This paper shows the neutronic availability for the increase of PWR cycle length by loading highly poisoned UO2 fuel rods. The lumped burnable gadolinium amount reaches up to 8% in UO2-Gd2O3 fuel rods loaded in French PWRs. In the new EPR™ GEN-3 reactor, Gd pins will be loaded in the 1st and following cores. The aim of this study is to demonstrate the qualification of the APOLLO2.8 code and the JEFF-3.1.1 nuclear data library for the depletion of such fuel rods. More than 341 radiochemical analyses were performed for 40 irradiated rod cuts in the GEDEON-II PWR-like assembly. Local moderation irradiation conditions were challenging for calculation tools, however the reaction rate validation against TRIPOLI4 calculation results shows the accuracy of the APOLLO2/8REL2005 scheme. The analysis of GEDEON-II experiment confirmed the good prediction of actinide build-up in PWR fuel pins using JEFF-3.1.1 library, as well as the trend to underestimate 238U(n, 2n). This work has demonstrated the satisfactory accuracy of the APOLLO2.8 calculation for the depletion of 155Gd and 157Gd poisoning isotopes: averaged C-E biases on their consumption throughout irradiation are -0.5 ± 1.0% and -0.7 ± 1.6% (RMS), respectively.
Bernard, D., & Santamarina, A. (2016). Qualification of gadolinium burnable poison: Interpretation of MELUSINE/GEDEON-II spent fuel analysis. Annals of Nuclear Energy, 87, 21–33. https://doi.org/10.1016/j.anucene.2015.02.034