J. Corcos And M. Nicolas Andra
1-7 rue Jean Monnet 92298 Chatenay-Malabry Cedex
France

Since its opening (january 1992), the near-surface disposal facility for short-lived LLW-ILW packages, the so-called Centre de l'Aube, has provided a successful implementation of french radwaste management system, which is briefly reminded in this paper.

Basic framework for radioactive waste management (i.e acceptance of waste package types with respect to technical specifications) has been set up for an increasing number of standardized packages. Figures are given, with repartition by types of waste, conditioning process, containers, and origins. Presentation also includes data on volumes, activities, and miscelaneous information on the disposal of radwaste.

Although the near surface disposal concept has remained the same from the beginning of Andra experience in the radwaste management field, general design was improved for the Centre de l'Aube disposal, regarding 30 years of experience as presented in this paper. Comparison between actual data issued from the operation (5 years statistics) and data based on previous estimates made by waste producers in 1991 is illustrated by figures.

Improvement of structures, in order to obtain more flexibility and to reduce disposal costs, is presented, with an overview on ANDRA's new challenges for specific waste packages.

This paper provides information on the monitoring plan, in effect at the Centre de l'Aube. The data, obtained from measurements performed from surrounding environment (air, water, plants, milk, ...), are quaterly published and are available for the public. This is one of the major reason of the very good integration of the Centre de l'Aube in the local communities. Public acceptance aspects are developped in this presentation, as well.

ANDRA (French National Agency for Radioactive Waste Management) is a state owned agency reporting to the Ministries of Industry, Research and Environment. ANDRA is responsible for long-term radioactive waste management and, among other duties, for management of long-term disposal facilities.

Waste classification in France is summarized on table I.

Short-lived, low and intermediate-level radioactive waste (LLW-ILW) are disposed in France in near-surface facilities. The disposal concept chosen consists of isolating the waste by using engineered barriers, until their radioactivity has decayed to insignificant levels, i.e after a monitoring period of 300 years ; then, an unrestricted access could be allowed.

The "multibarrier concept" defines 3 containment systems : the physico-chemical form of the waste (which can include container) ; the engineered structures ; the site by itself.

At time being, two near-surface disposal facilities have been operated by ANDRA : the Centre de la Manche (1969-1994), which is undergoing closure ; the Centre de l'Aube, which has been authorized by decree of september 4, 1989, and is in operation since january 1992.

The Centre de l'Aube surface is 100 ha, including 60 ha for nuclear area and 30 ha for disposal area. Its capacity is 1,000,000 m³ of radwaste ; about 170 persons are working today at the disposal facility. Main functions of the Centre de l'Aube are : first, disposal of radioactive waste packages ; second, conditioning with an hydraulic binder (i.e grouting of metallic boxes, and compaction of 200-liter steel drums which are reconditioned and grouted in 450-liter drums) of non-pregrouted packages sent by some waste producers ; and third, environment monitoring.

According to french legal framework for nuclear safety, the regulatory body, DSIN (Directorate for the Safety of Nuclear Installation, which reports to the Ministry of Industry and to the Ministry of Environment) draws up general safety objectives ; the operator, ANDRA, provides technical recommandations for achieving these objectives, and has primary responsability for nuclear safety relevant to its duties.

ANDRA establishes technical specifications relevant to Aube disposal facility, in accordance to regulations issued by DSIN. These regulations are Fundamental Safety Rules I.2 (for near-surface facilities) and III.2.e (for solid radioactive waste packages), issued before design of Aube disposal, and specific Technical Requirements issued for facility operating authorization.

Waste packages must be formally accepted before they can be delivered at the disposal facility. Acceptance is formalized by the issue of a certificate, which provides an official description of the standard waste package and lists the documentation that constitutes the acceptance file (description of the fabrication process, description of activity measurement method, characterization file, Q.A plan for fabrication).

ANDRA and the waste producers have developed a computerized waste package tracking system, which is based on identification of each package, verification of acceptability according to the acceptance file, and tracking from producer to final disposal structure.

Table II gives an overview on the various origins of waste packages delivered at the Centre de l'Aube, during 1996. Total volume was about 22,000 m³.

Reprocessing industry (COGEMA) represents now the half of total volume, and power plants (EDF) about one third. Considering that 375 TWh electricity are produced from nuclear plants, such data illustrate the great effort achieved by EDF to reach waste volume reduction. A better management and new design at the source of waste generation (exchange resins, filters, etc...) have allowed a 50 % decrease in a 10 years period (on 1986 at Centre de la Manche disposal facility, about 14,000 m³ were received from EDF, which represented at that time 46 % of total volume).

Table III gives figures on the number of acceptance certificates issued by ANDRA. After 5 years of Centre de l'Aube operational service, about 80 different standard packages are now accepted. It must be outlined than more than half of them were already accepted at time of the first operational year of the disposal facility.

Accepted waste packages can be classified according to the nature of waste, nature of conditioning matrix, level of activity, and the type of waste package.

27 % of acceptance certificates refer to homogenous waste (evaporator concentrates, exchange resins, sludges,...), and for a large majority of 73 %, to heterogenous (metallic or plastic miscellanous waste, filtration systems, demolition rubbles, ...).

Level of activity is a parameter issuing account for acceptance. Actually, ANDRA specifications are less stringent for low-level waste, when activities of radionuclides are under some thresholds (matrix is then only required for stabilization of waste) than for intermediate-level waste, when activities exceed these thresholds (immobilization matrix must demonstrate containment properties). 52 % of acceptance certificates refer to LLW, and 48 % to ILW. However, it must be noticed that a lot of certificates refer to LLW packages which are conditioned by several small producers, and which represent only a few amount (3 %) of total volume deliveries.

Matrix used by waste producers for conditioning are, mainly, hydraulic binders, and for some packages polymers (16 %) or bitumen (2 %).

Waste package types are, at time being, numerous in spite of the effort to reduce their number : metallic boxes, non-pregrouted or pregrouted ; metallic drums, pregrouted or for compaction at disposal site ; concrete (cylindrical or cubic) containers. 55 % of acceptance certificates refer to waste packages conditioned by producers. ANDRA is performing complementary conditioning for the remaining, mainly for EDF, and for some CEA centers and for almost all the small producers. Concrete containers represent less than 20 % of accepted packages, but delivered volumes are not at all at the same ratio (see Fig.1. hereafter).

The basis of the french regulations for radwaste were issued between 1984 and 1986. 1979 requirements applied to the Centre de la Manche were updated on 1985, with definition of typical disposal structures. Packages delivered to disposal were divided into three main categories : a) categories whose specific activities or conditioning requested disposal without a complementary barrier other than the protective cover against any seepage ; these were simply stacked on mound-shaped platforms, interstices of packages being filled with a backfill material ; b) categories whose characteristics requested a complementary barrier, either for containment or to boost the structure's mechanical strength ; these were disposed in reinforced concrete bins, and the intersticial voids filled with concrete as to create a monolithic structure ; c) categories requiring complementary conditioning (i.e grouting / compaction) before disposal.

At the very beginning of Aube concept (1988-1989), standard engineered structures were defined for the disposal of all the waste packages categories, whatever activity levels or kinds of packaging. Standardization of engineered structures, built in parallel rows, has allowed an optimization of the space usage for the disposal.

Each disposal unit was designed as to surround stacked packages as a box, with faces defined by : a) concrete platform (sitting at a sufficient elevation above the water table level) ; b) reinforced concrete top layer, grouted after structure filling ; c) reinforced concrete walls, on each side of the nearly 20 x 22 m structure. The only difference for disposal orientation is depending of categories of containers, short-term containers (i.e steel drums or boxes) being stacked and stabilized in disposal units with concrete grouting (intermediate layers and intersticial voids), and long-term containers (i.e concrete) being stacked in disposal units with gravel filled into the intersticial voids.

One important technological innovation at the Centre de l'Aube is the use of mobile roofs, as to shelter the disposal structures from rain and cover the packages during filling up the vaults. Another advantage of the mobile roofs is the ability to automate overhead handling systems, as well as waste package tracking using bar code labels and scanners ; remote handling of radwaste packages have tremendously reduced the exposure level, and therefore the integrated dose to workers, as detailed hereafter.

At the Centre de l'Aube, a network of underground tunnels built under the disposal units is used to collect rainwater that could have seeped through the vaults, thus monitoring the disposal facility.

The second evolution deals with computerized tracking system for waste packages. The time since opening of the first radwaste disposal in France was also the time of powerful computer revolution. Following of packages at Centre de la Manche was, partly, manual and data for the first shipments existed on paper only. Tracking system is now entirely computerized.

The third and last major evolution consists of the improvement of logistic devices surrounding the disposal by itself. The conditioning facility (a fully automatized grouting cell and a 1000 tonnes supercompactor) was designed with the up-to-date knowledge. A laboratory operated by ANDRA directly provides means for a monitoring plan.

During the disposal design phase, predicted annual deliveries were about 35,000 m³ ; therefore, the capacity of 1,000,000 m³ would have been filled up after 30 years of operating period.

As indicated on table IV, deliveries at time being are far away from that prediction, and according to latest evolution, a sixty years operating period becomes foreseeable.

During two years and half, between 1992 and 1994, the Centre de la Manche and the Centre de l'Aube were both in operation ; that explains the modest figures for the three first years. Since July 1994, the Centre de l'Aube is the only disposal in France in operation for short-lived, low and intermediate-level radiactive waste (LLW-ILW).

Total deliveries to the Centre de l'Aube by the end of 1996 represented 141,664 waste packages, corresponding to a total volume of 64,700 m³ .

Distribution according to the types of package is given on figure 1, with a forecast for the following years.

Waste packages treated in conditioning facilities (compaction or grouting) represent about 30 % of total if volume is considered, but 60 % regarding the number of packages. In particular, it must be noticed that, at time being, 58 % of the delivered packages (i.e 81,500) were non-grouted drums, for compaction. Figures for volumes are, of course, smaller according to drums size (200 l) and to concrete containers size (0.6 to 5 m³) respectivly. Percentage of drums for compaction has gradually decreased from 1994 (67 %) to 1996 (57 %), but it must be outlined that commissioning of a new low-level incineration and melting facility could tremendously reduce figures. As, therefore, percentage of drums for compaction will be strongly lowered, forecast total volume of delivered waste packages is approximatly 13,700 m³ for year 2000.

Figure 2 gives numbers of closed engineered disposal units per year from 1992 to 1996, with the distribution between structures with concrete grouting and structures filled up with gravel. At the end of 1996, 25 units were closed on the disposal site. It must be outlined that, after the begining of operating period, when grouted disposal units were the majority, next years will confirm a better balance of the two kinds.

The compaction and conditioning units confirmed their excellent performance and reliability, particularly because of an extensive preventive maintenance programme. In 1996, 4,185 maintenance operations were performed. Preventive maintenance concerned 58 % of operations.

At the end of 1996, total disposed waste packages in the disposal represent 6 % of total volume capacity.

Technical requirements for Centre de l'Aube disposal define capacities for alpha and beta/gamma radionuclides. After 5 years of operating period, total disposed alpha activities represent 2,5 % of authorized capacity (18,5 Tbq). No beta/gamma radionuclide is above 3 % of relevant capacity.

Safety is, of course, one of the major goals of the Agency. Figures on nuclear incidents are perhaps the best indicator on the matter : since Aube disposal opening (january 1992) until 1997, only 11 incidents had to be declared to DSIN ; 4 were classified below threshold of International Nuclear Safety Scale (INES) ; 3 were classified at INES level 0 ; 4 were classified at level 1.

During the first five years of the Centre de l'Aube operational phase, it turned out that the reduction of received volume did not result in simplifications for radwaste management because, at the same time, the variety of geometries used for waste packages turned out to be more important than predicted (15 types are received at time being).Taking into consideration the spectrum of waste packages, 6 mobile roofs were equipped with 6 bridge cranes (3 T, 10 T, 35 T capacity). 3 of them are dedicated to disposal units with gravel filling up, the 3 others to grouted disposal units. 4 bridge cranes operate automatically, the two remaining (35T) are equipped with an operator cab. Waste packages disposal is performed according to a predefined cartography, and placement coordinates are recorded and transferred to the information processing system.

Improvement of brigde cranes, handling devices and storing cartography was a major goal for Centre de l'Aube disposal facility, as both to increase flexibility of packages positioning, and to optimize filling up of each disposal unit. 3 T and 10 T bridge cranes are now both used for the main types of metallic drums. 35 T bridge cranes are dedicated to a larger spectrum of concrete containers.

Optimization of disposal units was also implemented. A new generation of "monoblock" units was defined, with the same concrete platform as for 4 or 5 vaults ; removal of intermediate walls has therefore increase the usable volume by 10 %. The Separative Water Collection System ("SWCS") beside the disposal structures was modified, as to link two parallel disposal units rows with the same underground tunnel.

As to balance forecast decreasing of deliveries, Agency has started design studies on the disposal of non standardized waste packages. Types of predictable wastes are diverse (for exemple, elements of nuclear reactors such as steam genarators or vessel closure heads) ; acceptance procedures and disposal processes will be completly new, according to waste dimensions and radioactive characteristics.

As the general policy of the main waste producers is to pay less by minimizing delivered volume, and by concentrating the activity within specified activity limits, evolution of LLW/ILW ratio is foreseeable.Therefore, the Agency must adapt its management accordingly.

Design of new facilities for exchange resins or sludges conditioning is also on the agenda.

Lastly, it must be outlined that, because a lot of non-destructive and destructive testing on received waste packages were performed since Centre de l'Aube opening (respectively, about 550 and 50), ANDRA had completly subcontracted their implementation, mainly to nuclear research centers (i.e C.E.A). At time being, a new mobile gamma spectrometry equipment designed for all types of delivered cylindrical packages is used at the Aube disposal facility. 300 to 400 non-destructive expertises per year are expected after 2000.

Disposal radiological safety service is responsible for this monitoring. On-site laboratory performs the regulatory radiological analysis, according to its analytical capabilities : a total gamma activity measurement system ; 3 total alpha/beta measurement systems ; 1 gamma/X ray spectrometer ; 2 alpha spectrometers ; 1 liquid scintillation beta spectrometer. Chemical and ecological monitoring are subcontracted to outside qualified laboratories.

Legal framework for radiological monitoring is defined with respect both to DSIN requirements and to OPRI (i.e Office of Protection against Ionizing Radiation) directives. These two Authorities implement their own separate inspections on the matter (44 surveys since 1992). Raw data are sent monthly to the OPRI register and to ANDRA headquarters (Safety Directorate) ; quaterly leaflets are edited for the general public and a detailed yearly document is sent to DSIN. OPRI monitors also cross-check analysis as to qualify ANDRA data continuously.

Monitoring plan includes : radiation measurements, both of personnel (film dosimeters) and collective (fixed and portable detection equipment ) ; sampling and analysis programme, both on-site and off-site, of water, air, vegetation and milk.

Required dosimetry complies with ICRP 26 and 60. On 1996, some 4,500 film badges of personnel had been assigned and developed since the disposal facility begin operations ; of these, 32 film badges indicated significant doses of around 0,35 mSv. The maximum integrated dose for the year by a category "A" worker was 1.05 mSv, i.e 2.1 % of the maximum dose allowed by the regulations, and 21 % of ANDRA target (5 mSv). These data are confirmed by records, from the electronic dosimeters assigned to the controlled area or all around the site fence and from diverse sensors (conditioning facility, crane cabs, ...).

Requirements for maximum activity concentration in "A" (i.e potentially contaminated) effluents, SWCS water and in the storm basin are : tritium 400 Bq/l ; alpha emitting elements 0.8 mBq/l ; all radioelements combined exluding tritium and potassium 40 (those present in concrete not taken into consideration) 0.8 Bq/l. It must be outlined that these figures are far below regulatory limits for drinkable water. Sampling frequency depends on item : before each releasing for SWCS water and effluents from facilities ; every 3 days from storm basin ; every week, for biological purification plant, rain water collection system, and off-site freshwater ; monthly for on-site and off-site piezometers. Repeated results on 5,000 analysis are below detection limits for total alpha and beta activity (i.e < 0.2 Bq/l). Maximum beta concentration spreads from below the detection limits (on "Les Noues d'Amance" neighbouring river) to 60 Bq/l (on SWCS water). All the "A" effluents have been therefore classified as releasable, and no change was noticed compared with reference, i.e analytical data obtained from 1987 to 1988 and from 1990 to 1991.

Results for air monitoring (both on-site and at waste conditioning and site service buildings), environmental monitoring, including aquatic vegetation, sediment, samples from piezometers, analysis of milk (quaterly taken in neighbouring villages), confirm results of water monitoring. For exemple, average cesium 137 activity concentration in milk was always below detection limits of used equipments (i.e 1 Bq/l), while sanitary level is 1,000 Bq/l.

The natural environment of the Centre de l'Aube is characterized by a wooded area, with a lot of game. When the disposal site was setting up in the forest, plantations were carried on by ANDRA, as to compensate trees elimination.

An environmental monitoring plan has been implemented since 1994, as to follow flora and fauna evolution on a defined superficy of about 9 km² around Aube disposal. Data were compared with references, recorded before disposal facility implementation (1989-1990).

Ecological survey leads to the conclusion that, collectively, species constituting fauna remain diverse, including birds or mammals which are protected in France because they get scarce. Existing circulating pathways of mammals have not been affected. For some of them (e.g. wildcats), population has decreased because of forest discontinuity ; however, others like roe deers, population have increased because they appreciate, on the contrary, edges as being created at the border of the site and of the surrounding forest. Same trend occurs for bird population, with new species coming with the opening of the forest (e.g skylarks). The numerous forested ponds lead to a great diversity of aquatic birds and their population remain stable.

No changes were noticed on flora. A good general health of trees was verified using an E.U standardized protocol. Some scarce species are living in neighbouring forest.

Fresh water quality was checked both in the river called "Les Noues d'Amance" and in water table. Physico-chemical and biological analysis were performed in surface water, and lead to the following conclusions : no pollution, especially by metallic particles was detected ; quality of river water is good to medium (standard being defined in reference to regional data and procedure), with no specific impact of the disposal facility.

Regional integration of disposal facility was accurately studied, before and during the first years of operational phase. ANDRA has defined a master plan as to avoid errors which, unfortunatly, have occured in France or outside on such a critical matter than radwaste management.Transparency is a basic element of such a policy, that implies, of course, quality of information : information is therefore regular, diverse and as open as possible.

A "Local Commission on Information matters" acts as a representative body between ANDRA and regional population. It must be outlined that such interfaces have been implemented in France for each nuclear facility. There are 27 members of Commission, plus several permanent guests (elected councillors, one member of Parliament, mayors of neighbouring villages, members of chambers of commerce, delegates from environmentalist societies, newspapers and radio reporters, etc...). Commission is presided by an elected councillor. Meeting of the Commission are scheduled three times a year. ANDRA has to inform it of any nuclear incident (Agency has decided to give information on even those classified at level "0", which is not mandatory)

Disposal facility can be visited by individuals or groups, even on sundays during summer. About 7,000 visitors were recorded on 1996. Scholars and students represented 40 % of total. 9 % came from foreign countries, in majority from Western Europe, but there were also representatives of all parts of the World. Special "open gates" days allow, once a year, direct dialogue between general public and ANDRA personnel.

General information is given through various documents : synthetic annual report for Commission, disposal newspaper, 5,000 copies distributed quaterly to local population ; a quaterly report on environment measurements, both for Commission and the general public.

Local integration of Centre de l'Aube disposal is also gradually supported with its involvement as an actor in economic, cultural or even sport fields. ANDRA has become, for exemple, promoter of a local football team or for scientific exhibitions.

It has been demonstrated in France that short-lived low and intermediate radioactive waste can be managed in industrial conditions and in a safe and cost-efficient manner. The integrated waste management system has been implemented by ANDRA with about three decades of operating experience in France, and in particular since Aube disposal facility opening. Only fully accepted waste packages, from various origins and with diverse shapes, have been delivered after an acceptance phase. Constant changes on waste generation upstream management have induced gaps between forecast and actual deliveries. Accordingly, the Agency has adapted its procedures and facilities accordingly, including engineered structures.

Effective implementation of concept and management explains why french technology, developed in France for radwaste treatment and disposal, has also been choosen by other countries.

Positive operating experience for near-surface radwaste disposal was, lastly, essential for ANDRA to conduct future activities, in particular the research program on long-lived and high level waste.

BACK