First Reloads with 4.7% Enriched Assemblies in Paks NPP

Beliczai Botond; Paks NPP

25th Symposium of AER on VVER Reactor Physics and Reactor Safety (2015, Balatongyörök, Hungary)
Fuel management issues


In Paks NPP 4.7%-enriched, Gd-containing fuel assemblies had to be introduced for the
realization of 15-month long fuel cycles. The geometrical structure of these assemblies is the
same as the 4.2%-enriched ones. The above mentioned fuel assemblies differ from each other
in the enrichment and the enrichment distribution of fuel pins and in the number and the
position of fuel pins with Gd burnable absorber.
In fall of 2014 12 of such 4.7% enriched fresh assemblies (test assemblies) ? along with
4.2% enriched fresh ones ? were placed into the core of the 3rd unit, so that their
reactorphysical and thermalhydraulical behaviour during the fuel cycle could be checked.
Thermocouple and SPN detector measurement signals of 4.7% enriched FAs were compared
to the calculated values, and the differences were evaluated statistically. Based on these
investigations we gained some invaluable experience which can be used in the future for
planning C15 reload patterns.
This August 48 of 4.7%-enriched fresh FAs along with 54 of 4.2%-enriched fresh ones were
placed into the core of the 2nd unit. Reactorphysical parameters which were measured during
the physical startup tests were in good agreement with the calculated ones, and the unit can be
operated on 100% power level since startup without any problem. The evaluation of
thermocouple and SPN detector measurements vs. calculation is continuous.
Results of the above mentioned investigations will be presented in this paper and during the

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