powder-metallurgy experiments and manufacturing studies on

10th International Conference on Environmental Remediation and Radioactive Waste Management

Session: 45: Beneficial Uses of Depleted UraniumGlasgow, Scotland; September 7, 2005

Oak Ridge National LaboratoryP.O. Box 2008, Oak Ridge, Tennessee 37831-6165

United States of AmericaE-mail: [email protected]

Powder-Metallurgy Experiments and Manufacturing Studies on DUO2─Steel Cermets for SNF

CasksCharles W. Forsberg

Terry N. TiegsVinod K. Sikka

*Managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. The submitted manuscript has been authored by a contractor of the U.S. Government under contract DE-AC05-00OR22725. Accordingly, the U.S. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for U.S. Government purposes. File name: ICEM05.Cermet

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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY

Outline

• Cermet Cask Description

• Manufacturing Options

• Laboratory Tests

• Conclusions

GNS Storage and Transport Cask

3


Cermets Combine the Best Properties of Ceramics (Shielding, Hardness, etc.)

and Metals (Strength, Ductility, etc.)

04-070

Main Battle Tank Armor

Cutting Tools

Brake Shoes

Cask Body

Clean Steel

Metal Matrix

Ceramics

- Strength- Thermal

Conductivity

- Armor (Al2O3, SiC)

- Neutron Shielding (DUO2, Gd2O3)

- Gamma Shielding (DUO2)

Cermets Are Used for

Demanding Applications

Cermet Body Cross Section

4


Cermet Casks will be Adopted if Manufacturing Costs are Low

• Two manufacturing options are being examined in the United States− Forged Cermet Cylinder (FCC) Process− Cermet Extrusion Section (CES) Process

• Both processes use powder metallurgy techniques

• Manufacturing studies are underway to understand the economics

5


FCC Process

6


Forged Cermet Cylinder Process(United States Patent: 6,811,745: November 2, 2004)

02-090R3

Add Steel/DUOParticulate Fill

to AnnularPreform

2

Seal Preformand Degas

HeatPreform

Steel/DUO2Particulate Fill

Steel Shells

Future CaskLid Mating

Surface

Powder Mix

Weld andVacuumDegas

Consolidate Particulates to Cermet

Forge or Roll

Weld Bottomonto Package(Steel-to-Steel Weld)

Machine Cask LidMating Surfaces

DriveRoller

IdleRoller

CermetPreform

AxialRollers

Anvil

7


Step 1: Manufacture of Cask Preform

03-105

• Preform dimensions are slightly larger than the final cask

• Preform becomes the final inner and outer surfaces of the cask• Wall thickness: 1–3 cm• Flange

• Thickness: 10–20 cm• Face for lid

Future Top Flange

Outer Surface ofFinal CaskInner Surface

Void

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Step 2: Empty Preform is Mounted Upside Down on Turntable and Filled

with Cermet Particulate Mixture

02-119R

Feed System

Preform

Advanced OptionIntegrated Cermet

Cask Bottom

Different CermetParticle Mixes

ParticulateMix

Future TopFlange

InsideBottomof Cask

ParticulateFill Line

RotatingPlatform

TampingArm

HydraulicLift

MaterialsFeeder

Cask Preform(Near FinalDimensions)

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Step 3: Loaded Preform is Sealed and Degassed

03-107

• Weld annular ring to seal preform

• Degas− Heat− Vacuum

• Send sealed package to forging operations

Future Top Flange

Outer Surface ofFinal Cask

Inner Surface

Particle Mix

10


Step 4: Cermet Consolidation by Hot Forging (Several Forging Options)

02-116

Anvil

CermetPreform

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Step 5: Cask Finishing Operations

03-104

• All finishing operations involve steel preform (No contact with cermet)

• Cask bottom is welded to the cask body− Option for integrated

cask bottom− Option requires

complex forging operation

• Cask machining− Machine lid surface and

bolt holes− Cask surfaces

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CES Process

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CES Production Process (Assembly)

• Cask consists of:− External steel shell− Internal steel shell− Cermet sections

• Cermet sections have a steel exterior and a cermet interior

• Considering 12 to 48 cermet sections per cask

Cermet

CaskOuter layer

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Modern Extrusion Techniques Allow Production of Cermet Segments

• Cermet mixture placed in long rectangular box− Layer of powder mixture

added− Layer compressed− Steps repeated until box

is full

• Box welded shut

• Box heated and gases removed

• Box heated and extruded to final form

15


Powder Extrusion Process(Ram Pushes Heated, Canned Powder

Through a Die)

05-056

Powder(Hot)

Can

DieHydraulic

Ram

Laboratory Experiments to Define Manufacturing

Conditions for Both Processes

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Powder Mix Segregation Tests

• Powder mixtures can separate on handling

• Tests define allowable thickness of powder before compression− 7-cm cylinder of HfO2

mix and iron powder− 2-hours on vibration

table− Limited segregation

• Tests define maximum layer of powder mixture before pre-compaction

0 10 20 30 40 50

6

20

37

55

73

91

Steel Powder Content (wt%)

Dis

tanc

e fro

m B

otto

m o

f Sam

ple

(%)

37.4

42.6

44

44

44.3

44.8

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Compression Testing

• Powder mix compressed to minimize high-temperature consolidation

• Tests to determine optimum forces for compression− Low pressure

minimizes cost− High pressure

maximizes density− Warm compaction

above Tg of binder improves density 10

30

Compaction Pressure (ksi)

Den

sity

(% T

.D.)

15 20 25 30 3550

40

50

60

70

8025º C120º C

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Advantages For Each Process

FCC Process CES Process

• Maximize cermet content of cask (no steel inside cask body)− Maximize performance− Maximize DUO2 usage

• Minimum number of process steps− Advantage for large

volume production

• Small manufacturing equipment (low capital cost)− Attractive for limited

production runs

• Lower research and development costs

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Conclusions

• Two methods for cask manufacturing are being investigated

• Both methods use powder metallurgical fabrication processes

• Each has specific advantages and disadvantages

• Experiments are required to determine manufacturing times to allow reliable estimates of manufacturing costs

• Cost estimates to be developed latter this year

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