Sensitivity and uncertainty analysis of Gundremmingen-A assembly B23 sample I2680 depletion calculation with Serpent 2

The work described in this report presents sensitivity and uncertainty calculations in EU project EURAD work package 8 Spent Fuel Characterization and Evolution Until Disposal (SFC) subtask 2.1. Sensitivity and uncertainty analysis is performed in Serpent 2 depletion calculations of one sample in a 6x6 BWR assembly. Calculated sensitivites and uncertainties to decay heat and concentrations of several nuclides are presented. The Serpent calculated nuclide concentrations are compared to measured concentrations available in SFCOMPO-2.0.
The calculations were performed on a two dimensional assembly. Sensitivities and uncertainties on several operating history parameters, fuel properties and computational methods were calculated. Uncertainties in burnup were by far the most significant uncertainty component for decay heat and the studied nuclides 14C, 36Cl, 137Cs, 148Nd, 235U, 236U, 238U, 238Pu, 240Pu, 241Pu, 242Pu, 242Cm and 244Cm. The only exception was 239Pu that was most sensitive to water density (moderator density and void fraction). Other generally rather significant contributors to uncertainty were water density (moderator density and void fraction) and fuel density. Uncertainties in pin radius or 234U enrichment had small or insignificant impact to the uncertainties of the calculated quantities. Uncertainties in decay data had some impact only on 242Cm concentration and decay heat at 0 cooling time. The impact of the other studied uncertainty components, power density, water and fuel temperature, 235U enrichment and 238U content, were more dependent on the calculated quantity. According to the sensitivity studies fuel swelling, cross section data and fission yield data may have significant impact on many of the calculated quantities.