Some Example of Release of Materials and Sites, Including Measurement Techniques

Summary

Many test reactors and some power reactors have already been decommissioned and partially or entirely dismantled. Although same materials are classified as radioactive waste, others may be considered as ordinary waste or reutilized for nuclear or non-nuclear work. There is no international recommendation on activity limits for the unconditional reutilization of material. The levels applied in the various countries differ according to the materials and their use or destination. In Germany the limits applied for dismantling the Otto Hahn reactor were 10^-4 μCi.g^-1 and 10^-5 μ ci.cm^-2. In France there are no statutory limits for release for public use. Each case is submitted for authorization to the Service Central de Protection contre les Rayonnements Ionisants (Central authority for protection against ionizing rays), a department of the Ministry of Health, which decides on the basis of the characteristics of the waste in question. We give examples of release in Germany (GKSS), France (CEA) and the United Kingdom (UKAEA).

In Germany, the reactor on the ship NS Otto Hahn was dismantled between 1980 and 1982, after 10 years’ operation. The secondary circuit, with low contamination, was decontaminated. Monitoring of the surface activity before unconditional release required more than 1 million measurements. In September 1982 the ship was resold and in the following months was equipped with a diesel engine. We also describe the dismantling of some French reactors, in particular PEGASE and GL. In the case of the latter, the building and the interior equipment, such as the gantry, were reused for non-nuclear work. Some materials such as steel and copper pipes can be considered as uncontaminated. In the PEGASE reactor, the vessel and tanks were reused after decontamination, for the temporary storage of irradiated fuels. The steel loops were sent, after decontamination, to the smelting works.

At the Harwell site a series of low-power reactors built between 1947 and 1965 have since been decomnissioned and the buildings reused for non-nuclear work. This was the case, in particular, with BEPO, a 6.5 MW air-cooled-graphite reactor, and with LIDO, a 300 kW swimming pool reactor.