Impact of control blade insertion on the deformation behavior of SiC-SiC channel boxes in BWRs

G. Singh, J. P. Gorton, D. Schappel, B. S. Collins, Y. Katoh, N. R. Brown, B. D. Wirth

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

This article describes the analysis of distortion of a silicon carbide fiber-reinforced, silicon carbide matrix (SiC-SiC) composite channel box under in-reactor conditions of a boiling water reactor (BWR). The BWR core has significant gradients in the fast neutron flux across the channel box due to the presence of water rods within the fuel assemblies, and these gradients increase further with the insertion of control blades. As a result of the temperature and neutron flux dependent irradiation-induced swelling of SiC, the SiC-SiC composite channel box can undergo distortion. In this work, we evaluate the SiC-SiC channel box distortion for three different control blade positions. This analysis is based on the neutron flux and temperature distributions in the BWR core calculated using the neutronics code MPACT and thermal-hydraulics code CTF. This calculation is coupled through temperature feedback. Subsequently, we have performed structural analysis based on the calculated neutron flux and temperature distributions to determine the deformation and stress development in the channel box. The structural analysis was performed using the fuel performance modeling code BISON and the commercial finite element analysis software Abaqus. The results indicate that large gradients in fast neutron flux (up to 35–40% across a single axial level) will develop across the channel box. Due to these gradients, the channel box will undergo time-dependent bending for all the control blade positions in the assembly. The time-dependent bowing behavior is dominated by the transient swelling of SiC-SiC material under non-uniform neutron flux, and changes with variation in the control blade position. The bending will cause temporary interference between the channel box and control blade, and the interference is expected to be most severe for the fully inserted control blade position. The developed stresses due to differential swelling in the channel box exceed the proportional limit stress of the material, which may cause matrix microcracking in the channel box. However, the stresses remain below the tensile strength of the material, and therefore, development of a full, through-thickness crack in the channel box is not expected. Further work is recommended to explore and evaluate the mitigation strategies.

Original languageEnglish
Article number110621
JournalNuclear Engineering and Design
Volume363
DOIs
StatePublished - Jul 2020

Funding

The authors acknowledge numerous helpful discussions in the formulation and completion of this research with Dr. Andy Nelson and Dr. Kurt Terrani (ORNL). This research was performed under funding provided by the Advanced Fuels Campaign – Nuclear Technology Research and Development program of U.S. Department of Energy, Office of Nuclear Energy, and supported in part by an appointment to the Oak Ridge National Laboratory NESLS Program, sponsored by the U.S. department of Energy and administered by the Oak Ridge Institute for Science and Education. The authors acknowledge numerous helpful discussions in the formulation and completion of this research with Dr. Andy Nelson and Dr. Kurt Terrani (ORNL). This research was performed under funding provided by the Advanced Fuels Campaign – Nuclear Technology Research and Development program of U.S. Department of Energy , Office of Nuclear Energy , and supported in part by an appointment to the Oak Ridge National Laboratory NESLS Program, sponsored by the U.S. department of Energy and administered by the Oak Ridge Institute for Science and Education .

FundersFunder number
U.S. Department of Energy
Office of Nuclear Energy
Oak Ridge National Laboratory
Oak Ridge Institute for Science and Education

    Keywords

    • Accident tolerant fuel
    • BWR
    • Channel box
    • Deformation analysis
    • SiC
    • SiC/SiC composite
    • Silicon carbide

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