Large-eddy simulation, fuel rod vibration and grid-to-rod fretting in pressurized water reactors

Abstract

Grid-to-rod fretting (GTRF) in pressurized water reactors is a flow-induced vibration phenomenon that results in wear and fretting of the cladding material on fuel rods. GTRF is responsible for over 70% of the fuel failures in pressurized water reactors in the United States. Predicting the GTRF wear and concomitant interval between failures is important because of the large costs associated with reactor shutdown and replacement of fuel rod assemblies. The GTRF-induced wear process involves turbulent flow, mechanical vibration, tribology, and time-varying irradiated material properties in complex fuel assembly geometries. This paper presents a new approach for predicting GTRF induced fuel rod wear that uses high-resolution implicit large-eddy simulation to drive nonlinear transient dynamics computations. The GTRF fluid-structure problem is separated into the simulation of the turbulent flow field in the complex-geometry fuel-rod bundles using implicit large-eddy simulation, the calculation of statistics of the resulting fluctuat-* Corresponding author.

A hybrid incremental projection method for thermal-hydraulics applications

“…This section presents several verification problems to illustrate the convergence characteristics of the hybrid projection algorithm. A more detailed validation study using implicit large-eddy simulation maybe found in [42,43], along with several verification and validation studies using multiple RANS models in [42].…”

A multi-stage approach of simulating turbulence-induced vibrations in a wire-wrapped tube bundle for fretting wear prediction

“…When the turbulent, fluctuating pressure field is obtained through LES, it can be used as the excitation in a one-way coupled FSI simulation to obtain the displacement response. This has been done in earlier work to assess FIV in PWR [22][23][24] and LMFR [18]. It is assumed that feedback from structural displacement on the flow is negligible, as the displacements in TIV are usually rather small.…”

“…This rubbing type of contact provokes fretting wear. Fretting wear is often the root-cause of fuel failure, recent works indicate that more than 70 % of fuel failures in PWR reactors are related to fretting [24,39,40]. Fretting is a complex wear process, resulting from highly non-linear contact dynamics.…”

“…They have often been subject of research using a numerical approach [42][43][44][45]. Similarly also steam generators [38,[46][47][48][49], CANDU fuel bundles [50][51][52] and more recently a complete fuel string [53], and grid-to-rod-fretting (GTRF) in PWR [24,[54][55][56] have been investigated. To the authors' knowledge, this kind of numerical analysis has not yet been performed for a wire-wrapped bundle geometry.…”

Axial-flow-induced vibration experiments on cantilevered rods for nuclear reactor applications

“…In coupled CFD/SD simulations, a high-resolution CFD calculation provides the instantaneous pressure field and associated turbulent fluid force on the fuel rod surface, which is then used as input to SD simulations that yield the fuel rod motion. Large computational grids (several tens of million cells) and advanced turbulent models (large eddy simulation) are typically required to properly capture the intricate geometry of nuclear fuel bundles and faithfully reproduce instantaneous pressure fields and mechanical loads (Conner et al, 2010;Yan et al, 2011;Elmahdi et al, 2011;Zhang and Yu, 2011;Delafontain and Ricciardi, 2012;Bakosi et al, 2013;Christon et al, 2016).…”