Neutronics characterization of an erbia fully poisoned PWR assembly by means of the APOLLO2 code

Recently, increasing demands on the reduction of fuel cycle costs have led to higher burnup fuel designs. According to the erbia-credit super high burnup fuel concept, developed by mixing low content of erbia to UO₂ powder directly after reconversion process so that all fuel pins in a given fuel assembly are homogeneously doped, the present study aims at characterizing, from a neutronic point of view, a 17*17 pressurized water reactor assembly enriched to 10.27 wt.% in ²³⁵U with an erbia content of 1 at.% (i.e. 0.7 wt.%) by means of the deterministic neutronic code APOLLO2. For this purpose, a simplified thermal-hydraulic analysis was performed in order to evaluate the effects on fuel thermal conductivity of adding erbia to uranium oxide. The results obtained allow us to conclude that an Er-doped assembly enriched to >5 wt.% in ²³⁵U represents an advantageous solution for very long fuel cycles, and it is so suited for very high burnups. (authors)