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The consequences of hypothetical post-closure criticality

Published online by Cambridge University Press:  05 July 2018

R. M. Mason ,
P. N. Smith ,
B. D. Turland  and
C. P. Jackson
R. M. Mason*
Affiliation:
AMEC, Kimmeridge House, Dorset Green Technology Park, Dorchester, Dorset DT2 8ZB, UK
P. N. Smith
Affiliation:
AMEC, Kimmeridge House, Dorset Green Technology Park, Dorchester, Dorset DT2 8ZB, UK
B. D. Turland
Affiliation:
AMEC, Kimmeridge House, Dorset Green Technology Park, Dorchester, Dorset DT2 8ZB, UK
C. P. Jackson
Affiliation:
AMEC, Building 150, Thomson Avenue, Harwell, Didcot, Oxfordshire OX11 0QB, UK
*
*E-mail: robert.mason@amec.com
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Abstract

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The Environment Agency Guidance on Requirements for Authorisation (GRA) of a geological disposal facility (GDF) requires a demonstration that "the possibility of a local accumulation of fissile material such as to produce a neutron chain reaction is not a significant concern." A neutron chain reaction that is just self-sustaining is also known as critical.

Waste packages can be designed to ensure that criticality is impossible during the transport and operational phases of a GDF, and for a significant period post-closure. Over longer times, however, packages may degrade, and groundwater flows could lead to a localized accumulation of fissile material. Hence, even though the initial distribution of materials would need to change substantially, criticality cannot be ruled out completely.

This paper describes how an accumulation of fissile material could, hypothetically, lead to a critical configuration; how such a system could evolve; what the local consequences could be; and how the engineered and geological barriers could be affected. The conclusion from studies to date is that, even for large (and very unlikely) fissile accumulations, the consequences of a post-closure criticality event are not a significant concern.

Keywords

disposalpost-closurecriticality
Type
Research Article
Information
Mineralogical Magazine , Volume 76 , Issue 8 , December 2012 , pp. 3155 - 3163
Creative Commons
Creative Common License - CCCreative Common License - BY
© [2012] The Mineralogical Society of Great Britain and Ireland. This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY) licence (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 2012

References

Armishaw, M. and Cooper, A.J. (2007) Current Status and Future Direction of the MONK Software Package. Eighth International Conference on Nuclear Criticality Safety, 264–267.Google Scholar
Cummings, R., Smith, P.N. and Ghabaee, K. (2007) Understanding Criticality Under Repository Conditions: Results of Static Calculations. Serco Report to the Nuclear Decommissioning Authority, SA/ENV- 0770 Issue 3.Google Scholar
Cummings, R., Jackson, C.P. and Kelly, M. (2008) Repository Post-closure Criticality Consequences Assessment. Serco Report to the Nuclear Decommissioning Authority, SERCO/TAS-1017 Issue 1.1.Google Scholar
Environment Agency and Northern Ireland Environment Agency (2009) Geological Disposal Facilities on Land for Solid Radioactive Wastes: Guidance on Requirements for Authorisation. Environment Agency, Bristol, UK and the Northern Ireland Environment Agency, Belfast, UK.Google Scholar
Mason, R.M., Smith, P.N. and Cummings, R. (2007a) Sensitivity Studies Using the QSS Solver. Serco Report to the Nuclear Decommissioning Authority, SA/ENV-0830 Issue 2.Google Scholar
Mason, R.M., Smith, P.N., Ghabaee, K. and Cummings, R. (2007b) Sensitivity Studies Using the RTM Solver. Serco Report to the Nuclear Decommissioning Authority, SA/ENV-0846 Issue 2.Google Scholar
Mason, R.M., Cummings, R., Kudelin, Y., Martindill, J., Smith, P.J. and Smith, P.N. (2009a) A Suite of Calculations Using the QSS and RT Models. Serco Report to the Nuclear Decommissioning Authority, SA/ENV-0944 Issue 2.Google Scholar
Mason, R.M., Cummings, R., Hosking, J.G., Powney, D., Smith, P.J. and Smith, P.N. (2009b) Further Calculations Using the QSS and RT Models. Serco Report to the Nuclear Decommissioning Authority, SERCO/TAS-1004 Issue 4.Google Scholar
Mason, R.M., Smith, P.N., Sweet, D.W., Eaton, M.D., Goddard, A.J.H., Gomes, J.L.M.A. and Pain, C.C. (2009c) A Summary of Verification, Validation, Benchmarking, Uncertainty and Sensitivity for the FETCH, QSS and RTM Computer Models. Serco Report to the Nuclear Decommissioning Authority, SERCO/TAS/P3648/W001 Issue 2.Google Scholar
Mason, R.M., Turland, B.D. and Martin, J.K. (2011) Comparison of the QSS Model with the Oklo Natural Reactors. Serco Report to the Nuclear Decommissioning Authority, SERCO/TS/P6386/ W001 Issue 2.Google Scholar
Mason, R.M., Martin, J.K., Smith, P.N. and Turland, B.D. (2012) Comparison of a post-closure transient criticality model with the Oklo natural reactors. Mineralogical Magzine, 76, 3145–3153.Google Scholar
Nirex (1997) Development of the Nirex Reference Vault Backfill; Report on Current Status in 1994. Nirex Science Report S/97/014.Google Scholar
Nirex (1998) Post-Closure Performance Assessment: topical Report on Post-Closure Criticality Safety Assessment. Nirex Science Report S/98/004.Google Scholar
Nuclear Decommissioning Authority (2009) The NDA’s Research and Development Strategy to Underpin Geological Disposal on the United Kingdom’s Higher-activity Radioactive Wastes. NDA Report No. NDA/RWMD/011.Google Scholar
Nuclear Decommissioning Authority (2010a) Geological Disposal : St e p s Towards Implementation. NDA Report No. NDA/RWMD/ 013.Google Scholar
Nuclear Decommissioning Authority (2010b) Geological Disposal: An Introduction to the Generic Disposal System Safety Case. NDA Report No. NDA/RWMD/061.Google Scholar
Nuclear Decommissioning Authority (2010c) Geological Disposal: Criticality Safety Status Report. NDA Report No. NDA/RWMD/038.Google Scholar
Smith, P.N., Mason, R.M. and Cummings, R. (2007a) Understanding Criticality Under Repository Conditions: QSS - A Model for Quasi-Steady-State Criticalities. Serco Report to the Nuclear Decommissioning Authority, SA/ENV-0771 Issue 3.Google Scholar
Smith, P.N., Mason, R.M. and Cummings, R. (2007b) Understanding Criticality Under Repository Conditions: RTM - A Model for Rapid Transient Criticalities. Serco Report to the Nuclear Decommissioning Authority, SA/ENV-0772 Issue 3.Google Scholar
Smith, P.N., Mason, R.M., Cummings, R., Ghabaee, K., Goddard, A.J.H., Pain, C.C. and Ziver, A.K. (2008) Understanding Criticality Under Repository Conditions: Comparison of Results from Rapid Transient Models. Serco Report to the Nuclear Decommissioning Authority, SA/ENV-0773 Issue 3.Google Scholar