Thermal-Hydraulic Study of ARIES-CS
Ceramic Breeder Blanket Coupled with a
Brayton Cycle
Presented by A. R. Raffray
With contributions from L. El-Guebaly, S. Malang, X. Wang
and the ARIES team
ARIES Meeting
University of Wisconsin, Madison
June 16-17, 2004
June 16, 2004/ARR
1
Outline
•
Considerations on choice of blanket design and power cycle
•
Ceramic breeder blanket design for ARIES-CS
•
Constraints in evolving design configuration and operating
parameters
•
Brayton cycle configuration
•
Example optimization studies
•
Conclusions and future plans
June 16, 2004/ARR
2
Considerations on Choice of Module Design and
Power Cycle
•
The blanket module design pressure impacts the amount of structure required, and,
thus, the module weight & size, the design complexity and the TBR.
•
For a He-cooled CB blanket, the high-pressure He will be routed through tubes in the
module designed to accommodate the coolant pressure. The module itself under normal
operation will only need to accommodate the low purge gas pressure (~ 1 bar).
•
The key question is whether there are accident scenarios that would require the module
to accommodate higher loads.
•
If coupled to a Rankine Cycle, the answer is yes (EU study)
- Failure of blanket cooling tube + subsequent failure of steam generator tube can lead to
Be/steam interaction and safety-impacting consequences.
- Not clear whether it is a design basis (<10-6) or beyond design basis accident (passive means ok).
•
To avoid this and still provide possibility of simpler module and better breeding, we
investigated the possibility of coupling the blanket to a Brayton Cycle.
June 16, 2004/ARR
3
Low-Pressure Requirement on Module Leads to
Simpler Design
•
Simple modular box design with
coolant flowing through the FW and
then through the blanket
-
-
•
In general modular design well
suited for CS application
-
June 16, 2004/ARR
4 m (poloidally) x 1 m (toroidally)
module
Be and CB packed bed regions aligned
parallel to FW
Li4SiO4 or Li2TiO3 as possible CB
accommodation of irregular first wall
geometry
module size can differ for different port
location to accommodate port size
4
Ceramic Breeder Blanket Module Configuration
•
He flows through the FW cooling tubes in
alternating direction and then through 3-passes in
the blanket
• Initial number and
thicknesses of Be
and CB regions
optimized for
TBR=1.1 based on:
- Tmax,Be < 750°C
- Tmax,CB < 950°C
- kBe=8 W/m-K
- kCB=1.2 W/m-K
- dCB region > 0.8 cm
• 6 Be regions + 10
CB regions for a
total module radial
thickness of 0.65 m
June 16, 2004/ARR
5
Example Brayton Cycle:
350 MWE Nuclear CCGT (GT-MHR) Designed by U.S./Russia
Power Conversion
Module
Generator
Reactor
Core
Turbine
Recuperator
Compressor
Inter-Cooler
Pre-Cooler
June 16, 2004/ARR
Reactor
6
He-Cooled Blanket + Brayton Cycle:
Blanket Coolant to Drive Cycle or Separate Coolant + HX?
•
Brayton cycle efficiency increases with increasing cycle He max. temp. and
decreases with increasing cycle He fractional pressure drop, DP/P
-
-
Using blanket coolant to drive power cycle will increase cycle He DP/P
With a separate cycle He, DP/P can be reduced by increasing system pressure
(~15 MPa)
From past studies on CB blanket with He as coolant, a max. pressure of ~ 8 MPa
has been considered
Utilizing a separate blanket coolant and a HX reduces the maximum He
temperature in the cycle depending on DTHX
•
Tradeoff study required on case by case basis to help decide whether or not
to use separate He for cycle
•
For this scoping study, a separate He cycle and a HX are assumed to enable
separate optimization of blanket and cycle He conditions (in particular
pressure) and to provide independent flexibility with increasing cycle He
fractional pressure drop
June 16, 2004/ARR
7
Two Example Brayton Cycle Configurations Considered
Brayton I:
- A more conventional
configuration with 3-stage
compression + 2 intercoolers and a single stage
expansion
Brayton II:
- A higher performance configuration with 4-stage
compression + 3 intercoolers and 4-stage
expansion + 3 re-heaters
(shown on next slide)
- Considered by P. Peterson
for flibe blanket
June 16, 2004/ARR
8
Brayton II
He Blanket Coolant
Brayton Cycle with 4Stage Compression +
Inter-Coolers, and 4Stage Expansion and
Re-Heaters
4-Stage
Compression
Tin
Tout
Tin T
out
Tin T
out
Tin T
out
Re-Heaters
Heater
1A
2A
1B
2B
1C
5B
5C
4C
4D
4A
5D
6
3
Recuperator
June 16, 2004/ARR
G
e
n
e
r
a
t
o
r
s
2C
5A
4B
Pre-Cooler
1D
2D
4-Stage
Turbine
Expansion
Inter-Coolers
9
Comparison of T-S Diagrams of Brayton I and Brayton II
T
1
Brayton I:
• 3-stage compression + 2 intercoolers and a single stage
expansion
1B
10
2´
2
9´
9
7´
6
8
3
5´
4
S
T
1A 1B 1C 1D
6
5D
4D
5D´
5C´
4C
4B
5B´ 5A´
2D´
2A 2B 2C
2D
• More severe constraint on
temperature rise of blanket
coolant
3
4A
S
June 16, 2004/ARR
Brayton II:
• 4-stage compression + 3
inter-coolers and 4-stage
expansion + 3 re-heaters
10
Procedure for Blanket Thermal Hydraulic and Brayton Cycle
Analysis
• Start with number of breeder and multiplier regions from initial neutronics
optimization calculations to provide the required breeding, TBR=1.1
- 6 Be regions + 10 CB regions for a total module radial thickness of 0.65 m
• Perform calculations for different wall loading by scaling the qvol’’’ in the different
regions and setting the individual region thicknesses and coolant conditions to
accommodate the maximum material temperature limits and pressure drop
constraints.
-
Tmax,Be < 750°C; Tmax,CB < 950°C; Tmax,FS < 550°C or 700°C (ODS)
kBe=8 W/m-K; kCB=1.2 W/m-K
dCB region > 0.8 cm; dBe region > 2 cm
P pump/P thermal < 0.05 (unless specified otherwise)
• Coolant conditions set in combination with Brayton cycle under following
assumptions:
- Blanket outlet He is mixed with divertor outlet He (assumed at ~750°C and carrying ~15%of
total thermal power) and then flown through HX to transfer power to the cycle He with
DTHX = 30°C
- Minimum He temperature in cycle (heat sink) = 35°C
- hTurbine = 0.93; hCompressor = 0.89; eRecuperator = 0.95
- Total compression ratio < 2.87
June 16, 2004/ARR
11
Radial Build from Original
Neutronics Optimization
Calculations
• qvol’’’ based on wall
load of 4.5 MW/m2
and scaled for
different wall loads
• qplasma’’ unspecified
and assumed as 0.5
MW/m2 in all
calculations (unless
otherwise specified)
June 16, 2004/ARR
Radi al Builds
Layer 1, FW Steel
Layer 2, FW Cooling channel
Layer 3, FW Steel
Layer 4, Be #1
Layer 5, CP #1
Layer 6, SB #1
Layer 7, CP #2
Layer 8, Be #2
Layer 9, CP #3
Layer 10, SB #2
Layer 11, CP #4
Layer 12, Be #3
Layer 13, CP #5
Layer 14, SB #3
Layer 15, CP #6
Layer 16, Be #4
Layer 17, CP #7
Layer 18, SB #4
Layer 19, CP #8
Layer 20, SB #5
Layer 21, CP #9
Layer 22, Be #5
Layer 23, CP #10
Layer 24, SB #6
Layer 25, CP #11
Layer 26, SB #7
Layer 27, CP #12
Layer 28, Be #6
Layer 29, CP #13
Layer 30, SB #8
Layer 31, CP #14
Layer 32, SB #9
Layer 33, CP #15
Layer 34, SB #10
Layer 35, CP #16
Breede r+Mu ltipl ier+FW (per modu le ) =
Back wall + Manifold =
Total Blanket Modu le Thickness =
Thickness (m )
4.00E-03
2.00E-02
4.00E-03
2.00E-02
6.00E-03
9.00E-03
6.00E-03
2.20E-02
6.00E-03
1.00E-02
6.00E-03
2.50E-02
6.00E-03
1.00E-02
6.00E-03
3.00E-02
6.00E-03
1.00E-02
6.00E-03
1.10E-02
6.00E-03
4.00E-02
6.00E-03
1.30E-02
6.00E-03
1.40E-02
6.00E-03
5.40E-02
6.00E-03
1.80E-02
6.00E-03
2.00E-02
6.00E-03
2.00E-02
6.00E-03
0.45 m
0.2 m
0.65 m
q'''(MW/m3)
5.48E+01
8.93E+00
4.99E+01
2.17E+01
2.36E+01
4.70E+01
2.15E+01
1.65E+01
1.87E+01
3.67E+01
1.68E+01
1.25E+01
1.44E+01
4.04E+01
1.29E+01
9.22E+00
1.07E+01
3.71E+01
9.54E+00
3.38E+01
8.41E+00
5.77E+00
6.64E+00
2.13E+01
5.84E+00
1.85E+01
5.06E+00
3.25E+00
3.77E+00
1.04E+01
3.27E+00
7.49E+00
2.81E+00
6.60E+00
2.42E+00
12
Example Optimization Study of CB Blanket and Brayton Cycle
• Cycle Efficiency (h) as a
function of neutron wall load
(G) under given constraints
• The max. h corresponds to G
~3 MW/m2:
Tmax,FS<550°C; h ~ 36.5%
Tmax,FS<700°C; h ~ 44%
T
D
<750°C;T
max,Be
=0.65m; DT
HX
=30°C
=750°C
out,div
q''
0.5
<950°C
max,CB
blkt,radial
0.55 T
Cycle Efficiency
• For a fixed blanket thickness
(Dblkt,radial) of 0.65 m (required
for breeding), a maximum G
of 5 MW/m2 can be
accommodated with:
Tmax,FS<550°C; h ~ 35%
Tmax,FS<700°C; h ~ 42%
0.6
=0.5 MW/m
Brayton with
4-comp.+ 4-exp.
T
<700°C
2
plasma
max,ODS-FS
P
/P
thermal
>>0.05
0.45
T
0.4
Brayton with 3comp.+ 1-exp.
P
0.35
<700°C
max,ODS-FS
pump
T
/P
<0.05
thermal
<550°C
max,FS
P
pump
• The max. h ~ 47% for G ~3
MW/m2 for Brayton II.
pump
/P
<0.05
thermal
0.3
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
2
Neutron Wall Load (MW/m )
• However, as will be shown,
Ppump/Pthermal is unacceptably
high in thisJuneBrayton
II case.
16, 2004/ARR
13
5.5
6
Corresponding He Coolant Inlet and Outlet Temperatures
T
<950°C; DT
<750°C; T
max,Be
max,CB
HX
=30°C
2
Ppump /Pthermal<0.05; q''plasma=0.5 MW/m ; Dblkt,radial =0.65m
800
Blanket He Coolant Temperature (°C)
T
<550°CT<700°C
<700°C
Blanket
= 650
°C
He,out
Brayton comp.+exp.stages: 3+1; 3+1; 4+4
DP/P
max,FS
700
0
• Difference in blanket He
inlet and outlet temperatures
much smaller for Brayton II
because of reheat HX
constraint
0.02
0.05
600
Outlet
0.07
- Major constraint on
accommodating temperature
and pressure drop limits
0.1
500
Inlet
400
300
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
2
Neutron Wall Load (MW/m )
June 16, 2004/ARR
14
Corresponding Maximum FS Temperature
<950°C; DT
<750°C; T
T
max,CB
max,Be
HX
=30°C
2
Ppump /Pthermal<0.05; q''plasma=0.5 MW/m ; Dblkt,radial =0.65m
800
= 650 °C
T
Blanket<700°C
<550°C
He,out <700°C
Tmax,FS
750
• For lower G (<~3 MW/m2),
Tmax,FS limits the
combination of blanket
outlet and inlet He coolant
temperatures
3+1
Brayton compres. + expans. stages:
FS Temperature (°C)
700
4+4
650
600
• For higher G(>~3MW/m2),
Tmax,CB and Tmax,Be limit
3+1
the combination of blanket
outlet and inlet He coolant
temperatures
550
500
FW
Blkt Cooling Plate
450
400
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
2
Neutron Wall Load (MW/m )
June 16, 2004/ARR
15
Corresponding Ratio of Pumping to Thermal Power for Blanket
He Coolant
• An assumed limit of
Ppump/Pthermal < 0.05 can be
accommodated with
Brayton I.
• With Brayton II the
smaller coolant
temperature rise requires
higher flow rate (also for
better convection) and
Ppump/Pthermal is much
higher particularly for
higher wall loads
• On this basis, Brayton II
does not seem suited for
this type of blanket as the
economic penalty
associated with pumping
power is too large
June 16, 2004/ARR
16
Effect of Changing Blanket Thickness on Brayton Cycle Efficiency
0.6
T
<750°C;T
max,Be
<950°C
• Decreasing the total
blanket thickness to
from 0.65 m to 0.6 m
allows for
accommodation of
slightly higher wall
load, ~ 5.5 MW/m2
and allows for a gain
of 1-2 points in cycle
efficiency at a given
neutron wall load
max,CB
Brayton with 3-comp.+ 1-exp.
DTHX =30°C;Tout,div= 750°C
0.55
Cycle Efficiency
2
q''
=0.5 MW/m
plasma
T
<700°C; P
0.5
max,ODS-FS
pump
/P
<0.05
thermal
0.45
0.4
D
=0.65m
D
blkt,radial
=0.6m
blkt,radial
• But is it acceptable
based on tritium
breeding?
0.35
0.3
2
2.5
3
3.5
4
4.5
5
5.5
6
2
Neutron Wall Load (MW/m )
June 16, 2004/ARR
17
Effect of Changing the Plasma Surface Heat Flux on Brayton I
Cycle Efficiency
0.6
Cycle Efficiency
0.55
0.5
T
<750°C;T
max,Be
<950°C
max,CB
Brayton with 3-comp.+ 1-exp.
DT =30°C;T
=750°C
HX
• The efficiency decreases
significantly with
increasing plasma
surface heat flux.
out,div
Wall Load = 2 MW/m
T
<700°C
max,ODS-FS
D
=0.65m
2
blkt,radial
• This is directly linked
with the decrease in He
coolant temperatures to
accommodate max. FS
temp. limit in the FW
(700°C).
(see next slide)
0.45
P
pump
/P
thermal
<0.05
up to q'' of 0.8 MW/m
0.4
2
0.35
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
2
Plasma Surface Heat Flux (MW/m )
June 16, 2004/ARR
18
Effect of Changing the Plasma Surface Heat Flux on Blanket He
Temperatures
800
T
<750°C;T
max,Be
Brayton with 3-comp.+ 1-exp.
DT =30°C;T
=750°C
750
HX
He Coolant Temperatures
• The key constraint is
the max. FS temp.
limit in the FW
(700°C).
<950°C
max,CB
700
out,div
Wall Load = 2 MW/m
T
<700°C
max,ODS-FS
D
=0.65m
650
2
• To accommodate the
increase in plasma
heat flux, the He
coolant temperatures
must be decreased, in
particular the outlet
He temperature
blkt,radial
Blkt+Div. outlet
temperature
600
550
Blanket outlet
temperature
500
Blanket inlet temperature
450
400
0.4
0.5
0.6
0.7
0.8
0.9
1
2
Plasma Surface Heat Flux (MW/m )
June 16, 2004/ARR
1.1
• Challenging to
accommodate this
design with a Brayton
cycle for plasma heat
flux much higher than
0.5 MW/m2
19
Observations from Scoping Study of ARIES-CS Ceramic Breeder
Blanket Coupled with a Brayton Power Cycle
•
A Brayton cycle seems possible with He-cooled CB blanket under certain conditions
-
This would remove a potential safety problem associated with steam generator failure in the
case of a Rankine cycle
Blanket coupled to power cycle via a He/He HX
•
Scoping studies indicate the possibility of accommodating G = 5-5.5 MW/m2 for
Tmax,FS<700°C with corresponding h = 0.42-0.43 (for Brayton I cycle) for total blanket
module radial thickness of 0.6-0.65 m (to be set by TBR requirements).
•
For this CB blanket, cycle efficiency optimization seems to correspond to G = 3-3.5
MW/m2 with h = 0.365 for Tmax,FS<550°C and h = 0.44 for Tmax,FS<700°C.
•
A max. h ~ 47% can be obtained for G ~3 MW/m2 with the high performance Brayton
II cycle.
•
However, the smaller coolant temperature rise in this case requires higher flow rate
(also for better convection) and Ppump/Pthermal is unacceptably large (particularly for
higher wall loads).
•
On this basis, the Brayton II cycle does not seem suited for this type of blanket as the
economic penalty associated with pumping power is too large
20
June 16, 2004/ARR
Observations from Scoping Study of ARIES-CS Ceramic Breeder
Blanket Coupled with a Brayton Power Cycle (cont.)
•
The key constraint in accommodating higher plasma surface heat fluxes is the
maximum FS temperature limit in the FW.
•
To accommodate the increase in plasma heat flux, the He coolant temperatures must
then be decreased, in particular the outlet He temperature, with a significant decrease
in the corresponding cycle efficiency.
•
Challenging to accommodate this design with a Brayton cycle for plasma heat flux
much higher than 0.5 MW/m2
•
These results tend to give a good indication of the relative performance of such a
blanket coupled with a Brayton cycle and provide a good scoping study basis for the
comparative assessment of the different blanket concepts within the next few months.
June 16, 2004/ARR
21
Original Plan for Engineering Activities
Maintenance
Scheme 2
Maintenance
Scheme 1
Blkt/
shld/
Phase 1 div.
1
Phase 2
Blkt/
shld/
div.
2
Blkt/
shld/
div.
3
Optimize
configuration
and maintenance
scheme
Blkt/
shld/
div.
1
Blkt/
shld/
div.
2
Blkt/
shld/
div.
3
Optimize
configuration
and maintenance
scheme
Machine
Parameters and
Coil
Configurations
Maintenance
Scheme 3
Blkt/
shld/
div.
1
Blkt/
shld/
div.
2
Blkt/
shld/
div.
3
Optimize
configuration
and maintenance
scheme
Evolve in
conjunction
with scoping
study of
maintenance
scheme and
blkt/shld/div.
configurations
Optimization in
conjunction with
maintenance
scheme design
optimization
Overall Assessment and Selection
Phase 3
June 16, 2004/ARR
Detailed Design Study and Final Optimization
22
Engineering Activities: Phase 1
•
Perform scoping assessment of different maintenance schemes and
consistent design configurations (coil support, vacuum vessel, shield, blanket).
- Maintenance schemes:
1. Field-period based replacement including disassembly of modular coil system
(e.g. SPPS, ASRA-6C)
2. Replacement of blanket modules through small number of designated
maintenance ports (using articulated boom)
3. Replacement of blanket modules through maintenance ports arranged
between each pair of adjacent modular coils (e.g. HSR)


- Blanket/shield concepts:
1. Self-cooled liquid metal blanket(Pb-17Li) (probably with He-cooled divertor
depending on heat flux)
a) with SiCf/SiC
b) with insulated ferritic steel and He-cooled structure

2. He-cooled blanket with ferritic steel and He-cooled divertor
a) liquid breeder (Li)
b) ceramic breeder
3. Flibe-cooled ferritic steel blanket
(might
need He-cooled divertor depending on heat flux)
June 16, 2004/ARR


23

Future Engineering Activities
•
On the engineering front, we are making good progress in many areas:
- Blanket/vessel/coil configuration
- Maintenance scheme
- Ready to start converging on a couple of concepts for more detailed study within
the next few months
- Start detailed point design study within a year
•
However, one key area where we are lagging is the divertor
- Need better definition of location and heat loads
- Need an idea of divertor design for proceeding with more detailed blanket studies
to make sure that they are fully compatible
- Should be the focus of our immediate effort
- Tools for calculating heat flux on physics side (UCSD,PPPL,RPI)
- Further scoping analysis of generic He-cooled configuration under high heat
fluxes (~10 MW/m2 or more) (UCSD, GaTech)
•
In response to Farrokh’s questions:
- Are we missing analytical tools? Yes, to calculate divertor heat loads and location.
- Are there technical areas receiving insufficient attention? Yes, the divertor.
- What should be the priorities for our research direction? The divertor.
June 16, 2004/ARR
24
Extra Slides
June 16, 2004/ARR
25
Blanket Module Structure
June 16, 2004/ARR
26
• For CB blanket concepts,
max. THe from past studies
~ 450-600°C
0.6
• This range is in 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 needs to
be made based on the specific
design
Cycle Efficiency
0.5
1200
Blanket Cool. Inlet Temp.
for Rankine Cycle:
B
200°C
J
250°C
H
300°C
F
350°C
1
400°C
Brayton
1100
1000
900
800
1F
H
F
H
J
1F
H
J
0.4
H 1
1F
700
J
600
Brayton
1F
H
J
500
F
H
J
B B
JB B B
0.3
400
300
B
200
0.2
300
400 500
600 700
800
100
900 1000 1100 1200 1300
Blanket Coolant Outlet Temperature (°C)
June 16, 2004/ARR
27
Optimum Blanket Coolant Inlet Temperature (Brayton) (°C)
Comparison of Brayton and Rankine Cycle Efficiencies as a
Function of Blanket Coolant Temperature (under previously
described assumptions)