Document Type

Grant

Publication Date

2-4-2005

Abstract

Transmutation work at Los Alamos National Laboratory is currently focused on mono-nitride ceramic fuel forms, and consists of closely coordinated “hot” actinide and “cold” inert and surrogate fuels work. Matrix and surrogate materials work involves three major components: (1) fuel matrix synthesis and fabrication, (2) fuel performance, and (3) fuel materials modeling. The synthesis and fabrication component supports basic material studies, as well as actinide fuel fabrication work through fuel fabrication process development. Fuel performance studies are examining the tolerance of nitride-type fuel to heavy irradiation damage. The fuel materials simulation work involves both atomistic and continuum scale modeling employing first principals, molecular dynamics, and thermo-chemical calculations. This modeling work is closely integrated with fuel design and experimental work where it provides prediction of phase transformation and stability, reaction kinetics, radiation damage mechanism and tolerance, and fission product retention. Results for fuel fabrication and radiation tolerance studies based on the proposed ZrN fuel matrix material will be reviewed as well as experimental surrogate studies for volatilization and phase stability. The actinide fuel effort at LANL emphasizes in synthesis and fabrication of actinide-bearing nitride fuel pellets. These pellets are designed for being inserted into the Advanced Test Reactor and contain varying amounts of Pu, Am, Cm, and Np.

For now, fuel materials simulation work which involves atomistic and continuum scale modeling, molecular dynamics, and thermo-chemical calculations is purely based on a theoretical understanding of crystal structure and microstructure of inert matrix fuels. We intent to support the AFCI program by delivering real structural data on surrogate and radioactive fuels. We will determine crystal structure and nano structures of the individual fuel type, oxides and nitrides, as considered for GEN IV fuels. Furthermore we will mainly apply two different ways to synthesis fuels: (1) wet chemical route (precipitation from solution, calcinations, grinding, pelletization, sintering with binder and PEG, grinding, pelletization, and sintering with carbon-thermal reduction (later for nitride fuels only), and (2) dry chemical route (grinding of oxides, pelletization, sintering with binder and PEG, grinding, pelletization, and sintering with carbon-thermal reduction (later for nitride fuels only). The chemical behavior of the ceramics under repository, reprocessing, and reactor conditions will also be examined. This data will provide the basis for a full analysis of the fuel in an advanced fuel cycle.

We will analyze the impact of fuel processing parameters on the crystal structure and nano structure of the inert matrix fuel desired for GEN IV reactors. Therefore we will - beside other analytical techniques - mainly apply (1) X-ray powder diffraction (XRD) in combination with Rietveld structure refinement to refine or to determine actinide occupancies within the crystal lattices of the fuels, and (2) high resolution electron microscopy (transmission electron microscopy) in combination with, nano probe X-ray spectrometry (EDS), parallel energy loss spectroscopy (PEELS), energy-filter electron microscopy, and scanning transmission electron microscopy. We will use stateof- the-art analytical instrumentation on X-ray diffraction (PANalytical X-Pert Pro with X’Celarator solid state detector and Bruker AXS Topas2 Rietveld structure refinement software), and high resolution electron microscopy (Tecnai F 30 STEM with a FEG field emission gun, scanning option, PEELS, EDS, Energy-Filter, 300 kV acceleration, and a point resolution of 2.2 Å). We can take advantage of two fully equipped sample preparation laboratories, one for the preparation of surrogate fuel, one for the preparation of radioactive fuel specimens. The analytical work scope as proposed will promote the Harry Reid Center for Environmental Studies of UNLV as the top academic institution in the U.S. for analyzing radioactive fuel samples on nano-scale.

Keywords

Mixed oxide fuels (Nuclear engineering); Nuclear fuels; Solid oxide fuel cells; Transmutation (Chemistry)

Disciplines

Nuclear | Nuclear Engineering | Oil, Gas, and Energy

Language

English


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