Measurement of long-lived radionuclides in proton-irradiated accelerator components

During operation of an accelerator its components, the biological shield and surrounding materials will be activated due to (un)intentional beam losses. In the past, waste from accelerators did only play a minor role in nuclear waste management, because of the small quantity of material and the relatively low activity. However, with the advent of high power accelerator facilities such as spallation neutron sources like SINQ, SNS, JSNS and the development of accelerator driven systems (ADS) the situation changed drastically and analysis of the irradiated material is required. The Paul Scherrer Institute (PSI) operates one of the most powerful proton accelerators worldwide, the 590 MeV ring cyclotron with beam currents up to 1.8 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. These inventories are essentially different from those known from nuclear power plants. Therefore, a method to determine the nuclide inventory by calculation was developed at PSI, which has to be validated continuously. This method includes both estimations by mathematical predictions and analysis of sample material. Long-lived radionuclides are of special interest in this context due to their potential safety risk. In most of the cases, these isotopes cannot be determined by conventional γ-spectrometry because of the long half-lives or their decay properties. In the present work we report on the results for the long-lived radionuclides 36Cl, 63Ni, 26Al and 59Ni, which have been determined by AMS (accelerator mass spectrometry) or LCS (liquid scintillation counting) after chemical separation. The data are compared with theoretical values. (orig.)