HAPL Blanket Strategy

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
Outline

• Background
• Strategy
• MFE Blanket Options
• Example Trade-Offs
• Summary

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.

4
A 2-Phase Strategy is Envisioned
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

• Participants
• - UCSD and UW ad-hoc individual participation
  as needed
• - Close coordination with first wall/armor
  effort, Materials Working Group and system
  studies

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
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 RD 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 RD)
• - Example of such concepts developed for MFE are
  summarized in the following viewgraphs

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 6Li 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/m2

Struc. Tmaxlt800C Cool. Tin/Tout400/750C
Cool. P lt 1MPa Cycle Eff. 46 (Brayton) Energy
Multip. 1.21 Lifetime 15 MW-a/m2
Need more detailed neutronics and design
integration studies for IFE application
8
Example MFE Ceramic Breeder Be and Ferritic
Steel Concept with He as Coolant (EU HCPB Concept)
Blanket box with stiffening grid and exploded
back wall

• CB (Li2TiO3 or Li4SiO4) 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

Cool. Tin/Tout 300/500C Cool. P 8 MPa Max FS
Temp. lt550C Max. Be Temp. lt 750C Max CB Temp.
lt920 Energy Multip. 1.25 TBR 1.14 Cycle Eff.
37 (Rankine) Lifetime 15MW-a/m2
Blanket breeder unit
9
Example MFE Self-Cooled or Dual Cooled Pb-17Li
Ferritic Steel Concept

• Pb-17Li is an attractive breeder material
• Good tritium breeding capability
• Possibility to replenish 6Li 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. Tmax550C Pb-17Li Tmax700C He Cool.
Tmax/P 480C/14 MPa Cycle Eff. 45
(Brayton) Energy Multip. 1.17 Lifetime 15MW-a/m2

• 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 SiCf/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 mms
  ODS layer at higher temperature FW location

10
Blanket Design Procedure
Develop FW/Blanket concept compatible with FS
as structural material and W as armor
material - Dont 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
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
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. (TcoolTsteam,cycle) gt 10C - Pmin
0.15 bar
13
Effect of Constraint on (TcoolTsteam,cycle) lt
10C
14
Rankine Efficiency and Corresponding Water
Pressures as a Function of Coolant Outlet
Temperature for Example Rankine Cycle
15
Example Brayton Cycle Considered
Set parameters for example calculations - DT
between coolant and He in HX 50C - Minimum He
temperature in cycle (heat sink) 35C -
3-stage compression - Optimize cycle
compression ratio (but lt 3.5 not limiting
for cases considered) - Cycle fractional DP
0.07 - Turbine efficiency 0.93 - Compressor
efficiency 0.89 - Recuperator effectiveness
0.95
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 750C - Pb-17Li
700C - Ceramic breeder/He
500C 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
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!