Utilization of a finite element model to verify spent nuclear fuel storage rack welds Page: 1 of 14
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UTILIZATION OF A FINITE ELEMENT MODEL TO VERIFY SPENT
NUCLEAR FUEL STORAGE RACK WELDS1M. E. Nitzel
Idaho National Engineering and Environmental Laboratory
Lockheed Martin Idaho Technologies Company
Idaho Falls, IdahoR IVE
JU .14 199
0 9-T IABSTRACT
Elastic and plastic finite element analyses were performed for
the inner tie block assembly of a 25 port fuel rack designed for
installation at the Idaho National Engineering and Environmental
Laboratory (INEEL) Idaho Chemical Processing Plant (ICPP). The
model was specifically developed to verify the adequacy of certain
welds joining components of the fuel storage rack assembly. The
work scope for this task was limited to an investigation of the stress
levels in the inner tie welds when the rack was subjected to seismic
loads. Structural acceptance criteria used for the elastic calculations
performed were as defined by the rack's designer. Structural accep-
tance criteria used for the plastic calculations performed as part of
this effort were as defined in Subsection NF and Appendix F of Sec-
tion III of the ASME Boiler & Pressure Vessel Code.
The results confirm that the welds joining the inner tie block
to the surrounding rack structure meet the acceptance criteria. The
analysis results verified that the inner tie block welds should be
capable of transferring the expected seismic load without structural
failure,-
INTRODUCTION
A subcontractor performed the design and analysis of spent
fuel storage racks for installation at the INEEUs ICPP. As required
by Department of Energy Standard 1020-94 (U. S. Department of
Energy, 1994), the design and the associated calculations, were
subjected to an independent peer review as part of the overall
quality assurance plan.
During the course of the independent review, questions were
raised regarding the adequacy of certain welds to withstand the
loading that would be imposed by the motion of the adjacent fuel
racks during a seismic event. The welds in question were those that
join the various structural components in the immediate areas of the
1. Work performed under U. S. Department of Energy Contract No.
DE-AC07-941D13223.inner tie block. The subcontractor based the original'design of these
welds on hand calculations. The independent-reviewer questioned
the weld adequacy based on an alternate set of calculations that were
performed as part of the review process. To resolve the adequacy
questions it was suggested that analyses be performed by a third
party. The purpose of the work described in this paper was to
perform this verification analysis and provide results suitable for
use in resolving the issue surrounding the adequacy of the subject
welds. The Applied Mechanics Group within INEEL's Specialty
Engineering & Sciences Department was asked to perform the
analysis. As a result, a finite element model representing portions
of the fuel rack structure encompassing one inner tie block assembly
was developed. This paper describes the details of the finite element
analyses performed on the the model and the results obtained.
SCOPE OF ANALYSIS
The inner tie block structure addressed in this paper was taken
from a 25 port fuel rack assembly. The storage ports in this design
are arranged in a 5 X 5 grid array. The scope of the analysis was
limited to the specific components described below.
Independent reviewer questions regarding the integrity of the
welds joining the inner tie blocks to the surrounding rack structure
initiated the analysis effort. To address these questions and limit the
scope of the analysis effort, a finite element model was developed.
The model represents an inner tie block and a portion of the rack
structure (top plate, port tubes, soffit plate, and back plate) that
immediately adjoin it. Details of the structural components were
obtained from the applicable drawings. The finite element model
represents only a section of the rack surrounding one of the inner tie
blocks. This was deemed sufficient to satisfy the intent of the
analysis.
The elastic analysis results were compared to allowable values
used by the rack's designer. Plastic -analyses were eventually
performed and these results were compared to allowable values
found in Subsection NF and Appendix F of the American Society
of Mechanical Engineers Boiler & Pressure Vessel Code (hereafterMA SEF
OFThS TU-4r,
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Nitzel, M.E. Utilization of a finite element model to verify spent nuclear fuel storage rack welds, article, July 1, 1998; Idaho Falls, Idaho. (https://digital.library.unt.edu/ark:/67531/metadc710196/m1/1/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.