Clearance Measurements prior to the Shut-Down of ERAM

Low and intermediate level radioactive waste was emplaced in the Morsleben Repository (ERAM), a former salt mine, until 1998. Now the German Federal Office for Radiation Protection (Bundesamt fuer Strahlenschutz - BfS) has applied for the decommissioning of the plant. The ERAM's own radioactive waste requires clearance as far as it may not remain in the repository. The German Mining Law also demands all non-mining typical waste to be removed from the mine when being decommissioned and the Waste Avoidance, Recovery and Disposal Act demands waste to remain within the economy cycle if this is economically justifiable. Therefore new clearance measuring devices have to be applied using gamma and beta radiation to determine the contamination of objects and substances regarding the special nuclide spectra in the ERAM. Even if a very multifaceted radionuclide spectrum is to be expected due to the fact that the emplaced waste results from various applications such as nuclear engineering, medicine, research, and military, numerous investigations have confirmed that only a few radionuclides have to be considered. To facilitate this procedure the controlled area of the ERAM is to be classified according to different contamination categories. Assumptions about the radionuclide mixture are permanently controlled by routinemore » measurements and the evaluation of possible contamination events. The considerations about the radionuclide mixture and the structure of the controlled area will be described in this presentation. Furthermore a new methodology to measure Sr-90 is discussed which uses the Cerenkov effect and the low level of background gamma radiation in the salt mine. (authors)« less