ANALYSIS OF APPLICATION OF VARIOUS VERSIONS OF FUEL ROD AXIAL PROFILING IN VVER-1000 USING THE SOFTWARE SAPFIR_95&RC
24th Symposium of AER on VVER Reactor Physics and Reactor Safety (2014, Sochi, Russia)
Reactor physics calculations, experiments and code validation
Abstract
ANALYSIS OF APPLICATION OF VARIOUS VERSIONS OF FUEL ROD AXIAL PROFILING IN VVER-1000 USING THE SOFTWARE SAPFIR_95&RC
Zuev А.А., Ustinov А.N., Fateev М.V., Kurakin K.Yu. OKB “GIDROPRESS”
ABSTRACT
Now transition to one-and-a-half-year fuel cycle with power uprating up to 104 %Nnom comes to the end at Balakovo, Rostov and Kalinin NPP. The use of increased amount of fuel in the core and its enrichment means by the extended fuel cycles implemented at these Units, power uprating, this is provided due to application of FA with increased fuel stack: TVS-2М and TVSA-PLUS.
Experience in design and operation of such extended fuel cycles showed that the value of maximum linear power of fuel rods which is implemented in the upper part of the core comes near to the limiting design value and can reach it closer to the end of cycle. The revealed effect is of nonmonotonic power of FA during cycle because of non-uniform burnup of fuel in the core made up from FAs with a large (to 24-27 pcs) and, at the same time, a little (6 pcs) number of Gd-duel rods and becomes apparent, especially, in the cores, which comprise FA with extended fuel part.
Similar situation limits and complicates operation of Units and can be in some cases lead to power decrease. To avoid similar situations the specialists of RRC “Kurchatov Institute” proposed a method for decrease in linear heat rates of fuel rods by means of application of FA in axially-profiled Gd-fuel rods due to removal of gadolinium oxide from the end face parts of Gd-fuel rods or reduction of its content, this make possible, by the preliminary assessments, to decrease the maximum linear power of fuel rods within the range with minimum margin to the limiting design dependence and, thus, to increase this margin up to limiting design restrictions.
The paper represents detailed analysis of application of axial profiling of Gd-fuel rods by means of an example of equilibrium fuel loading of 18-month fuel cycle at Rostov NPP, Unit 2, by the results of the core neutronics calculations performed using the certified SP SAPFIR_95&RC_VVER. The activities aimed at optimization of Gd-fuel rod section height for profiling have been performed.
Separately, the computer code ReMi (ReadMicro) intended for processing of binary files (calculation results) of the RC code has been upgraded within the scope of the activity, this made possible to perform automatic processing of data on power distribution and burnup in the reactor core and substantially to accelerate the process of obtaining the final result