Determination of long-lived radionuclides in accelerator waste

The Paul Scherrer Institute (PSI) operates one of the most powerful proton accelerators worldwide, the 590 MeV ring cyclotron with beam currents up to 2 mA. Activated components from this facility, which are dismounted during maintenance or reconstruction, thus might cause radioactive waste problems. Before the permission for conditioning the waste for intermediate or final disposal is given, a declaration of the radionuclide inventories is requested by authorities. A method to determine the nuclide inventory by calculation was developed and has to be validated continuously. Therefore the radionuclide inventory of the beam dump of the old 'Target E' was determined using γ, β, α-spectroscopy as well as AMS (Accelerator Mass Spectrometry). In this contribution we focus on the measurement of the long-lived radionuclides 36Cl (T1/2=3.0x105 a), 10Be (T1/2=1.6x106 a), 60Fe (T1/2=1.5x106 a), 59Ni (T1/2=7.5x104 a) and 26Al (T1/2=7.2x105 a), which are present in this radioactive waste in considerable amounts and are subject of concern with respect to the long-term safety after closure of a final repository. The chemical separation techniques necessary for isolation of several element fractions as well as the AMS measurements are described in detail. The results serve as a validation for the calculation method mentioned before. The measured values are compared with the theoretical predictions and are rated according to their relevance for final disposal