Laser-Driven IFE Power Plants—Initial Results from ARIES-IFE Study

Farrokh NajmabadiFor the ARIES Team

Third US-Japan Workshop onLaser-Driven Inertial Fusion Energy

Jan.25-27, 2001Lawrence Livermore National Laboratory

Electronic copy: http://aries.ucsd.edu/najmabadi/TALKS

ARIES Web Site: http://aries.ucsd.edu/ARIES

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

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

ARIES-IFE Is a Multi-institutional Effort

Program ManagementF. Najmabadi

Les Waganer (Operations)

Mark Tillack (System Integration)

Program ManagementF. Najmabadi

Les Waganer (Operations)

Mark Tillack (System Integration)Advisory/Review

Committees

Advisory/Review

Committees

OFESOFESExecutive 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

An Integrated Assessment Defines the R&D Needs

Characterization

of target yield

Characterization

of target yield

Target

Designs

Chamber

ConceptsCharacterization

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

DriverDriver

Target fabrication,

injection, and tracking

Target fabrication,

injection, and tracking

Assess & Iterate

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

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).

• 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 (2nd US/Japan Workshop)Feasibility of Dry Wall Chambers Was in Question

Target injection Design Window Naturally Leads to Certain Research Directions

Chamber-based solutions:Low wall temperature: Decoupling of first wall & blanket temperaturesLow gas pressure: More accurate calculation of wall loading & response

Advanced engineered materialAlternate wall protection Magnetic 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

Reference Direct and Indirect Target Designs

NRL Advanced Direct-Drive Targets

DT Vapor0.3 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 Vapor0.3 mg/cc

DT Fuel

CH Foam + DT

5 CH

.122 cm

.144 cm

.162 cm

CH foam = 75 mg/cc

1

10

100

1000

0 5 10 15time (ns)

laser power •NRL Direct Drive Target Gain Calculations (1-D) have been corroborated by LLNL and UW.

LLNL/LBNL HIF Target

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%)

Gammas 0.0046 (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

0.013 0.57

Total 154 458

X-ray spectrum is much harder

for NRL direct-drive target

Ion Spectra from Reference NRL Laser-Driven Direct –Drive Target

Slow Ions

Fast Ions

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.

Vaporization Threshold for NRL target in 6.5m graphite chamber:

LLNL target specturm + knock-ons

600

700

800

900

1000

1100

1200

1300

1400

1500

0 0.05 0.1 0.15 0.2 0.25 0.3

Xe Density (Torr)

Init

ial

Wal

l T

emp

erat

ure

(C

)

Wallsurvives

Wallvaporizes

Sombrero >>

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)

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 (~1100oC) while keeping SiC structure temperature below 1000oC 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:

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-17Lioutin

He

BlanketPb-17Li (70% of Thermal Power)

He

FW (30% of Thermal Power)

~50°CIHX

Example Case: For a TFW of ~100-150°C, the

average surface Twall at target injection can be lowered to ~600°C while maintaining a cycle efficiency of 50%

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

• 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 diameter1.5-2.5-mm length1-2% packing fraction

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

Laser-Final Optics Threat Spectra

Final Optic Threat Nominal Goal

Optical damage by laser >5 J/cm2 threshold (normal to beam)

Nonuniform ablation by x-rays Wavefront distortion </3 (~100 nm)Nonuniform sputtering by ions 6x108 pulses in 2 FPY:

2.5x106 pulses/atom layer removed

Defects and swelling induced Absorption loss of <1%by -rays and neutrons Wavefront distortion of < /3

Contamination from condensable Absorption loss of <1%materials (aerosol, dust, etc.) >5 J/cm2 threshold

Two main concerns: Damage that increases absorption (<1%) Damage that modifies the wavefront –

spot size/position (200m/20m) and spatial uniformity (1%)

85Þ

stiff, lightweight, actively cooled, neutron transparent substrate

1 m

11.5 m

Safety and Environmental Activities in ARIES-IFE Chamber Assessment

In-vesselActivation

Ex-vesselActivation

Waste Assessment

Waste Metrics

Energy Source Radiological and Toxic Release

Metrics

Evaluation

Decay Heat

Calculation

Tritium and ActivationProduct

Mobilization

Debris or Dust

ChemicalReactivity

ToxicMaterial

(Performed jointly by INEEL, UW, LLNL)

• 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

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

Accident Initiators - Rogue Pellets

1

0.1

0.01

1E-03

1E-04

1E-05

1E-06

1E-07

1E-08

1E-09

1E-10

1E-11

1E-12

Operational occurences

Unlikely event

Extremely unlikely event

Beyond design basis events/severeaccidents

Failure probability per year

Nuclear valve andpump failure rate

Passive pipingfailure rate

Electronic components andcomputer chips

1 shot per 1010

1 shot per 100 millionFrequency of rogue shot

1 shot per 1012

1 shot per 1014

Anticipated event

Crane load drop

"Fly by wire" controlsystems in jets

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