Toughening the Nanostructured Ferritic Alloys for High Temperature Reactor Applications
Monday Colloquium | April 2 | 4-5 p.m. | 3105 Etcheverry Hall
Dr. Thak Sang Byun, senior R&D staff member in the Materials Science & Technology Division at Oak Ridge National Laboratory
Abstract: In the past decade the nanostructured ferritic alloys (NFAs) have been developed as core structural materials for future high temperature reactors. One of the critical drawbacks of the extremely strong materials is poor fracture resistance at reactor operating temperatures. This talk will discuss the key mechanical characteristics of NFAs, origin of low fracture toughness, and program efforts to improve their high temperature fracture toughness. The unique nanostructure of NFAs that produced shallow plasticity layer and low-ductility grain boundaries produced by powder-metallurgy processing were found to be the main causes of the poor fracture toughness. Results from the ongoing efforts exhibit a good possibility of developing high toughness NFAs.
Development of Neutron Generators for Replacement of Radiological Sources
Colloquium | March 19 | 4-5 p.m. | 3105 Etcheverry Hall
Dr. Thomas Schenkel, Senior Scientist, Group Leader of the Ion Beam Technology Group in the Accelerator and Fusion Research Division at Lawrence Berkeley National Laboratory
Neutron based techniques are widely used in a broad range of areas including materials analysis, detection of special nuclear materials and well logging. In many cases, neutrons are generated with radioactive sources such as AmBe or Californium. While their use is simple and reliable, it is desirable to gradually replace these radiological sources due to risks in environmental contamination and malevolent use. Electronic neutron generators are also commercially available but exhibit stringent trade-offs in performance (neutron yields and spectra), size and cost. In this presentation I will outline opportunities for the development of advanced neutron generators that can reliably replace radiative neutron sources and present results form our R&D efforts at LBNL.
The Next Generation Safeguards Initiative’s Spent Fuel Nondestructive Assay Project – A Technical Challenge Ripe for University and National Laboratory Collaboration
Colloquium: Monday Colloquium | March 12 | 4-5 p.m. | 3105 Etcheverry Hall
Reducing the spread of nuclear weapons is a challenge; one facet to addressing this challenge is reducing the probability that spent nuclear fuel produced by the commercial nuclear fuel cycle can be misused. The talk will begin with an overview of the challenge: How much plutonium is in spent fuel, and why do we care? How does the IAEA currently infer Pu mass in an assembly? Why is quantifying Pu mass such a challenge? And what instruments are currently used? We will give a brief overview of a five-year effort, undertaken by the DOE’s Next Generation Safeguards Initiative, to measure the mass of plutonium in spent fuel. The talk will then spend significant time focused on two particular neutron-generator-based nondestructive assay techniques: Differential Die-Away (DDA) and Delayed Neutron (DN). DDA works by detecting prompt neutrons following the interrogating burst while DN detects the neutrons emitted from fission fragments. These techniques are particularly harmonious in that the DDA signal emphasizes the presence of fissile plutonium while the DN signal emphasizes the presence of fissile uranium.
Dr. Andrea Favalli, Scientist, Los Alamos National Laboratory, Nuclear Nonproliferation Division, Safeguards Science and Technology Group; Dr. Vladimir Henzl, Technical Staff Member, Los Alamos National Laboratory, Nuclear Nonproliferation Division, Safeguards Science and Technology Group; Dr. Martyn T. Swinhoe, Technical Staff Member, Los Alamos National Laboratory, Nuclear Nonproliferation Division, Safeguards Science and Technology Group; Dr. Stephen J. Tobin, Technical Staff Member, Los Alamos National Laboratory, Nuclear Nonproliferation Division, Safeguards Science and Technology Group
Colloquium: Monday Colloquium | March 5 | 4-5 p.m. | 3105 Etcheverry Hall
Dr. Paul R. Renne, Director of the Berkeley Geochronology Center, and a Professor in Residence in the Earth and Planetary Science Dept. at UC Berkeley
The K-40 to Ar-40 decay offers the most broadly applicable means of determining geologic age for materials ranging in age from the early solar system 4.6 billion years ago to a few thousand years. The accuracy of this powerful technique has been historically limited by the imprecisely determined K-40 half-life and Ar-40/Ca-40 branching ratio. Recent work has improved the situation dramatically through an optimization analysis that includes normalization to the precisely-determined U-238 half-life. Further improvements to the accuracy and precision of this chronometer are expected from application of deuteron-deuteron (D-D) fusion neutrons to activation of K-39 to Ar-39 as a proxy for K-40. This talk will describe a project currently underway to build a D-D neutron generator for this purpose.
Paul Renne is the Director of the Berkeley Geochronology Center, and a Professor in Residence in the Earth and Planetary Science Dept. at UC Berkeley. Renne’s research is focused on using radioisotopes to date important events in the history of Earth, such as mass extinctions, catastrophic volcanism, human evolution, and interactions with other objects in the Solar System. His specialty is the application of the K-40 based chronometer.
Investigating Radiation at the Nanoscale
Colloquium | February 13 | 4-5 p.m. | 3105 Etcheverry Hall
Dr. Khalid Hattar, Senior Member of Technical Staff, Dept of Radiation Solid Interactions, Sandia National Laboratories
This presentation will highlight some of the new research directions that have been initiated utilizing the unique capabilities of Sandia’s new Ion Beam Lab. This included the use of small scale mechanical testing and in-situ ion irradiation TEM to investigate the microstructural and property evolution at high displacement damage of potential generation IV cladding materials. In addition, the initial results and research direction currently undertaken to investigate the fundamentals of corrosion mechanisms in dry storage containers via in-situ TEM liquid and gas phase experiments will be shown. This presentation will conclude with recent work comparing the photoluminescence, cathodoluminescence, and ion beam induced luminescence of advanced radiation detectors ranging from metal-organic-frameworks through nanoparticle to Cs3Gd2Br9:Ce3+ single crystals.
Khalid Hattar is a Senior Member of the Technical Staff of Sandia National Laboratories. He received a B.S. in Chemical Engineering from University of California, Santa Barbara in 2003, and a Ph.D. in Materials Science and Engineering from University of Illinois, Urbana-Champaign in 2009. He joined the Radiation-Solids Interaction group at Sandia in December 2008. He specializes in determining the property-microstructure relationship for a variety of structural, electrical, and optical materials through in-situ TEM in various extreme environments.