Ceramic Materials for Nuclear Energy Research and Applications: Non-oxide Ceramics for Nuclear Applications I
Sponsored by: TMS Structural Materials Division, TMS: Advanced Characterization, Testing, and Simulation Committee, TMS: Energy Committee, TMS: Nuclear Materials Committee
Program Organizers: Xian-Ming Bai, Virginia Tech; Yongfeng Zhang, Idaho National Laboratory; Maria Okuniewski, Purdue University; Donna Guillen, Idaho National Laboratory; Marat Khafizov, Ohio State University; Thierry Wiss, European Commission- JRC -Institute of Transuranium Elements – Germany

Wednesday 8:30 AM
March 1, 2017
Room: Palomar
Location: Marriott Marquis Hotel

Session Chair: Xianming Bai, Virginia Tech; Yong Yang, University of Florida

8:30 AM  Invited
Progress in Development of Non-Oxide Ceramic Nuclear Fuels: Andrew Nelson1; 1LANL
    The joint drivers of improvements to accident tolerance and a desire for increased reactor performance have motivated exploration of nuclear fuels that improve upon the deficiencies of reference uranium dioxide. Non-oxide ceramic nuclear fuel forms are being explored to provide improvements to thermal conductivity, fracture strength, and uranium density. Uranium nitride and uranium silicide compounds have received the bulk of recent attention from industry, government-sponsored research programs, and academia, but less familiar uranium compounds are also receiving study to catalogue their basic properties to facilitate further assessment. Initial screening of the basic properties of uranium borides, uranium monosulfide, and uranium monophosphide is ongoing. This talk will provide an overview of the processing-structure-property-performance relationships as presently known for candidate non-oxide ceramic nuclear fuels systems. Discussion will also focus on key areas of uncertainty in assessment of these compounds for commercial light water and other advanced nuclear reactor service.

9:00 AM  Invited
Radiation-Stability of Zirconium Carbide and Nitride Ceramics for Advanced Fuel Cycles: Yong Yang1; 1University of Florida
    Zirconium carbide and nitride ceramics have properties desired as advanced fuel form for fuel matrix materials and as a high temperature alternative to SiC in TRISO fuels in a gas-cooled reactor. To understand the microstructural development of candidate fuel forms under controlled temperature irradiation is a critical data need for fuel development. ZrC and ZrN were irradiated using a proton beam at various temperatures up to 1200C, and the irradiated microstructures were characterized using transmission electron microscopy. Both ZrC and ZrN show relatively good radiation stability and the irradiated structures were mainly featured with dislocation loops. The irradiation induced lattice distortion was evaluated using X-ray diffraction, and observed lattice expansions were mainly attributed to the irradiation produced point defects. Fracture toughness measurements using micro-cantilever beam show increases of fracture toughness relative to the unirradiated materials.

9:30 AM  Cancelled
Spark Plasma Sintering of Boron Carbide Ceramics for Nuclear Applications: Meral Cengiz1; Onuralp Yucel1; Gultekin Goller1; Bulent Buyuk1; Asiye Tugrul1; Filiz Sahin1; 1Istanbul Technical University
    Boron carbide ceramics are characterized by very high hardness and low density desirable for many industrial applications such as control rods and nuclear waste containers. However, the use of monolithic boron carbide is limited by its low strength, low toughness, poor sinterability and machinability and those disadvantages are tried to be overcomed by Ti metallic addition to boron carbide structure. Boron carbide powders were mixed with various amount of Ti metallic powders and granulated. Samples were spark plasma sintered at 1500 C and 1550 C by applying 40 MPa uniaxial pressure with a heating rate of 100 C/min. under 1 atm. argon atmosphere. The effect of various amounts of metallic Ti and other sintering parameters were investigated on the final products. Density measurements were carried out by using Archimedes’ Principle. Radiation testing and characterization of monolithic B4C samples and B4C-Ti samples are accomplished in terms of gamma shielding properties.

9:50 AM Break

10:10 AM  Invited
Ionization-Induced Damage Annihilation in Silicon Carbide: Yanwen Zhang1; Haizhou Xue2; Ritesh Sachan1; Olli Pakarinen1; Matthew Chisholm1; Peng Liu3; William Weber2; 1Oak Ridge National Laboratory; 2University of Tennessee; 3Shandong University
    Silicon carbide materials are being considered as key engineering materials in nuclear energy applications. Results show that the energy transferred to the electrons in SiC by MeV ions via inelastic ionization processes can effectively anneal pre-existing defects and restore the structural order. This self-healing process is activated at an unexpectedly low threshold value using ionizing ions with energies from a few of MeV to a few tens of MeV, compared with a few tens of keV/nm reported for swift heavy ions with energy from a few hundreds of MeV to GeV. The results conveyed here can have a considerable impact not only on functionalizing SiC-based devices by providing a room-temperature approach to anneal defects and repair damaged crystalline structure, but also for predicting material performance in nuclear environment and space applications. This work was support by U.S. DOE, BES, MSED.

10:40 AM  
Multi-scale Modeling of Fracture Behavior in SiC with a Phase Field Fracture Model: Shuaifang Zhang1; Michael Tonks1; 1Pennsylvania State University
    Due to its outstanding creep and oxidation resistance, high temperature strength, and radiation tolerance, silicon carbide (SiC) composites are being considered as an accident tolerant concept for nuclear fuel cladding[1]. However, fracture behavior of SiC is one of the most important issues that should be addressed, to help prevent fracture-induced failures. In this work, we employ numerical simulation to analyze the fracture behavior. Numerous models have been developed to model fracture and crack propagation, including discrete damage models, continuum damage models and phase field fracture models. In the phase field method, the fracture surface is approximated by a phase field parameter which indicates whether the material is fractured via solving a coupled system of PDEs. Here, microcracking behaviors of SiC are modeled with the phase field method. Since the fracture behavior is influenced by microstructural features, the influence of pores and voids on the fracture behavior is also studied.

11:00 AM  
A TEM Study of Microstructure of Hi-Nicalon Type S SiC Composite beyond Ultimate Shear Strength: Yun Yang1; Mehdi Balooch1; Joseph Kabel1; Cameron Howard1; David Frazer1; Peter Hosemann1; 1University of California, Berkeley
    The objective of this research is to investigate possible changes in the characteristic SiC-SiC interphase once the material passes over the ultimate shear strength. Micro-pillar samples containing inclined fiber/matrix interfaces are prepared and subsequently compression-tested using nano-indentation techniques are conducted. Using focus ion beam techniques, a thin lift-out of axial cross-section is prepared for TEM studies. The micro-structural changes of the fractured carbon and SiC interphase is subsequently investigated by STEM, HRTEM and EELS techniques. Preliminary results show the 3C SiC polytype of fiber and matrix adjacent to the interphase before and after compression tests are unchanged. HRTEM and EELS analyses reveal that the secondary carbon phase within the fiber is more graphitic in nature than diamond-like. However, the graphitic nature of interphase carbon changes from ordered to more chaotic during deformation at the interface layers.

11:20 AM  
Micro-Mechancial Interphase Property Evaluation for SiC-SiC Composites: Joseph Kabel1; Mehdi Balooch1; Yun Yang1; Kurt Terrani2; Takaaki Koyanagi2; Peter Hosemann1; 1University of California Berkeley; 2ORNL
    SiC-SiC composites exhibit exceptional high temperature properties including high strength at high temperatures, and low thermal neutron cross section and is a candidate for accident tolerant fuel cladding and high temperature reactor components. In order to overcome the inherent brittleness of the ceramic, engineers have developed composites that exploit pseudo-ductility through interfacial shear and increased crack propagation length at the fiber-matrix interface. The goal of this research is to evaluate the SiC-SiC composite interface properties via advanced micro-mechanical testing techniques. Focused ion beam milling was used to cut a variety of geometries that promote fracture at the interface during compressive loading. In Situ micro-pillar compression provided the most reliable data. The obtained data leads to resolved normal and resolved shear stress plots for a variety of inclines which enabled precise extraction of the internal friction coefficient of 0.25 0.03, and a debond shear strength of 266 31 MPa. Contribution form ORNL was sponsored by the U.S. DOE, Office of NE, for FCRD program under contact DE-AC05-00OR22725 with ORNL managed by UT-Battelle, LLC