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The scenario considered here is that waste drums such as those used for the storage and disposal of ILW in the Nirex repository in the UK, could be manufactured from recycled steel produced from LLW arisings within the UK Nuclear Industry. For the purposes of evaluating the economic and technical feasibility of the scenario it is assumed that a combined melting and manufacturing plant can be set-up at the site where a suitable proportion of the waste for recycling arises. An integrated melting and manufacturing plant such as that proposed for the Idaho Falls Project in the US [7] has been assumed.

Quantity of Stainless Steel Required and Arisings of Suitable Stainless Steel The recommended packages for disposal of ILW within the UK Nirex Repository are detailed in [22]. These are 500 litre drums manufactured from stainless steel (grade 316 L), or for items which cannot be conveniently packaged in drums, the 3m3 box, also manufactured from stainless steel. There are several slightly different designs of 500 litre

dimensions which conform to the Nirex waste drum specification which has been used as a basis for the assessment.

The drum dimensions are 0.8 m diameter, 1.2 m height with an average drum wall thickness of 2.5 mm. A typical weight of drum is stated to be 130 kg. An average 500 litre drum is shown in Figure 3. The method of construction is welded from stainless steel plate

The current planned combined volume of ILW and LLW required for disposal in the UK Nirex repository is around 275,000 m3 (1996), with the estimated ratio of ILW disposal volume to LLW disposal volume of around 3:1 based on 1995 estimates of planning volumes. Thus if all planned ILW waste arisings of 206,250 m3 were assumed to be disposed of in 500 litre drums then 412,500 drums would be required. Some of the waste arisings would be expected to be packaged in 3m3 boxes (or the equivalent). As a conservative estimate of the amount of waste that would need to be packaged in boxes rather than drums a figure of 50% of total ILW waste arisings has been taken. Thus the total number of drums required to package all ILW arisings for disposal in the Nirex repository could reduce to 206,250 drums. Using this estimate the total quantity of stainless steel that would be required for production of this number of drums would be 26,800 tonnes.

Reference [17] identified the quantity of stainless steel wastes arising for the UK as a whole as around 2,000 t per annum with peaks between 2020 and 2029 of 4,400 t per annum. Thus over the period 2020-2029 potentially 44,000 t of material are available. The total UK stainless steel arisings are much greater than the potential sink for the material for manufacture into waste drums.

Process Steps for Scenario 3

The steps identified in the manufacture of stainless steel drums from stainless steel scrap are given below:

• Segmentation scrap for transport.

• Transport and monitoring of radioactive material.

• Reception, sorting and storage in the melting plant.

• Preparation of scrap for melting.

• Loading of furnace and melting.

• Ingots production.

• Storage and characterisation.

• Selection of ingots for remelting.

• Reheating ingots.

• Hot rolling manufacturing.

• Finishing mill.

• Cooling bed and coiled.

• Cutter plates.

• Manufacturing of 500 litre drums.

• Transport of secondary wastes to disposal site.

The maximum permitted activity for final products has been estimated to be 100 Bq/g (as for all steel recycling scenarios). Doses to workers involved in the recycling facility have been estimated based on the IAEA dose model and are presented in Appendix 3.

Technical Details of Scenario 3

Drums such as the 500 litre drum considered here are manufactured from steel plate of thickness 2.5 mm and constructed by welding. Heights of 1.2 m are required for the 500 litre drum, with the diameter of 0.8 m giving a length of plate of around 2.5 m. Thus the type of rolling mill required for the production of such plates would be as detailed for scenario 4 for the ISO containers. Information on the type of plant required for a scenario such as that considered here can be found in [7] and is not repeated here. Reference [7] discusses a US study into a melting, casting, rolling and fabrication facility for recycled contaminated stainless steel carried out at the Idaho National Engineering Laboratory and gives a detailed account of the facilities required for melting, casting and rolling recycled contaminated stainless steel scrap into plate which can be fabricated into boxes suitable for the storage of contaminated waste or rubble.

As noted in the introduction, it is assumed that a combined melting and manufacturing plant will be set-up at the site where a suitable proportion of the waste for recycling arises ie BNFL Sellafield. Literature presently available indicates that furnaces can be set up at the site where the waste arises, such as assumed in the stainless steel recycling scenarios, or alternatively the waste can be recycled at a specially adapted plant, such as is considered in the carbon steel recycling scenarios carried out by ENRESA. Thus only minimal transportation of the waste to the site of the melter would be required for this scenario. For other scenarios the waste may need to be transported in an acceptable container to the recycling plant.

Although the activity and type of material can be identified from the National Radioactive Waste Inventory in the UK [23], additional information such as the specification of the material needs to be known. The type of stainless steel required for the manufacture of 500 litre drums is grade 316L. This is required in order to meet the criteria for an acceptable package for storage in the Nirex repository. The exact material specification of the waste is not a problem for the scenario detailed here, as the content of the metal can be controlled in the melt and the composition adjusted accordingly to meet the required grade of steel for the package.

Economic Evaluation of Scenario 3

The following section examines the economic incentive for the recycling of radioactive scrap stainless steel from decommissioning activities and its fabrication into waste containers. The alternative to recycling radioactive scrap steel is to dispose of it in a low-level waste disposal facility. This process requires cutting and packaging the waste metal for transportation and disposal and could also involve decontamination to reduce worker exposures and melting to reduce volume.

• Cost of setting up a recycling facility at the site where the waste arises

• Operating cost of facility / year for required timescale of recycling operations

• Cost of disposal of secondary wastes (e.g. slag and filters) including processing, packaging and transport

The above costs can be used to derive a cost of fabrication/drum. In addition to the above the costs of producing drums from raw stainless steel (ie without recycling of waste) should be addressed since the cost of buying a 500 litre drum is obviously higher than the cost of fabrication from raw stainless steel plate. The cost for raw stainless steel will include costs associated with mining and refinement of ore etc. mentioned above.

For the purposes of economic assessment the cost data for melting and rolling have been obtained from a US study into an integrated facility to produce steel plate from stainless steel arisings from the US nuclear industry for fabrication into waste boxes. Reference [7] includes the detailed design and costs associated with setting up a melting, casting, rolling and fabrication facility at the site where the waste arises. The study is based on the premise that the most cost effective way to produce stainless steel is to use the same processes employed by companies in the production of high-quality stainless steel within normal industry. The US plant considered here is quite a large plant in terms of the amount of waste metal that can be processed per year, estimated to be 20,000 tonnes output per year. The capital costs for setting up the recycling facility are estimated to be 97 M ECU (£68m) (based on US figures for labour rates etc). The additional running costs per year from the US data are approximately 14 M ECU (£10m) per year. The figures for waste steel arisings presented in Section 3 suggest that approximately 1-3 years production is all that would be required to produce enough 500 litre drums to satisfy the planned UK ILW disposal volume.

The cost of disposal of secondary waste also needs to be estimated. The amount of slag produced per charge is approximately 3-5 % of the total charge. Assuming that this will be disposed of as LLW in the Nirex Repository the cost of disposal will be 53 kECU/m3 (£37k/m3 ) (1995 prices) assuming transport charges are negligible, since the waste will be generated at the same site as the planned site of the repository. Assuming all of the stainless steel required for manufacture of the required number of drums is processed (26,800 tonnes) results in a secondary waste volume of 170 m3, resulting in a disposal cost of 9 M ECU (£6.3m) plus the cost of disposal containers (340) which is 730 k ECU (£510k). The total cost for disposal of secondary waste from container manufacture would then be around 9.7 M ECU (£6.8m). Thus suggests that the total cost of setting up and operating a recycling facility for 3 years would be 140 M ECU (£98m) with the added cost of disposal of secondary waste giving a total cost of 150 M ECU (£104.8m). In addition an allowance needs to be included for decommissioning of the plant and is assumed to be 50% of the capital cost. Transport costs have been omitted because the facility is set up at the site where the waste arises and also at the disposal site (Sellafield) so no transport of secondary wastes would be required. The total cost of the recycling option is estimated to be 200 M ECU (£139m). Associated Costs of Disposal Option

The costs involved in the disposal option include:

• Costs of disposal of Low-Level Metallic Waste (LLMW) in UK repository, including processing, packaging and transport

• Additional costs of monitoring LLW prior to opening of UK repository

The cost of purchasing a 500 litre drum, assumed in UKAEA strategic planning studies is 2.15 k ECU (£1.5k) per drum. If the estimate of 206,500 drums is used, then the total cost of purchasing enough drums to dispose of all the planned ILW arisings would be around 444 M ECU (£310m). This is likely to be an upper bound estimate of the cost of purchasing drums. The UKAEA strategic planning study value will most likely be for the purchase of the AEA design 500 litre drum. Therefore it would be expected that the cost per drum would be reduced if all drums were purchased from the same supplier and made to the same design. Currently the disposal charges are estimated to be 53 kECU/m3 (£37k/m3) for both LLW and ILW. For steels this is equivalent to 6.7 k ECU/t (£4.7k/tonne). Assuming that the waste arisings that could be recycled and manufactured into drums would have to be disposed of gives a total mass of 26,845 tonnes. This waste could be directly packaged for disposal (probably resulting in ~30% voidage within packages), or more likely would undergo some form of volume reduction, such as supercompaction prior to disposal. Alternatively the method of melting can be used for volume reduction. Assuming that the waste requires no processing prior to disposal results in an estimated cost for disposal of 181 M ECU (£126m). If no supercompaction is performed and 30% voidage results in packages this increases to a total disposal cost of 235 M ECU (£164m). The cost of disposal containers for packaging of this waste is estimated to be 115 M ECU (£80m), based on a container cost of 2150 ECU and a packaging volume of 0.5 m3 per drum.

The cost of producing 500 litre drums in the above plant from uncontaminated stainless steel scrap has also been considered. The cost of stainless steel at current prices is 717 ECU/t (£500 /tonne) for solid 304 type stainless steel scrap (10 April 1996). This has been taken as an indication of the likely cost of buying scrap steel for the manufacturing of drums. Thus the 26,845 tonnes required to manufacture 206,500 drums would cost 19.2 M ECU at current prices.

Re-evaluation of Scenario 3 with Common Cost Assumptions

The costs for each of the main stages in the scenario are summarised here using two disposal charges - one typical of a near surface disposal facility and another typical of a deep geological repository. The cost analysis below includes common assumptions relating to transport costs and scrap handling charges. The calculation of disposal costs for secondary waste and for the disposal option includes minimal volume reduction prior to disposal. Supercompaction of some wastes may be carried out but calculations have assumed a packing density of 1.2 t/m3 for secondary wastes from processing and 1.5 t/m3 for direct disposal of wastes. In addition this re-evaluation considers a reduced cost for the purchase of 500 litre drums of 720 ECU rather than the assumed cost of 2150 ECU.

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Capital cost of plant 97,471,000

Decommissioning costs of plant 48,736,000 (50% of capital cost)

Costs of containers for disposal of secondary wastes (each) 2150 Total disposal charge for secondary waste (shallow) 4,708,000 Total disposal charge for secondary waste (deep) 45,285,000 Costs for handling of wastes/scrap and transport (717 ECU/t) 19,208,000 TOTAL (shallow) 213,124,000

TOTAL (deep) 253,702,000

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Cost of buying final product (each) 720

Costs of containers for disposal of wastes (each) 2150 Costs for handling of wastes/scrap and transport (575 ECU/t) 15,366,000 TOTAL (shallow) 217,147,000

TOTAL (deep) 680,698,000

Cost of recycling - disposal (shallow disposal) -4,022,550 Cost of recycling - disposal (deep disposal) -426,996,000 Scenario 3 - Conclusions

The economic analysis suggests that the rolling plant will be under capacity for normal rolling mills and that only 3 years production would be required in order to process all the steel for production into steel waste drums. This is a considerable sum of money to invest in a plant with a short lifetime if other products could not be identified.

It is estimated that there is a considerable surplus of material arising from the waste stream considered that could not be utilised in the scenario suggested here. Thus the scenario is better considered as part of a wider strategy including the free release of material and the recycling of material by dilution for specified public use. This integrated strategy would make better use of a controlled melting facility which could then also be considered for melting for waste volume reduction purposes as well as for recycling for reuse. The US data suggested that plant sizes which are normal for industrial use will be over-capacity for nuclear use within the UK. Thus again there is an incentive for melting of other activities of waste or for a Europe-wide facility rather than a country-wide facility. Stainless steel arisings based on the volumetric arisings from one waste stream at Sellafield, UK (2D109) suggests that there is no incentive for bringing the recycling strategy forward in time for the UK.