Screening sensitivity analysis of a PWR fuel assembly FEM structural model

Andreas Wanninger, Marcus Seidl, Rafael Macián-Juan

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

2 Scopus citations


Within the present project computational methods to describe the static mechanical response of PWR fuel assemblies (FA) in the reactor core are developed. For this purpose a structural model of a PWR fuel assembly has been implemented with the Finite Element Method (FEM) using the ANSYS APDL Mechanical code. The purpose of the model is to investigate the long-term creep deformation of the fuel assemblies in the reactor core, commonly known as fuel assembly bow. FA bow is considered to be a complex process with a large number of influencing mechanisms and many only roughly known boundary conditions. Uncertainty and sensitivity analyses are a common way to investigate the predictive power and reliability of such complex models. Hence, as a first approach to understand the importance of the many model parameters, a qualitative sensitivity analysis of the model was conducted using the screening method proposed by Morris. In the first part of the paper, the FA structural model and its principal parameters are presented. The second part presents first the different simulation experiments used for the screening analyses. Based on the model description, relevant input parameters are then identified and a typical range of values is determined. The sensitivity analysis is performed in two subsequent steps. First, the model is screened for influential stiffness parameters with the objective of stiffening the FA structure. Second, the influence of the uncertain boundary conditions and material models on the FA creep deformation is tested. For the considered FA design it is concluded that the influence of the involved uncertainties is comparable to the influence of the parameters which can deterministically increase the stiffness. An integral approach accounting for these uncertainties is hence necessary to predict FA bow reliably in order to take additional measures for a further reduction of FA bow amplitudes.

Original languageEnglish
Title of host publicationTop Fuel 2016
Subtitle of host publicationLWR Fuels with Enhanced Safety and Performance
PublisherAmerican Nuclear Society
Number of pages10
ISBN (Electronic)9780894487309
StatePublished - 2016
EventTop Fuel 2016: LWR Fuels with Enhanced Safety and Performance - Boise, United States
Duration: 11 Sep 201615 Sep 2016

Publication series

NameTop Fuel 2016: LWR Fuels with Enhanced Safety and Performance


ConferenceTop Fuel 2016: LWR Fuels with Enhanced Safety and Performance
Country/TerritoryUnited States


  • FEM structural model
  • PWR fuel assembly
  • Screening sensitivity analysis


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