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Parametric Evaluation of Seismic Behavior of Freestanding Spent Fuel Dry Cask Storage Systems (NUREG/CR-6865)
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Publication Information
Manuscript Completed: December 2004
Date Published: February 2005
Manuscript Completed: December 2004
Date Published: February 2005
Prepared by
V.K. Luk1, B.W. Spencer1, I.P. Lam2
R.A. Dameron3
1Sandia National Laboratories
Operated by Sandia Corporation for the
U.S. Department of Energy
Albuquerque, NM 87185-0744
2Earth Mechanics, Inc
Fountain Valley, CA 92706
3David Evans and Associates, Inc.
San Diego, CA 92123
S.K. Shaukat, NRC Project Manager
Prepared for
Division of Engineering Technology
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001
NRC Job Code W682
Availability
Notice
Abstract
One of the high priority issues for the continuous operation of nuclear power plants is how to manage and
store spent fuel. In recent years, dry storage of spent fuel above ground has become a de facto fuel "repository" solution worldwide. Arrays of dry cask storage systems have been installed at Independent
Spent Fuel Storage Installations (ISFSI) at many nuclear power plant sites. Most of these storage systems
are freestanding, leading to stability concerns in terms of potential excessive sliding displacements and
tipping over in an earthquake event. Sandia National Laboratories has been contracted by the Office of
Nuclear Regulatory Research of the U.S. Nuclear Regulatory Commission (NRC) to conduct a research
project to develop a comprehensive methodology for evaluating the nonlinear seismic behavior of these
storage systems. The main objective of this effort is to perform parametric analyses to characterize the
sensitivity of the cask response to a number of important input parameters, which provides a guideline to
the range of applicability of analysis results. The results from these parametric analyses have been
compiled in nomograms to facilitate the safety review of licensing applications by the staff at the Office
of the Nuclear Material Safety and Safeguards (NMSS). This report documents the details of analysis
models and all parametric analysis findings.
In this research effort, the cask response is investigated using the finite element method with explicit time
integration. The ABAQUS/Explicit code is used to analyze three-dimensional coupled models consisting
of a freestanding cask, a concrete pad, and a soil/rock foundation interacting with frictional contact at
interfaces. This modeling approach allows a realistic simulation of soil-structure interaction effects and
the nonlinear cask behavior after the onset of cask rocking or rolling motion due to applied ground
motions. The earthquake ground motions applied to the model are derived from actual recorded ground
motions, fitted to conform to selected spectral shapes, and adjusted using a deconvolution procedure that
enables the ground motion to be applied at the base of the foundation model.
Prior to performing parametric analyses, the coupled finite element models were developed for three site specific analyses including three-module rectangular Transnuclear West module/cask, and HI-STORM
100 casks at Hatch Nuclear Power Station and at Private Fuel Storage Facility. The lessons learned from
the site-specific analyses help guide performing the much broader based parametric analyses.
The parametric analyses involve two cask system designs: the horizontal rectangular module with an
aspect ration of 0.58 defined as ½ the shorter width divided by the height of the center of gravity from the
base and the vertical cylindrical cask with an aspect ratio of 0.56 defined as ½ the base diameter divided
by the height of the center of gravity from the base. The seismic behavior of these cask designs was
investigated with three different foundation types (soft soil, stiff soil, and rock) and three coefficients of
friction (0.20, 0.55, and 0.80) at the cask/pad interface. Three spectral shapes (Regulatory Guide 1.60,
NUREG/CR-0098, and NUREG/CR-6728) were selected, and for each of these spectral shapes, five
different earthquake ground motion records were chosen. These ground motion records were linearly
scaled to result in surface peak ground accelerations (PGA) ranging from 0.25 to 1.25 g. A total of 1165
analysis cases were performed in this investigation.
Nomograms of median cask responses +/- one standard deviation of maximum cask top sliding
displacements and angular rotations versus peak ground accelerations are plotted at a 5% damped 1 Hertz
frequency (1 second period) of pseudo spectral acceleration (PSA) after compiling from the pool of
parametric analysis results. These nomograms may provide a meaningful and practical tool to cask
designers and reviewers in interpreting the seismic behavior of dry cask storage systems.
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