UO₂ Versus MOX: Propagated Nuclear Data Uncertainty for k_eff, with Burnup

Precise assessment of propagated nuclear data uncertainties in integral reactor quantities is necessary for the development of new reactors as well as for modified use, e.g., when replacing UO₂ fuel by mixed-oxide (MOX) fuel in conventional thermal reactors.
This paper compares UO₂ fuel to two types of MOX fuel with respect to propagated nuclear data uncertainty, primarily in k_eff, by applying the Fast Total Monte Carlo method (Fast TMC) to a typical pressurized water reactor pin cell model in Serpent, including burnup. An extensive amount of nuclear data is taken into account, including transport and activation data for 105 nuclides, fission yields for 13 actinides, and thermal scattering data for H in H₂O.
There is indeed a significant difference in propagated nuclear data uncertainty in k_eff; at zero burnup, the uncertainty is  0.6% for UO₂ and ∼ 1% for the MOX fuels. The difference decreases with burnup. Uncertainties in fissile fuel nuclides and thermal scattering are the most important for the difference, and the reasons for this are understood and explained.
This work thus suggests that there can be an important difference between UO₂ and MOX for the determination of uncertainty margins. However, it is difficult to estimate the effects of the simplified model; uncertainties should be propagated in more complicated models of any considered system. Fast TMC, however, allows for this without adding much computational time.