Neutron fluence calculations for embrittlement surveillance specimens in VVER-1000

Neutron fluence spectrum calculations have been performed for the reactor pressure vessel of a VVER-1000, applying the Monte Carlo code TRAMO. Activities measured earlier in Balakovo-1 by fluence monitors, placed in special Charpy surveillance containers, are compared to TRAMO results. The average deviation from the measurements is about 5%. A good agreement of the fluence spectra near the RPV inner side, at the height of the core beltline, to the spectra at the Charpy probe positions on top of the radial reflector has been demonstrated.