1. February 5-6, 2004 HAPL meeting, G.Tech. 1 HAPL Blanket Strategy A. René Raffray UCSD With contributions from M. Sawan and I. Sviatoslavsky UW HAPL Meeting Georgia Institute of Technology Atlanta, GA February 5-6, 2004

2. HAPL meeting, G.Tech. 2 Outline Background Strategy MFE Blanket Options Example Trade-Offs Summary

3. February 5-6, 2004 HAPL meeting, G.Tech. 3 Background Distinguish between transient and quasi steady- state conditions -Separation of armor function and structural + blanket functions -W armor designed to transient conditions -Blanket, first wall and cycle designed to quasi steady-state conditions Focus HAPL chamber effort on IFE-specific armor/FW issues from the start Blanket/system effort starts later (“later is here”) -Make the most of information from MFE blanket/FW effort. -At least one credible IFE-specific blanket concept must be developed, compatible with the choice of armor (W) and structural material (FS). - Chamber configuration needs then be considered in an integrated system context to show that this can lead to a credible and attractive laser IFE power plant. Coolant (h) FS W q

4. February 5-6, 2004 HAPL meeting, G.Tech. 4 A 2-Phase Strategy is Envisioned Participants -UCSD and UW + ad-hoc individual participation as needed -Close coordination with first wall/armor effort, Materials Working Group and system studies HAPL Blanket/FW Effort Concept I Choice for detailed design study Scoping study of a few concepts for Laser IFE Choice for ETF testing Detailed design study Input from MFE Concept II Concept III Armor/FW Effort Materials Working Group System Studies Phase I Phase II Phase I: Scoping study (about a year) -Several (2-4) blanket concepts will be developed to the point where we can intelligently evaluate then in terms of key issues, including: -Performance, reliability, simplicity, safety and perception from the outside -Down-selection to one (or perhaps 2) preferred option(s) for more detailed study during Phase II -First year effort ~ 1 FTE Phase II: Detailed design analysis (following year(s)) -One (or perhaps 2) preferred option(s) selected from Phase I -Cover all key aspects to end up with a strongly- credible and attractive integrated design. -fabrication, operation, maintenance and integration -Additional effort would be required

5. February 5-6, 2004 HAPL meeting, G.Tech. 5 Example of Blanket Concepts Currently Considered for MFE Structural material: FS or ODS FS International effort Concepts cover a range of breeding materials: ceramic breeder, Pb-17Li, Li and flibe From A. R. Raffray, et al., “Breeding blanket concepts for fusion and material requirements,” Jour. Nuc. Mat.,307-311 (2002) 21-30

6. February 5-6, 2004 HAPL meeting, G.Tech. 6 Several Possible Blanket Concepts from MFE Resources and time only allow for consideration of 3(or 4) concepts during Phase I Some concerns with using water as chamber coolant: -Potential safety issues with Pb-17Li, and/or Li as breeding material and Be as multiplier -Corrosion issues -High pressure -Limited cycle efficiency For Phase I, focus on He as coolant and/or self-cooled blanket concepts -Self-cooled Li -He-cooled ceramic-breeder -He-cooled or dual cooled Pb-17Li -Dual or He-cooled molten salt (if possible, but requires more R&D and is lower priority) -Fully self-cooled Pb-17Li and/or molten salt (flibe) blankets are not included due to their poor heat transfer performances and the difficulty of accommodating IFE heat fluxes and material constraints with reasonable performance (cycle efficiency) and power densities. Above concepts cover a good range of performance and potential risk (e.g. in terms of issues required additional R&D) -Example of such concepts developed for MFE are summarized in the following viewgraphs

7. February 5-6, 2004 HAPL meeting, G.Tech. 7 Self-Cooled Li/FS Configuration Adapted from ARIES-AT and ARIES-CS Concepts (presented at last meeting) Example Li/FS Concept Lithium provides the advantages of: –High tritium breeding capability, –High thermal conductivity, –Immunity to irradiation damage –Possibility of unlimited lifetime if 6 Li burn-up can be replenished Concern includes safety perception Simple box-like structure 2 blanket regions: first replaceable region and second life of plant region Multiple flow passes in the blanket provide the capability for FW surface heat flux ~1 MW/m 2 Struc. T max <800°C Cool. T in /T out ~400/750°C Cool. P < 1MPa Cycle Eff.~46% (Brayton) Energy Multip. ~1.21 Lifetime =15 MW-a/m 2 Need more detailed neutronics and design integration studies for IFE application

8. February 5-6, 2004 HAPL meeting, G.Tech. 8 Example MFE Ceramic Breeder + Be and Ferritic Steel Concept with He as Coolant (EU HCPB Concept) CB (Li 2 TiO 3 or Li 4 SiO 4 ) and Be in form of pebble beds -Good compatibility with FS and He 2-mm W armor on first wall Modular design -Dimension up to 4m x 2m x 0.8m -Module box designed to withstand coolant pressurization -Stiffening grids (~20 cm spacing) -Breeder unit design compatible with CB or Pb-17Li concepts Blanket box with stiffening grid and exploded back wall Blanket breeder unit Cool. T in /T out =300/500°C Cool. P =8 MPa Max FS Temp. <550°C Max. Be Temp. < 750°C Max CB Temp. <920° Energy Multip. =1.25 TBR = 1.14 Cycle Eff. ~37% (Rankine) Lifetime = 15MW-a/m 2

9. February 5-6, 2004 HAPL meeting, G.Tech. 9 Example MFE Self-Cooled or Dual Cooled Pb-17Li + Ferritic Steel Concept Example Dual Coolant Concept: FZK DC Uncouple FW cooling from blanket cooling –He coolant for more demanding FW cooling (no MHD uncertainties) –Self-cooled Pb-17Li with SiC f /SiC flow channel insulating inserts for blanket region –(Note: more flexibility when applying this concept to IFE since there is no MHD effect) Use of ODS-steels would allow for higher temperature but more demanding welding requirements –Compromise: ferritic steel structure with ~mm’s ODS layer at higher temperature FW location Pb-17Li is an attractive breeder material –Good tritium breeding capability –Possibility to replenish 6 Li on-line –Almost inert in air –In general limited extrapolation of blanket technology Simplest FS and Pb-17Li concept is a self-cooled configuration (ARIES-ST and FZK DC concepts) Struc. T max =550°C Pb-17Li T max =700°C He Cool. T max /P =480°C/14 MPa Cycle Eff.=45% (Brayton) Energy Multip. =1.17 Lifetime =15MW-a/m 2

10. February 5-6, 2004 HAPL meeting, G.Tech. 10 Blanket Design Procedure Develop FW/Blanket concept compatible with FS as structural material and W as armor material - Don’t re-invent the wheel; utilize information from MFE blanket design effort -Consider each concept in series for better focus of group effort Self-cooled Li (complete early work) (~ 2-3 months) He-cooled ceramic-breeder (~ 3-4 months) He-cooled or dual cooled Pb-17Li (~ 3-4 months) Dual or He-cooled molten salt (if possible, but lower priority) Comparative assessment and selection (~ 1 month ) -Maximize performance Choose power cycle providing highest efficiency for expected coolant temperatures: Brayton or Rankine cycle Maximize cycle efficiency for given material constraints -Design simplicity as a measure of reliability Minimize welds, channels, joints and coolant pressure (if possible) -Adequate tritium breeding

11. February 5-6, 2004 HAPL meeting, G.Tech. 11 Example comparison illustrated next Blanket Scoping Study Will Also Help to Better Understand and Appreciate the Trade-Offs between Different Blanket Characteristics as Applied to IFE High performance v. lower performance options -Mostly linked with maximum coolant temperature that can be achieved within design constraints -Choice of power cycle (Brayton v. Rankine) -Final assessment through system studies Self-cooled v. separately cooled options -Combining heat removal and breeding functions v. separation of functions Liquid breeder v. solid breeder options -Safety impact and perception of using Li or Pb-17Li v. Be (required with CB blankets to achieve tritium breeding goal) -Other issues for both classes of concepts

12. February 5-6, 2004 HAPL meeting, G.Tech. 12 Example Rankine Cycle for Use with Chamber Coolant via Heat Exchanger Superheat, single reheat and regeneration (not optimized) For example calculations, set: -Turbine isentropic efficiency = 0.9 -Compressor isentropic efficiency = 0.8 -Min. (T cool –T steam, cycle ) > 10°C -P min = 0.15 bar S T 2 3 4 5 6 8' 7 reheat superheat P max P int 4' 8 9 P min 2' 10 10' 1 m 1-m T cool,in T cool,out

13. February 5-6, 2004 HAPL meeting, G.Tech. 13 Effect of Constraint on (T cool –T steam,cycle ) < 10°C S T 2 3 4 5 6 8' 7 reheat superheat P max P int 4' 8 9 P min 2' 10 10' 1 m 1-m T cool,in T cool,out

14. February 5-6, 2004 HAPL meeting, G.Tech. 14 Rankine Efficiency and Corresponding Water Pressures as a Function of Coolant Outlet Temperature for Example Rankine Cycle

15. February 5-6, 2004 HAPL meeting, G.Tech. 15 Example Brayton Cycle Considered Set parameters for example calculations: -  T between coolant and He in HX= 50°C - Minimum He temperature in cycle (heat sink) = 35°C - 3-stage compression -Optimize cycle compression ratio (but < 3.5; not limiting for cases considered) -Cycle fractional  P ~ 0.07 -Turbine efficiency = 0.93 -Compressor efficiency = 0.89 -Recuperator effectiveness = 0.95

16. February 5-6, 2004 HAPL meeting, G.Tech. 16 Comparison of Brayton and Rankine Cycle Efficiency as a Function of IFE Chamber Coolant Temperature (under previously described assumptions) For blanket concepts to be considered, the max. coolant temperatures from past studies are: -Li: ~750°C -Pb-17Li: ~700°C -Ceramic breeder/He:~ 500°C These values are illustrative and will probably change when applied to our IFE case Still they fall close to the region where at higher temperature it is clearly advantageous to choose the Brayton cycle and at lower temperature the Rankine cycle The choice of cycle would need to be made on a case by case basis and confirmed through the system studies

17. February 5-6, 2004 HAPL meeting, G.Tech. 17 Summary A 2-phase strategy is envisioned for the HAPL blanket effort -Phase I: Scoping study of 3-4 concepts over the first year -Phase II: Downselect to 1 (or 2) concepts for more detailed study Blanket effort will be carried out in close coordination with other chamber effort (armor/FW and system) and MWG Make the most of information from MFE blanket design effort Consider each concept in series for better focus of group effort -Self-cooled Li (complete early work) (~ 2-3 months) -He-cooled ceramic-breeder (~ 3-4 months) -He-cooled or dual cooled Pb-17Li (~ 3-4 months) -Dual or He-cooled molten salt (if possible, but lower priority) -Comparative assessment and selection (~ 1 month) Team is assembled, strategy has been laid out….we are ready to go!