2009 Report to Government on National Research and

APPENDIX A EXAMPLES OF R&D ISSUES
A.1 As highlighted in paragraphs 6.1 and 6.2, a substantial body of knowledge exists
about the conditioning, packaging, s<strong>to</strong>rage and geological disposal of higher
activity wastes. This knowledge base is sufficient for CoRWM <strong>to</strong> be confident that
geological disposal is the right way forward. During its work CoRWM became
aware of a number of <strong>to</strong>pics, given in this Appendix, which it believes may require
significant R&D. This list of <strong>to</strong>pics, while extensive, should not be taken as a
reason for not proceeding with geological disposal. It simply highlights that there
are still uncertainties and knowledge gaps, inevitable in such a large undertaking,
which will need <strong>to</strong> be addressed by further R&D.
Waste Package Specifications, Post-Closure Safety and Retrievability
A.2 The waste package specifications used by the NDA were developed by Nirex and
are closely linked <strong>to</strong> its concepts for geological disposal of ILW (Nirex, 2007). The
post-closure safety cases for these concepts did not take any credit for the waste
container or the physical durability of the waste form. However, they assumed
cementitious waste forms and <strong>to</strong>ok in<strong>to</strong> account a contribution of these <strong>to</strong> the
alkaline environment which would exist within a disposal facility, largely as a
result of the cementitious backfill. The package specifications now include a
target container life (500 years) and target time for the waste form <strong>to</strong> retain its
integrity (200 years) based on s<strong>to</strong>rage, emplacement in a GDF and the potential
for the GDF <strong>to</strong> remain open for a few hundred years with waste packages readily
retrievable (NDA, 2008a). Post-closure safety is dealt with in the LoC process by
assessing whether the proposed waste form will be compatible with the assumed
cementitious backfill, rather than by explicit specifications. This lack of a clear link
between the safety case and the waste package specifications causes confusion
and makes it difficult <strong>to</strong> specify R&D requirements on the behaviour of waste
packages after disposal.
A.3 In the IoP S<strong>to</strong>rage meeting (CoRWM doc. 2519) the issue of the impact of the
need for retrievability on R&D programmes was emphasised. However, like the
issue of s<strong>to</strong>re lifetime, the lack of clarity on retrievability makes defining R&D
programmes difficult for those in the industry. In its 2006 recommendations
CoRWM made it clear that it did not see retrievability as a necessary prerequisite
of any geological disposal concept for the UK’s higher activity wastes. However,
<strong>Government</strong> decided (Defra et al., 2008) that host communities should have a
role in deciding on the time for which a GDF is designed <strong>to</strong> remain open, with
waste packages retrievable.
A.4 NDA waste package specifications are currently based on an assumption that
retrievability may be needed for up <strong>to</strong> 300 years. This leads <strong>to</strong> a target container
life of 500 years. Demonstrating this target could be met would require
considerable R&D. It is thus important <strong>to</strong> clarify the status of the target. This in
turn requires an examination of the technical implications of retrievability. In
addition, earlier waste packages have been prepared <strong>to</strong> different, less stringent
specifications, and it is uncertain whether these will comply with the newer, more
demanding specifications.
CoRWM Document 2543, Oc<strong>to</strong>ber <strong>2009</strong> Page 98 of 151