Uncertainty Analyses Applied to the UAM/TMI-1 Lattice Calculations Using the DRAGON (Version 4.05) Code and Based on JENDL-4 and ENDF/B-VII.1 Covariance Data
Journal article, 2013
The OECD/NEA Uncertainty Analysis in Modeling (UAM) expert group organized and
launched the UAM benchmark. Its main objective is to perform uncertainty analysis in light
water reactor (LWR) predictions at all modeling stages. In this paper, multigroup microscopic
cross-sectional uncertainties are propagated through the DRAGON (version 4.05) lattice code in
order to perform uncertainty analysis on kinf and 2-group homogenized macroscopic cross-sections.
The chosen test case corresponds to the Three Mile Island-1 (TMI-1) lattice, which is
a 15*15 pressurized water reactor (PWR) fuel assembly segment with poison and at full
power conditions. A statistical methodology is employed for the uncertainty assessment, where
cross-sections of certain isotopes of various elements belonging to the 172-group DRAGLIB
library format are considered as normal random variables. Two libraries were created for such
purposes, one based on JENDL-4 data and the other one based on the recently released
ENDF/B-VII.1 data. Therefore, multigroup uncertainties based on both nuclear data libraries
needed to be computed for the different isotopic reactions by means of ERRORJ. The
uncertainty assessment performed on kinf and macroscopic cross-sections, that is based on
JENDL-4 data, was much higher than the assessment based on ENDF/B-VII.1 data. It was
found that the computed Uranium 235 fission covariance matrix based on JENDL-4 is much
larger at the thermal and resonant regions than, for instance, the covariance matrix based on
ENDF/B-VII.1 data. This can be the main cause of significant discrepancies between different
uncertainty assessments.