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what types of waste?
Deep underground
disposal is envisaged both for low-level and/or short-lived waste and
for high-level and long-lived waste. In the case of the latter, the disposal
solution offers protection for periods of time that exceed all those contemplated
within the framework of conventional industrial projects (several tens
or even hundreds of thousands of years). It is only after these extremely
long periods of time that the radioactivity of this waste will be reduced
by natural decay and reach a value that is only a fraction of the natural
radiation to which we are all exposed.
The generic concept of deep disposal Internationally, scientists believe that deep disposal in stable geological layers is an appropriate solution for the long-term management of radioactive waste. Among the host formations generally considered are salt (layer or dome), crystalline rock (granite) and clay. More and more countries, however, opt for clay (Switzerland and France among others) In Belgium, the matter has been the subject of regular discussion for over 25 years. The research carried out by ONDRAF/NIRAS must determine whether disposal in the poorly indurated layers of clay (such as the Boom clay in the north-east of the country) can guarantee protection of man and his environment in the long term. The salt rock used in Germany in particular is not found in the Belgian subsoil. Granite formations, such as those used for the disposal in Sweden and Finland lie more than 2,000 meters deep. They have never been explored. Boom clay has been stable for several million years so it should remain so for the periods required for radioactive waste to become harmless. The generic
concept of deep disposal studied in Belgium takes the form of a network
of concrete underground galleries (1) hollowed out in a poorly indurated
layer of clay (2) in which the waste would be buried. These galleries
would be linked together by one or more main galleries (3) accessible
by shafts (4).
The safety
of a deep repository depends on a succession of natural or man-made barriers,
each with its specific long-term safety function. They all contribute
in their own way to the isolation of the waste from man and the environment.
While the overall repository architecture is identical for all classes
of waste, certain barriers would differ depending on the class of waste
to be disposed of.
The main
barrier on which the safety of the repository depends is the geological
layer in which this facility could be built, that is to say, a layer of
poorly indurated clay. Given its low permeability and high capacity for
retaining radionuclides, this barrier alone would be sufficient to guarantee
a high degree of both short-term and long-term safety. The repository here also takes the form of a network of underground concrete galleries (4) in which the "supercontainers" are buried. When all the galleries are full, the repository is entirely closed off with backfilling material and plugs. The repository infrastructure is thereby completely isolated from the outside world. The main barrier on which the safety of the repository rests here again is the geological layer in which this facility could be constructed, i.e. a layer of poorly indurated clay. This barrier is the most important as it is the one that has to slow the migration of radionuclides towards the biosphere for a sufficiently long time when the man-made barriers are no longer effective (i.e. after the thermal phase). So it is the site's geology that must ensure that the long-term radiological impact of the waste in the repository stays below the nationally and internationally (IAEA) allowable limits and is therefore significantly lower than natural radioactivity. Indeed, the lasting quality of the man-made barriers cannot be guaranteed over the extremely long periods of time to be taken into account (several tens or even hundreds of thousands of years). What are the results of the research carried out so far? The SCK·CEN (Belgian Nuclear Research Centre) began research in 1974 to determine whether radioactive waste can be buried in Boom clay and an underground research laboratory named HADES was set up (at a depth of over 200 meters) in the early 80s to study this clay as a potential host formation. Since its creation in 1980, ONDRAF/NIRAS has managed and coordinated the Belgian Research & Development programme in close collaboration with the SCK·CEN and with financial support from the European Commission. In 1995, this collaboration led to the creation of an Economic Interest Group known as EIG PRACLAY. In 2000, EIG PRACLAY was renamed EIG EURIDICE. The Belgian
Research & Development programme is a methodological programme dedicated
to determining whether it is technically and economically possible to
come up with a safe solution for the deep geological disposal of radioactive
waste. This programme, which is necessarily multidisciplinary and progressive,
can be divided into three phases: A socially acceptable solution The SAFIR 2 report was limited to scientific and technical aspects. It evaluated confidence in the safety, feasibility and the soundness of the disposal system studied. However, a long-term radioactive waste management solution must not only be safe and technically feasible, it must also be acceptable to society and ONDRAF/NIRAS was particularly conscious that even if a solution were scientifically correct, it could not go ahead without political consensus and social acceptance. In the case of low-level and/or short-lived waste, this is the reason why the deep disposal solution and the way in which this waste will be disposed of are being discussed by local partnerships. In the case of high-level and long-lived waste, it is ONDRAF/NIRAS's opinion that social dialogue between all concerned should be encouraged to the full. This is why, in coming years, the ONDRAF/NIRAS Research & Development programme will try to re-establish equality between the technico-scientific and societal dimensions. In concrete terms, this means that the participation of society will take the form of real dialogue which is open to all parties involved. Indeed, a decision-making process must be put in place that is capable of responding to society's expectations. Clearly, ONDRAF/NIRAS, will have to establish structures representing society as a whole that will be in a position to influence the continuation of the Research & Development programme. For
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