There are a number of nuclear licensed sites in the UK. The NDA owns 20 sites spread across the UK. These sites were formally operated by BNFL and UKAEA, and date back to the start of the UK nuclear programme. There are also further sites operated by other organisations, notably British Energy which operates the Advanced Gas Cooled Reactor (AGR) sites and the Pressurised Water Reactor (PWR) at Sizewell.

The NDA sites contain a wide range of facilities and decommissioning challenges. The sites comprise: [35]

• Twelve reactor sites (five in each of Magnox North and Magnox South, two included within Sellafield)

• A research reactor site at Dounreay

• Two research sites (Harwell and Winfrith)

• A fuel manufacture plant at Springfields

• The Low Level Waste Repository (LLWR).

These facilities will produce the majority of the waste that must be managed in the UK but contributions will also arise from British Energy reactors and others.

The total liabilities associated with these NDA sites are shown in Figure 2.6 Direct decommissioning activities total around £10bn while associated waste management activities make up a proportion of a further £10bn. The total discounted liability for the UK is around £45bn; internationally the challenge is even greater.7

The sites vary markedly in the scale and nature of the decommissioning required. Sellafield is responsible for handling highly radioactive spent fuel and has a correspondingly high decommissioning liability. Some of the plants at Sellafield date back to the early years of the UK nuclear industry and decommissioning these old structures in a safe manner is challenging. Reactor sites, once defueled, have a greatly reduced radioactive burden, which can be further reduced by allowing a ‘‘safe store’’ period of up to 75 years. Reactors therefore form a smaller contribution to the decommissioning liability than Sellafield. Springfields manufactures fuel and does not handle spent, highly active fuel, and so poses less of a decommissioning challenge and requires

correspondingly less money to complete. Research sites pose challenges not present on the other sites, for example Dounreay has stored large quantities of liquid sodium alloy used as a coolant in a test reactor which now must be treated.

The committee on radioactive waste management (CoRWM) has produced an inventory of materials requiring management.8 Their findings are shown in Table 1.

The high level waste (HLW) and recovered uranium and plutonium derive from operations and POCO at Sellafield and so are not associated with decommissioning. The key wastes arising from decommissioning will be intermediate level waste (ILW), low level waste (LLW) and very low level waste (VLLW).

The Sellafield integrated waste strategy9 suggests that around half of the ILW arising at Sellafield will be associated with decommissioning; this is around 140 000 m3, while the Magnox South integrated waste strategy10 suggests about 26 000 m3 of ILW will arise from decommissioning. Further contributions will be made from Dounreay 9000 m3,11 and from Sellafield contaminated land 1600 m3.9 In total at least 60% of the ILW requiring management derives from decommissioning — over 200 000 m3.

Much of the waste arising from decommissioning will be low level waste (LLW) or very low level waste (VLLW). Predicted volume arisings beyond 2030 are dominated by decommissioning activities.12 Total volume arisings are shown in Figure 3 while Figure 4 shows the breakdown into different materials. It is clear from Figure 4 that much of the VLLW material is soil and rubble from decommissioning operations, it would also be expected that a significant proportion of the metals would be associated with vessels and metal reinfor­cement associated with decommissioning. Overall perhaps around 75% of the VLLW (around 1.3 million m3) results from decommissioning operations. A smaller, but still significant proportion of the LLW is also associated with decommissioning.