Shutdown margin calculations for the determination of the limiting position of control fuel assemblies on Dukovany NPP
26th Symposium of AER on VVER Reactor Physics and Reactor Safety (2016, Helsinki, Finland)
Core surveillance and monitoring continues
Abstract
SHUTDOWN MARGIN CALCULATIONS FOR THE DETERMINATION OF THE LIMITING POSITION OF CONTROL FUEL ASSEMBLIES ON DUKOVANY NPPMartin Šašek, Zdeňka Neduchalová, Svatobor Štech E-mail: martin.sasek@skoda-js.cz, Tel: +420 378 042 835 ŠKODA JS a.s., Orlík 266/15, 316 00 Plzeň, Czech RepublicABSTRACTNew realistic approach for the determination of control fuel assembly (CFA) position limiting curve presented last year on AER symposium resulted in lower CFA positions than previous conservative approach. However, further investigation of Dukovany NPP operations showed that a limiting curve based on shutdown margin (SDM) and CFA ejection could lead to more flexibility for the NPP operators during transition processes (TP) without compromising the NPP’s operation safety. That’s why comprehensive SDM calculations were performed for static calculations and transition processes of the realistic approach. Coarse mesh calculations were used for basic orientation in the problem and were followed by fine mesh calculations of selected scenarios. Results of these fine mesh calculations and their analysis are presented in this contribution. Analysis is aimed mainly on finding out which scenarios and at which conditions are the limiting ones. Considered conditions include time in cycle at which the TP began, TP power or elapsed time during the TP. As a conclusion, new limiting curve based on the shutdown margin calculation is proposed together with information on how this new approach could be included in the current operation procedures of the Dukovany NPP. 26th Symposium of AER on VVER Reactor Physics and Reactor Safety 34 10 – 14 October 2016, Helsinki, Finland