Abstract
The goal was to evaluate the neutronic behavior during the fuel burnup changing the amount of burnable poison and fuel enrichment. For these analyses, it was used a 17 x 17 PWR fuel element, simulated using the 238 groups library cross-section collapsed from ENDF/BVII.0 and TRITON module of SCALE 6.0 code system. The results confirmed the effective action of the burnable poison in the criticality control, especially at Beginning Of Cycle (BOC) and in the burnup kinetics, because at the end of the fuel cycle there was a minimal residual amount of neutron absorbers (155Gd and 157Gd), as expected. At the end of the cycle, the fuel element was still critical in all simulated situations, indicating the possibility of extending the fuel burn.
Highlights
The burnable poison is a substance, which has a high neutron absorption crosssection, which reduces the reactivity of a reactor core [1]
The main difference between graphics is predominant at the Beginning Of Cycle (BOC), period of effective action of the burnable poison
This allows the reduction of control rods at the Beginning Of Cycle (BOC)
Summary
The burnable poison (or poison) is a substance, which has a high neutron absorption crosssection, which reduces the reactivity of a reactor core [1] These neutron absorbers are chosen because they transmute by neutron capture into isotopes with low capture cross sections, somewhat faster than fuel burnup, leaving a residual minimum amount of burnable poison at the end of the fuel cycle [2]. Such characteristics of burnable poison improve fuel utilization, contributing to a more homogeneous power distribution into the reactor core and are able to control nuclear reactivity. The best way to improve the fuel utilization is based on the burnup extension and poison kinetics at BOC, since the lowest remaining residual concentration of the burnable poison is expected at the end of the cycle in order to stop neutrons absorption and to reduce any core excess reactivity
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