Fluence calculation and activity determination at the reactor pressure vessel and their Support of VVER reactors

In the first part, Niobium, nickel and technetium isotopes from RPV trepans of the decommissioned NPP Greifswald (VVER-440) have been analyzed. The activities were determined by TRAMO (Monte-Carlo) fluence. The ratios of calculated to measured (C/E) 93mNb gamma activities for several trepan samples are between 0.43 and 0.97. Up to 20 to 40% lesser fluences have been computed for Nickel and Technetium. The fact that all C/E ratios are below unity suggests that the measured values may have been additionally heightened by activities from other nuclides.
In the second part, VVER reactor support structures (RSS) and reactor pressure vessel (RPV) welds should be undergone the neutron dosimetry analysis to understand their status of criticality relatively a problem of reactor equipment integrity. DORT synthesis and TRAMO Monte Carlo neutron transport calculations were used for fast neutron fluence rates and reaction rates evaluations. Neutron activation measurements by iron foils in ex-vessel cavity near RPV and RSS points of interest are used for testing calculation results. The study has shown that neutron load parameters of RSS and RPV may be enough reason to require the analyses of the resistance against the brittle fracture of these components.