Isotopic uncertainty assessment due to nuclear data uncertainties in high-burnup samples - 5-09

The aim of this paper is to study the importance of nuclear data uncertainties in the prediction of high-burnup spent fuel content and its effect in the criticality safety assessment. Calculations described in this paper were performed for a typical pin-cell in a water moderated infinite lattice configuration. This fuel rod with an initial ²³⁵U enrichment of 4.5 wt% is irradiated to an average burnup of about 78 MWd/kgU. We conclude for this prediction that: (i) decay data uncertainties have a negligible effect on the isotopic prediction both in actinides and fission products, the maximum relative errors are found for ¹⁵⁵Eu (7.3%), ¹⁰⁶Ru (0.6%) and ²⁴³Cm (0.4%) (ii) fission yield data uncertainties induce relative errors in fission products below 5%, the maximum relative errors are found for ⁹⁵Mo (4.9%) and ¹⁴⁹Sm (4.8%); and (iii) larger uncertainties in concentrations were found due to cross section data uncertainties.We have performed a burnup criticality uncertainty analysis for this high-burnup LWR pin-cell with TSUNAMI code showing that relative error in k_eff at EOC can reach ∼900 pcm, being the most important source of uncertainty: ²³⁹Pu(nu-bar), ²³⁸U(n,n'), ²³⁸U(n,γ) and ²³⁹Pu(n,fission). At BOC, with low relative error in k_eff ∼500 pcm, being ²³⁵U(nu-bar), ²³⁸U(n,n') and ²³⁵U(n,γ) the most important reactions. The contribution of the concentration uncertainty of major-minor actinides and fission products is also assessed