One of the key issues in nuclear energy is to elaborate acceptable and safe solutions for the radioactive waste produced during the various stages of the nuclear fuel cycle. The worldwide option, as recommended by international organisations such as the IAEA (International Atomic Energy Agency) is to concentrate and contain the radioactive waste. This means that radioactive waste should be reduced to minimal volumes, and be contained, for instance within metallic, corrosion resistant canisters.
Surface or deep disposal
The current approach is to develop a multibarrier system to contain and isolate the radioactive waste from the biosphere. The immobilized waste (most widely within cement or glass) is inserted into a canister, and disposed in either geological formations (= natural rocks) or surface sites.
In between the canisterized waste and the natural rock (the current options are granite, clay, rock salt) one or more engineered barriers are added. These engineered barriers may be for instance a corrosion resistant container, cement, and/or bentonite clay. These engineered barriers primarily must be compatible (chemically, physically, etc) with both the natural rock and the immobilized waste.
The entire disposal concept (immobilized waste, engineered barriers, natural rock, further natural formations above) must provide an isolation of the radioactive waste from the biosphere for as long as necessary – hundreds to hundreds of thousands of years depending of the type of waste. The present Belgian disposal "supercontainer" concept for high-level radioactive waste is shown below, as an example.
Geological formations are currently studied for radioactive waste that is either heat emitting, or contains a certain amount of long-living radionuclides. Surface sites are currently considered for low-level radioactive waste. There are several surface disposal sites operational worldwide (e.g., Spain, France). Only one geological disposal site is currently in operation (USA), but several sites are close to license.
Belgium is studying since more than 30 years a Boom Clay formation as a potential natural host rock for a geological disposal of the long-living and heat-emitting radioactive waste produced by its national nuclear activities. The programme is managed by NIRAS/ONDRAF.
SCK•CEN is very strongly involved in this research, as it initiated for instance the construction of an underground research laboratory in Boom Clay underneath its site. Another important national partner is ESV EURIDICE, that operates the underground laboratory.
In 2006, after long evaluations the Belgian government decided to select the Mol-Dessel area to locate a surface disposal site for low-level radioactive waste. The programme is managed by NIRAS/ONDRAF as well.
Both programmes are subject to very intensive research efforts. Below we identify a number of key areas of research, that are presented in more detail on the following webpages.
Volckaert Geert , Van Iseghem Pierre