Investigation of the radioactive inventory in the reactor pressure vessel of a nuclear power plant - a key for efficient nuclear waste disposal

One of the most important activities after the decommissioning process of the nuclear power plant NPP is the determination of the neutron activated radionuclides RNs in the construction material of the reactor. Our work is mainly focused on the dismantled units of reactor pressure vessel RPV of Greifswald NPP. For this aim, both nondestructive and destructive methods were employed. Firstly, surface analysis methods based on scanning electron microscopy / energy dispersive X-ray spectroscopy SEM / EDX were performed, in order to understand the impact of the neutron fluencies on the RPV steel shielding material during the long-term operation. Furthermore, gamma spectrometry measurements were done for the analysis of the activity of the gamma emitting RN of Co-60 in the decommissioned RPV units. On the other hand, the determination of the long lived beta emitting RNs such as C-14 was determined by employing a commercial sample oxidizer, followed by liquid scintillation counting LSC measurements. Radiochemical procedure including precipitation, anion exchange chromatography and extraction steps was developed for the separation and purification of Ni-63 and Fe-55 prior to their activity determination.