Deep geological disposal

Geological disposal in a mined repository is the most likely option for HLW, SF, SRS and long-lived LILW (IAEA, 2003a ; Ahn and Apted, 2010). The main concepts of geological disposal are wet and dry, typically at depths from 500 to 1,500 m.

The wet option is a mined and engineered repository located so that eventual water ingress and saturation is inevitable. Various types of host rock are being considered governed largely by the local geology including hard rock (e. g., granite as in the Swedish and Chinese concepts) and soft rock (e. g., clays in France and Belgium).

The dry mined and engineered repository concept was favoured in the US, including high and dry (Yucca Mountain, Nevada) and shallow and dry (the Waste Isolation Pilot Plant (WIPP) located in salt in Carlsbad, New Mexico. However, technical (and other) problems at Yucca Mountain, including that it was not as dry as hoped, have led to the demise of that programme.

Figure 1.22 shows a range of GDF concepts (NDA, 2010b). The concept that will be chosen for the GDF is dependent on rock type, volume of rock available and wastes. Various combinations of tunnel, backfill and waste may be appropriate and different wastes may be kept in different parts of the repository. In the UK, a range of options are being considered while the MRWS process progresses. Until a site and geology is selected, these remain concepts but they do allow initial work on safety cases to start. For example, the concept in Fig. 1.22(a) would be used for ILW in vaults in

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image26"(d)

1.22 ( a-d) A range of disposal options for a mined GDF being considered in the UK.

lower strength rock with cement grout backfill, while that in Fig. 1.22(b) is appropriate for SF in vertical boreholes in high strength rock (granite) with clay buffer and backfill. The concept in Fig. 1.22(c) is for SF in horizontal tunnels in waste containers in a low strength sedimentary rock (clay) with clay buffer and that in Fig. 1.22(d) covers ILW in vaults in higher strength rock with a cement grout backfill.

image27"The UK concept is for multiple vaults in the same region (Fig. 1.23) to accommodate the complex array of waste forms that we have, a legacy of our early indecision on which reactor type to build and of military and research programmes. A clear research need is to understand waste form evolution during storage and disposal and the eventual interaction of the corrosion products from the different parts of the GDF.

In 1980, the IAEA-sponsored International Nuclear Fuel Cycle Evalua­tion (INFCE) waste management and disposal report recommended that proposals ‘for establishing multinational and international repositories should be elaborated’ due to their non-proliferation advantages. In 2003, Mohamed El Baradei, Director-General of the IAEA, said to the UN General Assembly: ‘We should… consider multinational approaches to the management and disposal of spent fuel and radioactive waste. Over 50 countries currently have spent fuel stored in temporary locations, awaiting reprocessing or disposal. Not all countries have the appropriate geological conditions for such disposal — and, for many countries with small nuclear programs, the financial and human resources required for the construction and operation of a geological disposal facility are daunting. . Centralised facilities for disposal of spent fuel and/or vitrified high-level wastes would reduce the diversion risk and be more economical.’ More recently, in 2011, the Council of the European Union adopted a Directive on the responsible and safe management of spent fuel and radioactive waste, highlighting that each member state has ultimate responsibility for management of the spent fuel and waste generated in its territory. However, the door was left open for small countries with limited volumes of waste to share regional

Surface facilities

SILW/LLW vaults

SF vaults

HLW vault

Underground facilities

SILW/LLW vaults

UILW vaults

1.23 The UK’s current multi-vault GDF concept.

repositories. The main message is that the option of EU Member States sharing repositories is included by Clause 3 in Article 4 on General Princi­ples which states that ‘Radioactive waste shall be disposed of in the Member State in which it was generated, unless at the time of shipment an agreement… has entered into force between the Member State concerned and another Member State or a third country to use a disposal facility in one of them. ’ This implies that regional cooperation could be an important aspect of the detailed plans that the EC expects Member States to produce within four years. Austria, Bulgaria, Ireland, Italy, Lithuania, Netherlands, Poland, Romania, Slovakia and Slovenia, have resolved to move towards setting up a European Repository Development Organisation (ERDO).

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