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 MW/m 2 Surface Heat 11 MW/m 3 Volumetric Heating 17.5 Coolant Pressure 10 MPa Bulk Coolant 600 C Temperature

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

Fracture Results Results for Crack Results for Crack on Previous Slide Perpendicular to Cracks Shown 4.0 16 Stress Intensity (MPa-m 1/2 ) 3.5 14 c/a=2 Stress Intensity (MPa-m 1/2 ) 3.0 12 2.5 10 2.0 8 1.5 c/a=2 6 c/a=6 1.0 4 Crack Face c/a=10 0.5 2 0.0 0 0.2 0.4 0.6 0 Crack Depth (mm) 0 0.1 0.2 0.3 0.4 0.5 0.6 Crack Depth (mm) 8 7 Stress Intensity (MPa-m 1/2 ) 6 Results for 5 Crack in Notch 4 c/a=2 (at shutdown) 3 c/a=6 c/a=10 2 1 0 0 0.2 0.4 0.6 Crack Depth (mm)

Effect of Transients 2001 Vary nominal heat flux 2000 by +/-20% and apply Temperature (oC) 20 cycles 1999 1998 No discernible variation below 1997 surface 1996 0 0.01 0.02 0.03 0.04 Time (s) 1715.40 Surface T emperature Temperature (oC) 1715.38 1715.36 1715.34 T emperature 1715.32 2.5 mm below 1715.30 surface 0 0.01 0.02 0.03 0.04 Time (s)

Surface Effect of “Small” ELM Assume 1.95 MJ deposited on divertor surface over 1.2 milliseconds 4000 Melt layer is 20 microns thick 3500 Melt Temp. Temperature ( o C) 3000 2500 Surface 2000 Depth = 17.7 um Depth = 26.6 um 1500 1000 0 0.2 0.4 0.6 0.8 1 Time (ms)

Thermal Creep 6 Displacement (mm) 5 Add Thermal Creep Model for Tungsten 4 3 Creep rates are excessive at 11 2 MW/m 2 1 0 0.14 0 5000 10000 15000 20000 0.12 Time (hr) Creep Strain (%) 0.10 Total Creep Nominal Heat Flux 0.08 Thermal Creep Pressure Creep 0.06 0.04 0.02 Reduced 0.00 Heat Flux 0 5000 10000 15000 20000 Time (hr)

Design Modifications 0.0014 0.0012 Creep Strain 0.001 0.0008 6.0 0.0006 Normalized Creep Strain 0.0004 Baseline 5.0 Heat Flux 0.0002 Reduced 4.0 Notch 0 Pressure 0 5000 10000 15000 20000 3.0 Time (hr) 2.0 1.0 Reducing Notch Depth 0.0 0.7 0.8 0.9 1 1.1 1.2 1.3 Normalized Parameter Value Varying Surface Heating or Coolant Pressure

Conclusions  We have not identified any “show- stoppers” with respect to an all-tungsten divertor for ARIES  Many uncertainties are still unresolved