Ph. Pradel and Ph. Fournier
COGEMA

P. Miquel, C. Veyer
SGN
1 rue des Hérons, Montigny-le-Bretonneux
78182 St-QUENTIN YVELINES CEDEX - FRANCE
BP 508, 50105 BEAUMONT LA HAGUE CEDEX - FRANCE

The total volume of high level and TRU waste produced at La Hague is already less than what would result from the direct disposal of spent fuel. The excellent performances of modern reprocessing plants have opened the way to further waste minimization. The paper describes the recent or planned modifications aimed at reducing the volume of waste intended for deep disposal.

In addition, waste management of the back end of the fuel cycle now accounts for the operation of MOX fuel fabrication plants, through deliberate reduction of the volume and of the contamination of the waste and implementation of centralized waste processing facilities.

As a result, the proportion of plutonium sent to deep disposal with the residues from the whole back end of the fuel cycle will be limited to about 0.1 of the Pu present in the reprocessed fuel, in a volume of waste already lower than 0.5 m³/t.

Tremendous efforts are also made to reduce the volume of low level waste, through improved sorting, recycling and new treatment units.

Since the start-up of the "Melox" MOX fuel fabrication plant in 1995, the French reprocessing/recycling policy has entered a phase of industrial maturity. In a near future, a yearly amount of 115 t of mixed oxides will be recycled into a number of French LWR reactors, with a possibility to increase this capacity in the future.

The major entities involved in closing the backend of the fuel cycle in France are :

• UP3 and UP2-800 plants, at La Hague, where the spent fuel is reprocessed in order to recover and purify reusable materials (U, Pu) and where the other spent fuel constituents are concentrated and immobilized into safe and durable forms,
• the MELOX facility, where the recovered plutonium is used to fabricate MOX fuel.

These facilities are operated by one single operator, COGEMA, with the constant will of minimizing releases, reducing the amount of long-lived alpha (TRU) waste liable to be disposed of in a deep repository and concentrating the waste into very stable forms with the smallest possible volume. This policy led to seeking the best integration for waste management over those facilities, with particular emphasis on systematic identification of waste sources, reduction of activity and/or volume contributions for each of these sources, standardization of packages and implementation of centralized facilities to perform selected processing operations.

For low-level and short lived waste, liable to be disposed of in shallow-land repositories, efforts are focusing on volume reduction, through the addition of new centralized facilities (incineration, fusion) to the existing waste management system.

The La Hague site houses two reprocessing facilities, UP3, designed to reprocess 800 t/yr. of spent UO2 PWR and BWR fuels, was commissioned first in 1990. UP2-800, designed to reprocess 800 t/y of spent UO2 and MOX PWR and BWR fuels was commissioned in 1994.

UP3, the first large size commercial reprocessing plant, incorporated innovative features designed to maximize the performance of the process while minimizing the releases and the volume of waste [1, 2] : containment of most of the b g activity, in the highly active part of the plant, systematic recycling of the major reagents (acid, solvent, diluent), in-line waste conditioning of all waste streams to produce originally four categories of residues:

• vitrified high level waste holding more than 99% of the b g activity from the fuel, in stainless steel canisters, 1.3 m high and 0.43 m across,
• fuel structural material (hulls and end-pieces) grouted in large stainless steel containers,
• bituminized precipitation sludges arising from the decontamination of liquid low and medium level effluents, in stainless steel drums,
• technological solid waste conditioned in fiber-concrete containers.

From the very beginning, it appeared that plant performances were excellent both in terms of separation efficiency and waste generation. Most design objectives were largely exceeded, as shown in previous publications [3, 4].Similar features were implemented in UP2-800 which confirmed the good performance of the concept.

In terms of waste management, one important feedback of the very satisfactory operation of the reprocessing plants was that the volumes and activities of low and medium level aqueous effluents were, from the beginning, significantly lower than estimated at the design stage. This made it possible to further improve liquid waste management and suppress one of the original streams of intermediate level activity residues intended for deep disposal - bituminized precipitation sludges -, as described in previous publications [5, 6].

The new aqueous waste treatment scheme is based on a more sophisticated segregation of the effluents according to chemical and activity contents and the implementation of additional evaporating capacities in the plant. Most of the aqueous effluents are thus separated into a Very Low Activity fraction which can be released to the sea after filtration and monitoring, with no significant increase of the overall annual activity release, and a concentrated fraction holding most of the activity, which is routed to HLW vitrification.

An additional specific treatment is applied to the effluents from the analytical laboratory, since they may hold at the same time significant alpha contamination and chemicals unwanted for the vitrification. This treatment, described in details in a previous publication [7], consists of :

• Segregation of the effluents according to their chemical contents, so that as many compatible effluents as possible are directed to the above effluents treatment facilities.
• Alpha decontamination of the remaining 100 m³/yr. of effluents by ferric coprecipitation with optimized amounts of reagents followed by cross-flow ultrafiltration. The decontamination solution is monitored and adjoined to the Very Low Activity effluents. The observed plutonium decontamination is such that most of the time during the two first years of operation, the plutonium concentration in the solution was below the detection limit. The resulting plutonium decontamination factor ranged from higher than 1000 to higher than 10.000.
• The concentrated pulp, holding the bulk of the activity, is redissolved using nitric acid before being routed to the vitrification facility where its contribution to the overall glass volume is negligible.

This effort, which resulted in a decrease of the high activity and long-lived waste volume below 1 m³/t is still going on, to further reduce the radiotoxicity and volume of long-lived wastes by optimizing the use of equipments, implementing increasingly sophisticated effluent and waste management policies and building new dedicated facilities.

Until 1995, the fuel structural material (hulls and end-pieces) was conditioned by grouting. Following the decision by COGEMA to implement a new compaction process, the grouting facilities were shut down and the hulls and end-pieces are now stored in drums pending the start-up of the future ACC facility.

This ACC (French acronym for "Hulls Compaction Facility") scheduled for commissioning around the year 2000, will process the fuel structural material arising from both UP3 and UP2-800 head-ends, together with other solid technological wastes intended for deep geological disposal.

In the ACC facility, the hulls and end pieces will be dried, poured into compaction cans and compacted. The solid technological wastes will be received, unloaded, inserted into compaction cans and compacted. The compacted discs will be inserted into so called "CSD-C" Universal Canisters, with an outer geometry similar that of the "CSD-V" Universal Canisters presently used to pour the HLW glass. The characterization and safety assessment of this new type of packaging is nearing completion [8]. The annual production capacity of ACC will be around 2200 CSD-Cs.

The implementation of this new conditioning technique is expected to bring down the volume of conditioned structural waste by a factor of 4. Since, after the suppression of bituminized waste, this waste stream contributed the largest volume to the waste intended for deep disposal, it will be indeed a significant step in the overall volume reduction of conditioned long-lived waste.

In addition, the standardisation dimensions and outside characteristics of the new packages will allow the standardization of handling and transportation systems for a large part of the residues intended for deep disposal.

The two HLW vitrification facilities of La Hague, R7 and T7, continue their steady operation, producing an average overall volume of about 115 l of conditioned glass/t of reprocessed fuel, for a fuel burnup of 33.000 MWd/t. By the end of September, 1997, 5300 glass canisters had been produced. COGEMA also closely follows the development of the cold crucible melter at the CEA.

The solid technological waste intended for deep disposal consists of operational waste (tools, failed equipment, filters...) coming from the most contaminated parts of the facilities. Prior to packaging, they are decontaminated, sorted and preconditioned in the facilities of origin or in specific centralized facilities. They are then dispatched to the centralized solid waste processing facility (AD2) on the La Hague site where the waste intended for deep disposal is conditioned in fiber-concrete CBFC-2 containers. These 1.18 m³ containers, certified by ANDRA, have also received a "HIC" agreement by the US-NRC in March, 1995.

Following the start-up of UP3, the solid technological waste management has considerably evolved, according to the experience gained in maintenance and repairs and as a result of the equipment reliability. At present the volume of conditioned solid technological waste intended for deep disposal amounts to about 0.3 CBFC-2 container per t of reprocessed U. Further minimization of this volume is expected, through the use of various technologies, such as plutonium decontamination of solid waste (see below), compaction and development of equipment repair techniques.

At present, the implementation of the various improvements described above allow to constrain the volume of conditioned waste intended for waste disposal to about 0.5 m³ per tonne of reprocessed U.

One of the major features of the advanced Purex process implemented in UP3 and UP2-800 is the improved solvent management, with intensive recycling and purification of the solvent and diluent streams in an innovative solvent distillation process [9]. This scheme allows to reduce the amount of organic material to be disposed of to a very small stream holding the solvent degradation products and residual activity.

Very soon, this last small amount of organic residue, together with other organic contaminated fluids (lubrificants, oil...), will be transformed into a mineral form which can be grouted like any other mineral low level waste. The resulting package has received an agreement by ANDRA, the French waste management operator, for disposal into a shallow-land repository. The pyrolysis process developed for that purpose and implemented in the new facility is described elsewhere. At the time of printing, the MDS-B facility is ready for start-up as soon as the operating license is granted.

From September 1998, a new facility will condition the spent resins from pool water treatment by grouting into fiber concrete containers. The resulting packages are intended for disposal in a shallow land repository.

The management of low activity and short lived waste has also considerably evolved.

Originally, all the low-level and short-lived solid technological wastes intended for shallow-land disposal were conditioned in CBFC-1 fiber-concrete containers with performances similar to those of the previously mentioned CBFC-2 containers. However, in France, the low level waste disposal specifications make a distinction between the lower activity waste which must only be mechanically stabilized and the more active waste for which stabilization and radionuclide containment are required. Since, from the first years of operation of the new plants, it appeared that the activity of the waste was lower than expected, it was decided to take advantage of the situation by sorting the waste according to their activity and, after eventual compaction, conditioning the lower activity waste by grouting in "CO" stainless steel drums for stabilization, the use of the more expensive CBFC-1s being reserved for the waste requiring radionuclide containment.

The implementation of this new sorting policy from the beginning of 1995 allowed a decrease by a factor of 3 of the volume of this type of conditioned waste. In 1995, the volume of conditioned low level solid technological waste amounted to 1.4 m³/t U.

At mid-1998, a second significant volume reduction step will be implemented when the CENTRACO centralized incineration and fusion facility will start-up. The incinerator will process combustible waste (cottonwool, paper, plastics) with alpha and beta activities lower than 50 Bq/g and 20.000 Bq/g respectively. The ashes will be grouted in "CO" - type drums. The fusion facility will process metal waste with the same levels of activity into ingots. Both ultimate residues are intended for shallow-land disposal.

The implementation of this policy will allow a further volume reduction to less than 1 m3/t U for conditioned low level solid technological waste.

The successful industrial implementation of plutonium recycling relies on three major principles :

• Pu recovery from the fuel must be efficient.
• Pu recovery should not leave aside significant quantities of non re-usable plutonium. Therefore, an efficient plutonium management must deal with Pu-containing scraps and americium accumulation if needed.
• As much as possible, the overall Pu activity in the waste must be limited.

These above principles have been included early into the design of the back-end of the commercial Pu cycle, resulting in the following management concepts :

• Purification and recycling of non-directly usable materials (scraps and aged Pu).
• Recovery and recycling of Pu from the waste generated during the operation and maintenance of Pu-processing facilities, in association with volume reduction techniques.

The efficiency of Pu separation from the fuel is ensured by a very selective extraction process allowing the recovery of more than 99.8 % of the plutonium fed to the two La Hague reprocessing plants. A new R4 plutonium final purification and conversion facility is under construction in the UP2-800 plant. The start-up is scheduled for 2001.

For aged Pu or scraps, recovery consists in dissolving oxide materials (PuO2 powder, UO2 + PuO2 powders or UO2 + PuO2 pellets) in nitric acid and injecting the resulting nitric solution at selected locations of the reprocessing plants to purify this recovered plutonium. For the dissolution step, a method based on oxidative dissolution of PuO2 using electrochemically generated Ag(II) has been selected based on extensive development by CEA [10].

The first small size industrial facility of this kind, able to dissolve batches of 1 kg of PuO2 powder in 4 hours, was commissioned in 1989 in the T4 facility of UP3 at La Hague to recycle the remnants of PuO2 samples and dust recovered from the T4 PuO2 processing facility itself. More recently (1994), a centralized large capacity industrial unit able to perform the recycling of aged Pu and of the scraps from MOX fuel fabrication has been commissioned in the R1 facility of UP2-800 at La Hague. This unit - URP - is able to process PuO2 powder as well as mixed UO2/PuO2 powders and sintered pellets from various origins. The dissolution liquor is diluted and recycled either at the head of the plant or at the entrance of the Pu purification line.

The general principles applied for Pu contaminated waste management may be summarized as follows :

• Careful selection of equipment to provide easily processable waste.
• Sorting of the waste according to nature (stainless steel, plastics, ...) and activity at the source of generation (Pu production facilities at La Hague, MOX fuel fabrication facilities). Recovery of the entrained Pu (ex : dusting of filters).
• Safe preconditioning in drums at the source of generation.
• Processing in centralized solid waste treatment facilities, for further decontamination and/or compaction if required. Some of the facilities able to perform these operations have not been commissioned yet. The sorted and preconditioned waste are at present in interim storage facilities at the production sites, awaiting for their start-up.
• Ultimate conditioning together with the other waste intended for deep disposal at centralized solid waste processing facilities at La Hague.

To decrease the amount of Pu associated with solid waste, a leaching process has been designed for solid waste, based on the same oxidative dissolution principle as that used for scraps or aged plutonium, with process adaptations.

A small size unit of this type, manually operated in glove boxes, has been commissioned for the specific use of the T4 facility in UP3 plant. The 40 l electrolyzer is able to process annually around 100 batches of stainless steel filters, failed metal equipments and some plastics.

A large size centralized unit - UCD - located in the R2 facility at La Hague, has been installed to process solid Pu-contaminated waste from all La Hague facilities, from MOX fuel fabrication plants and from TRU waste interim storage facilities.

The solid waste (metal cans or filters, some plastics) are received in drums, unloaded, sorted in batches according to the type of material, cut, ground ..., leached in a specific, conventional geometry tank by electrogenerated Ag(II) ions, rinsed and dried prior to unloading, control and preconditioning. The facility is able to process 400 batches of waste per year. The decontaminated waste, preconditionned in drums, will then be dispatched to the AD2 centralized waste conditioning facility on the La Hague site. Most of it will be compatible with disposal in a shallow-land facility after eventual compaction and conditioning. The waste remaining for deep disposal is inserted in fiber concrete containers and a significant part of it will be able to be comported in the future. The recovered solution is purified from undesirable chemicals in a specific extraction cycle prior to being sent to the first extraction cycle of the reprocessing plant.

The objective is to upgrade about 80 % of the TRU waste processed in this facility for shallow-land disposal.

The management of waste associated to the back end of the fuel cycle reflects the will of limiting as much as possible the flow of TRU waste liable to be disposed of in a deep repository, as required by the philosophy inherent to the reprocessing / recycling concept.

The implementation of this rigourous policy will allow to limit the proportion of plutonium sent to deep disposal to 0,1 to 0,2 % of the amount found in the reprocessed spent fuel. When compared to the 100 % figure corresponding to direct disposal, the impact on radiotoxicity and long term safety of deep disposal will be very favourable (future up to 10).

The use of centralized facilities allows the standardisation of residues. Almost all of the long-lived and high activity residues will be conditioned in small size, easily handled universal canisters.

The contribution of recycling in itself (and more specifically MOX fuel fabrication) to the overall volume of long lived waste is low. The total volume of waste intented for deep disposal is expected to represent, in a very near future, less than 500 l/t reprocessed HM.

1. W. FOURNIER, D. HUGELMANN, G. DALVERNY, C. BERNARD, P. MIQUEL, A. LEUDET - "Purex Process Improvements for the UP3 Spent Fuel Reprocessing Plant at La Hague, France" - ISEC'90.
2. C. BERNARD, P. MIQUEL, M. VIALA - "Advanced Purex Process for the New Reprocessing Plants in France and in Japan" - RECOD'91.
3. D. ALEXANDRE, P. LEDERMANN, C BERNARD - "Operational Performance of the Reprocessing Plants of COGEMA La Hague site". - RECOD'94.
4. K. ASADA, C. BARANDAS, C. BERNARD, Ph. BRETAULT, C CREUSOT, D. HUGELMANN, Y TAKAOKU - "Experience Feedbacks of La Hague Plants to the Design of the Reprocessing Design of the Rokkasho Reprocessing Plant". -GLOBAL'97.
5. Ph. PRADEL, Ph. FOURNIER, P. MIQUEL - "Waste minimization in modern reprocessing plants at La Hague" - GLOBAL'95.
6. P. LEDERMANN, P. MIQUEL, B. BOULLIS - "Optimization of Active Liquide and Solid Waste Management at the La Hague Plant" - RECOD'94.
7. R. LIBERGE, FJ. PONCELET, G. SENENTZ - "Treatment of Active Laboratory Liquid Wastes by Ultrafiltration" - GLOBAL'97.
8. G. MAURIN, G. LIMEUL, P. KAPLAN, F. CHOTIN, X GENIN - "Quality and Safety of COGEMA Universal Canister filled with Compacted Hulls, End-Pieces and Technological Waste" - GLOBAL'97.
9. F. DRAIN, JP. MOULIN, D. HUGELMANN, P. LUCAS - "Advanced Solvent Management in reprocessing : 5 years of industrial Experience" - ISEC'96.
10. FJ. PONCELET, MH. MOULINEY, V. DECOBERT, M. LECOMTE - "Industrial use of electrogenerated Ag(II) for PuO2 dissolution" - RECOD'94.