Tome Architecture and management of a geological repository - Andra

5 – B waste repository zoneproduced, taking the conditioning hypotheses set out below). Since this is largely due to cobalt, theresidual heat rating of the package drops rapidly as the cobalt decays. As an illustration, the heat ratingis divided by 2 after 5 years of cooling, by 3.5 after 10 years of cooling and by 6 after 15 years ofcooling. Another consequence of this radiological inventory is the high level of radiation of thepackages. Thus, the equivalent ß-γ dose rate in pseudo-contact with the package (i.e. at a distance of5 centimetres) is roughly 50 sieverts per hour (Sv/h), at the time of its production. This is mainlyattributable to 60 Co, but also to silver-108m ( 108m Ag) whose half-life is 420 years, and remains at arelatively high level even after 10 years' cooling (around 15 Sv/h).The conditioning hypothesis considered in the study 22 is compaction of the waste placed in holders 23 , thentransfer to stainless steel containers known as "Standard Compacted Waste Containers" (CSD-C) in smallformat (see Figure 5.1.2).Figure 5.1.2Standard compacted waste containers (CSD-C)The conditioning hypothesis assumes a weight of 400 kilograms of waste per package, made up of amixture of different types of activated waste in the following proportions: 5% neutronic poison rods,78% control rods and 17% various metal wastes. The weight of the finished package is around510 kilograms.It should be noted that these packages contain no organic materials and are not liable to produce gas(hydrogen) by radiolysis.5.1.2 Bituminised liquid effluent processing sludgeThe second group of B wastes comes from radioactive liquid effluents resulting from the operation offuel reprocessing facilities. The effluents considered here are generated at various stages of fuelreprocessing and during work carried out on equipment and facilities (decontamination, flushing).These effluents are collected in treatment stations where they are decontaminated by chemicalprocesses before discharge. The residual waste is then recovered in the form of sludge.In the “STEL” effluent treatment station at Marcoule and STE3 at La Hague, opened in 1966 and 1989respectively, this sludge has been conditioned by embedding in bitumen, which is then put in steeldrums. On the other hand, sludge from effluents produced and chemically treated at La Hague STE2(Effluent Treatment Station No. 2) from 1966 to 1990 have been gradually stored in tanks and silos atthe plant, awaiting conditioning. The planned conditioning method for these sludges is also embeddingin a bitumen matrix.2223An alternative conditioning mode, not dealt with here, is being studied at EDFLarge rods and CIS thimbles are cut into sections before being placed in compaction holdersDossier 2005 Granite - ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL REPOSITORY98/228