Innovation in Power Maneuvering Mode for NPP Hanhikivi with WWER- 1200 reactor

Abstract

The possible innovative methods of maneuvering are investigated on the example of NPP Hanhikivi with WWER-1200 reactor in a frame of AES-2006 project. Stationary fuel loading analysis was performed for the for the most significant graph of daily manoeuvring (100-50-100)% Nnom with the rate of power change 1-5 % Nnom per minute, that are the European Utility Requirements. The improvement is ensured by maintaining a constant average coolant temperature in the core "Tav = const" (by changing the pressure in SGs) and a constant boron content in the primary coolant "CB = const". The change of power and Xenon concentration during power manoeuvring is compensated by special movement of the special chosen grey CRs in the core instead of CB change. CB is changed in usual way only for fuel burnup compensation during reactor campaign. The mode "Tav = const" is normally used for the control of power of PWRs in wide diapason and it reduces the amount of radioactive primary water discharges and the mechanical fatigue of the RCS components. Implementation of both – main mode "Tav = const" and auxiliary mode "CB = const" leads to positive effect of synergy. The mode "Tav = const" facilitates the implementation of the mode "CB = const" very much, and they together allow to completely eliminate the production of liquid waste during maneuvering and ensure load following practically for the full length of reactor campaign. Presence of large CRs quantity (121 pieces) in the WWER-1200 allows using part of them as grey CRs without safety violation due to small decrease of EP efficiency. The efficiency of grey CRs is 2-3 times less than of usual black CRs that allows more softly maintain criticality, AO and power peaking factors in their acceptable diapasons at CB = const. Analysis is performed with Russian 3D code BIPR-7 only for neutronics aspects without considering strength cyclic characteristics of the equipment and nuclear fuel.