ANATECH Corporation

San Diego, CA, United States

ANATECH Corporation

San Diego, CA, United States

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Montgomery R.,Pacific Northwest National Laboratory | Tome C.,Los Alamos National Laboratory | Liu W.,ANATECH Corporation | Alankar A.,Indian Institute of Technology Bombay | And 2 more authors.
Journal of Computational Physics | Year: 2017

Accurate prediction of cladding mechanical behavior is a key aspect of modeling nuclear fuel behavior, especially for conditions of pellet-cladding interaction (PCI), reactivity-initiated accidents (RIA), and loss of coolant accidents (LOCA). Current approaches to fuel performance modeling rely on empirical constitutive models for cladding creep, growth and plastic deformation, which are limited to the materials and conditions for which the models were developed. To improve upon this approach, a microstructurally-based zirconium alloy mechanical deformation analysis capability is being developed within the United States Department of Energy Consortium for Advanced Simulation of Light Water Reactors (CASL). Specifically, the viscoplastic self-consistent (VPSC) polycrystal plasticity modeling approach, developed by Lebensohn and Tomé [1], has been coupled with the BISON engineering scale fuel performance code to represent the mechanistic material processes controlling the deformation behavior of light water reactor (LWR) cladding. A critical component of VPSC is the representation of the crystallographic nature (defect and dislocation movement) and orientation of the grains within the matrix material and the ability to account for the role of texture on deformation. A future goal is for VPSC to obtain information on reaction rate kinetics from atomistic calculations to inform the defect and dislocation behavior models described in VPSC. The multiscale modeling of cladding deformation mechanisms allowed by VPSC far exceed the functionality of typical semi-empirical constitutive models employed in nuclear fuel behavior codes to model irradiation growth and creep, thermal creep, or plasticity. This paper describes the implementation of an interface between VPSC and BISON and provides initial results utilizing the coupled functionality. © 2016 Elsevier Inc.

Ravichandran N.,Clemson University | Taylor L.M.,ANATECH Corporation
International Journal of Geomechanics | Year: 2016

A uniform gradient (UG) element formulation for a four-node quadrilateral element is derived and implemented for solving the fully coupled governing equations for the dynamics of a saturated porous medium. An hourglass control scheme is also derived for eliminating the hourglass modes that arise when using the UG element formulation. The effectiveness of the new formulations is investigated by simulating the quasi-static and dynamics response of a footing and the dynamic response of an earth dam. The results show that the level of excitation of hourglass modes is problem-dependent and mesh-dependent. The proposed method for controlling the hourglass modes is shown to be effective with minimal effect on the computed response. © 2015 American Society of Civil Engineers.

Capps N.,University of Tennessee at Knoxville | Montgomery R.,Pacific Northwest National Laboratory | Sunderland D.,Pacific Northwest National Laboratory | Sunderland D.,ANATECH Corporation | And 2 more authors.
Nuclear Engineering and Design | Year: 2016

Missing pellet surface (MPS) defects are local geometric defects in nuclear fuel pellets that result from pellet mishandling or manufacturing. The presence of MPS defects can cause significant clad stress concentrations that can lead to through-wall cladding failure for certain combinations of fuel burnup, and reactor power level or power change. Consequently, the impact of MPS defects has limited the rate of power increase, or ramp rate, in both pressurized and boiling water reactors (PWRs and BWRs, respectively). Improved three-dimensional (3-D) fuel performance models of MPS defect geometry can provide better understanding of the probability for pellet clad mechanical interaction (PCMI), and correspondingly the available margin against cladding failure by stress corrosion cracking (SCC). The Consortium of Advanced Simulations of Light Water Reactors (CASL) has been developing the Bison-CASL fuel performance code to consider the inherently multi-physics and multi-dimensional mechanisms that control fuel behavior, including cladding stress concentrations resulting from MPS defects. This paper evaluates the cladding hoop stress distributions as a function of MPS defect geometry with discrete pellet radial cracks for a set of typical operating conditions in a PWR fuel rod. The results provide a first step toward a probabilistic approach to assess cladding failure during power maneuvers. This analysis provides insight into how varying pellet defect geometries affect the distribution of the cladding stress, as well as the temperature distributions within the fuel and clad; and are used to develop stress concentration factors for comparing 2-D and 3-D models.

Rashid J.Y.R.,ANATECH Corporation | Yagnik S.K.,EPRI | Montgomery R.O.,Pacific Northwest National Laboratory
JOM | Year: 2011

Light water reactor fuel is a multicomponent system required to produce thermal energy through the fission process, efficiently transfer the thermal energy to the coolant system, and provide a barrier to fission product release by maintaining structural integrity. The operating conditions within a reactor induce complex multi-physics phenomena that occur over time scales ranging from less than a microsecond to years and act over distances ranging from inter-atomic spacing to meters. These conditions impose challenging and unique modeling, simulation, and verification data requirements in order to accurately determine the state of the fuel during its lifetime in the reactor. The capabilities and limitations of the current engineering-scale one-dimensional and two-dimensional fuel performance codes is discussed and the challenges of employing higher level fidelity atomistic modeling techniques such as molecular dynamics and phase-field simulations is presented. © 2011 TMS.

Rashid J.,ANATECH Corporation | Machiels A.,EPRI
15th International High-Level Radioactive Waste Management Conference 2015, IHLRWM 2015 | Year: 2015

Hydride reorientation during dry storage is a potential issue because of its impact on cladding integrity when spent fuel assemblies are subjected to impact loading under normal and hypothetical transportation accident conditions. Mechanical property tests performed on cladding tube specimens, both in the unirradiated, hydrogen-charged and in the irradiated, defueled conditions, subjected to hydride reorientation treatments, show significant reduction in ductility and, in some cases, failure in the elastic regime. These laboratory tests have provided a much better understanding of hydride reorientation phenomena and of their impact on mechanical properties compared to the prior state of knowledge, but they may not be good simulations of actual dry storage conditions. This paper brings forward some additional information that supports the contention that hydride reorientation during dry storage and the effects of radial hydrides on cladding susceptibility to failure can be assessed under actual conditions of transportation and handling accidents. Specifically, a sufficiency criterion is proposed for Zircaloy-4 cladding in the form of a safety margin for radial hydride concentration that would eliminate the threat to cladding integrity during regulatory accidents.

Koga K.,ANATECH Corporation | Minohata T.,Shimadzu Corporation
Proteomics | Year: 2011

We assessed whether the G-electrode-loading method (GELM) was helpful in the protein analysis. GELM in 2-DE was compared with the slip-loading, the in-gel rehydration and the cup-loading in 2-DE. GELM showed the best results for protein separation. A total of 14 spots that showed an increase with GELM were analyzed by MALDI-TOF MS. In GELM, all of these spots were identified with a high score and a high sequence coverage. A membrane-associated protein was identified and determined to have phosphorylated site. These tests show that GELM has several advantages for protein analysis compared with the traditional methods. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

PubMed | Kitasato University, ANATECH Corporation and Japan National Institute of Radiological Sciences
Type: | Journal: Neuroscience research | Year: 2016

Epidemiological studies have shown that maternal infection during early pregnancy increases the risk of neurodevelopmental disorders (i.e., schizophrenia or autism) in offspring. Recently, diagnostic/stratification biomarkers for the maternal immune activation background in patients with neurodevelopmental disorders have been energetically searched for in the patient blood. Here, we report a novel serologic marker candidate for the disorders found in the maternal immune activation (MIA) rat model. Serum proteome analysis of the MIA rat showed that the immunoglobulin (Ig) light chain is reproducibly augmented. The Ig light chain in sera takes two forms - free form or bound to the Ig heavy chain. Only the former is an inflammatory disease marker, but pro-inflammatory cytokine levels in the sera of the MIA rats were below detectable limits of the ELISA protocol we used. We thereby carried out serum assays of Ig light chains and pro-inflammatory cytokines of commercially available schizophrenia patient sera for research. Although the number of samples was limited, we found augmentation of free Ig light chains but not pro-inflammatory cytokines in sporadic schizophrenia patient sera. Our findings suggest that Ig light chain assay of the schizophrenia/autism patient sera would be worthy to be validated in larger scale.

Murcia-Delso J.,Parque Cientifico y Tecnologico de Bizkaia | Dunham R.S.,ANATECH Corporation | Parker D.R.,ANATECH Corporation | James R.J.,ANATECH Corporation
Improving the Seismic Performance of Existing Buildings and other Structures 2015 - Proceedings of the 2nd ATC and SEI Conference on Improving the Seismic Performance of Existing Buildings and Other Structures | Year: 2015

This paper presents the three-dimensional finite element analysis of squat RC walls using a continuum constitutive model for concrete developed at ANATECH. The concrete model is based on the smeared-cracking concept and an elastic-plastic formulation that permits the simulation of cracking and other particular response characteristics of concrete. The laws governing the normal and tangential stresses on a crack are suitable for the simulation of shear failures and crack closing and re-opening under load reversals. Finite element models have been developed to reproduce experiments on squat walls found in the literature. These tests were conducted on walls with rectangular and non-rectangular sections subjected to cyclic lateral loading. The finite element models provide a good representation of the nonlinear response and shear failure of these walls. Results of a blind simulation of a five-story shear wall building tested on a shake-table, in which a diagonal shear failure was well predicted, are also presented. © 2015 ASCE and ATC.

Khvostov G.,Paul Scherrer Institute | Lyon W.,ANATECH Corporation | Zimmermann M.A.,Paul Scherrer Institute
Annals of Nuclear Energy | Year: 2013

A methodology for the analysis of cladding failures caused by Pellet-Cladding Interaction (PCI) that may result in the Stress Corrosion Cracking (SCC) during power ascension at a PWR reactor start-up is presented. The proposed approach is based on the capabilities of EPRI's FALCON MOD01 code - as developed by ANATECH Corp. - with the PSI in-house model GRSW-A for the micro-structural processes occurring in the fuel. The methodology allows for analysis of the impact of missing pellet surface (MPS) on the failure-related characteristics of the cladding, particularly the peak local hoop stress, along with the accounting for the transient gaseous fuel swelling and FGR. The application of the developed methodology to the ramp tests with PWR fuel samples from the SUPER-RAMP project, carried out in Studsvik (Sweden) in 1980s, is presented. This analysis has been conducted in the framework of the PSI participation in Fuel Modeling Programme FUMEX III, recently carried out by IAEA. As a result, the capability of the new methodology to differentiate between the power ramps with failure and without failure of the claddings of non-defect fuel rods is shown, and the appropriate failure thresholds for the selected criteria are determined. The results of calculation for the stress-concentration factors caused by MPS, as a function of the angular size of the MPS defect, are in good agreement with previous similar studies, specifically with the one undertaken by the principal FALCON MOD01 code developer - ANATECH Corp. Furthermore, the predicted effects of MPS defect size is compared with the effects related to the power ascension rate, with the power ramp level being kept the same. A reduced power ascension rate is determined, which is capable of 'neutralizing' the detrimental effect on the local stress concentration in the cladding caused by the MPS defect under consideration. © 2013 Elsevier Ltd. All rights reserved.

ANATECH Corporation | Date: 2012-01-17

Computer software for the mathematics of analyzing structures, engineering bridges, and simulating nuclear fuel performance. Consulting services in the areas of structural analysis and design, bridge engineering, scientific consulting in the field of nuclear Fuel Technology, Finite Element Analysis and Simulations, Material Modeling and Applied Science.

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