poundbury, Dorchester DT1 3BW, UK
J. K. Martin
Affiliation:
Amec Foster Wheeler, Kings Point House, Queen Mother Square, Poundbury, Dorchester DT1 3BW, UK
P. N. Smith
Affiliation:
Amec Foster Wheeler, Kings Point House, Queen Mother Square, Poundbury, Dorchester DT1 3BW, UK
R. J. Winsley
Affiliation:
Radioactive Waste Management, Curie Avenue, Building 587, Harwell, Oxford OX11 0RH, UK
*
*E-mail: robert.mason@amecfw.com
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Abstract

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In support of the Radioactive Waste Management (RWM) safety case for a geological disposal facility (GDF) in the UK, there is a regulatory requirement to consider the likelihood and consequences of nuclear criticality. Waste packages are designed to ensure that criticality is not possibleduring the transport and operational phases of a GDF and for a significant period post-closure. However, over longer post-closure timescales, conditions in the GDF will evolve.

For waste packages containing spent fuel, it can be shown that, under certain conditions, package flooding couldresult in a type of criticality event referred to as 'quasi-steady-state' (QSS). Although unlikely, this defines a 'what-if' scenario for understanding the potential consequences of post-closure criticality. This paper provides an overview of a methodology to understand QSS criticality andits application to a spent fuel waste package.

The power of such a hypothetical criticality event is typically estimated to be a few kilowatts: comparable with international studies of similar systems and the decay heat for which waste packages are designed. This work has built confidencein the methodology and supports RWM's demonstration that post-closure criticality is not a significant concern.

Keywords

geological disposalpost-closurespent fuelcriticality

Information

Type
Research Article
Information
Mineralogical Magazine , Volume 79 , Issue 6 , November 2015 , pp. 1505 - 1513
Creative Commons
Creative Common License - CCCreative Common License - BY
Copyright © The Mineralogical Society of Great Britain and Ireland 2015. This is an open access article, distributed under the terms of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2015

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