Dominant substructural vibration modes for fully-loaded spent nuclear fuel canisters

Abstract

This paper investigates the dynamic characteristics of a multilevel structure for the transportation and storage of spent nuclear fuel (SNF) from commercial power plants. The nuclear fuel is stored in slender rods that are grouped together into fuel assemblies (FA). In a sealed cylindrical container called "canister", the FA are inserted into a honeycomb basket. The objective of this paper is to develop a computational model that accurately describes the structural dynamics of the canister, based on measurements collected from its external surface. Based on these measurements, the computational model is intended to capture the signature of the structural integrity of the internal components (FA and fuel rods). The numerous components lead to a large finite element (FE) model and numerous vibration modes and eigenfrequencies. Nevertheless, the localized connections between components enable an efficient domain decomposition with few interface coordinates. Craig-Bampton (CB) substructuring is thus used to perform the modal analysis. However, the high modal density yields a large-scale CB eigenvalue problem that necessitates a sparse solver. A block factorization by Schur complement that exploits the sparsity of the CB matrices allows an efficient calculation of the numerous eigenpairs. Many local vibration modes contribute little to the dynamics of the SNF canister. The main contribution of this paper is the development of an efficient methodology for determining the importance of each of

Updating an uncertain and expensive computational model in structural dynamics based on one single target FRF using a probabilistic learning tool

“…The admissible set is the support of the prior probability distribution of the uncertain control parameter. This situation, which we have just described, is that of the fully-loaded spent nuclear fuel canisters studied in [1,2,3] and depicted in Fig. 1.…”

“…Those are multiscale structures made up of repeated components at various scales, which require fine mesh discretizations and which also exhibit numerous local structural elastic modes that are associated with the isolated vibrations of each of the numerous components. In [3], an HDM was constructed based on nearly half-a-million modes from a finite element model of about 130 million dof. Adapted algorithms were developped allowing a single run of the HDM to be performed in about 40 minutes using a cluster of 50 nodes.…”