UK GDF planning is in its infancy and subject to change, however, a number of important guiding principles for GDF implementation were outlined in the MRWS White Paper:1

extended history of nuclear power generation and nuclear weapons production (see section 3.3.4).

(iii) The GDF design process will be informed by international experience and best practice (see section 3.2 and Table 1).

(iv) The Government currently favours the construction of a single GDF that is capable of housing all current and potential future HAWs and spent fuel (if this is declared as waste). The construction of separate GDFs at one or multiple sites (one for HLW/spent fuel and one for ILW) is also possible, but will have an increased cost and environ­mental impact compared to a single GDF.

(v) Economic and security considerations favour rendering GDF wastes as irretrievable in the long term, but planning, design and construction must be conducted in a way that does not exclude the option of a relatively extended period of retrievability pending a final decision.

(vi) As GDF implementation will take several decades, HAWs should be conditioned to increase stability (see section 3.3.5) and interim storage must be improved to ensure the safe containment of wastes prior to GDF emplacement (see section 3.3.6).

(vii) Further to the MRWS White Paper, the NDA-RWMD published a summary report Geological Disposal: Steps towards Implementation14 that (i) outlined the preparatory work undertaken by the NDA in lieu of a final GDF site decision, and (ii) identified a prospective timeline for GDF implementation. Importantly, the preparatory work has involved the development of several GDF reference scenarios (including geological and engineering considerations) and this is dis­cussed in section 3.3.7. The prospective timeline estimates initial GDF waste emplacement in 2040 and site operation over several decades during which waste will be monitored and could be potentially retrieved (see Figure 3).