Current Arrangements and Requirements for the Conditioning, Packaging and Storage of Intermediate Level Radioactive Waste: Joint RWMAC/NuSAC Report

3. INTERMEDIATE LEVEL WASTE

3.1 This chapter outlines the nature of intermediate level radioactive waste (ILW), and provides an overview of its ownership, recording, current holdings and future arisings.

Nature of ILW

3.2 Radioactive wastes are divided into four categories according to the nature and quantity of the radioactivity they contain and its heat generating capacity. ² The categories are high level waste (HLW), intermediate level waste (ILW), low level waste (LLW) and very low level waste (VLLW). This ordering broadly reflects the decreasing radioactivity content of the waste. ILW is defined by reference to other waste categories: it is waste which does not have the level of heat generation that is associated with HLW, but whose radioactive content is too great for it to be classified as LLW.

3.3 ILW covers a multitude of waste types, activities and half lives. It consists principally of materials that have been irradiated in a nuclear reactor (for example, fuel cladding and reactor components), and equipment and materials that have arisen from the reprocessing of spent reactor fuel (for example, ion exchange resins and filters). ILW requires radiation containment and/or shielding to protect the workers who deal with it.

3.4 There is at present no policy in the UK for the long-term management of ILW. As explained in chapter 4, this policy is currently under review. In the meantime, ILW is held in a variety of storage forms at licensed nuclear sites across the UK, and strategies are being developed for its interim management.

Ownership and recording of ILW holdings

3.5 At the present time, ILW is produced and owned ^* within the UK primarily by four organisations. Three - British Nuclear Fuels plc (BNFL), the United Kingdom Atomic Energy Authority (UKAEA) and the MoD are publicly owned organisations. The fourth - British Energy (BE) - is a privately owned company. Some small amounts of ILW are also generated and held by Amersham and AEA Technology and arise from use of radioactive sources by "small users" such as hospitals, research and educational establishments, and industry.

3.6 Holdings and forecast arisings of the various categories of radioactive waste are recorded in the UK Radioactive Waste Inventory, which is a valuable resource jointly sponsored by the Department for Environment, Food and Rural Affairs (Defra) and Nirex. The last fully reported Inventory is that which had a reference holding and forecast date of 1 April 1998 ³. There is ongoing work to update this to an Inventory with a holding and forecast date of 1 April 2001. This work had not been completed at the time of preparation of this report.

"As Stored" and "As Conditioned" volumes

3.7 In recording current holdings and predictions of future arisings of ILW for the UK Radioactive Waste Inventory, two waste states are distinguished: "as stored" and "conditioned". Conditioning is the term applied to the processes used to prepare the wastes for longer-term storage and/or disposal. Conditioned wastes are packaged in steel containers, usually having been encapsulated in cement or some suitable grout. Wastes that have not yet been finally conditioned may have undergone some form of preliminary treatment for the purpose of storage. Volumes recorded in the Inventory under the "as stored" heading refer to the actual volumes that wastes occupy in store, and include untreated wastes, and those in interim or final conditioned form. Henceforth in this report, amounts of ILW will be quoted in terms of their fully conditioned equivalent volumes.

Overview of volumes and types of ILW holdings

3.8 The United Kingdom Radioactive Waste Inventory estimated UK stocks of ILW on 1 April 1998 to be 74,100 cubic metres (m³). Predicted future arisings will add a further 140,900m³. These figures equate to arisings from the UK's existing nuclear installations, given their currently anticipated lifetimes and work programmes ^#.

3.9 A broad breakdown of these figures by source is given in Table 1.

TABLE 1: ILW HOLDINGS AND PREDICTED FUTURE ARISINGS

(Source: 1998 UK Radioactive Waste Inventory. Basis: fully conditioned equivalent form)

* The Devonport and Rosyth Naval Base figures mainly cover decommissioned nuclear submarine waste. The amount of operational waste is relatively small. The latter wastes are subject to a strategy of "store and decay", so that they can eventually be disposed of as LLW. The wider implications of this strategy have not been assessed in this study.

3.10 The Table 1 breakdown provides an overview of the main ILW-producing sites within the UK. It shows the predominance of BNFL's Sellafield site, along with that company's Calder and Chapelcross reactors, as the main producers of ILW in the UK. Combined figures for the nine ex-Magnox Electric reactors (three of which are now being decommissioned) and the seven Advanced Gas-Cooled Reactors (AGRs) owned by BE are also given. The figures for the UK's most recent reactor, BE's Sizewell B Pressurised Water Reactor (PWR), are also provided for comparative purposes. Other important ILW-producing sites are the UKAEA establishments at Dounreay and Harwell, AWE Aldermaston and the Devonport and Rosyth Naval Bases. The "Other" category includes mainly other minor BNFL, UKAEA and MoD ILW-producing sites, Amersham (Nycomed Amersham at the time of the 1998 Inventory) and the waste of other, smaller, non-nuclear waste producers.

3.11 Table 2 provides figures, which disaggregate ILW holdings and forecast arisings into operational and decommissioning wastes for the main producers, to give a broad indication of their types. The "Other" category in this table includes Amersham and the smaller, non-nuclear producers. Both tables indicate a total 1 April 1998 holding of ILW of 74,100m³ and forecast future arisings of 140,900m³.

TABLE 2: BREAKDOWN OF ILW HOLDINGS AND FORECAST ARISINGS INTO OPERATIONAL AND DECOMMISSIONING WASTES

(Source: 1998 UK Radioactive Waste Inventory. Basis: fully conditioned equivalent form)

3.12 The figures in Table 2 show that "current holdings" of ILW come predominantly (over 98 per cent) from operational sources. Holdings from decommissioning activities are small. For forecast arisings, ILW from decommissioning predominates (by over a factor of 2:1). Ultimate arisings of ILW holdings will be distributed approximately 55:45 between operational and decommissioning sources. About 94 per cent of the ILW, both already held and forecast, comes from plant and activities already committed ³.

* In this report, the term "waste producers" is often used as a shorthand for waste producers and owners. With the creation of the LMA (see chapters 4 and 9), the distinction between waste owner and producers will become more important.

# The figures include holdings and predicted arisings from the reprocessing of overseas spent fuel at Sellafield. Figures in a previous RWMAC report, reference 4 suggest that 1,500m3 or less of the total current holdings of 74,100 m3 came from this source. Future arisings from the reprocessing of overseas fuel under existing contracts would be of the order 3,000m3 . This compares with the total forecast future arisings of 140,900m3.