Co-60 calculation methods for the waste form documentation. Example: disposal of reactor pressure vessel internals of the NPP Stade (KKS)

In the frame of the reactor dismantling project of the NPP Stade the reactor pressure vessel and the internals are dissected, packed and dried since 2007. Due to the high neutron flux the reactor internals are highly activated and partially show a strong activation gradient. The authors demonstrate an activity calculation technique (esp. for the leading radionuclide Co-60) based on underwater dose rate measurements of the reactor internals that will allow to optimize the maximum utilization of the interim storage plant at the NPP site and ti reach the dose limits for the final repository Schacht Konrad. The authors show that the use of methods based on heterogeneous source term distributions provides a significantly reduced Co-60 activities.