WASTE MANAGEMENT ISSUES, A SET OF TECHNOLOGIES

Transcription

1 WASTE MANAGEMENT ISSUES, A SET OF TECHNOLOGIES Jean Jacques GAUTROT Senior Director, Business and Programs Department COGEMA, Fuel and Recycling Branch ABSTRACT As any other industry, nuclear fuel cycle back-end raises the major issue of waste management. In France, spent fuel is considered as valuable materials and only the ultimate waste are considered as actual waste. Accordingly, waste issue is as follows : a sorting out has to be done, in order to separate valuable materials from actual wastes, put any outlet flow under a stable form and condition them appropriately to their respective recycling or disposal routes. This implies the implementation of a comprehensive set of technologies. Actually, it is an industrial reality, as the COGEMA Group has for a long time set up a reprocessing and conditioning strategy in its plants. Waste management issues are common to many activities. European as well as French regulators already introduced the twofold necessity to reduce waste volumes, and to dispose of only ultimate waste as concerns industrial and household waste mainly. In this objective, French nuclear reprocessing and recycling industry may be seen as a breeding ground of well-proven technologies and management options. Actually, processes used can also give an answer to such different issues as excess plutonium immobilization, sites cleaning up (including for instance treatment of the liquid HLW legacy), dismantling wastes management. There are a number of operations to be dealt with worldwide that will find a solution in any of the technologies implemented and optimized in COGEMA facilities. Based on the COGEMA Group know-how, the present paper will describe those technologies and explain how they can solve the other stringent waste management issues worldwide. INTRODUCTION As any other industry, nuclear fuel cycle back-end raises the major issue of waste management. In France, spent fuel is considered as valuable materials and only the ultimate waste are considered as actual waste. Accordingly, waste issue is as follows : a sorting out has to be done, in order to separate valuable materials from actual wastes, put any outlet flow under a stable form and condition them appropriately to their respective recycling or disposal routes. This implies the implementation of a comprehensive set of technologies. Actually, it is an industrial reality, as the COGEMA Group has for a long time set up a reprocessing and conditioning strategy in its plants. Waste management issues are common to many activities. European as well as French regulators already introduced the twofold necessity to reduce waste volumes, and to dispose of only ultimate waste as concerns industrial and household waste mainly. In this objective, French nuclear reprocessing and recycling industry may be seen as a breeding ground of well-proven technologies and management options. Actually, processes used can also give an answer to such different issues as excess plutonium immobilization, sites cleaning up (including for instance treatment of the liquid HLW legacy), dismantling wastes management. There are a number of operations to be dealt with worldwide that will find a solution in any of the technologies implemented and optimized in COGEMA facilities.

2 Based on the COGEMA Group know-how, the present paper will describe those technologies and explain how they can solve the other stringent waste management issues worldwide. A SET OF TECHNOLOGIES AND MANAGEMENT OPTIONS In its facilities, the COGEMA Group offers a technically mastered solution for spent fuel reprocessing. Actually, a near 30-years experience at La Hague demonstrates its industrial mastery. This unique industrial complex uses a comprehensive set of technologies in order to sort out, treat and safely condition high quality valuable materials as well as every kind of ultimate waste arising from spent fuel treatment, in order to offer a global answer to its clients waste management issues. Moreover, the COGEMA Group continuous commitment to spent fuel smooth management and minimization of waste volume involves R&D activities. First of all, the reference process used at La Hague is the PUREX process. The main stages involves dissolution in hot nitric acid followed by selective extraction of uranium and plutonium in order to separate valuable materials (U, Pu) from fission products and other actinides. Final products are then prepared : uranyl nitrate and plutonium oxide which is sent to MELOX plant to be further processed into recyclable MOX fresh fuel. The implementation of the PUREX process has led to design and optimize new industrial equipment compatible with nitric acid media such as the zirconium row dissolver. In addition, solvent extraction technologies have been further refined to achieve a plutonium recovery rate greater than 99.8%, including optimization of chemical media solvent and extracting TBP as well as equipment : mixer-decanters, pulsate columns and centrifuge extractors. Second, separated plutonium as oxide powder is processed into MOX fuel in the MELOX facility. The reference process is the A-MIMAS process, which is based on the well-proven MIMAS process, qualified in the DESSEL and CADARACHE plants. The PuO 2 powder is micronized with UO 2 powder to form a primary blend of 30 % Pu content. The primary blend is then diluted with UO 2 powder to obtain a secondary blend at the specified enrichment. Scraps can be recycled at different stages in the process line after a specific treatment. The next stages are pelletizing, sintering, grinding, pellets sorting, cladding, rods control and sorting and rods bundle assembling. To comply with the evolution of the Utilities requirements (product specifications and quantities), COGEMA has proven its capability of adaptation with the MELOX fuel Customization Building and its PWR and BWR multi-design assembling line. The MELOX plant evolution has been conceived with the strong support of R&D programs implemented in the CDA, the COGEMA Group Advanced Development Center. In MELOX the nuclear material is separated from the operator and the outside world by several successive barriers in order to minimize the personnel dose uptake and to protect the environment. In consequences, the operations are automated and computer controlled. Nevertheless, thanks to the excellent cooperation between the three parties concerned, EURATOM, the French national authorities and the operator, the safeguards implemented at MELOX are effective and efficient.

3 Third, ultimate waste are sorted, treated and conditioned as follows: - As for HLW containing fission products, the internationally recognized vitrification process has been adopted. The R7/T7 calcination, vitrification and storage of glass canister facilities were commissioned, respectively in 1989 and Each unit was designed to produce more than 550 glass canisters per year. The operation is based on a continuous process developed by the French CEA (Commissariat à l Energie Atomique) and operated since 1976 at the AVM (Atelier de Vitrification de Marcoule). Today, vitrification of the fission products contained in one ton of spent fuel amounts to 0.1 m 3 of glass, or about 0.7 Universal Canister. However, the COGEMA Group pursues its R&D on vitrification, in the form of the cold crucible promising technology. - As for ILW containing structural parts of fuel elements (hulls and end-fittings) with long-lived radionuclides, they will be compacted in the ACC facility in the shape of discs. Each canister will be filled with 5 to 7 discs according to their thickness. Up to 2,400 canisters will be produced per year at the ACC. The ACC, a new compacting facility, will be commissioned by the end of year 2000 at La Hague site. This new facility results from an important R&D program, including technical and economical feasibility demonstration as well as inactive and active testing. The goal is to produce less than 1.5 Universal Canister per ton of reprocessed spent fuel. - Less active waste are constituted by a variety of low and intermediate level short-lived or TRU residues. It comprises resins and sludge from effluents treatment as well as operating and maintenance waste. For each of these flows, appropriate technologies and/or management options for treatment or conditioning has been developed and implemented. - As for resins, a cement stabilizing process has been demonstrated and is in commissioning stage. - As for sludge, optimization has already been done and this flow was discontinued, as part of an innovative and comprehensive program including extensive recycling (Advanced Active Effluent Management in 1996). - Two workshops are dedicated to the recovery of most of plutonium contained in α contaminated waste and scraps produced on the COGEMA Group facilities, by means of an electrochemical leaching process. - As for short-lived technological waste, the NGD program (Nouvelle Gestion des Déchets, i. e. Advanced Waste Management System) is based on sorting out at the workshops where waste are generated, including zoning of the workshops according to waste type and accurate measurement of activity contained in primary waste drums. Then waste is either conditioned on site or sent for treatment to the CENTRACO plant, with two units operational since 1999 for two kind of waste : - Melting of short lived metallic waste (1,500 t/y), - Incineration of combustible technological wastes (which include gloves and clothes) as well as liquid waste. The incinerator design capacity is 3500 t/year of solid waste and 1500 t/year of liquid waste. This centralized installation creates a large upheaval in the management of LILW from nuclear facilities for different reasons: - it results in a drastic reduction of volumes of waste to be disposed of, - the characteristics of the waste are very different, and in particular they present themselves under a solid stable form, - it will result in packages ready for disposal

4 Besides, the implementation of NGD implies among others a tool adapted to low levels of activity measurements. The AD2 workshop allows a precise measurement of α and β activity (drums are X-rayed) contained in waste prior to their treatment in the CENTRACO incinerator, or their on-site conditioning (in C0 metallic drums or CBF fiber concrete drums). Final, the COGEMA Group has cumulated on its La Hague and Marcoule sites more than 200,000 hours operations similar to decommissioning works. Experience has been carried out in different parts of the process dealing with very variable levels and nature of radioactivity : from the very high level to the low and very low level, including an alpha or beta dominant radioactivity : unloading, decanning, dissolution, purification, plutonium conversion, uranium purification, vitrification. The COGEMA Group has thus acquired a great feedback experience on chemical decontamination processes as well as robotics and measurement techniques. WASTE MANAGEMENT ISSUES Waste management issues are not specific to nuclear industry. Actually, they are one of the sensible points of any industry if sustainable development is considered. European and French legislation have as early as 1975 stressed out the necessity to minimize industrial and household waste volumes. In France, it was further completed by the 1992 waste law which introduced the ultimate waste notion as a waste resulting or not from a treatment, and which is not liable to be treated considering the current technical and economical conditions, especially by extraction of its valuable parts or by reduction of its polluting or hazardous properties. This law set out the deadline of 2002 to dispose of ultimate waste only. Moreover, two decrees issued in 1992 stressed out the necessity for ultimate waste to be stabilized prior to their disposal in the current landfills dedicated either to banal or toxic waste. Considering the French status for the back-end of nuclear fuel cycle, waste management issues are solved. Moreover, the available set of technologies may worldwide prove useful in many other fields of nuclear or non-nuclear activities. In the nuclear field, main waste management issues are constituted by the various activities related to decommissioning, dismantling and site cleaning up, among others: the legacy of plutonium arising from weapon dismantling, the liquid HLW resulting from past reprocessing activities, the decommissioning of outdated facilities. Besides, some countries also have to deal with less active waste. EXCESS PLUTONIUM IMMOBILIZATION The US National Academy of Science (NAS) has called the plutonium stockpile from strategic weapons a clear and present danger and defined a standard for the definition of disposition option: the spent fuel standard. That is to say that the excess weapon-grade plutonium has to be transformed into a plutonium as inaccessible and unattractive for retrieval and weapon use as the residual plutonium contained in spent fuel from commercial reactors. The MOX option is most appropriate for achieving the spent fuel standard. It consists in fabricating a Mixed OXide Fuel and burning it in commercial reactors, leading to a degradation of the plutonium isotopic composition. As a consequence of the Strategic Arms Reduction Treaties START I and II signed in 1991 and 1993 between the U.S. and Russia for the disarmament of strategic weapons, both the US and the Russian Federation are considering the MOX option for the management of their weapon plutonium. Actually, in addition to providing

5 all the guarantees of nuclear safety and safeguards, the MOX option make advantage of the high energy potential of weapon-grade plutonium. MOX fuel fabrication is an option which benefits from a thirty-years experience in Europe and particularly in the COGEMA Group. It is a fully operating industry with proven reliability of deliveries and products quality, operating under the control of relevant national and international Authorities, in particular the IAEA and EURATOM. Actually, the COGEMA Group and US companies Duke and Stone & Webster regrouped under the consortium DCS have signed in March 1999 a first contract of US$ 130 million with the USDOE. DCS will provide a comprehensive service, including the design, construction management, operation and deactivation of a MOX fuel fabrication plant. The consortium will also be responsible for obtaining license from the NRC to operate the facility. The contract covers a 17 years period and involves 33 tonnes of weapon-grade plutonium. Fuel fabricated should be used in 6 American civil reactors. Consequently, the team will also modify these existing LWR to use the MOX fuel. As for Eastern stockpiles, France and Germany have developed bilateral cooperation programs with the Russian Federation as early as 1992 to assess the feasibility of recycling weapon-grade plutonium in Russian reactors: it was demonstrated for WWER 1000 and fast reactors. In 1996, they decided to combine their efforts in a joint initiative. Consequently, the COGEMA Group and Siemens have launched together with MINATOM the DEMOX project, which include the design, construction and start-up of a MOX demonstration plant in the Russian Federation. The DEMOX facility will implement the A-MIMAS process for WWER fuel fabrication. For BN fuel fabrication, the COGEMA Group experience is also available. Actually, this technology has been developed for thirty-years at the Cadarache facility, accumulating a manufacturing experience of 135 thm of FBR fuel. SITES CLEANING UP : TREATMENT OF THE LIQUID HLW, ILW AND LLW LEGACY Sites cleaning up includes a variety of waste management issues concerning various activity levels as well as physical waste forms. In the case of liquid waste, the most appropriate and durable immobilization option is constituted by vitrification. For instance, in Italy, a vitrification unit using the French technology of the cold-crucible melter is being designed for the conditioning of some 200 m 3 of the HLW and LLW currently stored at the EUREX plant from former reprocessing of CANDU and MTR fuels (CORA project). The cold crucible melter process is based on the use of a water-cooled metallic structure that is transparent to the electric field produced by an induction coil surrounding it, allowing currents to be generated inside the glass contained in the structure. This process has among others the advantages of being very flexible for a wide range of waste and glass formulations, of being compliant with very corrosive materials and of generating a very low volume of secondary waste. The contract for the project was signed in 1997 with a joint venture including the COGEMA Group engineering company SGN. The vitrification station should begin operating in The main liquid HLW waste management issue concerns four USDOE sites dispersed throughout the country. These wastes have been stored in large underground tanks, some of them for nearly 50 years. They are a by product resulting from the reprocessing of spent nuclear fuel of weapon or research grade in order to extract valuable materials. These waste were essentially produced at

6 the Savannah River Site in South Carolina, the Hanford site in Washington State, the Idaho National Engineering and Environmental Laboratory (INEEL) in Idaho and the West Valley Demonstration Project in New York State. The management program set up by the DOE aims in particular at retrieving the waste and treating them to obtain an acceptable form for disposal in a federal underground repository. At Savannah River Site, the Savannah River Site Defense Waste Processing Facility (DWPF) near Aiken began radioactive operations in March The DWPF facility is designed to immobilize by vitrification radioactive waste stored in 51 underground storage tanks at SRS. In 1997, the operational closure of two tanks was performed. Since bulk waste removal had already been performed on those tanks, they were known to have rather low level of residual radioactivity. As a consequence, the technology used for the immobilization of residual waste was the in-tank grouting. At INEEL, most of the acidic HLW has already been retrieved and processed. It leaves HLW residues and waste resulting from decontamination activities. Different clean up options are under consideration, from complete removal of tank facilities and clean up of contaminated soils, to bulk waste removal and stabilization of residues. As for the West Valley Demonstration Project, the major part of the liquid HLW stored - resulting from Purex and Thorex processes - has been immobilized though vitrification under a borosilicate glass form in Tanks closure efforts currently aims at selecting between various alternatives, from in-tank stabilization to complete removal and processing. At Hanford site lays the largest number of HLW storage tanks. There are 177 underground tanks at the former military facility. Moreover, as a number of different spent nuclear fuels reprocessing approaches were applied on this site, the waste are more heterogeneous than on the other sites. The overall strategy is to retrieve the waste and immobilize it for subsequent disposal. The low level and hazardous chemical waste will be vitrified into glass forms that can then be disposed of at Hanford. As for the HLW, they require a more complicated vitrification process. They are highly caustic and present different forms: liquids, slurries, saltcakes and sludge. Once vitrified, waste will be conditioned into stainless steel canisters for disposal in an underground repository. DOE waste will be disposed of in the same repository as civilian spent fuel. All of the waste must be removed from the underground storage tanks at Hanford and stabilised by Within the framework of the Hanford Tank Waste Remediation System Project and the phase 1.A. Hanford Privatization Feasibility study, the COGEMA Group nuclear engineering company SGN was responsible of the HLW facility design, for the implementation of the cold-crucible technology. The cleaning and decommissioning operations at the UP1 reprocessing plant on the Marcoule site started in A joint venture including the COGEMA Group under the name of CODEM was officially created in CODEM is responsible for the overall management, funding and control of the decommissioning and dismantling operations, while respecting the constraints of nuclear safety, environmental protection and cost-effectiveness. The Marcoule plant, first of a kind in France, was commissioned in During its lifetime, tons of spent fuel (AGR) were reprocessed. The cleanup operations of Marcoule site are scheduled for a 30-years period and are divided into 3 main programmes: - Deactivation of the UP1 plant and its associated facilities. - Decommissioning and Dismantling (D&D) of facilities leading to a final status of Facility Classified for the Protection of the Environment (ICPE). - Handling and conditioning of radioactive waste temporarily stored on site.

7 Remote technologies and robotics are widely used in the COGEMA Group plants for operations such as maintenance, which are somewhat similar to those to be conducted for D&D. Thus, when the Marcoule D&D project started, it was expected that remote technologies and robotics would be extensively used. Actually, it turns out that chemical decontamination could be good enough to allow operator intervention in most cases, thus reducing the use of remote technologies to very specific fields such as: - mapping out radiation levels in the facilities, - D&D specific equipment. DISMANTLING WASTES MANAGEMENT In France, EDF is currently in the process of finally shutting down 4 reactors (CHINON A3, SAINT LAURENT A1 and A2 Gas Cooled Reactors and the PWR CHOOZ A reactor). After shutdown, the dismantling policy is to quickly carry out fuel unloading. Then drainage or removal of equipment and material connected with the installations (fluids, filters, and resins) is performed: the technologies for treating them are already available. Then the partial dismantling of some annex facilities is carried out. Complete dismantling of the most active parts is postponed for a period of about 50 years. In this first phase, the wastes produced consist mainly of insulating material, steel and technological waste. They are characterized by: - a low activity level, - a very large volume, compared to plant operation waste. Nature Quantities per reactor Activity Insulating 250 tons < 10 Bq/g Scrap Iron 2000 tons < 1000 Bq/g Technological waste 4500 X 200 l steel drums a few Bq/g The CENTRACO facility for fusion and incineration will be a major asset for the management of these wastes, from the economic viewpoint as well as for preventing contamination dissemination. Such a facility will make it possible to acquire experience which, at the start of the new century, will result in treating scrap iron from dismantled nuclear power plants under the best safety condition, and assure the recycling of what can be re-used. Actually, the COGEMA Group currently offers all the best available technologies needed in nuclear facilities D&D operation waste management: - Remote technologies, - Low level activities measurement techniques, - Chemical decontamination mastery, - Technologies for liquid waste management - CENTRACO type facility for the treatment of the solid waste large volumes that will arise from dismantling operations.

8 OPERATION WASTE MANAGEMENT Waste management issues may also arise from the operation stage. With its eleven reactors, Korea has to cope with growing volumes of low and intermediate level operational waste currently stored on-site. It was thus expected that storage capacity would be saturated by year 2010 unless a waste reduction program was launched. Waste management issues became a national concern and different processes were studied for waste volume reduction. It was then envisioned to apply vitrification technology to LILW. In this objective, a pilot vitrification facility has been opened in This facility will simulate operation of a future industrial scale facility for processing and conditioning LILW. Its aim is to demonstrate the technical feasibility as well as the economic viability of the cold crucible process on an industrial scale. This process has been developed by the French CEA and adapted for industrial use by the COGEMA Group nuclear engineering company SGN. This facility is part of a US$10 million joint R&D program between SGN and KEPCO. In the non-nuclear field, numerous applications of techniques developed for the purpose of radioactive waste management industry may be found. One of the most widely used techniques lies in measurement devices. For instance, landfills for conventional waste are not authorized to accept any radioactive waste, which are to be disposed of in dedicated centers. In this objective, they are equipped with devices developed within the COGEMA Group in order to detect and measure very low specific activities in different objects ranging from small samples to big-bags or even large drums. Other technologies are used: for instance the rare earth and ore processing industries benefit from the experience developed in the COGEMA Group as concerns solvent extraction technology. However, the most promising transfer of know-how lies in the field of toxic waste (so-called special industrial waste in France). Household refuses as well as conventional and special industrial waste are often treated by incineration. Residues from off-gas treatment (the so-called REFIOM and REFIDI) concentrate the toxic heavy metals initially contained in primary waste. As of now, they are ultimate wastes. In France, their annual tonnage amounts to 300,000 to 400,000 t and due to their high polluting characteristics, they must be either disposed of in dedicated underground repositories or stabilized prior to their disposal in specific surface landfills. A most satisfying valorization treatment of these residues is constituted by vitrification. This process guarantees pollutant destruction and resulting inert ultimate waste may be reused in road works. The COGEMA Group nuclear and chemical engineering companies offer comprehensive services for the processing of household and industrial waste. Other applications could be found, especially in the medical field. Waste management issues arising from healthcare activities lays in the highly polluting potential of the so-called healthcare risk waste. A global management system has to be set up, including sorting out and appropriate evacuation pathways. These could benefit from the experience acquired in the nuclear industry. CONCLUSION The technologies and the experience feedback acquired by the COGEMA Group since their implementation may worldwide prove useful in many other fields of nuclear industry. In fact, there are a number of waste management issues to be dealt with worldwide, in the nuclear field or

9 not. These waste issues often threaten the whole industry from which they arise: they have to be safely managed otherwise the fate of the whole industry, however beneficial, will be at stake, either technically or to the general public opinion. Many of these waste management issues do have a technologically mastered solution that has already or could be implemented on the basis of any of the technologies existing and optimized in the COGEMA Group facilities. Let us guess that the global market for new high technologies in waste management will consider nuclear fuel cycle technologies as a huge reserve of ideas, proven processes and cost effective solutions.