Jan-Marie Potier
ANDRA
France

William J. Gallagher
COGEMA Technologies, Inc.

This paper describes France’s experience in the management of low- and intermediate-level short-lived radioactive waste (LILW). This experience results from several decades of operational activities in the nuclear industry, covering the entire fuel cycle, from electricity production to spent fuel reprocessing. Consequently, large quantities of radioactive waste are generated by this extensive nuclear program. Currently, 20,000 m³ of LILW are delivered to and disposed of in surface facilities each year.

The first repository for LILW, known as the Centre de la Manche, started operation in 1969 and received the final waste delivery in 1994. This facility features two disposal concepts: tumuli and monoliths, presented in this paper. A new surface repository called the Centre de l’Aube was licensed in 1992. Its design capacity will accomodate 1,000,000 m³ of LILW over 50 years of operation. The new facility, managed by France’s radioactive waste management agency, ANDRA, promotes a safe and cost efficient disposal system based on multiple containment barriers. The Centre de l’Aube disposal concept has become a worldwide reference for LILW surface repositories and has been adopted by many countries.

In France, low- and intermediate-level wastes (LILW) primarily result from electricity generation and fuel reprocessing operations. Currently, 55 nuclear power reactors representing a total power of 60 GWe produce more than 75% of France’s electricity.

Since 1979, the management of all radioactive wastes generated in France has been the responsibility of the National Radioactive Waste Management Agency, ANDRA, encompassing surface operations and deep disposal projects. Through the Centre de la Manche repository, which was operated for 25 years and received 525,000 m³ of LILW, and the new Centre de l’Aube facility, which started operations in 1992 and already accomodated 50,000 m³ of waste, France has gained valuable experience in surface disposal of radioactive waste.

In France, the government has considered that only a public organization, independent from the industry, can guarantee the continuity required for long-term management of radioactive waste, keeping responsibility to future generations.

Therefore, the National Radioactive Waste Management Agency (ANDRA) was established in 1979 within the French Atomic Commission (CEA). In December 1991, under the Radioactive Waste Management Act, ANDRA was transformed into an independent and responsible state-owned organization, under the threefold authority of the Ministers of Industry, Research and the Environment.

The 1991 Act specifically delegates the following responsibilities to ANDRA:

• Establishment of waste acceptance criteria for disposal;
• Siting and implementation of new radwaste repositories;
• Management of existing disposal facilities;
• Participation in research on long term management of long-lived and high-level radwaste, including construction and operation of underground research laboratories;
• Inventory of all sites containing radioactive materials on the French territory.

Consequently, the Agency is simultaneously an operator, a research organization, and a public service company with a staff of 390 employees and a yearly budget of 1,200 million French Francs (U.S. $200 million) in 1998 totally financed by its clients, the waste generators.

The Ministries of Industry and of the Environment are the governmental authorities responsible for matters pertaining to nuclear safety. Operation and post-closure performance objectives regarding radwaste disposal facilities are specificied in terms of radiation dose limits through Fundamental Safety Rules (FSR) by the Regulatory Authority, the Directorate for the Safety of Nuclear Facilities (DSIN). DSIN is also involved in licensing and control of nuclear facilities, along with the Office for Protection against ionizing radiation (OPRI) which reports to the Ministry of Health.

The generators are responsible for the characterization and conditioning of their radwaste. They must submit acceptance files to ANDRA for all new waste forms to demonstrate compliance with ANDRA’s disposal criteria. ANDRA carries out quality audits and inspections at the generators’ premises.

The radwaste producers are the major contributors to the financing of waste management, including ANDRA’s activities.

In France, LILW is managed in compliance with Fundamental Safety Rules (FSR) which set performance objectives for radwaste disposal facilities both on the short term during operation and on the long term, after closure.

FSR I.2. stipulates that short-lived LILW may be disposed of in surface facilities.
FSR III.2.e defines waste forms acceptable for disposal in surface repositories.

According to these Rules, the disposal system must protect the general public and the environment and allow reuse of the site after a monitoring period of 300 years. Isolation of radioactivity contained in the waste is achieved through a multiple-barrier system consisting of:

• waste packages,
• engineered disposal structures, earthen cap and water collection system, and
• site geological formation.

The integrity of the waste containment system must be maintained throughout the operating period (a few decades) and the Institutional Control Period (not to exceed 300 years).

Waste acceptance criteria for surface disposal are derived from these safety requirements. Waste containing primarily beta/gamma emitters with half lives of less than 30 years are accepted. Low amounts of long-lived alpha emitters may be disposed of within specific activity limit of 3.7 GBq/t (0.1. Ci/t) per individual waste package or .37 GBq/t (0.01 Ci/t) on average for the overall facility.

Waste acceptance criteria also require waste to be solid or solidified, contain no free-standing liquids, no organic liquids, no pyrophorics, less than 0.1 gram of fissile material per liter of waste form.

Currently, about 20,000 m³ of LILW are produced in France each year and delivered to l’Aube facility. LILW originates from three main sources:

• The utility, Electricité de France (EDF), for 7,000 m³ from all NPP sites;
• The nuclear fuel cycle company, COGEMA for 8,000 m³ from La Hague and Marcoule reprocessing plants;
• The Atomic Energy Commission (CEA) for 3, 000 m³ for all R&D activities related to civil and defense programs.

Since 1988, efforts made by the nuclear industry have contributed to significant volume reductions: 32,000 m³ in 1988 and 17,000 m³ in 1997.

In the near future, two new waste treatment facilities dedicated to incineration and melting of LLW will be commissionned. Further waste volume reductions are expected, down to a total quantity of 12,000 m³ in the year 2000.

In the early 1960s, the nuclear research activies development highlighted the need to set up a radioactive waste management system. The establishment of a disposal facility for low- and intermediate-level waste was conceived as early as 1968 near the reprocessing facility of La Hague in Normandy, and to be overseen at the time by the French Atomic Energy Commission (CEA). The decree, authorizing the CEA to implement the Centre de la Manche, was delivered in June 1969. From 1969 to 1994, a total volume of 525,000 m³ were delivered to the Centre de la Manche and disposed of in structures built at ground level.

The first disposal units, built in 1969 by the Infratome Company, which ran the center, were simple trenches in the earth, similar to other facilities around the world at that time as could be found in the United States, U.K., and Russia.

Very low-level waste was then simply packaged in steel drums. More active waste was conditioned in concrete blocks or stabilized in steel drums. The trenches were drained, and covered with a plastic liner and a layer of earth.

After few months of operation, because of difficult weather conditions and ground stability problems, the disposal technique evolved and new types of structures appeared:

• Below-ground level, for intermediate-level waste, drained engineered trenches subdivided in small 15 or 30 m³ disposal cells built with prefabricated concrete panels. Voids between waste packages are filled with a cement mortar.
• Above-ground level, for low-level waste, on a 2,000 to 3,000 m² stabilized and drained area, packages, either concrete containers or steel drums, are stacked forming 4 m-high pyramids.

These two disposal concepts were widely used during the 1970s. During the same period, site environmental monitoring showed in 1976 abnormal activity levels due to tritium in the nearby Sainte Hélène River.

This incident contributed to a general awareness of the need to better define waste acceptance criteria, improve waste conditioning, implement control procedures on waste packages, strengthen site environmental monitoring, improve the water drainage system to separate run-off from leachate.

In 1979, a new entity was created, ANDRA, the National Radioactive Waste Management Agency within the French CEA. Soon after, ANDRA took over from Infratome and became the operator of Centre de la Manche facility.

Further evolution of the disposal concept occured in the 1980s and improvements implemented by ANDRA resulted in new disposal structures known as monoliths and tumuli. These structures are described in the following section. During that period, a major achievement was the construction of a new water drainage system. Its purpose was to collect water seeping into the disposal units which might be contaminated and keep it separate from run off water. The waterpipe system was installed inside buried concrete galleries to facilitate control and maintenance.

As presented in Figure 1, two types of disposal structures have been used at Centre Manche since the early 1980s till the end of operation in 1994:

- Monoliths, generally constructed below ground level, consisting of reinforced concrete walls and top and bottom slabs. The monoliths are dedicated either to medium-level waste packages or to low-level waste whose packaging does not provide by itself sufficient containment of radionuclides. Some peripheric walls are not made of concrete but consist of stacked up concrete containers. Spaces between waste packages are grouted with concrete or cement mortar. Unit capacity varies from 50 to 80 m³.

• Tumuli, generally constructed above ground level and on top of monoliths. Pyramid-shaped tumuli are constituted with concrete containers at the periphery and metallic drums containing waste in the center. Tumuli are dedicated either to very low-level waste or to waste whose conditioning and packaging provide adequate radionuclide containment. Voids between waste packages are backfilled with gravel to ensure stability of the tumuli.

All disposal structures are drained. Leachate is directed via a separative water collection system (SWCS) towards monitoring tanks. Leachate composition and activity are monitored. Effluent treatment is provided by the nearby COGEMA plant.

After operation, the disposal structures are covered with a several meter-thick earthen cap. This temporary impervious cover minimizes infiltration of rainwater into the structures. Data on the Centre de la Manche are presented in Table I.

The Manche disposal facility ceased operation in June 1994. Figure 2 shows an aerial view of the Manche facility in 1994. Construction of the multiple-layer earthen cap started in 1990 and was completed in 1996. In the near future, the facility will be licensed by the Regulatory Authority to enter the Institutional Control Period. ANDRA will be responsible for the monitoring of site environment and for providing maintenance or any additional works as required during the 300 years of the surveillance period.

According the French Fundamental Safety Rule, the disposal site is required to contribute an additional guarantee of the adequate isolation of waste from water, which is the only foreseeable mechanism for the transfer of radioactivity during the 300 years of the Institutional Control Period, following the operation. Therefore, the site must possess hydrological and geochemical properties that would mitigate a potential failure of one of the barriers of the waste isolation system, by controlling the release of radionuclides into the ground. The site must also feature simple hydrogeological characteristics that enable modelling to be performed for safety assessment purposes.

The Centre de l’Aube site features simple and favorable characteristics which garantee that any infiltrated waster would re-exit the disposal system at a short distance. The water outlet of the site constituted by the nearby Noues d’Amance River, is clearly identified and easy to control. Site radiation monitoring at the water outlet allows overall verification of the safety of the disposal facility. Abnormal amounts of radiation would be detected at very low levels by highly sensitive monitoring equipment.

Another favorable hydrogeologic aspect at the Aube’s site is the low water table which prevents groundwater from reaching the bottom of disposal structures whatever the future meteorological conditions may be.

The geochemical characteristics of the Aube subsurface geological formations are quite favorable. The clay layer presents high sorption capability for radionuclides such as cesium contained in waste.

At the Centre de la Manche facility, all waste handling operations were performed by means of cranes or forklifts.

At ANDRA’s Centre de l’Aube, the dose objectives for site workers were set for design purpose at 5 mSv per year and 10 mSv over 5 years, which is one tenth of the regulatory limits. To comply with this constraint the decision was made either to automatize or to remotely control all handling operations. Currently, the workers’ maximum integrated dose rates do not exceed a fraction of mSv per year and fully comply with ICRP 60 recommendations.

The weather conditions of the Centre de la Manche, with high rainfalls and strong winds, resulted in operational difficulties. The water collection system collected high volumes of potentially contaminated water that required control and treatment. The design approach selected for the Centre de l’Aube consists in a better protection of the waste packages and disposal units against rainwater during operation by means of mobile shelters. Consequently, high volumes of water are kept away from the potential source of contamination and remain clean. They may be discharged directly to the environment through a storm basin to regulate the outflow. Water volumes infiltrating through the disposal units and routed to the separative water collection system remain minimal. One major advantage is that the low volume of liquid effluents which require treatment can be easily collected and stored before off site treatment. A liquid effluent treatment plant is not required on site.

Because of numerous sources and streams of LILW generated in France each year, a large number of waste forms and package geometries are produced and delivered to the Aube facility. Despite the generators’ efforts to reduce the waste volumes and standardize the packages, provision has been made by ANDRA in designing the facility to accomodate all types of waste packages : from 100-l drums to 10 m³ metallic boxes, and from 0.8m³ concrete packages to 5-m³ concrete containers. The disposal vaults accomodate both types of waste containers: metallic and concrete. However, the material used to fill in the spaces is different: gravel or concrete.

Flexibility is a major feature of the Aube facility which facilitates adjustment of operation to new waste types or fluctuations of deliveries.

Like the Centre de la Manche repository, the Aube disposal system will provide long-term isolation of radioactivity and protection of the general public through multiple containment barriers.

Since the start-up of radwaste disposal operations in France in the late 1960s, nuclear safety regulations have been strengthened and performance objectives raised. Consequently, the waste acceptance criteria have been revised and the engineered structures improved. One particular issue deals with the acceptance of long-lived radionuclides in surface disposal facilities. In order to comply with the objective of minimizing restrictions on site use after 300 years, the specific activity of long-lived emitters has been specified and some long-lived waste such as radium or thorium have been prohibited.

The dose limit for the facility has been set at 0.25 mSv per year for the general public.

The rise of the French nuclear program led to the government’s decision, announced in 1984, to develop a new disposal center for radioactive waste. In October 1984, the siting process began began in three departments where zones presenting favorable characteristics had already been identified. Following geological, hydrogeological, and geochemical characterization, ANDRA was granted the authorization to pursue its investigations in the Aube department in July 1985.

All regulatory steps, including the public hearings involving local populations concerned by future disposal facilities, were undertaken from mid-1985 to mid-1987.

The construction of the disposal facility took three years, from fall 1987 to December 1991. Operations began in January 1992 when the first radioactive waste packages were delivered to the Center. At the end of 1997, 75,700 m³ of waste had been delivered.

The Centre de l’Aube is located 200 km east of Paris, in the Aube Department. It is serviced by a railway terminal located in the town of Brienne-le-Château, 13 km away from the site. Nestled in the middle of a large forest, the facility is linked to a network of roads via a 4-km access route. The entire property covers approximately 100 hectares.

The disposal area of the Centre de l’Aube encompasses about a third of the facility’s land. The disposal vaults (about 420) will eventually cover 30 hectares for a total capacity of 1,000,000 m³.

The industrial buildings situated in the controlled zone consist of:

• The waste conditioning building, including a waste supercompactor and a grouting facility for metal drums;
• A transit building for the temporary storage of certain waste packages;
• The maintenance workshop;
• The network and the collecting and monitoring tanks for drainage water.

The service buildings, including access locker rooms to the controlled zone, the radiological monitoring laboratory and the storm basin collecting the site’s run-off water are located outside the controlled zone.

The other buildings are located in guarded areas:

• Security station
• Administrative building
• Restaurant
• Ancilliary facilities (electrical substation, water treatment, fire network).

The visitors center, located at the entrance of the compound, on the edge of the access road, receives about 7,000 visitors per year.

The design developed by ANDRA for the Centre de l’Aube provides a sound and durable engineered system consisting of waste containers stacked in concrete vaults ultimately covered after operation by a slab and lined with a waterproof coating. During operation, the vaults are protected from the rain by movable steel-framed shelters, as shown on Figure 4.

Beneath the vaults, a water-collection system is used to collect and to detect the presence of infiltration water in the disposal units. Water collected in the system is routed to an impoundment basin, where it is monitored for radioactivity and treated if necessary before release.

Remotely operated overhead cranes handle waste containers from the transport trucks to their final location in the vaults. For tracking purpose, each waste package is identified by a bar code label. Upon delivery, each package is tracked and its final location is recorded through a computerized system.

Two types of concrete vaults are used for the final disposal of radwaste. Long-lived waste packages, such as concrete containers, are placed in disposal structures, whose void spaces are filled with gravel. Steel drums which are considered as short-lived envelopes are placed in vaults where spaces are grouted with concrete.

Six different disposal vaults are simultaneously operated:

• Three gravel vaults equipped with 3 t, 10 t and 35 t capacity cranes
• Three concrete vaults equipped with similar waste handling devices.

After a structure has been filled, an impervious material is sprayed on the concrete walls and roof to prevent water infiltration and the shelter is moved to the next structure.

After operation, a multiple-layer cap will be placed on the disposal structures to limit water infiltration and prevent waste leaching and release of contaminants. The permanent cap system will be designed to meet the following requirements :

• To restrict infiltration of water to less than a few liters per sq. meter and per year;
• To resist erosion weathering and bio-intrusion in order to minimize the need for maintenance and repair;
• To allow monitoring of water infiltration rate and facilitate detection and localization of cap failure.

The Aube permanent cap design may be similar to La Manche multiple-layer cover, which complies with the same requirements.

Data on the Centre de l’Aube are presented in Table II.

The French experience in radwaste management has shown significant progress over 30 years of operational activities. Low-and intermediate-level waste can be managed in a safe and cost efficient manner and disposed of in surface facilities, with good public acceptance. Various key issues have contributed to the success of the radwaste management program in France:

• Appropriate organization with clearly defined responsibilities between the Regulatory/licensing authority, the Waste Management Agency ANDRA and the radwaste generators;
• Well established nuclear safety and environmental protection objectives and performance requirements for disposal facilities;
• A sound and solid engineered system consisting of multiple containment barriers;
• Public involvement and consultation during the siting process;
• Full transparency towards the public regarding all disposal activities;
• Active contribution to the regional economic development.

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