Going Beyond UO2 Pellets
David F. Williams([email protected])
Nuclear Science and Technology DivisionOak Ridge National Laboratory
March 15, 2006MIT American Nuclear Society Student Chapter
Cambridge, MA
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Different Communities look at AdvancedFuels Differently
Commercial Interestsdriven by economics
Inexpensive fabrication
Meets necessary requirements
Minimal requirements for:new equip., processes, licensing
Achieves system-level advantages
Short-term focus“Competitive fuel”
Quantified risk, timetable, andinvestment advantage
R&D Communitydriven by peak performance
High density, conductivity, m.p.
Stability:thermochemistryclad interactions
accident behavior
Low parasitic captureProper moderation
Long-term focus“super-fuel”
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Subject for Presentation:Fuel Types that are Ripe for Deployment
Alternate Oxide Forms:Particle bed fuels (“sphere-pac”)Annular geometriesInert Matrix - Dispersion Fuels
CERMETCERCER
Alternate Fuel Matrix:carbide - nitride - metal
- hydrideMicro-fuel
coated-particle, graphite-matrix - TRISO
water-cooled and
fast-reactors
fast reactorsspectral shift
Gas-cooledHTR’s
All options benefit from better tools for selection and analysis
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Particle-Bed Fuels continue to be studied
Original focus was remote fabrication:U-233 recycle
Multi-recycle U-Pu fuel
“spiked” fuel
Avoids “powder metallurgy” grinding, milling
Potential performance improvements to LWR fuel were found:
Less fuel-clad chemical interaction
Less fuel -clad mechanical interaction
Better thermal performance (for equivalent smear density)
transient response ?
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
One Option for Implementing Sphere-Pac
Conventional Fab.Fissile Spheres
concentrated nitratesolution
Gel-precipitationCo-conversion
~98% denseoxide spheres
(300-1200 microns)
Remote Fab.Minor ActinideMicrospheres
dilute nitrate solution from UREX
Resin-loadingCo-conversion
~50% denseoxide spheres(30-80 microns)
UO3•2H2O Sintered UO2
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Movie Demonstration of Sphere-Pac InfiltrationRod-Loading
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Typical Sphere-Pac Thermal Performance
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Extensive Testing and Development of Sphere-PacFuels was conducted (1)
sphere diameters
( m) Key Ratios
smear
density LHGR Tclad
d1 d2 d3 d1/d2 ID /d1 %TD w/cm °C flux %
fissile year
505 25 20.2 10.9 86 525 600 fast 20 1973
450 44 10.2 12.2 84 690 630 thermal 20 1973
400 50 8.0 16.0 81.5 920 500 thermal 18 1970
770 85 9.1 18.3 80 460 thermal 4.6 1974
700 60 11.7 8.3 80 1070 725 epi 15 1977
700 60 11.7 8.3 80 640 640 fast 15 1977
1125 90 12.5 12.7 77.8 650 230 thermal 1976
1200 300 30 4.0 7.0 87 400 300 thermal <5% 1986
MIT 77 2005
800 70 FUJI 11.4 8.4 81.5 650 400 thermal 20 2005
800 80 ORNL 10.0 10.5 83/73 5 2005
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Extensive Testing and Development of Sphere-PacFuels was conducted (2)
Nuclear Testing included:
Fast, epi-thermal, and thermal spectraSteady-state, ramp, and transient testingSingle rod and Assembly tests
Fabrication Development included:
Exxon Nuclear Pilot PlantDutch Vibrasol Pilot PlantAutomated “triple-blending” rod-loading
90 seconds per 2-meter rod
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Why wasn’t Sphere-Pac Deployed ?
Depressed MarketStagnant Reactor SalesOvercapacity of Fuel Production
Performance FactorsHoop Stress response in BOL transientPerformance for UO2 LWR fuel not a compelling advantageFast Reactor carbides developed cladding failures
Remote fuel fabrication was removed from the priority listMOX pellets were used for both LWR’s and FBR’s
Renewed sphere-pac motivation:return of need for remote fabricationcompelling performance advantage
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Avenues for Particle-Bed Fuel Development
Remote fabrication fuels/targetstransmutation of minor actinides”spiked” fuel for proliferation resistance
Improved Performance Applications
CERMET (Zr, SS, Mo) CERCER (MgO)Annular Geometry - internally cooled
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
CERMETs have filled the fuel performance gapfor key applications
Low-temperature, high fluxAluminum-UO2 CERMET fuel plates
Aluminum-CmOx CERMET targets for Cf
High-Temperature-High FluxMo-UO2 CERMET fuel for Space Nuclear Propulsion
Ni-alloy CERMETs for Aircraft applications
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
CERMETs have demonstrated performance ofkey features needed for fuels of the future
Glowing Cm product from operations at ORNL.
CmO1.71 – Al
CERMET
14 mm
Al CapPowder
6.3mm
Al Shell
ORNL Al-CERMETs rodsare irradiated to 50% FIMA
SNL CERMET annular plates were irradiatedto > 90% FIMA
These targets accepted large amounts offission gas and He.
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Key factors in CERMET fuel performance
• Nuclear properties of the metal• Melting point, vapor pressure,
and conductivity of metal• Chemical interactions with the
oxide phase• Density of composite• Volume % metal in the
composite
• ? recyclability
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Can the performance curve forCERMETs be shifted by a morefavorable topology
Russian Mo-UO2 CERMET
Can a useful continuous metal-phase beachieved with a low volume fraction ofmetal ?
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
HTR Fuel - Do we need to go beyondUO2 Kernels ?
• HTRs will gain significant competitiveadvantage from attaining higherburnup (>14% FIMA).
• The current German reference fueldoes not support both highertemperatures and higher burnup.
• What is needed for higher burnup ?− Effective oxygen management
• UCO• Getter-layers in the coating (UO2*)• Re-visit kernel additions to UO2(CeO2-x) Th-Pu Oxide
183,000 MW-days/tonne>95% Pu-239Transmuted
Pu Oxide747,000MWdays/tonne>95% Pu-239, and>65% all Putransmuted
Fuel Kernel(UCO, UO2)
Coated Particle
Outer Pyrolytic CarbonSilicon CarbideInner Pyrolytic CarbonPorous Carbon Buffer
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Improved Temperature Performancerequires other changes
• A more refractory coating (e.g. ZrC) may enable the fuel toendure higher accident temperatures
• A monolithic-prismatic fuel element will reduce thetemperature in the fuel compared to current pin-in-block ordrilled-block designs
− A German Company (HOBEG) produces such amonolithic molded-element
− This design eliminated one of the two gas-gaps in thecurrent GA fuel element design
− The molded element is a natural extension of overcoatingtechnology.
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Many Monolithic Prisms were Made
Monolithic Fuel Element made by HOBEG for the 1160 MWeHTGR design by GA. This block underwent extensive non-nuclear and nuclear testing to verify the improved performance[Trans. ANS 20, 1975, p.603].
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
We have new tools at our disposal toanalyze and select fuel candidates
•Advanced Characterization Instruments− Examples for TRISO fuel:
• Xray NDE of TRISO fuel• New Optical Ellipsometer for Pyrocarbon structure
•Powerful modeling and simulation tools− Permit a mining of the historical record− Can build on base of materials development experience
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Tour of new ORNL X-rayTomography Unit
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
High Resolution Tomography of TRISO
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Nano-structural characterization of referencematerials is necessary to validate the results ofcomplex simulations
0.6 angstrom resolution of Silicon Nitride doped with La2O3
http://www.ornl.gov/info/ornlreview/v37_3_04/article15.shtml
• We now have extraordinary tools for nano-characterization• We also have archived reference materials that should be characterized to providekey validation of simulations.
SeparationschemistryFuel
materials
German comparison of EXAFSand TRLFS with quantum theoryfor candidate An/Ln extractantsGLOBAL 2005
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
nm-µm
Fuels modeling involves multiscale time andlength scales
Length scale
Tim
e sc
ale
ps-n
sns
-µs
µs-
ss-
year
deca
des
Å-nm µm-mm mm-m
Point defect properties Ef, Em,…(Ab initio,
Quantum chemical)
Defect & fission product production(Molecular dynamics,
Fission track thermal spike)
Defect & fission product migration, bubble nucleation (Kinetic Monte Carlo)
Irradiated fuel chemistry & phase stability
(thermodynamic & chemical rate theory codes)
Fuel performance(thermal conductivity,
fission product accumulation, fuel swelling codes)
Fuel-claddinginteractions(fuel swelling,
fuel-clad chemistrycodes)
-900
-800
-700
-600
-500
-400
-300
-200
-100
0
FU
NC
TIO
N M
UO
2
500 1000 1500 2000 2500 3000
T
O/U=2.15 O/U=2.10 O/U=2.05 O/U=2.01 O/U=2.005 O/U=2.001 O/U=2.0001 O/U=2 Baichi analysis (2005) O/U=1.9999 O/U=1.999 O/U=1.995 O/U=1.99 O/U=1.95 O/U=1.9 O/U=2 Ruello(2001) O/U=2.0005 O/U=2 Matzke(1994) O/U=2 Lindemer(1985)UO2+x
50 GWd/MT MOX
g.b.g.b.
0
20
40
60
80
100
120
0.0001 0.001 0.01 0.1
60°C Irradiation
300°C Irradiation
Th
erm
al C
on
du
ctiv
ity
(W
/m-K
)
Damage Level (dpa)
0
Aluminum Nitride
Silicon Nitride
Effect of Low-Temperature Neutron Irradiationon the Thermal Conductivity of Nitride Ceramics
MD simulation of He mobility in UO2 gb
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Summary
The opportunity exists to develop new fuels for industrialdeployment:
for improved LWR performancefor Pu-burningfor transmutation of minor actinides
Key opportunities exist in:advanced oxide fuels which can be integrated into the current practiceprimary changes which provide compelling competitive advantages
CERMETs , particle fuels, and novel fuel element designs.