October 27-28, 2004 HAPL meeting, PPPL 1 Thermal-Hydraulic Analysis of Ceramic Breeder Blanket and Plan for Future Effort A. René Raffray UCSD With contributions from M. Sawan (UW), I. Sviatoslavsky (UW) and X. Wang (UCSD) HAPL Meeting PPPL Princeton, NJ October 27-28, 2004

HAPL meeting, PPPL 2 Outline Ceramic Breeder Blanket Layout and Choice of Power Cycle: Brayton Thermal-Hydraulics Analysis of Ceramic Breeder Blanket Concept and Power Cycle Optimization Next Step: Dual Coolant He/Pb-17Li Concept Summary

October 27-28, 2004 HAPL meeting, PPPL 3 Ceramic Breeder Blanket Module Configuration (based on ARIES-CS MFE configuration) Initial number and thicknesses of Be and CB regions optimized for TBR=1.1 based on: -T max,Be < 750°C -T max,CB < 950°C -k Be =8 W/m-K -k CB =1.2 W/m-K -  CB region > 0.8 cm 6 Be regions + 10 CB regions for a total module radial thickness of 0.65 m Preferable to couple to a Brayton cycle to avoid accident scenario that could result in Be/steam reaction and would require designing the module box to accommodate high pressure Li 4 SiO 4 or Li 2 TiO 3 as possible CB

October 27-28, 2004 HAPL meeting, PPPL 4 Adapting an MFE Blanket Design to Laser IFE Must Take into Account the Difference in Heat Loading Characteristics Key difference between MFE and economically- sized IFE Chambers: -MFE Wall Load > IFE Wall Load - But IFE eff. q’’ > MFE q’’ -IFE imposes more demand on first wall cooling

October 27-28, 2004 HAPL meeting, PPPL 5 Brayton Cycle Configuration Considered in Combination with CB Blanket + Intermediate HX to Provide Flexibility for Separately Setting Cycle He Fractional Pressure Drop 3 Compressor stages (with 2 intercoolers) + 1 turbine stage;  P/P~0.05; 1.5 < r p <  T HX ~ 30°C -  comp =  turb = Effect. recup = 0.95 As reported before, we also considered initially a more advanced cycle also with 4 compression stages & 4 turbine stages -It provided good performance but the pressure drop and pumping power were unacceptably large and this cycle was not further considered with the CB blanket.

October 27-28, 2004 HAPL meeting, PPPL 6 Optimization Study of CB Blanket and Brayton Cycle Using Scaled Volumetric Heat Generation from Neutronics Calculations Maximum cycle efficiency (  ) as a function of chamber radius (R) under the following assumed constraints: Be and CB: -T max,Be < 750°C -T max,CB < 950°C -  blkt = 0.65 m for breeding FS: 1.T max,FS < 550°C; and 2.T max,ODS-FS < 700°C Fusion Power: MW; and MW Coolant: -  T HX = 30°C -P pump /P thermal < 0.05  peaks at ~ 36% for R ≥ 9 m for T max,ODS-FS < 700°C and for both P fusion =1800 MW and 2400 MW For T max,ODS-FS < 550°C,  is very low, <29% (probably uncacceptable) Key constraint is max. FS temp. at FW because of high q’’ For this concept, we need T max,ODS-FS < 700°C; in this case, R=7 m and  seem a reasonable compromise.

October 27-28, 2004 HAPL meeting, PPPL 7 Corresponding He Coolant Inlet and Outlet Temperatures Maximum allowable temperature of FS limits the combination of outlet and inlet He coolant temperatures

October 27-28, 2004 HAPL meeting, PPPL 8 Corresponding Ratio of Pumping to Thermal Power for Blanket He Coolant The assumed limit of P pump /P thermal < 0.05 can be accommodated with this Brayton cycle.

October 27-28, 2004 HAPL meeting, PPPL 9 What If the Blanket Was Coupled to a Rankine Cycle With Same Inlet and Outlet Coolant Temperatures Gain a couple of points compared to Brayton ( more for lower coolant temperatures); e.g. 38% for R=8 m and T max,FS <700°C compared to 36% for Brayton Must be considered in combination with penalty of more massive module and possible steam/Be reaction in case of accidents Rankine T S ' 7 reheat superheat P ma x P int 4' 8 9 P min 2' 10 10' 1 m 1-m T cool,in T cool,out Example Rankine Cycle

October 27-28, 2004 HAPL meeting, PPPL 10 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 Considered with FS in a dual coolant 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

October 27-28, 2004 HAPL meeting, PPPL 11 Initial Considerations in Applying Dual Coolant Design to IFE Example concept consisting of an array poloidal modules -~ 0.35 m x 0.6 m x 10 m module -Use of SiC insulation to push Pb-17Li temperature to ~ 700°C (otherwise FS/Pb-17Li compatibility limit ~ °C) Illustration of Possible Dual- Coolant He/LiPb Concept Pb-17Li Breeding Zones: Large Inner Channels with SiC f /SiC Insulation Layer ~0.35 m ~0.6 m ~10 m For R= 7 m and 1800 MW fusion: -He: T in = 457°C; T out = 477°C P= 8 MPa -FW: V~70 m/s;  P/P ~ 0.01 in 1 cm x 2 cm channels Max. FW FS temp. =700°C -Pb-17Li: T in =477°C; T out = 700°C V~ 0.36 m/s -Cycle efficiency=45%

October 27-28, 2004 HAPL meeting, PPPL 12 Summary Scoping study of a Ceramic Breeder design adapted to IFE has been completed. High effective FW q’’ impacts design (or any design with He or other coolant with modest heat transfer performance). Overall, the achievable cycle efficiency is rather modest with a Brayton cycle (~0.36 or less) Rankine cycle would provide slightly better performance (by a couple of points) but would give rise to Be/steam reaction concerns and could lead to a more massive module design. Initial analysis indicates the good potential of a dual coolant He/LiPb concpet Future effort will focus on: - Finishing the scoping study of this concept (to be presented at next meeting) -Comparative assessment and down selection of the more attractive concept(s) for more detailed integrated studies.