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Albuquerque, NM, United States

Bean J.E.,Sandia Staffing Alliance LLC | Sanchez M.,Texas A&M University | Arguello J.G.,Sandia National Laboratories
46th US Rock Mechanics / Geomechanics Symposium 2012 | Year: 2012

An important application of expansive clay materials is their use as engineered barriers or seals in radioactive waste repositories. The low permeability of clays and the chemical interactions (e.g. sorption) between the clay minerals and radionuclides present in the radioactive waste are essential for reducing the migration distance of the radionuclides over time scales of interest for repository design. This paper describes the efforts underway to incorporate a constitutive model for expansive soils into the Sierra Mechanics finite element code framework being developed at Sandia National Laboratories. Several simple verification problems are described for evaluating the implementation of the model. Copyright 2012 ARMA, American Rock Mechanics Association.

Clayton D.J.,Sandia National Laboratories | Arguello Jr. J.G.,Sandia National Laboratories | Hardin E.L.,Sandia National Laboratories | Hansen F.D.,Sandia National Laboratories | Bean J.E.,Sandia Staffing Alliance LLC
Mechanical Behavior of Salt VII - Proceedings of the 7th Conference on the Mechanical Behavior of Salt | Year: 2012

Coupled thermal-mechanical, three-dimensional, finite-element analyses were used to evaluate generic design concepts for a repository in salt, for spent nuclear fuel and high-level waste. This work used heat generation by spent nuclear fuel (SNF) typical of that presently stored at reactor sites in the U.S. For waste packages containing 4-PWR SNF assemblies, the results show peak temperatures within previously identified ranges acceptable for salt media. Peak temperatures and maximum backfill consolidation occur at the package-salt interface. Significant consolidation of the backfill, and closure of the mined opening, is projected to continue after peak temperatures are realized. For larger 21-PWR SNF packages, the peak temperature could approach 450°C locally or lower, depending on the aging history of the fuel. This ongoing study suggests the feasibility of a SNF management strategy using decay storage and larger (e.g., 21-PWR) waste packages.

Stone C.M.,Sandia National Laboratories | Martinez M.J.,Sandia National Laboratories | Dewers T.,Sandia National Laboratories | Hansen F.D.,Sandia National Laboratories | And 3 more authors.
45th US Rock Mechanics / Geomechanics Symposium | Year: 2011

This paper describes the modeling efforts undertaken during a recently completed feasibility study of a generic shale repository for disposal of high-level radioactive waste within the United States. A coupled thermal-hydrological-mechanical-chemical analysis of the shale repository was performed using the SIERRA Mechanics code developed at Sandia National Laboratories. Because U.S. efforts have focused on the volcanic tuff site at Yucca Mountain, radioactive waste disposal in U.S. shale formations has not been considered for many years. However, advances in multi-physics computational modeling and research into clay mineralogy continue to improve the scientific basis for assessing nuclear waste repository performance in such formations. Disposal of high-level radioactive waste in suitable shale formations is attractive because the material is essentially impermeable and self-sealing, conditions are chemically reducing, and sorption tends to prevent radionuclide transport. Vertically and laterally extensive shale and clay formations exist in multiple locations in the contiguous 48 states. © 2011 ARMA, American Rock Mechanics Association.

Skogen E.J.,Sandia National Laboratories | Vawter G.A.,Sandia National Laboratories | Tauke-Pedretti A.,Sandia National Laboratories | Peake G.M.,Sandia National Laboratories | And 4 more authors.
2010 23rd Annual Meeting of the IEEE Photonics Society, PHOTINICS 2010 | Year: 2010

We demonstrate an optical gate architecture using electro-absorption modulator/photodiode pairs to perform AND and NOT functions. Optical bandwidth for both gates reach 40 GHz. Also shown are AND gate waveforms at 40 Gbps. ©2010 IEEE.

Boye R.R.,Sandia National Laboratories | Peters D.W.,Sandia National Laboratories | Wendt J.R.,Sandia National Laboratories | Shul R.J.,Sandia National Laboratories | And 6 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

Resonant subwavelength gratings have proven to be excellent devices for producing narrow resonances useful for filtering applications. In this paper we discuss the use of RSGs in a rotary position encoder intended for use in harsh environments. To avoid problems with routing electrical signals to the encoder, a single fiber optic connection is used to address the device with multiplexed wavelengths corresponding to position bits. Each wavelength has a corresponding RSG that is patterned in the appropriate position locations. A demonstration device utilizing RSGs with TiO2 and SiO2 films on a silicon substrate will be presented. The design and modeling effort provided several RSGs with resonances addressable by a single tunable laser source. Since multimode fiber is used to route the optical signals, the gratings were designed to be polarization insensitive. Additionally, the individual RSGs accommodate significant wavelength shifts to simplify the integration of the encoder system. The fabrication of the devices was based on electron beam lithography and details of this work will be presented. Measurements of the individual RSGs as well as a demonstration of the determination of rotary position using these gratings will be shown. © 2010 Copyright SPIE - The International Society for Optical Engineering.

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