1. Laser-Driven IFE Power Plants— Initial Results from ARIES-IFE Study Farrokh Najmabadi For the ARIES Team Third US-Japan Workshop on Laser-Driven Inertial Fusion Energy Jan.25-27, 2001 Lawrence Livermore National Laboratory Electronic copy: http://aries.ucsd.edu/najmabadi/TALKShttp://aries.ucsd.edu/najmabadi/TALKS ARIES Web Site: http://aries.ucsd.edu/ARIES

2.  ARIES-IFE Goals and Plans Program started in June 2000 at roughly $1M/year level.  Initial Results Accurate target output spectrum Detailed modeling of load on the chamber wall Chamber wall engineering On-going progress on advanced engineered material, target injection and tracking, final optics, and safety Outline

3.  Analyze & assess integrated and self-consistent IFE chamber concepts  Understand trade-offs and identify design windows for promising concepts. The research is not aimed at developing a point design.  Identify existing data base and extrapolations needed for each promising concept. Identify high-leverage items for R&D: What data is missing? What are the shortcomings of present tools? For incomplete database, what is being assumed and why? For incomplete database, what is the acceptable range of data? Would it make a difference to zeroth order, i.e., does it make or break the concept? Start defining needed experiments and simulation tools. ARIES Integrated IFE Chamber Analysis and Assessment Research -- Goals

4. ARIES-IFE Is a Multi-institutional Effort Program Management F. Najmabadi Les Waganer (Operations) Mark Tillack (System Integration) Program Management F. Najmabadi Les Waganer (Operations) Mark Tillack (System Integration) Advisory/Review Committees Advisory/Review Committees OFES Executive Committee (Task Leaders) Executive Committee (Task Leaders) Fusion Labs Fusion Labs Target Fab. (GA, LANL*) Target Inj./Tracking (GA) Materials (ANL) Tritium (ANL, LANL*) Drivers* (NRL*, LLNL*, LBL*) Chamber Eng. (UCSD, UW) CAD (UCSD) Target Physics (NRL*, LLNL*, UW) Chamber Physics (UW, UCSD) Parametric Systems Analysis (UCSD, BA, LLNL) Safety & Env. (INEEL, UW, LLNL) Neutronics, Shielding (UW, LLNL) Final Optics & Transport (UCSD, NRL*,LLNL*, LBL) Tasks * voluntary contributions

5. An Integrated Assessment Defines the R&D Needs Characterization of target yield Characterization of target yield Target Designs Chamber Concepts Characterization of chamber response Characterization of chamber response Chamber environment Chamber environment Final optics & chamber propagation Final optics & chamber propagation Chamber R&D : Data base Critical issues Chamber R&D : Data base Critical issues Driver Target fabrication, injection, and tracking Target fabrication, injection, and tracking Assess & Iterate

6.  ARIES-IFE Goals and Plans Program started in June 2000 at roughly $1M/year level.  Initial Results Accurate Target Output Spectrum Detailed Modeling of load on the chamber wall Chamber wall engineering On-going progress on advanced engineered material, target injection and tracking, final optics, and safety Outline

7. We Use a Structured Approach to Asses Driver/Chamber Combinations  Six classes of target were identified. Advanced target designs from NRL (laser-driven direct drive) and LLNL (Heavy-ion- driven indirect-drive) are used as starting points.  To make progress, we divided the activity based on three classes of chambers: Dry wall chambers; Solid wall chambers protected with a “sacrificial zone” (such as liquid films); Thick liquid walls.  We plan to research these classes of chambers in series with the entire team focusing on each.  While the initial effort is focused on dry walls, some of the work is generic to all concepts (e.g., characterization of target yield).

8. 1992 Sombrero Study highlighted many advantages of dry wall chambers. General Atomic calculations indicated that direct-drive targets do not survive injection in Sombrero chamber. A Year Ago (2 nd US/Japan Workshop) Feasibility of Dry Wall Chambers Was in Question

9. Target injection Design Window Naturally Leads to Certain Research Directions Chamber-based solutions: Low wall temperature: Decoupling of first wall & blanket temperatures Low gas pressure:More accurate calculation of wall loading & response Advanced engineered material Alternate wall protectionMagnetic diversion of ions* Target-based solutions: Sabot or wake shield, Frost coating* * Not considered in detail Target injection window (for 6-m Xe-filled chambers): Pressure < 10-50 mTorr Temperature < 700 C

10. Reference Direct and Indirect Target Designs NRL Advanced Direct-Drive Targets DT Vapor 0.3 mg/cc DT Fuel CH Foam + DT 1  m CH +300 Å Au.195 cm.150 cm.169 cm CH foam  = 20 mg/cc DT Vapor 0.3 mg/cc DT Fuel CH Foam + DT 5  CH. 122 cm.144 cm.162 cm CH foam  = 75 mg/cc NRL Direct Drive Target Gain Calculations (1-D) have been corroborated by LLNL and UW. LLNL/LBNL HIF Target

11. Energy output and X-ray Spectra from Reference Direct and Indirect Target Designs NRL Direct Drive Target (MJ) HI Indirect Drive Target (MJ) X-rays 2.14 (1%) 115 (25%) Neutrons 109 (71%) 316 (69%) Gammas0.0046 (0.003%) 0.36 (0.1%) Burn product fast ions 18.1 (12%) 8.43 (2%) Debris ions kinetic energy 24.9 (16%) 18.1 (4%) Residual thermal energy 0.0130.57 Total154458 X-ray spectrum is much harder for NRL direct-drive target

12. Ion Spectra from Reference NRL Laser-Driven Direct –Drive Target Slow Ions Fast Ions

13. The Spectrum Is Coupled With BUCKY Code to Establish Operating Windows for the First Wall Chamber gas pressure can be reduced substantially specially at lower wall temperatures. Dec. 2000 results Time of flight spread in ion-debris energy flux on the wall was not included. Wall survives Wall vaporizes Sombrero >>

14. Temporal Distribution of Ion-Debris Energy Flux Allows Operation at 700 C and Vacuum Ion thermal power on the chamber wall including time-of-flight (6.5-m radius chamber in vacuum) NRL advanced direct-drive targets with output spectra from LLNL & NRL target codes. Most of heat flux due to fusion fuel and fusion products. Chamber wall with C armor and initial temperature of 700 C survives. Results confirmed by Bucky (see talk by Peterson)

15. An Efficient Dry-laser IFE Blanket With Low Wall Temperature Is Possible  Simple, low pressure design with SiC structure and LiPb coolant and breeder.  Innovative design leads to high LiPb outlet temperature (~1100 o C) while keeping SiC structure temperature below 1000 o C leading to a high thermal efficiency of ~ 60%.  Simple manufacturing technique.  Very low afterheat.  Class C waste by a wide margin. Outboard blanket & first wall  As an example, we considered a variation of ARIES-AT blanket as shown:

16. An Efficient Dry-laser IFE Blanket With Low Wall Temperature Is Possible  IFE dry-wall blanket example: ARIES-AT blanket. First wall coated with C armor and is cooled by He. Coupled to advanced Brayton Cycle  Power loadings based on NRL targets injected at 6 Hz.  30% of power is in the first wall. Blanket (e.g. ARIES- AT) Sep. FW Pb-17Li out in He Blanket Pb-17Li (70% of Thermal Power) He FW (30% of Thermal Power) ~50°C IHX Example Case:  For a  T FW of ~100-150°C, the average surface T wall at target injection can be lowered to ~600°C while maintaining a cycle efficiency of 50%

17. Initial Results from ARIES-IFE have Removed Major Feasibility Issues of Dry Wall Chambers  Research is now focused on Optimization And Attractiveness  Trade-off studies are continuing to fully characterize the design window. We are analyzing response of the chamber to  Higher target yields  Smaller chamber sizes  Different chamber wall armor  Un-going activities in:  Engineered Material,  Effect of chamber environment on target trajectory  Final optics  Safety

18. Good parallel heat transfer, compliant to thermal shock Tailorable fiber geometry, composition, matrix Already demonstrated for high- power laser beam dumps and ion erosion tests Fibers can be thinner than the x- ray attenuation length. Advanced Engineered Materials May Provide Superior Damage Resistance Carbon fiber velvet in carbonizable substrate 7–10  m fiber diameter 1.5-2.5-mm length 1-2% packing fraction

19. Variations in the Chamber Environment Affects the Target Trajectory in an Unpredictable Way Forces on target calculated by DSMC Code “Correction Factor” for 0.5 Torr Xe pressure is large (~20 cm) Repeatability of correction factor requires constant conditions or precise measurements 1% density variation causes a change in predicted position of 1000  m (at 0.5 Torr) For manageable effect at 50 mTorr, density variability must be <0.01%. Leads to in-chamber tracking Ex-chamber tracking system MIRROR R 50 m TRACKING, GAS, & SABOT REMOVAL 7m STAND-OFF 2.5 m CHAMBER R 6.5 m T ~1500 C ACCELERATOR 8 m 1000 g Capsule velocity out 400 m/sec INJECTOR ACCURACY TRACKING ACCURACY GIMM R 30 m

20. Laser-Final Optics Threat Spectra Final Optic ThreatNominal Goal Optical damage by laser>5 J/cm 2 threshold (normal to beam) Nonuniform ablation by x-raysWavefront distortion < /3 (~100 nm) Nonuniform sputtering by ions 6x10 8 pulses in 2 FPY: 2.5x10 6 pulses/atom layer removed Defects and swelling induced Absorption loss of <1% by  -rays and neutronsWavefront distortion of < /3 Contamination from condensable Absorption loss of <1% materials (aerosol, dust, etc.) >5 J/cm 2 threshold Two main concerns:  Damage that increases absorption (<1%)  Damage that modifies the wavefront – spot size/position (200  m/20  m) and spatial uniformity (1%)

21. Safety and Environmental Activities in ARIES-IFE Chamber Assessment In-vessel Activation Ex-vessel Activation Waste Assessment Waste Metrics Energy Source Radiological and Toxic Release Metrics Evaluation Decay Heat Calculation Tritium and Activation Product Mobilization Debris or Dust Chemical Reactivity Toxic Material (Performed jointly by INEEL, UW, LLNL)

22. Several causes have been identified for rogue shots: imperfect targets; or incorrect target injection, laser pulse actuation control, laser energy deposition –Imperfect targets remain in fueling stream, ~ 10 to 50/day based on 1-5% defect rate in factory (current electronic mfg data) and 0.1% failed to be rejected –Improper target velocity/trajectory in IFE chamber, ~ 1E- 03/year based on high reliability gas injection system –Laser pulse actuation control fault, ~ 1E-05/year based on modern fly by wire digital control systems –Lasers deliver inadequate energy to target, ~ 1E-03/year based on critical nature of the component in the system Preliminary Initiator Frequency for IFE Rogue Shots

23.  Rogue shots should be considered “operational occurrences” until more is determined about quality control procedures and approaches for the approximately 1M targets produced per day.  Impact on the chamber of such a shot  Initiator of an accident (shrapnel possibly leading to a loss of coolant event)  Overall reliability of the facility Understanding the Impact of Rogue Shots On IFE Power Plant Operation is Essential

24. Accident Initiators - Rogue Pellets

25. Initial Results from ARIES-IFE have Removed Major Feasibility Issues of Dry Wall Chambers  Research is now focused on Optimization And Attractiveness  Trade-off studies are continuing to fully characterize the design window. We are analyzing response of the chamber to  Higher target yields  Smaller chamber sizes  Different chamber wall armor  Un-going activities in:  Engineered Material,  Effect of chamber environment on target trajectory  Final optics  Safety