R.C. Glibert, J. Crustin
BELGONUCLEAIRE

C. Renard
ONDRAF/NIRAS

R. Goetschalckx
BELGOPROCESS

The BELGONUCLEAIRE MOX plant is in operation since 1972 and was backfitted in 1985 to improve the fabrication process and the protection of the workers and to increase the capacity to 35 tHM/year. By the end of 1997, it had produced 344 tHM for LWR's which makes it the most experienced facility as regards radwaste from fuel fabrication.

The Plutonium Contaminated Solid Operating Waste (PCSW) is now about 23 m³. This represents therefore 12.7 m³ per ton of the total annual plutonium involved. This is an important reduction compared with the waste production in 1986 which was the beginning of the industrial operation of the Dessel plant.

The figures for the other categories of waste generated in the processes are given and their reduction in volume since 1986 is indicated.

The collection and sorting of all the main alpha-radwaste generated at BELGONUCLEAIRE's plant are described. The latter are transferred to the national organisation ONDRAF/NIRAS.

Pending approval by the Belgian Authorities, BELGOPROCESS (a subsidiary of ONDRAF/NIRAS) will operate the treatment and conditioning facilities for the accumulated and future alpha-radwaste. The main steps to be performed for the PCSW at these facilities, which are now at the design phase, are detailed and the expected output, expressed in conditioned packages, is given.

The BELGONUCLEAIRE MOX plant is in operation since 1972 and was backfitted in 1985 to improve the fabrication process and the protection of the workers, and to increase the capacity to 35 tHM/year.

By the end 1997 it had produced 344 tHM for LWR's which makes it the most experienced facility as regards radwaste from fuel fabrication.

Operating waste is comprised of solid and liquid waste produced in facilities and laboratories of the plant during normal activities : operation, maintenance, repairs, cleaning. It includes elements resulting from day-to-day facility and laboratory operation (personnel, machines and equipment) and small parts from the normal maintenance of equipment contained in glove-boxes or other fabrication areas (components of the presses, furnaces, bricks ....).

The various types of solid and liquid waste generated at BELGONUCLEAIRE=s facilities meet the specifications imposed by ONDRAF/NIRAS (the Belgian State organisation for radioactive waste and fissile material).

The A2X category comprises all solid suspected and slightly Pu-contaminated waste produced by controlled area activities, normally waste originating outside the glove-boxes. This category is not normally contaminated by Pu but it is not economically feasible to demonstrate the total absence of Pu.

Its maximum activity is defined by ONDRAF/NIRAS.

• Combustible waste, max. 0.4 GBq/m³
• Other waste, as a function of apparent density : from 1 to 4 GBq/m³.

The A3X category comprises all waste having a measured contamination greater than that of suspected waste and generally waste removed from glove-boxes and glove-boxes themselves (decommissioning related waste).

All solid Pu-contaminated and combustible waste which meet the requirements of ONDRAF/NIRAS and which the reference treatment scenario is the combustion. The total a activity of A31 waste may not exceed 5000 GBq/m³.

All solid Pu-contaminated and non-combustible waste which meets the requirements of ONDRAF/NIRAS and give, after repacking and cementation an end-product which is acceptable to ONDRAF/NIRAS.

The total a activity of A34 waste may not exceed 10.⁶ Gbq/m³.

This waste, which is produced in controlled areas outside containment areas includes water from sanitary installations (showers, wash basins, toilets), water from floor cleaning operations, and water from furnace cooling circuits.

This type of waste comprises specific liquids from glove-boxe equipment (e.g. oil from hydraulic circuits of the hydraulic presses), glove boxes decontamination fluids (specifically following a contamination incident) and analysis residues. Usually this waste contains up to 4 g Pu_tot per 25-litre flask.

• The collection points for this waste are situated in the production area (outside glove-boxes), the hall for checking and storing the fuel rods and the neighbouring corridors;
• The collecting unit is a canister with an internal volume of 22.5 litres.
• Types of waste collected : papers, Kleenex, cloth, plastic, rubber, wood, surgical gloves, pieces of cable, metallic parts, etc ... They are sorted by category, the canisters are closed, monitored to ensure there is no contamination, numbered and recorded in the waste management computer system.

Prior to its removal, the waste is repackaged in 220-litre drums.

This is normally generated inside the glove-boxes in which it is sorted by category and put into small packets (a few litres) packaged in welded double PVC bags (use of labels with a different colour per category).

After monitoring for the absence of external contamination on the packaging, they are placed in canisters, taking care not to mix the various waste categories in the same canister (labels of only one colour per canister).

The canisters are adapted so as to ensure ease of handling and also to permit the use of a measuring device to determine the amount of Pu contained (via a passive neutron measurement).

Using the activity measurement together with a knowledge of the origin of the waste, in terms of the fabrication campaign underway, the Pu_tot content of each canister is determined. The amounts of U, ²³⁵U and Pu in the waste contained in each canister are also included on the label (information required by internal and external regulations).

Next, the canisters are recorded in the specific accounting of fissile materials and in the specific accounts of waste management at the plant.

The canisters are stored in a specially equipped room.

Prior to its removal, the waste is repackaged in 220-litre drums.

The repackaging procedure consists first in choosing the canisters to place in the same drum.

The content of the canisters placed in the same drum must be waste of the same category : they must be selected so as to fill up the drum without exceeding the 250 kg total mass of the drum.

The canisters chosen are then opened in the presence of a representative of the radiation control section and the waste (packed in small parcels in plastic packaging) is transferred to a drum lined with a large internal PE bag. Once filled, the bag is closed, the 220-litre drum is closed and, after control for the absence of contamination, placed using a grab (which also serves as an immobilising system during transport) in a 400-litre drum (transport container).

The closed 400-litre drum (bolted lid) constitutes the packaging (15 drums/transport) for transport to the BELGOPROCESS storage facilities.

BELGOPROCESS which is a subsidiary of ONDRAF/NIRAS operates the storage, treatment and conditioning facilities for the radwaste generated in Belgium.

The 400-litre drums and internal grabs are returned to the plant so that the next transport can be prepared.

All the liquids are collected in 3 reservoirs of 10 m³ capacity from each of which samples are taken periodically to measure the activity.

When the activity threshold (2 Bq/litre) is exceeded, the waste water is considered to be contaminated and is transferred by special transport to BELGOPROCESS.

The flasks originate in the analysis Laboratories. They are monitored and transferred to BELGOPROCESS for processing, conditioning (bituminisation) and storage.

The fabrication capacity of the BELGONUCLEAIRE plant has been progressively increased since its backfitting in 1985.

As indicated in Figure 1, the plant has been operated since 1989 at production rates in excess of 30 tHM/year which is about 7 times higher than the 1986 level. The annual total Pu used in the fabrication process has now reached around 2000 kg, which corresponds to the nominal fabrication capacity of the BELGONUCLEAIRE plant : 35 tHM/year.

BELGONUCLEAIRE is devoting great effort to minimising the volume and the Pu content of the waste generated in its plant. To illustrate these achievements, Table I indicates the quantities of waste generated and Pu losses as a function of the period of fabrication since 1986. The quantities of waste and Pu losses are expressed in m³ per ton of Heavy Metal or ton of Pu processed in the fabrication line and compared with the values recorded during the period of production prior to the backfitting (1986).

For the most recent period, the Pu-contaminated solid waste generated in the process is about 0.67 m³ per ton of HM or 12.7 m³ per ton Pu, representing respectively a reduction of one tenth and more than a quarter of the corresponding figures before 1986.

Furthermore, the Pu content in the waste has been decreased to 0.08% from about 1% before 1986, i.e. by more than a factor of 10.

For the most recent period, the Pu-suspected solid waste arising from the fabrication process is about 0.7 m³ per ton of HM or 14 m³ per ton Pu, representing respectively a reduction of one twelfth and more than one fifth of the corresponding figures before 1986.

Pu-contaminated liquid waste has also been drastically reduced. The volumes generated in the last period were 0.026 m³ per ton of HM or 0.5 m³ per ton Pu which are respectively less than 1/34 and 1/13 of the corresponding figures given for 1986.

With respect to the nominal fabrication capacity of 35 ton HM/year, the annual mean values of waste production are in equilibrium as summarised in Table II.

The present yearly production represents an important reduction compared with the production in 1986, which was the beginning of the industrial operation of the BELGONUCLAIRE plant.

The main flows generated at a MOX fuel fabrication plant are solid suspected-waste and solid-contaminated waste. The alpha-bearing solid suspected waste will be processed after monitoring in the existing beta-gamma type waste treatment and conditioning facilities. It will be subjected to a volume reduction by compaction in the case of non-combustible waste and by incineration or compaction for combustible waste prior to conditioning in a cement matrix. The alpha-contaminated liquid waste is treated and conditioned in an existing bitumization facility.

The alpha-contaminated solid waste will have to be treated and conditioned in purpose-built facilities. The choice of processing techniques will depend on the waste disposal conditions for geological storage.

The Belgian Safety Authorities have laid down several criteria pertaining to the deep geological-disposal of alpha packages. The results of risk assessment studies being performed to reduce the long-term radiological impact of deep disposal will determine the treatment and conditioning criteria.

The risk associated with the presence of cellulose for packages with Pu contents above a certain level leads to the use of treatment and conditioning techniques that mineralise the cellulose. Thus, a heat treatment would be required for combustible waste.

In addition, the use of a 400-l cement lined container is envisaged (see Figure 2). This cement constitutes a basic medium which would fix the Pu complexes that might migrate towards the external wall.

The main steps in the management of PCSW are shown on the block diagram in Figure 3.

Design studies for these facilities were carried out by BELGONUCLEAIRE Engineering with the support of BELGOPROCESS and ONDRAF/NIRAS. The studies pertain to a volume of PCSW of around 1000 m³ which is the estimated cumulative Belgian production by the year 2008.

In this estimation, the amount produced at BELGONUCLEAIRE's MOX plant represents 2/3 or more of this figure. The waste produced so far is stored at BELGOPROCESS' facilities in 22.5-l canisters and 220-l drums. Some of these containers (known as "mixed containers") contain a mixture of combustible and non-combustible waste. They will require sorting before they are fed to the processes that meet the radiological disposal criteria.

Based on these design studies, the sorting facility that will be used to handle the mixed waste accumulated so far has been defined.

Starting from the 22.5 l canisters and the 220 l drums, the mixed waste will be separated into combustible waste placed in 220 l drums and non-combustible waste placed in geological storage type 400 l drums (see Figure 2).

After monitoring the Pu content, the older stored waste and the recently generated waste sorted into combustible and non-combustible waste will be processed on two distinct processing lines.

The non-combustible waste will be embedded in a cement matrix inside a geological storage type 400 l drum.

The combustible waste will be treated by pyrolysis and the resulting pitch will be put into 12 l cans. Twelve of these cans containing pitch will be embedded in a cement matrix and placed inside a geological storage type 400 l drum.

All the 400 l drums containing conditioned waste are stored temporarily (for a few decades) before their final geological disposal. This geological disposal will probably be made in a clay layer on the basis of the results of an experimental study now being carried out in Belgium (HADES project). Calculations based on the design study processing diagram described above, of volume reduction factors, pyrolysis techniques, cementation, useful volume of the 'geological' drum and distribution of combustible and non-combustible waste, show that an annual production of 21 m³ of conditioned waste is to be expected for a nominal fabrication of 35 tHM/year.

The generation of Pu contaminated waste has fallen sharply since the beginning of industrial production at BELGONUCLEAIRE's plant.

This reduction has been obtained through continuous control of the operation of the plant ; improvement in fabrication procedures and better design of the production facilities.

The amount of PCSW generated for a nominal fabrication of 35 tHM/year is about 23 m³.

Studies of facilities to manage the alpha-bearing waste produced in Belgium have been carried out by BELGONUCLEAIRE Engineering with the support of BELGOPROCESS and ONDRAF/NIRAS, already take into account the main criteria to be imposed on geological storage by the Belgian Safety Authorities.

These facilities will stabilise the PCSW in a conditioned form and will reduce the initial volume of PCSW generated at the BN plant by about 10%.

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