Transcript Status of Advanced Design Studies and Overview of ARIES

Overview of US Power Plant Studies:
A) Results from ARIES-IFE Study
B) Plans For Compact Stellarator
Farrokh Najmabadi
US/Japan Workshop
October 9-11, 2003
UC San Diego
Electronic copy: http://aries.ucsd.edu/najmabadi/TALKS
ARIES Web Site: http://aries.ucsd.edu/ARIES
ARIES Program charter was expanded in
FY00 to include both IFE and MFE concepts
ARIES activities in FY03:
 ARIES-IFE study was continued for another year (~50% of the
effort):
 The ARIES-IFE study is now officially completed.
 Work in FY03 was focused on thick-liquid wall concept (i.e.,
HYLIFE)
 Results from 2001 and 2002 research will appear in Journal of
Fusion Science & Technology (pre-prints available on ARIES Web
site).
 ARIES compact stellarator (ARIES-CS) was started (~50% of
effort)
 This is a three-years study
 All of ARIES Team effort will be devoted to ARIES-CS in FY04.
Selected Results from
ARIES-IFE Studies
(Laser-Driven Direct-Drive Systems)
ARIES Integrated IFE Chamber Analysis and
Assessment Research Is An Exploration Study
Objectives:
 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.
Approach:
 Six classes of target were identified. Advanced target designs from NRL (laserdriven direct drive) and LLNL (Heavy-ion-driven indirect-drive) are used as
references.
 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 research these classes of chambers in series with the entire team focusing on
each.
Reference Direct and Indirect Target Designs
NRL Advanced Direct-Drive Targets
1 m CH +300 Å Au
LLNL/LBNL HIF Target
CH Foam + DT
.195 cm
DT Fuel
.169 cm
DT Vapor
0.3 mg/cc
.150 cm
CH foam
 = 20 mg/cc
5  CH
CH Foam + DT
.162 cm
DT Fuel
.144 cm
.122 cm
DT Vapor
0.3 mg/cc
1000
laser power
CH foam
 = 75 mg/cc
100
10
1
0
5
ti me (ns)
10
15
•NRL Direct Drive Target Gain Calculations (1-D)
have been corroborated by LLNL and UW.
Energy deposition (J/m3)
Details of Target Spectra Has A Strong
Impact on the Thermal Response of the Wall
2
Energy
Deposition
(J/m ) of
inPenetration
C and W
Energy
Deposition
as a Function
Slabs
(NRL
Direct
Depth
for 154MJ
154 MJ NRL
DDDrive
Target Target)
1x10 11
1x10 10
C density = 2000 kg/m 3
W density = 19,350 kg/m
Debris ions, C
Fast ions, W

3

1x10 9 Photons, W
1x10 8

Photons, C
Fast ions, C
1x10 7

Debris ions,W
1x10 6
1x10 -8
1x10 -7
1x10 -6
1x10 -5
1x10 -4
1x10 -3
1x10 -2
Heat fluxes are much lower than
predicted in previous studies:
A much smaller portion of target
yield is in X-rays.
Time of flight of ions spread the
temporal profile of energy flux
on the wall over several s.
A cover gas may not be
necessary for protecting the
chamber wall
Penetration depth (m)

Photon and ion energy deposition falls by 1-2 orders of magnitude
within 0.1 mm of surface.
Dry Wall Concepts
Thermal Response of a W Flat Wall
3000
 NRL direct-drive target in 6.5-m
chamber with no gas protection:
100 microns
1800
1400
1000
600
1.0x10-5
9.0x10-6
8.0x10-6
7.0x10-6
6.0x10-6
5.0x10-6
4.0x10-6
200
3.0x10-6
Convection B.C. at
coolant wall:
h= 10 kW/m2-K
10 microns
2.0x10-6
Evaporation heat
flux B.C at incident
wall
5 microns
2200
1.0x10-6
Energy
Front
1 micron
0.0x100
Coolant at 500°C
2600
Wall Temperature (oC)
3-mm thick W
Chamber Wall
Surface
Time (s)



Temperature variation mainly in thin (0.1-0.2 mm) region.
Margin for design optimization (a conservative limit for tungsten is to avoid
reaching the melting point at 3,410°C).
Similar margin for C slab.
All the Action Takes Place within 0.1-0.2
mm of Surface -- Use an Armor
 Photon and ion energy deposition falls
by 1-2 orders of magnitude within 0.10.2 mm of surface.
Depth (mm):
0
0.02
1
3
Typical T Swing (°C): ~1000 ~300 ~10 ~1
 Beyond the first 0.1-0.2 mm of the surface.
First wall experiences a much more uniform
q’’ and quasi steady-state temperature (heat
fluxes similar to MFE).
~ 0.2 mm Armor
 Use an Armor
 Armor optimized to handle particle and heat flux.
 First wall is optimized for efficient heat removal.
Structural
Material
3-5 mm
 Most of neutrons deposited in the back where blanket and coolant
temperature will be at quasi steady state due to thermal capacity effect
 Blanket design can be adapted from MFE blankets
 Significant high-energy ion flux on the armor.
Coolant
IFE Armor Conditions are similar to those
for MFE PFCs (ELM, VDE, Disruption)
ITER T ype-I
ELM’s
Energy
Locat ion
Time
Max.
Temperature
Frequency
Base
Temperature
ITER VDE’s
<1 MJ/m2
~ 50 MJ/m2
Surface near div. surface
st rike point s
100-1000 µs
~ 0.3 s
melt ing/
melt ing/
sublimat ion
sublimat ion
points
points
Few Hz
~ 1 per 100
cycles
200-1000°C
~ 100°C
ITER
Disrupt ions
~ 10 MJ/m2
surface
~ 1 ms
melt ing/
sublimat ion
points
~ 1 per 10
cycles
~ 100°C
Typical IFE
Operat ion
(direct-drive
NRL target )
~ 0.1 MJ/m2
bulk (~m’s)
~ 1-3 s
~ 1500-2000°C
(for dry wall)
~ 10 Hz
~ >500°C
 There is a considerable synergy between MFE plasma facing components
and IFE chamber armor.
Target injection Design Window Naturally
Leads to Certain Research Directions
 Direct-drive targets (initial T=18K)
are heated during their travel in the
chamber by:
 Friction with the chamber gas
(mainly through condensation heat
flux) requiring
 Lower gas pressure
 Slower injection velocity
 Radiation heat flux from hot first
wall, requiring
 Lower equilibrium temperature
 Faster injection velocity
 Addition of a thin (~70m) foam
improves the thermal response
considerably.
Max.Equilibrium Wall Temp. to Avoid
Vaporization (C)
Design Windows for
Direct-Drive Dry-wall Chambers
3500
Graphite Chamber Radius of 6.5m
Thermal design window
 Detailed target emissions
 Transport in the chamber including
time-of-flight spreading
 Transient thermal analysis of
chamber wall
 No gas is necessary
3000
2500
2000
1500
1000
500
0
0
0.1
0.2
0.3
Xe Density (Torr)
Laser propagation
design window(?)
 Experiments on NIKE
0.4
0.5
0.6
Target injection design window
 Heating of target by radiation and
friction
 Constraints:
 Limited rise in temperature
 Acceptable stresses in DT ice
Wetted-Wall Concepts
Aerosol Generation and Transport is the
Key Issue for Thin-Liquid Wall Concepts
A renewable thin-liquid protection resolve several issues:
 It can handle a much higher heat fluxes compared to solid surfaces;
 It will eliminate damage to the armor/first wall due to high-energy ions.
A renewable thin-liquid protection, however, introduces its own critical issues:
 Fluid-dynamics aspects (establishment and maintenance of the film)
 “Wetted wall:” Low-speed normal injection through a porous surface
 “Forced film:” High-speed tangential injection along a solid surface
 Chamber clearing (recondensation of evaporated liquid)
 “Source term:” both vapor and liquid (e.g., explosive boiling) are ejected
 Super-saturated state of the chamber leads to aerosol generation
 Target injection and laser beam propagation lead to sever constraints on
the acceptable amount and size of aerosol in the chamber.
Two Methods for Establishment of ThinLiquid Walls Have Been Proposed
Liquid Injection
Wetted Film
~5m
X-rays
and Ions
Injection
Point
First Wall
Detachment
Distance xd
Forced Film
We Have Developed Design Widows for
Establishment and Stability of the Protective Film
“Wetted-wall” concept:
 Developed general non-dimensional charts for film stability over a wide
variety of candidate coolants and operating conditions.
 Model predictions are closely matched with experimental data.
 It will eliminate damage to the armor/first wall due to high-energy ions.
“Forced-flow” concept:
 Developed non-dimensional design widows for longitudinal spacing of
injection/coolant/removal slots to maintain attached protective film;
 A wetting first wall surface requires fewer injection slots than non-wetting
surface – Wetting surfaces are more desirable.
 Details are given in Prof. Abdel-Khalik’s Presentation.
Most of Ablated Material Would Be in
The Form of Aerosol
 FLiBe aerosol and vapor mass history in a 6.5-m radius following a
target explosion (ablated thickness of 5.5 mm)
 Most of ablated material remains in the chamber in aerosol form;
 Only homogeneous nucleation and growth from the vapor phase.
There Are Many Mechanism of Aerosol
Generation in an IFE Chamber
 Homogeneous nucleation and growth from the vapor phase
 Supersaturated vapor
 Ion seeded vapor
 Phase decomposition from the liquid phase
 Thermally driven phase explosion
 Pressure driven fracture
 Hydrodynamic droplet formation (May be critical in Thick-liquid Wall
Concepts”)
 Details are given in Dr. Tillack’s Presentation.
ARIES Research Plans
for FY03-FY05
We Have Initiated a Three-Years Study of
Compact Stellarators as Power Plants

Initiation of NCSX and QSX experiments in US; Successful operation of
LHD in Japan and construction of W7X in Germany;

Review committees have asked for assessment of compact stellarator
option as a power plant; Similar interest has been expressed by national
stellarator program.

Such a study will advance physics and technology of compact stellarator
concept and addresses concept attractiveness issues that are best
addressed in the context of power plant studies.

NCSX and QSX plasma/coil configurations are optimized for most
flexibility for scientific investigations. Optimum plasma/coil
configuration for a power plant may be different. Identification of such
optimum configuration will help compact stellarator research program.
ARIES-Compact Stellarator Program Was
Proposed as a Three-year Study
FY03: Assessment of systems options
1. Develop physics requirements and
modules (power balance, stability, a
confinement, divertor, etc.)
2. Develop engineering requirements and
constraints.
3. Explore attractive coil topologies.
FY05: Detailed system design and
optimization
FY04: Exploration of Configuration
Design Space
1. Physics: b, aspect ratio, number of
periods, rotational transform, sheer,
etc.
2. Engineering: configurationally
optimization, management of space
between plasma and coils.
3. Choose one configuration for detailed
design.
Comparison of Power Plant Sizes
m
ARIES-ST
Spherical Torus
3.2 m
8
ARIES-AT
Tokamak
5.2 m
6
Stellarators
|
4
ARIES-CS
8.2 m
2
0
5
FFHR-J
10 m
10
HSR-G
18 m
SPPS
14 m
15
Average Major Radius (m)
|
ASRA-6C
20 m
20
UWTOR-M
24 m
25
Status of ARIES-CS Study
 Because only half of ARIES effort was devoted to ARIES-CS in FY03
and reduction in funding in FY04, the study will probably stretch into
FY 06.
 We have developed two candidate configuration for a self-consistent
evaluation (Details in Dr. Mau’s Presentation).
 Our initial engineering assessment has highlighted maintenance as a
key driver for blanket selection. (Details in Dr. Raffray’s Presentation).
 An ARIES Town-Meeting with Stellarator physicist is planned for Dec.
5-6 in PPPL.
 We should explore possibilities of collaborations in the helical systems
in this workshop.