Fracture and Creep in an All- Tungsten Divertor for ARIES Jake - - PowerPoint PPT Presentation

Fracture and Creep in an All- Tungsten Divertor for ARIES

Jake Blanchard University of Wisconsin – Madison August 2012

Introduction

 The ARIES Project is exploring the

feasibility of using tungsten as a structural material for plasma-facing components

 For now, we are assuming the material is

pure tungsten, but alloys may be necessary

 This talk addresses two key failure modes

that must be addressed by these designs

• Fracture
• Thermal creep

The Design

Major Input Parameters

Parameter Value Units Surface Heat 11 MW/m2 Volumetric Heating 17.5 MW/m3 Coolant Pressure 10 MPa Bulk Coolant Temperature 600 C

Crack Location

Crack-Free Stress State Finite Element Model with Crack on Coolant Channel Surface

2 4 6 8 10 12 14 16 0.1 0.2 0.3 0.4 0.5 0.6

Stress Intensity (MPa-m1/2) Crack Depth (mm)

c/a=2 c/a=6 c/a=10

Fracture Results

1 2 3 4 5 6 7 8 0.2 0.4 0.6

Stress Intensity (MPa-m1/2) Crack Depth (mm)

c/a=2 c/a=6 c/a=10

Results for Crack on Previous Slide Results for Crack Perpendicular to Cracks Shown Results for Crack in Notch (at shutdown)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0.2 0.4 0.6

Stress Intensity (MPa-m1/2) Crack Depth (mm) c/a=2

Crack Face

Effect of Transients

Surface T emperature T emperature 2.5 mm below surface Vary nominal heat flux by +/-20% and apply 20 cycles No discernible variation below surface

1996 1997 1998 1999 2000 2001 0.01 0.02 0.03 0.04

Temperature (oC) Time (s)

1715.30 1715.32 1715.34 1715.36 1715.38 1715.40 0.01 0.02 0.03 0.04

Temperature (oC) Time (s)

Surface Effect of “Small” ELM

Assume 1.95 MJ deposited on divertor surface over 1.2 milliseconds Melt layer is 20 microns thick

1000 1500 2000 2500 3000 3500 4000 0.2 0.4 0.6 0.8 1

Temperature (oC) Time (ms)

Surface Depth = 17.7 um Depth = 26.6 um

Melt Temp.

Thermal Creep

Add Thermal Creep Model for Tungsten Creep rates are excessive at 11 MW/m2 Nominal Heat Flux Reduced Heat Flux

1 2 3 4 5 6 5000 10000 15000 20000

Displacement (mm) Time (hr)

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 5000 10000 15000 20000

Creep Strain (%) Time (hr)

Total Creep Thermal Creep Pressure Creep

Design Modifications

0.0 1.0 2.0 3.0 4.0 5.0 6.0 0.7 0.8 0.9 1 1.1 1.2 1.3

Normalized Creep Strain Normalized Parameter Value

Heat Flux Pressure 0.0002 0.0004 0.0006 0.0008 0.001 0.0012 0.0014 5000 10000 15000 20000

Creep Strain Time (hr)

Baseline Reduced Notch

Varying Surface Heating or Coolant Pressure Reducing Notch Depth

Conclusions

 We have not identified any “show-

stoppers” with respect to an all-tungsten divertor for ARIES

 Many uncertainties are still unresolved