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Advanced Chamber Concept with Magnetic Intervention: - Ion Dump with Phase Change (including Cu, Pb-17Li, Flibe) - SiC f /SiC + Pb-17Li or Flibe Blanket A. René Raffray UCSD With contributions from: M. Sawan, G. Sviatoslavsky, I. Sviatoslavsky UW HAPL Meeting PPPL, Princeton, NJ

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Advanced Chamber Concept with Magnetic Intervention:- Ion Dump with Phase Change (including Cu, Pb-17Li, Flibe) - SiCf/SiC + Pb-17Li or Flibe Blanket

A. René Raffray


With contributions from:

M. Sawan, G. Sviatoslavsky, I. Sviatoslavsky


HAPL Meeting

PPPL, Princeton, NJ

December 12-13, 2006

HAPL meeting, PPPL

Outline l.jpg

  • Possible options for large chamber in case W armor does not work include (follow-up from last meeting):

    • Allowing melt layer; momentary liquid wall (Look at possibility of Cu in addition to W and example be case presented before)

    • Moving solid wall (L. Snead)

    • Engineered W armor samples provided by PPI to UNC & ORNL to be tested; provision of samples for additional testing elsewhere to follow.

  • Separate ion dump chamber for magnetic intervention case

    • Possibility of solid armor with phase change (W, Be, Cu)

    • Possibility of wetted walls (Pb, Pb-17Li, flibe)

  • SiCf/SiC blanket for magnetic intervention case

    • Pb-17Li and flibe (see also posters)

    • In the process of evolving chamber core of MI case with a number of other contributors

HAPL meeting, PPPL

Momentary liquid walls allowing solid to melt and resolidify l.jpg





Momentary Liquid Walls (allowing solid to melt and resolidify)

• Allowing W armor itself to melt is an option but concerns about stability of melt layer and integrity of high temperature solid W under melt layer

• Other possibility is to use a lower MP material in a W structure

- e.g. >90%Cu in <10% W structure

- How to fabricate it?

- Structure size to provide good melt layer retention through capillarity (microstructure size to be optimized for melt layer retention and integrity)

HAPL meeting, PPPL

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Histories of Temperature and Phase Change Thickness for a Cu Armor as a Function of the Chamber Sizes for the 350 MJ Target

• 1-mm Cu on 3.5 mm FS at 580 °C

• No chamber gas

• Can the W mesh be maintained at a reasonable temperature acceptable lifetime? (~1250°C for 10.75 m chamber)

• Stability of ~3-10 m melt layer of Cu

• Minimal evaporation, ~0.0001 nm on average per shot for 10.75 m chamber, ~ 1 g per shot

HAPL meeting, PPPL

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Magnetic Intervention: Utilizing a Cusp Field to Create a Magnetic Bottle Preventing the Ions from Reaching the Wall and Guiding them to Specific Locations at the Equator and Ends

  • Utilization of a cusp field for such magnetic diversion has been experimentally demonstrated previously

    - 1980 paper by R.E. Pechacek et al.,

  • Following the micro-explosion, the ions would compress the field against the chamber wall, the latter conserving the flux. Because of this flux conservation, the energetic ions would never get to the wall.

    • One possibility would be to dissipate the magnetic energy resistively in the FW/blanket, which reduces the energy available to recompress the plasma and reduces the load on the external dumps

    - about 70% of ion energy dissipated in blanket

    - about 30% of ion energy in dump region

HAPL meeting, PPPL

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Seems Advantageous to Position Dump Plate In Separate Smaller Chamber

• Dry wall main chamber to satisfy target and laser requirements.

• Separate phase-change dry wall or wetted wall chamber to accommodate ions and provide long life.

• Have to make sure no unacceptable contamination of main chamber

HAPL meeting, PPPL

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Scoping Analysis of an Example Ion Dump Ring Chamber Smaller Chamber






• Some flexibility in setting chamber major and minor radii so as not to interfere with laser beams

• e.g., with Rmajor/Rminor =8/2.7 or 9/2.4 m, and assuming 35% of wetted wall area sees ion flux with a peaking factor of 1:

- Ion dump area = 300 m2

- From 0 to 0.5 s, q’’ = 4.51x1010 W/m2

- From 0.5 to 1.5 s, q’’= 6.53x1010 W/m2

• Dry Wall Armor with Phase Change

- Example results for W and Be previously presented.

- New case analyzed with Cu, possibly within high porosity W microstructure (~80-90%) for integrity and Cu melt layer retention

• Wetted Wall

- Example results for Pb previously presented

- New cases with Pb-17Li and flibe analyzed

HAPL meeting, PPPL

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Temperature and Phase Change Thickness Histories for W, Be, Cu, Pb, Pb-17Li and Flibe for Example Case

• 350 MJ target (ion energy = 87.8 MJ)

• Ion dump area = 300 m2

• From 0 to 0.5 s, q’’ = 4.51x1010 W/m2 (7.7% of ion energy)

• From 0.5 to 1.5 s, q’’= 6.53x1010 W/m2 (22.3% of ion energy)

HAPL meeting, PPPL

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Maximum Temperature and Phase Change Thicknesses for W, Be, Cu, Pb, Pb-17Li and Flibe as a Function of Ion Dump Area

• 350 MJ target (ion energy = 87.8 MJ)

• Evaporation loss per shot relatively modest for W but could be a concern for Cu or Be (1 nm/shot ~ 0.43 mm/day)

• Stability of melt layer is a concern (~10m for Cu or Be; ~ 1 m for W)

• For wetted wall in particular, the evaporated material (~10 m for Pb-17Li, Pb or flibe) must recondense within a shot and not contaminate main chamber

HAPL meeting, PPPL

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Wetted-Wall Concept Could Consist of a Porous Mesh Through Which Liquid (Pb-17Li or flibe) Oozes to Form a Protective Film

Liquid film

Porous mesh

Liquid flow


Liquid recycling

• Need to make sure that protective film is reformed prior to each shot

- radial flow through porous mesh

- circumferential flow of recondensed liquid

- no concern about any droplets falling in chamber

HAPL meeting, PPPL

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Film Condensation in Ion Dump Chamber for Which Liquid (Pb-17Li or flibe) Oozes to Form a Protective FilmPb-17Li and Flibe

• Scoping calculations previously done for Pb as example.

• Now extended to Pb-17Li and Flibe as they are used as breeder/coolant in the blanket.

• Ion energy from 350 MJ target = 87.8 MJ

- 7.7% of ion energy to dump over 0-0.5 s

- 22.3% of ion energy over 0.5-1.5 s

• Evaporated thickness and vapor temperature rise from ion energy deposition in ion dump chamber.

• Assume ion deposition area = 300 m2

- e.g. 35% of chamber with Rmajor = 9 m and Rminor = 2.4 m






jnet = net condensation flux (kg/m2-s)

M = molecular weight (kg/kmol)

R = Universal gas constant (J/kmol-K)

G = correction factor for vapor velocity towards film

sc, se = condensation and evaporation coefficients

Pg, Tg = vapor pressure (Pa) and temperature (K)

Pf, Tf = saturation pressure (Pa) and temperature (K) of film

HAPL meeting, PPPL

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Scoping Analysis of Pb-17Li Condensation in Example Ring Chamber

• Characteristic condensation time very fast, < 0.024 s

• It takes < 0.24 s for vapor density to reach saturation for final vapor temperature > 773 K (assuming linear temporal decrease of vapor temperature from initial to final value).

HAPL meeting, PPPL

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Scoping Analysis of Flibe Condensation in Example Ring Chamber

• Characteristic condensation time very fast, < 0.02 s

• It takes < 0.202 s is for vapor density to reach saturation for final vapor temperature > 773 K (assuming linear temporal decrease of vapor temperature from initial to final value).

HAPL meeting, PPPL

Blanket study for magnetic intervention chamber l.jpg
Blanket Study for Magnetic Intervention Chamber Chamber

• More detailed study of blanket using SiCf/SiC + Pb-17Li or Flibe

- Layout and thermal-hydraulics

- Neutronics

- Fabrication

- Assembly and maintenance

(presented by M. Sawan)

(presented by G. Sviatoslavsky)

HAPL meeting, PPPL

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Conical Chamber Well Suited to Cusp Coil Geometry and Utilizing SiCf/SiC for Resistive Dissipation

• Armored ion dumps

- designed for easier replacement than blanket

- shown inside the chamber but could also be in separate ring chamber

• SiCf/SiC blanket with liquid breeder

- TBR ~ 1.3 for Pb-17Li

• Water-cooled steel shield / vacuum vessel (~0.5m thick) is lifetime component and protects the coil.

• Design accommodates laser ports.

Example Chamber Layout

• Maintenance performed from the top by removing the upper shield and the blanket modules from the different region without having to move the coils.

HAPL meeting, PPPL

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Self-Cooled Pb-17Li +SiC Utilizing SiCf/SiC Blanket Optimized for High Cycle Efficiency

• Simple annular submodule design builds on ARIES-AT concept

• Pb-17Li flows in two-pass: first pass through the annular channel to cool the structure; and a slow second pass through the large inner channel where the Pb-17Li is superheated

• This allows for decoupling of the outlet Pb-17Li temperature from the maximum SiCf/SiC temperature limit

HAPL meeting, PPPL

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Submodule Configuration for Upper Mid-Blanket Region Utilizing SiC

• Submodule cross-section changes because of conical geometry

• Pb-17Li enters through annular channel at equator (C-C), turns at top (A-A), flows through inner channel and exits at A-A.

• 5 submodules joined (e.g. by brazing) to form a modular unit for assembly and maintenance

• Tight fit assembly so that all submodules are pressure-balanced by adjacent modules to avoid large stresses associated with long radial span (particularly at A-A)

radial/toroidal dimensions:

A-A: 1.06/0.196 m

B-B: 0.88/0.33 m

C-C: 0.7/0.47 m

HAPL meeting, PPPL

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Submodules Shaped at Module End for Tight Fit Assembly Utilizing SiC(Resistive Dissipation and Pressure-Balancing of All Submodules)




End sub-module profiles of neighboring modules allows natural fit

• Concerns exist about the possible domino effect on all submodules in case of a catastrophic failure of a submodule.

• Possible solutions include isolating a limited number of modules by including structurally independent wedges and/or using pressure-sensitive valve system to drain and decompress the coolant in such an accident case.

Module A

Module C

Module B

HAPL meeting, PPPL

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2-D Stress Analysis of First Wall Performed with ANSYS Utilizing SiC

• At B-B, maximum heat loads: q’’=0.11 MW/m2; qSiC’’’ = 31 MW/m3

• Pb-17Li pressure is ~1 MPa (accounting for hydrostatic pressure ~0.74 MPa for ~9 m elevation, Pblkt ~0.2 MPa and some margin).

• tot increases sharply as the wall thickness is increased, indicating the dominating effect of the increasing thermal over the decreasing pressure.

• For the present scoping design analysis, it seems reasonable to choose FW ~5 mm; the corresponding tot ~100 MPa for plane stress and ~230 MPa for plane strain , compared to an assumed limit of ~190 MPa for SiCf/SiC.

• If more margin is needed in the future, a slightly thinner wall of larger chamber could be used.

Chamber dimension = 6m

HAPL meeting, PPPL

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Possible Submodule Fabrication Method Utilizing SiC(rectangular submodules shown for illustration)

Issue:Complex concentric walls prevent assembly of inner and outer channels

Solution: Expendable core form fabrication

1. inner channel form

2. Lay-up & infiltrate inner channel

3. Two-piece form fitted over inner channel

4. Lay-up & infiltrate outer channel

6. Braze end caps

5. Consume both forms via chemical or thermal process

7. Braze 5 submodules together to form module

HAPL meeting, PPPL

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Self-Cooled Pb-17Li + SiC Utilizing SiCf/SiC Blanket Coupled to a Brayton Cycle though a Pb-17Li/He HX

• 3 Compressor stages (with 2 intercoolers) + 1 turbine stage; DP/P~0.05; 1.5 < rp< 3.5

- DTHX ~ 30°C

- hcomp = 0.89

- hturb = 0.93

- Effect.recup = 0.95

HAPL meeting, PPPL

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Thermal-Hydraulic Optimization Procedure Utilizing SiC

• Set blanket design parameters.

- SiCf/SiC FW=0.5 cm; annulus=0.5 cm

- only the blanket length is adjusted based on the chamber size

• Simple MHD assumption based on assumed 1 T field and flow laminarization with conduction only (probably conservative).

• For given chamber size and fusion power, calculate combination of inlet and outlet Pb-17Li temperatures that would maximize the cycle efficiency for given SiCf/SiC temperature limit and/or Pb-17Li/SiC interface temperature limit.

- SiCf/SiC Tmax<1000°C

- Pb-17Li/SiC Tmax<950°C

- Assume conservatively k=15 W/m-K for SiCf/SiC

HAPL meeting, PPPL

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Brayton Cycle Efficiency as a Function of Cone-Shaped Chamber Size and Corresponding Outlet and Inlet Pb-17Li Temperatures

• Pb-17Li/SiC Tmax < 950°C is more constraining than SiCf/SiC Tmax <1000°C

• Both P and Ppump show minima at a chamber dimension of 6 m corresponding to the largest T between Pb-Li inlet and outlet temperatures (and lowest flow rate).

• For a 6 m chamber, Pb-17Li Tout~1125°C; Brayton ~0.59

• Such a high-temperature also allows for the possibility of H2 production

• Question about whether such a high Pb-17Li Tout can be handled in out of reactor annular piping and in heat exchanger.

HAPL meeting, PPPL

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Effect of Varying the Pb-17Li/SiC Interface Temperature Limit

• It is not clear what the allowable SiC/Pb-17Li Tmax really is as it depends on a number of conditions.

• Earlier experimental results at ISPRA indicated no compatibility problems at 800°C, whereas more recent results indicate a higher limit.

• Decreasing the SiC/Pb-17Li Tmax from 950°C to 800°C results in a marked reduction in cycle efficiency, from ~59% to ~50%.

• Interestingly, the pressure drop and pumping power minima correspond to an interface limit of 950°C, and both increase significantly as the interface temperature limit is decreased and an increased in flow rate is required.

HAPL meeting, PPPL

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Adapting the Blanket for Flibe Requires a Be region for Tritium Breeding

• Flibe electrical resistivity well suited for resistive dissipation of magnetic energy

• 1-1.5 cm Be region sufficient for TBR~1.1

• A Be plate can be included in the previous submodule design

• Be also used for chemistry control of flibe

• The flibe flows in two-pass: a first pass through the annular channel to cool the structure; and a slow second pass through the large inner channel where the flibe is superheated

HAPL meeting, PPPL

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Effect of Varying the Flibe/SiC Interface Temperature Limit Tritium Breeding

• Flibe Tout < Pb-17Li Tout mostly because of its poorer heat transfer properties

• For 6 m conical chamber and 1000°C limit:

Flibe Tin/Tout = 673/1000°C; Be Tmax = 840 °C

P = 0.16 MPa; Ppump = 0.27 MW

Brayton = 0.57

• High temperature also

allows for possibility of

H2 production

• Lower density of flibe

results in lower primary

stresses in module

(design pressure ~0.4-0.5 MPa

compared to ~1 MPa for Pb-17Li)

6 m chamber

SiCf/SiC Tmax < 1000°C:

HAPL meeting, PPPL

Summary l.jpg
Summary Tritium Breeding

• Scoping study of self-cooled Pb-17Li or flibe + SiCf/SiC blanket concept for use in the magnetic-intervention cone-shaped chamber geometry performed

• Separate dump chamber with melted solid wall (W, Cu, Be) or wetted wall (Pb-17Li, flibe, Pb) assessed for magnetic intervention case

- Much relaxed atmosphere requirements for separate dump chamber

- Encouraging results as condensation is very fast

- Need to ensure no unwanted contaminants in main chamber

• Future work

- Complete overall chamber layout of MI core

- More detailed design of separate dump chamber

HAPL meeting, PPPL

Summary of blanket study for mi case l.jpg
Summary of Blanket Study for MI Case Tritium Breeding

• A scoping design analysis has been performed of a self-cooled Pb-17Li + SiCf/SiC blanket concept for use in the magnetic-intervention cone-shaped chamber geometry

- Simple geometry with ease of draining and accommodation of 40 rectangular laser ports with vertical aspect ratio

- Good performance, with the possibility of a cycle efficiency >50% depending on chamber size and SiCf/SiC properties and temperature limits

- Submodule side walls are pressure-balanced; only the first wall and back wall are designed to accommodate the loads

- Must be noted that SiCf/SiC is an advanced material requiring substantially more R&D than more conventional structural material (e.g. FS)

- Submodule design can be adapted to flibe as breeder by adding a layer of Be to ensure a TBR of 1.1 and provide for chemistry control

- The high coolant temperatures result in high cycle efficiency and could also be used for H2 production

- However, issues of what outside coolant tube and HX material(s) to use at these temperatures need to be further investigated

HAPL meeting, PPPL