Going Beyond UO2 Pellets - MIT - Massachusetts Institute ...web.mit.edu/ans/www/documents/seminar/S06/williams.pdf · All options benefit from better tools for selection and analysis

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

2

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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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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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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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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Movie Demonstration of Sphere-Pac InfiltrationRod-Loading

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Typical Sphere-Pac Thermal Performance

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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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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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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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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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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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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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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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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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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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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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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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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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Tour of new ORNL X-rayTomography Unit

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High Resolution Tomography of TRISO

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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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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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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.

Documents

Going Beyond UO2 Pellets - MIT - Massachusetts Institute ...web.mit.edu/ans/www/documents/seminar/S06/williams.pdf · All options benefit from better tools for selection and analysis