EUROPEAN COMMISSION
NUCLEAR SAFETY AND THE
ENVIRONMENT
Recycling and Reuse of radioactive
Material in the Controlled Nuclear
Sector
Executive Summary
A review of the feasibility of recycling and/or reuse of non-releasable components and materials arising from nuclear operations within the European Community has been undertaken. This review has comprised of an estimate of the amounts of low-level waste concrete, steel, copper and aluminium which may arise from routine operations and decommissioning of nuclear facilities around the EC and the timescales on which this material would arise. Detailed studies of twelve possible scenarios for utilisation of this material have been carried out and from the results of these analyses a strategic evaluation of the feasibility of controlled release recycling within the nuclear sector has been made.
The study concludes that the recycling of radioactive steels (carbon and stainless) is an already well researched area which requires no further development as regards the melting and refining of steel arising from nuclear facilities. Work within the nuclear sector has been driven by efforts to allow unrestricted release of this material into the conventional market-place and in general any restricted release into the nuclear sector is carried out according to legislation in the country concerned preventing its sale as scrap. Further development of controlled release recycling of steels into products from plate will be likely driven by market forces since considerable investment in a manufacturing facility will be required. The possibility of combined plants for free-release of materials, controlled release of materials and possibly volume reduction would give further cost savings for the operation of a steel melting and manufacturing plant.
There is a significant source of steel available, although current projected requirements across EC countries for products that could use recycled steel in their manufacture indicates that considerably more steel will be available than could be used in such products. The impact on decommissioning policies of adopting a controlled release strategy for steels is likely to be negligible given there is more material arising than can be reused. The phasing of decommissioning of plants is likely to give a steady state of material that will be suitable for manufacturing packaging for decommissioning wastes arising at a later stage. In countries with small nuclear programmes, the scope for controlled nuclear recycle would be more limited and unless a Europe-wide facility for rolling of plates was available only small scale applications could be carried out.
Recycling of copper scrap arising from nuclear facilities back into the controlled nuclear sector has been found to be unfeasible due to the nature of the smelting and refining process which will provide material capable for being released to the conventional scrap market. In the instance of aluminium the large arisings are generally surface contaminated only and again the resulting material will be able to be released to the conventional scrap market. Both sources suffer from considerable uncertainties in the estimation of the quantities of material and the extent of the contamination present.
In the case of concrete there are considerable arisings of concrete waste that will require disposal. Conventional uses of recycled aggregates from nuclear sources within the nuclear industry are limited and will only be able to utilise a small proportion of this waste. The
prospect of utilising recycled concrete for manufacture into concrete disposal boxes and within grout however would provide a considerable sink for a large proportion of this material. The cost drivers behind nuclear sector recycle of concrete are a need to avoid nuclear disposal costs for large amounts of waste, rather than for the release of material to conventional recycle markets. The low cost of recycled aggregates means that there is no market for recycled nuclear aggregates even if activity levels were to comply with those set for unrestricted release. There is a possibility that this waste may be disposed of at a landfill site however, with the advantages of lower disposal charges.
An examination of sources, sinks and timescales for utilisation of concrete suggests that if the use of crushed concrete as an infill in grout could be proven viable a significant proportion of concrete waste normally requiring disposal could be recycled. Again there is not clear incentive for modifying decommissioning timescales to utilise this waste. Analysis of economic data for recycling of concrete in this way suggests that if all concrete waste generated (~390,000 t) could be recycled in this way the cost savings would be in the region of 245 M ECU for near surface disposal charges to 9.5 B ECU if concrete were to be disposed of in a deep repository. It is recommended that further work into the feasibility of recycling concrete for incorporation into grout be undertaken.
Contents
1 Introduction
1
2 Assessment of the Quantities of LLW Arising from Nuclear
Operations within the European Community
2
3 Assessment of Scenarios for the Recycle/Reuse of Materials in
the Nuclear Sector
3
3.1 SCENARIO 1 - STAINLESS STEEL VITRIFIED WASTE PRODUCT
CANISTERS 4
3.2 SCENARIO 2 - CAST CARBON STEEL WASTE DISPOSAL BOX 5 3.3 SCENARIO 3 - STAINLESS STEEL WASTE DRUMS 5 3.4 SCENARIO 4 - CARBON STEEL ISO TRANSPORT CONTAINER 6 3.5 SCENARIO 5 - CARBON STEEL REINFORCING BARS 6 3.6 SCENARIO 6 - CARBON STEEL GRANULATE AND FIBRES 7 3.7 SCENARIO 7 - MANUFACTURE OF COPPER SPENT FUEL DISPOSAL
CONTAINERS 7
3.8 SCENARIO 8 - ALUMINIUM STORAGE CANISTER 8
3.9 SCENARIO 9 - CONCRETE CRUSH/RECYCLE - SHIELD WALLS 9 3.10 SCENARIO 10 - CONCRETE CRUSH/RECYCLE - PREFABRICATED
CONCRETE PIECES FOR REPOSITORY 10
3.11 SCENARIO 11 - REUSE OF FUEL PONDS AS INTERIM WASTE
STORES 10
3.12 SCENARIO 12: CONCRETE CRUSH/RECYCLE - IMMOBILISATION MEDIUM FOR DRUMS IN A CONCRETE DISPOSAL CONTAINER 11
3.13 CONCLUSIONS 12
4 Discussion of Strategy Related Issues for Controlled Release
Recycling
13
4.1 REVIEW OF SCENARIO ASSESSMENT AND RANKING OF SCENARIOS14 4.2 ESTIMATED REQUIREMENTS FOR FINAL PRODUCTS ACROSS
EUROPE 15
4.3 OTHER ISSUES RELATED TO STRATEGY DEVELOPMENT 17 4.3.1 Recycling for Controlled Nuclear Use and Unrestricted Use 17 4.3.2 Combination of Unrestricted and Restricted Use Recycling Plants 21
4.3.3 Public Relations Issues 22
4.3.4 Investment 22
4.3.6 Possible Uses of Recycled Products in Spent Fuel Management
Area 24
4.3.7 Implications of Decommissioning Strategies on Recycling 25 4.3.8 Availability of Disposal Facilities 26
4.4 SUMMARY OF STRATEGY REVIEW 27
5 Conclusions and Recommendations
30
6 Acknowledgements
32
7 References
32
Appendices
APPENDIX 1 ESTIMATE OF THE QUANTITIES OF LLW MATERIALS ARISING FROM NUCLEAR OPERATIONS IN THE EUROPEAN
COMMUNITY
APPENDIX 2 ASSESSMENT OF SCENARIOS FOR THE RECYCLING AND REUSE OF LLW MATERIALS IN THE EUROPEAN
COMMUNITY
APPENDIX 3 DISCUSSION OF DOSE CONSIDERATIONS FOR THE RECYCLING AND REUSE OF LLW MATERIALS
APPENDIX 4 INFORMATION ON DISPOSAL FACILITIES AND STRATEGIES CURRENTLY IN OPERATION IN THE EUROPEAN COMMUNITY
List of Tables
TABLE 1 ECONOMIC ANALYSIS OF RECYCLING SCENARIOS TABLE 2 DISPOSAL FACILITIES CURRENTLY IN OPERATION IN EC TABLE 3 REQUIRMENTS FOR DRUMS, BOXES, GROUTS IN EC
DISPOSAL FACILITIES CURRENTLY IN OPERATION TABLE 4 LIST OF ISSUES TO BE CONSIDERED IN STRATEGIC REVIEW
List of Figures
FIGURE 1 STAINLESS STEEL LLW ARISINGS IN EC FIGURE 2 OTHER STEEL LLW ARISINGS IN EC FIGURE 3 ALUMINIUM LLW ARISINGS IN EC FIGURE 4 COPPER LLW ARISINGS IN EC
FIGURE 5 CONCRETE LLW ARISINGS IN EC
FIGURE 6 SOURCE AND SINKS FOR CARBON STEEL (EUROPE) FIGURE 7 SOURCE AND SINKS FOR STAINLESS STEEL (EUROPE) FIGURE 8 SOURCE AND SINKS FOR CONCRETE (EUROPE)
1
Introduction
This paper reports the results of a study funded by the Directorate-General XI of the European Commission into whether it is feasible to recycle (or reuse) radioactively contaminated or activated waste materials arising from routine and decommissioning operations in nuclear plant within the controlled nuclear sector. This material is identified by its radioactivity limit which prevents free release routes being available.
A consortium of AEA Technology plc, based in the UK, and Empresa Nacional de Residuos Radioactivos SA (ENRESA), based in Spain, have undertaken the work programme utilising the combined expertise of the staff and the companies’ resources in the nuclear field.
The terms of reference for this project identifies a set of tasks as follows:
• Routes and scenarios for recycling and reuse in the nuclear sector - to provide an estimation of possible routes and scenarios for recycling and reuse which could be adopted within EC Member States within the controlled nuclear sector.
• Type and quantities of waste expected for recycling and reuse - to establish whether there are sufficient quantities of low level waste material likely to arise during the time period of the scenario in order to provide material for the recycling and reuse scenarios. This assessment would be limited to material arising in sufficiently large quantities to justify an evaluation i.e. carbon steel, stainless steel, aluminium, copper, concrete and reinforcement bars or structural steel in buildings.
• Selection of the most promising recycling routes and detailed analysis - approximately 12 of the most promising scenarios would be selected for further study.
• Recommendations for management by recycling - to develop a strategic view of the value of the promising recycle scenarios with reference to the range of decommissioning strategies being adopted across Member States. A key part of the strategic assessment would be to provide recommendations on the long term management of waste streams according to the phasing of construction and availability of disposal facilities.
Each of these areas are addressed in the following sections. For ease of reading the main text of the report contains summarised information from the more detailed appendices and a section that assesses the strategy for recycling and reuse. Section 2 gives an overview of the estimated quantities of steels, copper, aluminium and concrete arising as a result of nuclear operations within the nuclear sector that will have an activity level too high for unrestricted release with further details being given in Appendix 1. Section 3 gives a summary of the assessments of the twelve scenarios selected for detailed study. Details of these assessments are given in Appendix 2. Section 4 reviews these findings in the context of a strategy for the integration of recycling/reuse in decommissioning plans. Conclusions and recommendations are presented in Section 5.
2
Assessment of the Quantities of
LLW Arising from Nuclear Operations
within the European Community
Estimates of the volumes of steels (stainless and others), concrete, copper and aluminium low level waste arising from nuclear operations within the European Community have been based on data issued by waste producers and plant operators within the UK, Spain and France. These data have been used as a base dataset from which data for other European Member States have been estimated. These data have then been combined to produce an EC-wide estimate of the quantities of each specific material which could be considered for recycling/reuse and the timescale on which they arise. The assessment has included large-scale nuclear power plants and nuclear fuel cycle facilities where data is readily available. A sensitivity study has also been carried out to assess the total quantity of materials that could arise as a result of the decommissioning of small research reactors in the EC.
The estimates of quantities of materials arising in the UK, France and Spain are shown in Appendix 1 where the detailed methodology of extrapolating the data assembled for UK, Spanish and French nuclear power plants and facilities to nuclear facilities in the rest of the EC Member States is also described. For the UK and Spain, the material considered is that with radioactive content between 0.4 Bq/g and 12 kBq/g (i.e. the UK LLW band). This range of activities was chosen as data are readily available for this range of activity for UK sources and was stated as the range of activity that would be studied in the terms of reference for the project. Data are included for all nuclear facilities, including fuel cycle facilities. For the rest of the EC, where data were less readily available, information on the quantities of low level waste arising have been based on data reported in literature. As a result of this fuel cycle facilities outside the UK and Spain are not included in the current estimates as there is currently no data available on these facilities. As stated in Appendix 1, the omission of these facilities is not expected to significantly alter the overall amount of material arising in the EC that may be suitable for recycling into the nuclear sector.
The EC inventory of materials is shown on Figures 1 to 5. It can be seen from the figures that the potential quantities of material that could be considered for reuse/recycling are large. The quantities of metals available are dominated by decommissioning of nuclear power plants at Stage 3 when the reactor vessel and its containment are dismantled.
The estimate of steels show peaks of steel occurring at 2045 (see Figures 1 and 2). These appear when Stage 2 and Stage 3 decommissioning of nuclear power plants occur. During the 2040’s significant numbers of power plants are assumed to undergo decommissioning based on the assumed lifetimes and timescales for decommissioning. Data from Figure 1 for stainless steel suggest average annual arisings over the period to 2050 of around 5,000 t per annum with peaks of stainless steel occurring at 2045 when it is estimated that 13,000 t per annum would be produced. Figure 2 shows the predicted arisings of other types of steel (such as mild steel and carbon steel). The majority of this steel will arise during the period
2037-2048 when many reactors are estimated to undergo Stage 3 decommissioning. In 2045 a peak production of nearly 80,000 t per annum is predicted to occur. Estimated quantities of steel in the period to 2030 are predicted to be around 5,000 t per annum.
Figure 3 shows that much smaller amounts of aluminium are expected to arise than for steel. The data for the EC are dominated by the UK arisings figures where the majority of aluminium is predicted to arise from decommissioning of nuclear plant other than nuclear power plants. In the UK this mainly arises from the decommissioning of uranium enrichment plants. The amount of aluminium predicted to arise from the decommissioning of PWRs and BWRs is much smaller. In the UK the decommissioning of the diffusion enrichment plant yielded a large amount of aluminium, however this was only slightly contaminated and the majority of the scrap was able to be sent for free-release to commercial alloying companies. Data for the decommissioning of other uranium enrichment plants in the EC such as those in France, Germany and the Netherlands have not been included in the total estimates of materials as the decommissioning timescales and detailed waste arisings from the plants are not known at this time. It is likely that a significant amount of aluminium waste could arise from plants such as the gaseous diffusion plant in France, however data for the UK suggest that this could be readily decontaminated and sent for free-release.
The estimated quantities of copper arising as a result of nuclear operations are shown on Figure 4. The amounts of copper generated are generally around the 100 - 200 t per annum level, however peaks occur around 1998/2000 and later at around 2040 onwards with levels of 400 t per annum and above. Peak production is in 2045 with predicted levels rising to nearly 1000 t per annum.
The assessment shows however that there is a considerable amount of concrete available for recycling/reuse (see Figure 5). Most of the concrete is expected to arise in the period 2038-2048 when significant numbers of power reactors are assumed to be undergoing Stage 3 decommissioning. At this time concrete arisings are generally around the 15,000 t per annum level, although a peak of 25,000 t per annum is predicted in 2045. Concrete arisings in the early part of the next century arise from decommissioning operations within the UK on various small nuclear facilities.
3
Assessment of Scenarios for the
Recycle/Reuse of Materials in the
Nuclear Sector
The purpose of this part of the project is to identify a set of credible scenarios for the recycling of waste material into the controlled nuclear sector. A credible scenario is one where there is likely to be an economically significant source of waste material available to meet a defined requirement within the controlled nuclear sector. A brief summary of each of the twelve scenarios selected for study is given below with further detailed information being provided in
Appendix 2. The summaries below give a brief description of the product (dimensions, weight, type of material etc.), the process used in its manufacture and a summary of the cost assessment of the scenario comparing the cost of recycling and the cost of disposal. Further information on the technology of melting LLW contaminated steels and non-ferrous materials is also given in Appendix 2, along with information on the processing of concrete debris. Appendix 3 discusses generic assessments of dose for each of the main material recycling processes.
3.1
SCENARIO 1 - STAINLESS STEEL VITRIFIED WASTE
PRODUCT CANISTERS
This scenario involves the processing of stainless steel scrap via a melting and rolling facility for final manufacture into a stainless steel flask suitable for the storage of vitrified high level waste from fuel reprocessing operations. The manufacture of the vitrified waste canister was the most promising of the stainless steel products identified in the area of spent fuel management following a review of the literature available. Vitrified waste canisters are about 0.4 meters in diameter and 1.3 meters high and are constructed from stainless steel (SS309) with the weight of an empty container around 75 kg. The expected requirement for stainless steel containers of this type in the UK is a maximum of 675 containers per year giving a total requirement of around 2,530 t of stainless steel.
The cost of recycling scrap stainless steel and manufacture of steel plate from the melted scrap into vitrified waste containers is estimated to be around 165 M ECU. In contrast the cost of disposal of this scrap if it were not recycled is estimated to be between 80 M and 123 M ECU, depending on how the waste is disposed of i.e. in a near surface disposal facility or a deep disposal facility. The disposal option assumes that the number of containers required is at the maximum currently anticipated for the UK reprocessing facility. Even with this assumption a facility to produce these containers from recycled steel would be operating under capacity and would only require a small timescale for operation of the plant to produce all the required containers for the UK reprocessing industry. Thus the disposal option is considerably more attractive economically than that of recycling in the instance of vitrified product containers. The economic analysis has assumed that the rolling plant would only be required for one year and is therefore a considerable sum of money to invest in a plant with a short lifetime if other products could not be identified. Manufacture of this product could be integrated with manufacture of other products from stainless steel plate which could then be used for a variety of purposes. The economics of steel rolling suggest that rolling facility would only be feasible if sufficient demand for products within the nuclear industry as a whole could be identified to give the facility several years of operation at near capacity. The possibility of integrating production of vitrified product canisters and stainless steel waste containers would improve the economics of setting up such a plant. This conclusion is similar to that found in a US study and as a consequence of this the US has considered an alternative method of manufacture of vitrification canisters using back-extrusion. This process would not require an expensive rolling mill and forming facility dedicated to processing stainless steel ingots. The prospect of manufacture of these type of containers using back-extrusion offers an alternative approach. It has not been possible to evaluate this alternative manufacturing method, as no costs are available.
3.2
SCENARIO 2 - CAST CARBON STEEL WASTE DISPOSAL
BOX
The final product is a cast iron disposal box (CIDBOX) for medium and low level waste, which could be manufactured from radioactive carbon steel arising from the decommissioning of Spanish nuclear installations. The manufactured boxes are used instead of concrete containers at a near surface disposal site. The nominal capacity of the recycling plant would be of the order of 2000 - 3000 t per year with a furnace with a capacity of 4.5 t, giving the possibility of manufacturing in the region of 200 boxes per year. These boxes could than be used to substitute approximately 100 concrete containers from El Cabril. The proposed cast iron disposal box (CIDBOX) has a total volume of about 5 m 3 (2.25 m x 2.25 m x 1.1 m) with 50 mm thick walls and allows the storage up to 9 standard 200 l drums. The net weight (including lid) is 9500 kg with an additional estimated load of 3000 kg of radioactive wastes. The cost of recycling steel for manufacture into boxes has been estimated to be between 53 M ECU and 205 M ECU depending on the charge for disposal of secondary waste. The cost of disposal of this scrap rather than recycling is estimated to be between 42 M ECU and 734 M ECU. Assuming a disposal charge of 1.7 ECU/m3 the disposal costs and recycling costs are very close only being 20% different. When the costs of recycling and disposal are close any uncertainties in assumptions regarding conditioned waste volumes for disposal can have an important effect on the outcome of the economic assessment. In particular the waste volumes required for disposal here have assumed that no supercompaction is carried out.
3.3
SCENARIO 3 - STAINLESS STEEL WASTE DRUMS
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. 500 litre drums used in the UK for the disposal of ILW are manufactured from stainless steel (grade 316 L). For larger items which cannot be conveniently packaged in drums, the 3m3 box, also manufactured from stainless steel, is used. 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. A typical weight of drum is 130 kg. The total number of drums required in the UK required to package ILW arisings for disposal in the Nirex deep repository has been conservatively estimated as a total of 206,250 drums giving a total requirement for 26,800 t of stainless steel (see Appendix 2 for more details).
The cost of recycling scrap stainless steel and manufacture of steel plate from the melted scrap into waste drums for use in the UK nuclear industry is estimated to between 213 M and 254 M ECU. In contrast the cost of disposal of this scrap if it were not recycled is estimated to be between 217 M and 680 M ECU, depending on the disposal charges for waste. The large number of drums required in the UK alone suggest that a plant dedicated to the production of containers manufactured from steel plate would be economic even though the plant would be operating under capacity.
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.
3.4
SCENARIO 4 - CARBON STEEL ISO TRANSPORT
CONTAINER
The final products for this scenario are ISO transport containers which could be manufactured from radioactive carbon steel arising from the decommissioning of Spanish nuclear installations. ISO containers are manufactured from 2 m wide plates. An ISO container weighs around 4.5 t, approximately 2.5 t of which corresponds to plates and 2.0 t to commercial profiles. It is estimated that 10 ISO containers would be required per year in Spain with a plate production of 25 t per year. The minimum capacity of a rolling mill installation is 200,000 t per year. An economic assessment of this scenario has not been carried out because the extra capital cost required for a rolling mill would be such that the scenario would be economically unattractive, given the low rates of utilisation of such a plant. In general a large rolling mill and fabrication plant such as that considered in Scenarios 1 and 3 would be required.
This scenario has been considered to be unfeasible due to the extra capital cost incurred in the provision of a rolling mill to produce steel plates for the manufacture of ISO containers and the small utilisation of the plant for the ISO container manufacture requirements compared to its capacity. In addition the fact that an ISO container would be made of a slightly radioactive material raises problems in itself, with the administrative and radiological controls required for using this transport container. For all these reasons this scenario is not considered further.
3.5
SCENARIO 5 - CARBON STEEL REINFORCING BARS
The final products for this scenario are reinforcing bars which would be manufactured from radioactive carbon steel arising from the decommissioning Spanish nuclear installations. The manufactured reinforcing bars are transported to the disposal site and used instead of commercial reinforcing bars (total or partially) in the manufacture of concrete disposal containers. Concrete containers will be manufactured using reinforcing bars of 10 mm diameter and each concrete container has a reinforcing bars weight of around 620 kg. Thus the possible requirement for bars at the disposal site would be between 273 and 310 tons per year. Continuous casting is used for the manufacture of rebars. This requires a smaller melting and rolling facility than required for the production of plate. Details of the equipment required and the processes used are considered in Appendix 2.
The assessment indicates that the cost of recycling is around 15 - 40 M ECU depending on the disposal charges for secondary wastes. In contrast the cost of disposal is between 7 M ECU and 114 M ECU depending on whether the wastes would be disposed of in a near surface or deep disposal facility. Near surface disposal costs only have to rise slightly in order to make the recycling option economically attractive.
3.6
SCENARIO 6 - CARBON STEEL GRANULATE AND FIBRES
The final product for this scenario is the manufacture of granulate cast iron or cast iron fibres which could be manufactured from radioactive steel arising from the decommissioning of Spanish nuclear installations. The manufactured granulate can be used instead of sand (total or partially) in cement mortar which is used for infilling and immobilisation of wastes in drums. For fibres the final use is for placement between drums in disposal containers, where the fibres are incorporated into the cement matrix when the containers are infilled with grout. It is assumed that 50% of the sand in the grout mixture could be substituted by steel granulate giving a total of 7600 kg per container. Currently between 440 and 500 containers per year are used at the El Cabril disposal facility and therefore about 1670 tons of granulate could be used per year.
Manufacture of products such a granulate and fibres requires a melting facility with manufacturing equipment necessary to produce the granulate (i.e. a rapid cooling water jet) and fibres (i.e. a refrigerated cylinder for cooling). The auxiliary equipment required for granulate and fibre production is relatively simple including a tank and pump. The nominal capacity of the plant could be 2000- 3000 t per year and the furnace would be electric induction type of 4.5 t capacity. The equipment required for both fibre and granulate manufacture is described in Appendix 2.
The assessment indicates that the costs of recycling are between 50 M ECU and 176 M ECU depending on disposal charges for secondary waste. The cost of disposal of the waste if it were not recycled has been estimated to between 32 M ECU and 610 M ECU. This scenario is slightly different to the rest of those considered in that it is not manufacturing a product that is currently required in the disposal of waste. Thus the assessment of disposal costs has not included a cost for purchasing of the final product if it were not manufactured from recycled material. To make the scenario more cost effective a slight increase in near surface disposal charges would be required above the 1.7 k ECU/m3 currently assumed.
3.7
SCENARIO 7 - MANUFACTURE OF COPPER SPENT FUEL
DISPOSAL CONTAINERS
This scenario considers the manufacture of deep disposal canisters for irradiated fuel and High Level Waste (HLW) proposed in Sweden from recycled copper. Up to 4000 canisters will be required, each weighing approximately 8 t with an annual production rate of 200 to 210 canisters (requiring approximately 1600 t of copper material per year). This gives a total amount of copper material for the canisters of 32000 t over a 20 year period from 2020. The total amount of copper waste from nuclear plants in Europe has been estimated to be 16,000 t up to 2050. This amount is only half that required for the copper canister scenario considered here. Over the period 2020 - 2040 only 4,500 t will be generated that will not be suitable for consideration for unrestricted release. The manufacture of copper canisters requires high purity copper which requires melting and electrolytic refining. Details of these processes are given in Appendix 2.
The cost of recycling copper for manufacture into deep disposal canisters is estimated to be between 502 M ECU and 537 M ECU depending on disposal charges for secondary wastes.
The cost of disposal of the copper is estimated to be between 89 M ECU and 365 M ECU depending on whether the waste would be disposed of in a near surface or deep disposal facilities. The summary of scenario costs shows that the recycle of copper is much more expensive that the direct disposal options available. Since the amount of copper arising is not sufficient to manufacture all canisters required only 2000 canisters have been considered in the assessment. In addition the operating lifetime of the plant of 25 years has been assumed in order to accommodate the small arisings per year. The plant assumed here is operating considerably under capacity.
The majority of copper waste will arise as contaminated copper which can be decontaminated very effectively by the refinery methods employed for normal copper scrap. If this is undertaken the resulting copper will be high quality material which could be allowed back into the unrestricted scrap market and hence not into a controlled nuclear area except by virtue of it being manufactured for that purpose. By undergoing a refining process, the waste from the copper will accrue and contain only limited amounts of copper but significant amounts of radioactive material by virtue of the decontamination process incurred as part of the refining technique.
The further development of the copper scenario is influenced by the lack of large sources of copper with the acknowledgement that the recycling of copper is likely to yield high purity copper that can be released from regulatory control. The recycling of copper in general is dominated by the pressures to return the copper metal back into the world copper pool market. This is encouraged by the high levels of copper refining available to produce high quality copper material. Recycling of copper from radioactive waste streams is likely to contribute only a fraction of the copper recycling market. This is emphasised in this scenario by the fact that the total amount required to produce all the canisters required for spent fuel disposal is only 64% of the annual production of copper from a single copper refinery.
Since the costs of the recycle are much greater than the costs of disposal there is no advantage in pursuing the recycle option. This, together with the logistical problems of collecting, sorting and transportation of the wastes, makes such a scenario unattractive. This conclusion is compounded by the political and environmental pressures which will ensue during the collection and transportation of wastes between countries.
3.8
SCENARIO 8 - ALUMINIUM STORAGE CANISTER
The final product identified was a waste canister of the type used for the storage of irradiated fuel specimens in PIE facilities in the UK. The waste canisters are used by AEA Technology and BNFL at facilities in Sellafield and are typically small cylindrical containers with screw-top lids. Dimensions are typically 2 - 10 cm high and up to 10 cm in diameter. Canisters are “deep-drawn and formed” which involves pressing the former into a sheet of aluminium and then extruding it (similar to the manufacture of beverage cans). Discussions with staff at AEA Technology have determined that they use approximately 50 per year with usage at BNFL being about the same. Thus the requirement for the final product is somewhat limited and the arisings of aluminium far outweigh the amount of material required for the production of such canisters.
Because of the limited usage of these canisters the costs of a plant for the production of aluminium products will be significantly larger than the costs of disposal of the material. The costs of the aluminium canisters are typically less than 1 ECU. Thus the production of these type of canisters from aluminium waste arisings is obviously uneconomic given the cost and usage of the canisters and the economic analysis of this scenario has not been considered in detail further.
It is therefore considered that recycling of aluminium from the nuclear sector would be best considered in the context of recycling of free-release into the commercial market-place given the majority of aluminium arisings within the UK could be effectively decontaminated. Melted scrap that did not meet the requirements for free release could possibly be used for the manufacture of deoxidiser as used in the steel making industry for the steel recycling scenarios considered earlier.
3.9
SCENARIO 9 - CONCRETE CRUSH/RECYCLE - SHIELD
WALLS
This scenario considers the crushing of concrete debris produced during the decommissioning of nuclear facilities within the UK for the purposes of reusing the crushed concrete in place of aggregate in cast concrete blocks that could be used as shield walls. It is assumed that a concrete crushing facility and facilities for the casting of large concrete blocks will be set up at the site where a large proportion of concrete waste will arise. Although mobile crushers are used in commercial industry it is considered that it would not be possible to operate this type of crusher with appropriate environmental protection as regards generation of concrete dust. The number of shield walls produced from crushed and recycled concrete that may be required in the future is difficult to quantify. It is dependent on the number of new facilities that may require shield walls or the number of existing shield walls that may be replaced. Typically shield walls may be required during decommissioning operations or in temporary waste storage areas. However the requirement for shield walls would be assessed as the need arises. The total weight of pre-cast blocks required for construction of a cell from interlocking concrete blocks is estimated to be 1180 tonnes. Assuming that 100% of the sand or gravel may be substituted for recycled concrete aggregates then up to 998 tonnes of recycled aggregates may be used to construct such a facility.
The cost of recycling concrete for manufacture into 2,000 t of shielding blocks has been estimated to be between 6.4 M ECU and 10.7 M ECU depending on the disposal charges for secondary wastes. The costs of disposal of the concrete if not recycled have been estimated to be between 5.9 M ECU and 40.5 M ECU depending on whether the concrete was disposed of at a near surface or deep disposal facility. The UK the assessment showed that even for a throughput of only 2,000 t per year in such a plant the recycling option and the disposal option costs are very similar. This is based on the assumption that there would be sufficient demand for shield blocks to construct such facilities. The economics of this scenario are driven by the large amounts of concrete to be disposed of and the relatively cheap technology required to produce recycled aggregates and manufacture of final products.
3.10
SCENARIO 10 CONCRETE CRUSH/RECYCLE
-PREFABRICATED CONCRETE PIECES FOR REPOSITORY
In all types of deep geological repository (DGR), only for clay formations is concrete material acceptable for the reinforcement of excavated tunnels and galleries. So salt, granite and other type of host hard rocks were excluded and the scenario has studied the crushing of concrete and recycling of the product for the manufacture of prefabricated concrete beams for a deep geological repository in clay, known as DOVELAS. During the construction phase (7 years) the required amounts of prefabricated pieces are of the order of 58,517 t/year. During the operation period the requirements are 3,308 t. It has been estimated that 60% of the gravel in the prefabricated pieces could be substituted by radioactive crushed concrete from the decommissioning of nuclear installations. The substitution of 60% of the gravel by crushed contaminated concrete would be equivalent to using 96,785 t of this material.
Manufacture of the beams requires a crushing plant to generate recycled concrete aggregates from concrete debris and a concrete fabrication plant to produce the structural concrete beams. Details of the equipment and processes required for the scenario are given in Appendix 2. The costs of recycling the concrete and manufacturing the beams has been estimated to be between 129 M ECU and 1168 M ECU depending on the disposal charges for secondary wastes. In contrast the costs of disposing of the concrete wastes are estimated to be between 182 M ECU and 3504 M ECU depending on whether the concrete is disposed of in a near surface or deep disposal facility. The construction of this type of repository is programmed in Belgium and is one option being considered in Spain. At present in Spain ENRESA is developing three models for different types of host rock with one of them for clay formations. Consequently the authors consider that the expansion of concrete recycling in deep geological repositories is unlikely beyond the use of pre-cast concrete pieces in interior gallery cladding for clay formations. The analysis carried out in this scenario assessment has shown that the recycling of concrete for prefabricated concrete pieces is technically feasible and less expensive than simply disposing of the concrete waste in a near surface repository. When disposal in a deep geological repository is required for secondary wastes or waste that would otherwise have been recycled there are considerable cost savings for the recycle option. This is because of the large volume of concrete being processed in the recycling operation.
3.11
SCENARIO 11 - REUSE OF FUEL PONDS AS INTERIM
WASTE STORES
The scenario is unique among the twelve considered in that it considers the reuse of the materials without the processing steps required to turn the materials into suitable products. The scenario is based on the reuse of concrete fuel cooling ponds located adjacent to power and research reactors. The new use of the ponds are as interim waste stores to hold the wastes arising from decommissioning before the materials are sent to a final disposal site such as a near surface or deep underground repository. Appendix 2 gives a brief outline of the currently known plans and work undertaken on cooling ponds in the UK and in the rest of Europe. The details of modifications required for the reuse of fuel ponds are also given in Appendix 2.
A cost comparison between the costs of reusing a fuel pond as a waste store and those for a comparable purpose-built interim waste store are given below.
Cost Component Pond reuse scenario Purpose-built facility
Minimum Maximum Minimum Maximum
ECU/m³ ECU/m³ ECU/m³ ECU/m³
Capital or modification 513 1,088 1,413 84,570
Operating 421 51,600 421 51,600
Waste transfer 292 1,066 292 1,066
Decommissioning 282 17,000 282 17,000
7RWDOV
Overall there is a difference in costs of between 1.6 and 2.2 times greater for purpose-built facility costs compared to those for a pond reuse scenario. This difference is from the variations in capital or modification costs which likewise have a three to seventy-seven increase from a pond reuse scenario. This analysis emphasises the variations in costs associated with building a new interim store and reusing a facility that, although not specifically designed as a dry waste store originally, has sufficient similarities to justify its reuse from storing spent fuel to storing intermediate level waste packages.
The scenario is limited by the global assessment required to analyse the cost components for a waste store from a typical fuel pond. When the needs for individual station decommissioning are assessed then local circumstances such as contamination levels and waste type are likely to dictate the of waste storage conditions. The costs put forward must be treated with some caution and only be used as a guide to understanding the requirements for reusing a fuel pond as an interim store.
3.12
SCENARIO 12: CONCRETE CRUSH/RECYCLE
-IMMOBILISATION MEDIUM FOR DRUMS IN A CONCRETE
DISPOSAL CONTAINER
In a near surface disposal facility, drums containing radioactive waste are placed inside concrete containers which are then filled with grout/concrete for immobilisation. This scenario considers the substitution of 50% of the sand by recycled aggregate. Currently between 440 and 500 containers are used per year at El Cabril, giving a potential use of about 700 t of crushed concrete per year. The aggregates produced at the dismantling site will be transported in containers or drums to the repository. A mobile crushing plant will be installed to treat and crush the concrete producing a fine product that will be used instead of conventional sand and gravel in the grout/concrete mixture. Further details of the equipment and processes used in the manufacture of concrete infill for grout are given in Appendix 2. The costs of recycling the material as an additive to grout have been estimated to be between 10 M ECU and 87 M ECU. The costs of disposing of the concrete wastes have been estimated to be between 13 M ECU and 256 M ECU depending on whether the concrete is disposed of at a near surface or deep disposal facility. There are considerable cost savings if the recycle
option is pursued when waste would have to be disposed of in a deep repository. As noted in Section 4 the use of recycled aggregates in place of sand or conventional aggregates may cause additional problems as regards grout characteristics and further research in this area would be required. Appendix 2 details an alternative method of using crushed concrete in grouts producing a hydraulic material that would contribute to the compressive strength of the grout. The requirement for grouting of concrete boxes at El Cabril requires a relatively small amount of recycled concrete when compared to other possible uses around Europe and the plant used could process considerably more concrete than is assumed. The extrapolation of the economic data for this scenario to the rest of the EC would provide significant cost savings for the recycling of concrete in this way.
3.13
CONCLUSIONS
Scenarios which involve the rolling of metal to produce plate for fabrication into final products would only be economic if considered on a large scale due to the sizes of rolling mills readily available within the steel making industry. Thus it is concluded that the production of waste drums (whether constructed from stainless steel, such as in the scenario considered here, or from carbon steel) would only be economic to carry out if significant demand for the final products could be assured within the country of site of the facility. The possibility of plants producing several kinds of rolled products, or even the production of products from both stainless and carbon steel may make production of vitrified product canisters and ISO containers feasible. The alternative method of manufacture of some products, such as back extrusion offers cheaper manufacturing alternatives to rolling manufacture. Problems in the transport of materials and products across borders may introduce difficulties in the operation of a large rolling facility if carried out on a European scale. Scenarios involving the rolling of steel to produce reinforcement bars require much smaller rolling mills and would be more economic. Re-bars require much less finishing than that required for the fabrication of containers.
The scenario considering casting as the primary method of fabrication suggests that this scenario would be economic and could be operated on a much smaller scale than those involving rolling operations. This type of fabrication is normally reserved for carbon steel recycling since cast steel or iron containers are normally required for shielding purposes only. Thus stainless steel casting (in order to produce a final product) is not carried out for the production of waste containers. Where stainless steel is used (as a corrosive protecting generally), it is used in plate form and welded to form containers. The production of fibres or granulates for replacement of aggregates or sand requires a relatively cheap and simple production technique and is therefore economically attractive.
Recycling of copper for spent fuel disposal canisters is considerably more expensive than disposing of the copper waste as it arises and purchasing copper for production of canisters from uncontaminated material. Copper waste arising during nuclear operations could be effectively decontaminated using normal copper refining techniques employed in industry and hence would be suitable for unrestricted release.
Recycling of aluminium within the nuclear industry would be unfeasible and recycling for unrestricted release would be the most likely form of recycling to be carried out.
Given the low capital and operating costs of concrete crushing plants all three of these scenarios are economically attractive. It was found however that use of crushed concrete beyond that of additives to grout for encapsulation of wastes would be limited. If incorporation of recycled concrete within grout were to prove feasible the cost savings in avoiding disposal charges for this waste would be considerable.
During the investigation into the feasibility of recycling concrete debris the regeneration of raw cement materials by use of a kiln similar to that employed in conventional cement making was examined. Further details of this process are included in Appendix 2. As this is a novel procedure, it was not possible to include this in the scenarios studied in detail, however given the possible problems of incorporating non-hydraulic material in grout it has been included here to highlight alternative possibilities for incorporation of recycled concrete in grout. The procedure is untried to date as it is uneconomic for conventional materials. However the disposal charges for concrete waste suggest that it may be economic for nuclear debris, although extensive research would be required. Further discussion of this alternative use of concrete within grout is discussed in Section 4.
4
Discussion of Strategy Related
Issues for Controlled Release
Recycling
This part of the study develops a strategic view of the value of the promising recycle scenarios with reference to the range of decommissioning and disposal strategies being adopted across Member States. A key part of the strategic assessment is to provide recommendations on the long term management of waste streams according to the phasing of construction and availability of disposal facilities. Since the overall strategy recommendations are driven principally by cost considerations, a ranking technique based on the disposal charge required to make the costs of recycling and the costs of disposal equal has been used. From a generic assessment of dose uptakes to workers involved in the recycling processes it is considered that the aspect of dose uptake is unlikely to be a limiting factor in many of the scenarios considered here (see Appendix 3).
The strategic assessment has the following aims:
• To rank the scenarios to give an indication of the most suitable ones that could be successfully carried out.
• To generate economic models of the most suitable scenarios to test their sensitivity to influencing factors that may detract from or add to their suitability.
• To identify strategic issues that are common to some or all the scenarios considered suitable for implementation.
Consequently, the steps identified are as follows:
1. Rank the scenarios according to merit (by disposal charge required to make the disposal and recycling options equal).
2. Sort the scenarios into suitability for near surface or deep repository use (on basis of disposal charge above).
3. Filter out scenarios that are not viable (such as aluminium and copper as the refining processes required tend to favour free release rather than recycling in the controlled nuclear sector).
4. For most promising scenarios estimate sinks across EU using the data from the disposal facilities in the EU (disposal charges, disposal volume, types of containers to be used etc.). 5. Match sources to sinks (on an EU scale). The volumes of waste disposed of per year from
above can be used to estimate the quantities of steel required for containers or grout required for the infill of containers.
6. Factor in decommissioning, disposal availability and waste arisings timescales. From the sink assessment the overlap between steel materials availability and requirement for containers can be assessed. Also for concrete wastes, the availability of material and the requirement for grout can be compared.
Section 4.1 discusses the ranking of the scenarios with Section 4.2 discussing the requirement for products manufactured from recycled material across the European Community. Section 4.3 discusses the strategic issues associated with the adoption of controlled release recycling.
4.1
REVIEW OF SCENARIO ASSESSMENT AND RANKING OF
SCENARIOS
Table 1 gives a summary of the economic assessments carried out for each of the twelve scenarios. For each scenario the difference in the costs of recycling and the costs of disposal are given for two assumed disposal charges. A disposal charge typical of those for disposal at near surface disposal facilities and one for disposal in a deep repository have been used to assess the effect of disposal charges on the economics of the scenario. Using these two cost assessments the disposal charge required for the cost of recycling to break even with the costs of disposal have been calculated. This then enables the scenarios to be ranked in order of the most economically attractive. Scenario 4 (ISO containers) and scenario 8 (aluminium canisters) have not been included since initial assessments indicated that they would be economically unviable. Scenario 11 has also been omitted as this scenario gives indicative costs for a range of cases only.
Disposal cost to break even (ECU/m3)
1 Scenario 10 Concrete - prefabricated beams 510
2 Scenario 12 Concrete - grout 747
3 Scenario 3 Stainless steel drums 1,227
4 Scenario 9 Concrete shield blocks 2,532
5 Scenario 2 Cast steel box 2,792
6 Scenario 6 Steel granulate 3,684
7 Scenario 6 Steel fibres 3,776
8 Scenario 5 Steel rebars 6,775
9 Scenario 7 Copper canisters 90,305
10 Scenario 1 Vitrified waste product canisters 110,498
Based on the scenario ranking it can be seen that the most attractive scenarios from an economic view point are those for steels and concrete, for the construction of waste disposal containers or for use in disposal facilities. The copper scenario will not be considered further because the refining process is more likely to yield copper suitable for free-release. In addition there is insufficient copper arising as waste to run a plant dedicated to its refinement at full capacity.
In order to assess the sensitivity of the above analysis to the assumed costs for operating/decommissioning and for capital costs of plant, a sensitivity analysis has been carried out. This examines the effect of increasing the plant cost by 20%. The results of this analysis give the roughly the same orders of ranking of the scenarios and do not greatly affect the results of the critical ranking technique, the most economic scenarios are still those for steel and concrete. With increased capital, operating and decommissioning costs the ranking is the following:
Disposal cost to break even (ECU/m3)
1 Scenario 10 Concrete - prefabricated beams 604
2 Scenario 12 Concrete - grout 889
3 Scenario 2 Cast steel box 3,416
4 Scenario 9 Concrete shield blocks 4,046
5 Scenario 6 Steel granulate 4,417
6 Scenario 6 Steel fibres 4,516
7 Scenario 3 Stainless steel drums 5,869
8 Scenario 5 Steel rebars 8,249
9 Scenario 7 Copper canisters 111,155
10 Scenario 1 Vitrified waste product canisters 152,224
4.2
ESTIMATED REQUIREMENTS FOR FINAL PRODUCTS
ACROSS EUROPE
Uses of recycled materials other than in disposal facilities are limited. For example, in the area of spent fuel management, detailed plans for disposal of this waste are only in the planning stages for many countries thus limiting the scope for a plant dedicated to production of spent fuel disposal containers. Indeed the designs of containers and methods of management vary
considerably from one country to another, with France and UK favouring reprocessing and vitrification, Sweden and Finland favouring disposal in copper lined canisters and Germany favouring storage in steel flasks. In the approach to LLW/ILW waste disposal however there is much more similarity with all countries using grout cements as immobilisers, similar designs of concrete boxes and of course drums. Thus a European wide assessment has focused on those scenarios which appear to be economic and have widespread use in the nuclear industries around Europe. Details of disposal facilities currently in operation in Europe are summarised in Table 2 in order to identify the requirement for products such as those considered above. Information has been obtained from Refs. [1] - [9]. Further details of disposal facilities currently in operation in the EC are given in Appendix 4, along with details of spent fuel management options being considered in each country.
From the information gathered in Table 2, the requirements for steels for rebars, boxes, drums and concrete for boxes and grouts across Europe have been estimated. The results are presented in Table 3. The source data and sinks data for carbon steel, stainless steel and concrete are compared in Figures 6, 7 and 8 respectively.
A comparison of the total estimated arisings of steels and concrete and the total estimated requirements for steels and concrete in waste disposal boxes (either for manufacture of containers or for infill of containers) are summarised below.
Material Total Mass Material (t)
Arisings Requirements
Carbon Steel 1,110,000 441,000
Stainless Steel 290,000 54,000
Concrete 500,200 1,381,000
The amount of carbon steel that could be recycled into waste containers and rebars is around 40 % of Europe-wide arisings. For stainless steel the fraction of material generated that could be recycled is smaller at around 20 % of arisings. In contrast for concrete requirements exceed arisings by 2 times. This is because of the vast amount of grout required for waste packaging - virtually all disposal facilities use grout for immobilisation of wastes.
Examination of the timescales for arisings and requirements (Figure 6) indicates that for carbon steel up to around 2037 the arisings of material as waste and the requirements for steel for rebars, waste drums and waste boxes are generally well matched. After 2037 the estimated requirement for steel (based on currently operating disposal facilities) falls and the arisings of steel increase dramatically as many power stations reach Stage 3 decommissioning.
For stainless steel, which is used in the manufacture of boxes and drums for ILW, the requirement for final products appears to be much smaller than the predicted arisings (Figure 7). There is a generally steady underlying requirement for ~1,000 t of stainless steel per year up to 2050.
Timescales for the arisings of concrete and the requirement for recycled aggregates for use in grouts and for production of boxes appear mismatched and the requirement for recycled concrete greatly outweighs the arisings up to 2037 when arising from decommissioning of power stations increases (Figure 8). Post 2037 arisings always exceed demand for recycled
concrete, due partly to estimated requirements for products being based on data for currently operating disposal facilities. The largest part of the requirement for recycled concrete is for incorporation into grouts. Estimated requirements for concrete aggregates for boxes only amount to 532,390 t of recycled concrete i.e. only 39 % of the total requirement. The total requirement for recycled aggregates for manufacture of boxes is very similar to the total amounts of arisings of concrete wastes. However again the timescales on which recycled concrete may be required and the timescale on which it arises are not matched.
Examination of the timescales for demand of recycled products against the arisings of material that could be recycled to produce them has shown areas that need to be examined in more detail. One of the weaknesses in the present examination is that estimation of the sink for recycled products has had to be based on the information of currently operating disposal facilities. Many of these disposal facilities are only licensed up to 2010 or become full during the time period examined thus reducing the possible sinks for the product in disposal facilities. When the largest amounts of material become available during Stage 2 and 3 decommissioning of commercial nuclear power reactors, disposal plans are unclear and for many countries extra disposal (or storage capacity) would have to be sought. In particular planned disposal capacities in Germany are unclear after the licence for Morsleben expires in 2000. Also for Sweden disposal capacities from 2010 onwards are unclear. Sinks for steels and concrete are estimated to reduce at around 2037 which coincides with the capacity at L’Aube in France being reached. It is therefore expected that the requirement for packaging and disposal of decommissioning wastes will give further opportunities for recycling in these areas post-2037, probably exceeding the requirements in the early part of the 21st century. The prospect of recycling concrete debris for use in the manufacture of concrete waste boxes suggests that this may be a suitable sink for the majority of concrete waste arising until 2037. A large majority of the concrete boxes assumed to be required here are at L’Aube in France which uses them for packaging and disposal of wastes in drums (see Appendix 4). After 2037 the requirements for recycled concrete for the manufacture of concrete boxes falls, generally due to uncertainties in the number of concrete boxes that may be required for disposal facilities. The possibility of utilising crushed concrete debris within grouts for the immobilisation and encapsulation of wastes within boxes offers a considerable sink for waste concrete with a requirement double that of concrete boxes. The possibilities of reusing concrete in either of these ways would produce considerable savings in disposal charges if the scenarios were to prove viable.
4.3
OTHER ISSUES RELATED TO STRATEGY DEVELOPMENT
Table 4 lists some of the other issues, apart from timescales, that are for relevance to the issue of recycling within the controlled nuclear sector. Each of these issues is addressed in turn and discussed in the context of the identified feasible scenarios.
4.3.1 Recycling for Controlled Nuclear Use and Unrestricted Use
The recycling or reuse of materials or components (including buildings) can either be by restricted or unrestricted use. For restricted release (such as considered in this study) the materials/components remain under regulatory control. For unrestricted release the materials are no longer the subject of regulatory control and can be used anywhere because they have
been judged to represent negligible risk to the general public now and in the future. The IAEA has proposed a tiered system for the recycling and reuse of materials and components from the nuclear sector. For steels these tiers comprise of :
1. Direct release for recycling or reuse
2. Recycling by melting at a commercial foundry for subsequent unrestricted release or reuse 3. Recycling by melting at a controlled facility followed by remelting at a non-nuclear facility 4. Recycling by melting at a controlled facility for specified industrial use
5. Recycling by melting at a controlled facility for reuse within a controlled environment The first four of these steps result in the material being removed from the controlled environment, only for the last step does the material remain within the nuclear sector. For concrete recycling there would be fewer tiers because there is unlikely to be a market for recycled concrete outside the nuclear industry. The tiered approach to concrete recycling is more likely to be:
1. Direct release for recycling/reuse or disposal at landfill site
2. Recycling by crushing in a commercial crushing plant for subsequent unrestricted release/ reuse or disposal
3. Recycling by crushing at a controlled crushing facility for specified industrial use (e.g. foundations in runways, roads where public exposure may be minimal)
4. Recycling by crushing at a controlled facility for reuse within a controlled environment Recycling and reuse for controlled nuclear use must therefore be considered as part of a wider framework of recycling for unrestricted use or free-release. The decision whether to recycle (or reuse) materials and/or components for restricted or unrestricted use depends on many factors, some of which are specific to a facility or a country and others which are international [10]. These include:
• The availability of regulatory criteria giving activity levels for unrestricted use and those which may only be released of restricted use
• The availability of technology and facilities to recycle the items
• The availability of instrumentation to measure regulatory activity levels and quality assurance programmes to assure compliance with the criteria.
• The effect that recycling of materials will have on the extension of natural resources
• The economic implications including cost of decontamination, waste disposal, market value of recycled materials.
• The socio-political attitudes in the affected country or industry regarding the recycling/reuse of materials or components.
Many of the above factors are more important for the release of materials from regulatory control rather than their recycle and reuse within the nuclear sector. However some of the above have relevance or implications for the restricted use of materials as discussed below. Practices involving the recycling or reuse of components from the decommissioning of nuclear facilities must be controlled on the basis of the principles of radiological protection. These include three essential components - justification of a practice, optimisation of a
controlled release recycling as unrestricted recycling. Justification requires that no practice involving exposure to ionising radiation shall be adopted unless its introduction produces a positive net benefit. All exposure to radiation is assumed to involve some degree of risk and the optimisation of radiation protection requires that exposures should be kept as low as reasonably achievable (ALARA), economic and social factors taken into consideration. Appendix 3 discusses generic dose considerations of recycling for controlled nuclear reuse in order to give some indications for individual doses for recycling processes. It is concluded that recycling processes required for the most economic of the scenarios studied could be limited to conform to annual dose exposures recommended by the IAEA. In most cases extra radiological protection may be required to that used in normal industry but can be easily achieved although incurring extra capital cost for processing equipment and increased operating costs.
A working party sponsored by the EC is preparing a report in which radiological protection criteria are proposed for the recycling of scrap metal from the nuclear industry [11]. These proposed clearance levels for contaminated metal are given in terms of mass and surface activity concentration levels for specific radionuclides. The proposed clearance levels for metal scrap recycling are given in Table 3.1 of [11] and are repeated here:
Nuclide Clearance Levels for Metal Scrap Mass specific (Bq/g) Surface specific (Bq/cm2) H-3 C-14 Mn-54 Fe-55 Co-60 Ni-59 Ni-63 Zn-65 Sr-90 Nb-94 Tc-99 Ru-106 Ag-108m Ag-110m Sb-125 Cs-134 Cs-137 Pm-147 Sm-151 Eu-152 Eu-154 U-234 U-235 U-238 Np-237 Pu-238 Pu-239 Pu-240 Pu-241 Am-241 Cm-244 1000 100 1 10000 1 10000 10000 1 10 1 100 1 1 1 10 0.1 1 1000 10000 1 1 1 1 1 1 1 1 1 10 1 1 100000 1000 10 10000 10 10000 1000 100 1 10 1000 10 10 10 100 10 100 1000 1000 10 10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 1 0.10 0.10
For materials with levels of activity concentration above the proposed clearance levels, a case by case assessment of the kind currently performed by the competent authorities in accordance with national regulation may be required for a particular recycling application.
The recycling or reuse of components from nuclear facilities is currently handled in individual member states using various criteria based on existing legislation. Most member states having nuclear facilities have established permissible levels of surface contamination on objects intended to be removed from controlled areas. These values however vary from one country to another. The lack of European-wide criteria hinders the release of materials for recycling and introduces uncertainties with respect to the amounts of waste that may be suitable for recycling only in the controlled nuclear sector, since the assessment included in this study assumes that suspect radioactive material and easily decontaminated material will be sent for free-release rather than being available for restricted use.
Monitoring for compliance with release criteria is a relatively routine operation for many materials or components. In particular the melting of metal enables easy characterisation of material activity and demonstrating that release criteria have been met.
The aspect of resource extension is not directly applicable to recycling/reuse in nuclear industry as the amounts of materials recycled are generally very small when compared to recycling markets in commercial industries.
In many European Member states economic factors will be the most significant considerations in deciding whether to recycle or reuse materials in the controlled nuclear sector and recycle for free release. In all cases the overriding compulsion will be to recycle materials for free-release. In the case of metals such as stainless steel, aluminium and copper, scrap for unrestricted release are high-value metals. In contrast the demand for recycled concrete is low with cheap alternatives from non-nuclear sources being readily available. Here the economic drivers will be to avoid nuclear disposal costs if necessary by reducing levels of activity to allow disposal in a normal landfill site or by reuse of recycled aggregates within the nuclear industry.
Socio-political factors must also be considered. Since recycling of components or materials from decommissioning or refurbishment of nuclear installations is not a routine activity at present, considerable public concern may be anticipated in the case of unrestricted release of substantial amounts of materials. Even if the radiological risks from unrestricted release are negligible, public and government concern may force nuclear operators to recycle for restricted use or alternatively to dispose of the items. Recycling for restricted use (such as that considered here) should not experience the same level of opposition. Similarly, when deciding upon the future use of site of a decommissioned installation, public acceptance of a new nuclear facility on the same site may be easier than elsewhere which is a point in favour of continued nuclear use, especially if such sites are scarce.
The recycling of materials for controlled nuclear use provides a pathway for the use of materials that do not meet the release criteria but for economic or other practical considerations recycle or reuse may be prescribed for a limited (controlled) purpose. Such materials may be recycled within the nuclear industry if controls can ensure that the accidental release of the material for public use will not occur, or that other means of potential public exposure can be prevented and that the radiation exposure of workers within the nuclear industry can be kept as low as reasonably achievable (ALARA).
