CS Thermal Analysis Status

• Heating and Cooling of CS During Normal Operation - SN & DN Operation– Overall Heat Balance

– Heating of Center Stack

• First Cut Thermal-Stress Analysis of CS

• Study of Impact of CS Tile Size on Thermal Stress

Heating and Cooling of CS During Normal Operation

• ANSYS 2D Axisymmetric Model– CS radiatively Cooled to IBDhs, OBD, PP and VV– CS assumed perfectly insulated from OH & PF’s– CS Tiles assumed in perfect contact with Inconel Casing– IBDhs, OBD, PP and VV actively cooled

• Equivalent film coefficient used – need to review and verify for new design• For CS, only modest coiling assumed at IBDhs

• Single Null (SN) and Double Null (DN) modes– No Natural Divertor Mode defined in GRD (was worse case in original

design)• CS Surface emissivity varied

– 0.7 for Graphite (without Lithium)– 0.3 for Lithium Coated Graphite (best guess)

• 14 MW, 5s pulse, 1200s rep rate– Largest Power Fraction to IBDhs

– ~1/3 Power Uniformly Radiated to All exposed Surfaces

Applied Heat Fluxes

Average Heat removal rate thru Cooling Systems (IBDhs, OBD, PP and VV) should total 14e6*5/1200 = 58.3 kW after fully ratcheting (see plots)

Question: The GRD requirement for the CSFW is fairly modest.Are there scenarios not included here which could lead to higher heat fluxes?

End of 10th Pulse(Not yet fully ratcheted)

CSFW

CSAS

IBDHSIBDVS

CS Inconel CasingTavg = 342 C

Thermal EquilibrationWithin Tile

Cooling

CS Inconel CasingTavg = 455 C

CS Inconel CasingTavg = 286 C

CS Inconel CasingTavg = 370 C

Summary of Heating in CS Inconel Casing

Observations

• Highest Tile temperatures at IBDhs where largest fraction of Power is deposited– SN much higher than DN as expected

• PP Cooling picks up largest fraction of total heat with VV, OD & ID picking up comparable smaller amounts– Variation of heat load to cooling systems* not

significantly different for scenarios analyzed

• Highest Bulk Heating of CS Inconel Casing due to DN Operation (342C at =.7, 455C at =.3)

*For SN all IBDhs heat load to lower cooling system

First Cut Thermal-Stress Analysis of CS• Fully Ratcheted Temperature Distribution from Previous

Thermal Analysis of Single Null (highest tile temperatures) with emiss=.7 used

• CS Tile thermal stress only– Assuming ATJ Structural Properties (first cut - not temperature

dependent)– Initial Run as 2D axisymmetric, followed by 3D cyclically

symmetric– Compares single (very) large tile to segmented tile (at Inboard

Divertor Horizontal Section)• CS Casing thermal stress only

– Assumes Inconel 625 Properties (first cut - not temperature dependent)

– Model includes CS Casing, VV and Connecting Bellows

Temperature DistributionFollowing Fully Ratcheted Pulse

Graphite Only

AxisymmetricNo Split

AxisymmetricWith Split

Cyclically symmetricNo Split

Cyclically symmetricWith Split

Temperature DistributionFollowing Fully Ratcheted Pulse(At Max CS Average Temp)

Vacuum Boundary Only

Observations

• Segmenting of tile Poloidally has modest affect (slightly lower Seqv) but segmenting toroidally leads to higher stresses.

• Tile Stress levels (without including temperature dependency on Properties and allowables) show max stresses ~1/2 yield

• Inconel Casing Stress levels are also ~1/2 yield

Study of Impact of CS Tile Size on Thermal Stress

• Simplified Geometry – Segmented Cylinder• ATJ Graphite Properties assumed• 1 MW/m2 Heat Flux for 5 sec Pulse

– Much Higher than GRD Spec 0.1-0.2 MW/m2

• Freely supported tile (ie unconstrained)– Stresses from Thermal Gradients

• Results show stresses increase significantly with tile size

Results

CS Tile Thermal Stress vs Tile Size 1 MW/m2 for 5 sec

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

10 20 30 40 50

Mill

ion

s

Angular extent, deg, of ~square tile

Str

es

s, P

a

Sx+

Sx-

Sy+

Sy-

Sz+

Sz-

Sxy

Syz

Sxz

Seqv

Results show stresses increase significantly with tile size