Metallic Fuels for
Actinide Transmutation
B. A. Hilton, J. R. Kennedy, S. L. Hayes,
and D. C. Crawford

Presentation at the:9th OECD/NEA Information Exchange Meeting on
Actinide and Fission Product Partitioning and TransmutationNîmes, France
September 25-29, 2006

Outline of Presentation• Benefits of Metallic Fuels for Transmutation• Overview of Current US Metallic Fuels Program– Historic vs. Current Fabrication Methods– Characterization Activities– Irradiation Testing in the Advanced Test Reactor> Fuel Test Matrix and Irradiations in Progress> Postirradiation Examination Results– Metallic Fuels in the FUTURIX-FTA Experiment in Phénix• Conclusions and Future Work

Overview of U-Pu-Zr Metallic Fuel Behavior{ As-fabricated U-20Pu-10Zr

Zr-rich phases

X420B at 17% BU

X419 at 3% BU

X423A at 1% BU

Redistribution of U and Zr occurs early;
inhomogeneity does not affect fuel life.

Benefits of Metallic Fuels for Transmutation• Fabrication– Historic ease of fabrication on large scales,
remote environments– Process not sensitive to fuel composition(exception: Am)– Na-bonding allows for:> Loose tolerances on fuel diameters> Large fuel pin thermal margins• Irradiation Performance– Consistent over wide range of compositions– Large fuel swelling/high gas releaseaccommodated by design– Compatible with sodium coolant– Demonstrated high-burnup reliability; lowerdensity alloys for transmutation offer evenhigher burnup potential

Historic Metallic Fuel Fabrication• Fabrication by Injection Casting– Graphite crucible inductively heated to melt and homogenize fuel alloy– Furnace evacuated and molds inserted into melt
– Rapid pressurization of furnace forces melt into molds• Limitations for Transmutation Alloys– Long time-at-temperature– Substantial loss of volatile Am from melt

Current Fabrication with Minor Actinides• Rapid Melting, Homogenization, Casting– Use of arc-melter with either gravity or vacuum casting– Time-at-temperature reduced from hours to minutes– Am volatile loss virtually eliminated– Research-scale only, not considered scalable(See J.R. Kennedy poster on Fabrication & Characterization)

Characterization of Metallic Alloys• Phase Equilibria– Crystal structures andphase transitions identified
up to 1450°C

Pu-12Am-40Zr• Properties– Density, specific heat,
thermal expansion,
thermal diffusivity
measured up to 1200°C• Compatibility– Diffusion couple testingwith Fe and stainlesssteels underway

1500

U-29Pu-4Am-2Np-30Zr
1000

500

03040

5060
2-Theta (degrees)

708090Irradiation Testing of Metallic Fuels in the ATR

Capsule Assembly Mock-Up

Metallic Fuel Test Matrix in ATR
Tests Completed•

AFC-1B (8% BU)

Tests in Progress•

AFC-1D (currently at 28% BU)> Pu-40Zr & Pu-60Zr> Pu-40Zr & Pu-60Zr> Pu-12Am-40Zr> Pu-12Am-40Zr> Pu-10Am-10Np-40Zr> Pu-10Am-10Np-40Zr•

AFC-1G (currently at 13% BU)> Pu-10Np-40Zr•

AFC-1F (8% BU)•AFC-1H (currently at 15% BU)> U-29Pu-4Am-2Np-30Zr> U-29Pu-4Am-2Np-30Zr> U-34Pu-4Am-2Np-20Zr> U-34Pu-4Am-2Np-20Zr> U-25Pu-3Am-2Np-40Zr> U-25Pu-3Am-2Np-40Zr> U-28Pu-7Am-30Zr> U-28Pu-7Am-30Zr

Representative PIE Results from ATR Tests• Importance of Burnup Metric– Metallic fuels for transmutation use increased Zr content– Results in less-dense fuels than traditional U-20Pu-10Zr alloy– Comparable fission density results in much higher at.% burnup intransmutation alloys

Lower density
transmutation alloys may
be capable of much higherburnups.

PIE—Swelling Behavior of Transmutation Alloys
Pu-12Am-40Zr

U-29Pu-4Am-2Np-30Zr

4.2 at.%5.0x1020 f/cm3

4.6 at.%3.5x1020 f/cm3

Onset of swelling occurs at higher
burnup than historic database.

6.8 at.%4.7x1020 f/cm3

6.0 at.%6.8x1020 f/cm3

PIE—FGR Behavior of Transmutation Alloys

Incubation period may extend to slightly higher dose, butgas release quickly converges with historic database.

Metallic Fuels in FUTURIX-FTA• DOE 1: U-29Pu-4Am-2Np-30Zr• DOE 2: Pu-12Am-40Zr

Finished DOE 1&2 Pins
Arrived at CEA-Marcouleon September 6, 2006

Conclusions• Metallic Fuels an Attractive Option for Actinide
Transmutation– Simple, economic and remote fabrication appears viable– Irradiation performance over very wide range of alloy compositions
consistent with historic database– Very high burnup potential advantageous for transmutation mission• Future Work– Continued irradiation testing (e.g., RE additions in 2007, FUTURIX-FTA)(See W.J. Carmack poster on AFC-2 Test Design)– Design and demonstration of an engineering-scale injection casting
furnace to mitigate Am loss
> Very rapid (conventional) induction heating> Cold crucible/induction skull melter– Remote (hot cell) fabrication demonstration using recovered TRU