Justin L. Coleman

Modeling and Simulation of Used Nuclear Fuel During Transportation with Consideration of Hydride Effects and Cyclic Fatigue

The objective of this work is to understand the integrity of Used Nuclear Fuel (UNF) during transportation. Previous analysis work has been performed to look at the integrity of UNF during transportation but these analyses have neglected to analyze the effect of hydrides and flaws (fracture mechanics models to capture radial cracking in the cladding). In this study, the clad regions of interest are near the pellet-pellet interfaces. These regions can experience more complex stress-states than the rest of the clad during cooling and have a greater possibility to develop radially reoriented hydrides during vacuum drying.

Establishing Outcrop Time Series at Various Depths in a Nonlinear Soil Column: An Iterative Approach

Abstract Seismic soil-structure interaction (SSI) analysis of nuclear facilities is an important consideration during design and retrofit. SSI tools used in the nuclear industry are currently based on an equivalent linear (EL) approach. Procedures for developing input ground motion for EL approaches are well established. However, the procedures for establishing input ground motion for nonlinear soil-structure interaction (NLSSI) analysis of nuclear facilities are not well established. A collaborative research group at Idaho National Laboratory has recently developed analytical methods and numerical tools for using NLSSI analysis for nuclear facility seismic calculations. NLSSI analysis for a nuclear facility allows for calculation of seismic wave motion through a near-field soil domain using either (a) vertically propagating shear and compressive waves, which is the current industry practice, or (b) a three-dimensional nonvertical wave field. This technical note presents an iterative procedure for establishing outcrop motion at a depth in the soil column for NLSSI analysis that uses vertically propagating shear waves. The approach presented in this technical note starts with a known ground motion at the surface that is deconvolved to a depth, and then the obtained motion is convolved up to a different desired location of input for the NLSSI model. To demonstrate the validity of the approach, a finite element soil column that is representative of a nuclear facility site in the United States is used to produce compatible outcrop seismic time series for reduced nonlinear soil mesh depths. The developed approach for reducing the nonlinear soil column model depth is a two-step iterative method. The first step is establishing an outcrop time series at the lowest depth considered that produces the top-of-soil response spectrum of an actual recorded ground motion. The second step is providing compatible outcrop time series at a shallower depth based on the information from the first step. A comparison of the 5% damped response spectrum from the resulting acceleration time series based on the iterated outcrop motions and the original acceleration time series is conducted. The study shows that the proposed iterative approach produced comparable results within 1% range of the original recorded time series results when sufficient iterations were performed.

Determination of Anelastic Attenuation Factor (Q) and Decay Factor (K) from Ground Motion Records of the Intra-plate Region

Attenuation of seismic waves in the frequency domain for near- and far-source sites is the key parameter for inferring source properties, simulating ground motions and hazard analysis. The seismic devastation is directly related to the attenuation characteristics of the medium and the amount of seismic energy released during an earthquake. Based on the detailed literature review, it is observed that studies have been done worldwide to understand the attenuation characteristics by estimating frequency-dependent shear-wave attenuation factor (Q) for inter-plate region but very limited studies have focused on intra-plate region. This research paper focuses primarily on the determination of kappa factor (κ) and quality factor (Q) for intra-plate region as this region has scarcity of observed ground motion data sets. Around 105 recorded ground motions were collected from Canada and USA, monitored by Idaho National Laboratory, USA, during 2005–2015. This data is used to determine the farfield source geometric attenuation, kappa factor and inelastic attenuation of Q-value. An attenuation model of Fourier spectral amplitudes for a shear window for both horizontal and vertical components is also determined. Stochastic simulation of the ground motion records using EXSIM was carried out and very well comparable with the recorded ground motion data. It is also observed that spectral analysis of the ground motions shows a reliable match between the simulated and recorded spectra which supports the validity of the source parameters derived in this study. Also the results show that coefficients developed from vertical components are not applicable for horizontal components. Developed parameters kappa and quality factor are very well comparable with existing relationships from the literature. These parameters developed by considering the large data set from USA and Canada can be used for a wide intra-plate region.