June 16, 2004/ARR1

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 MeetingUniversity of Wisconsin, Madison

June 16-17, 2004

June 16, 2004/ARR2

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/ARR3

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/ARR4

Low-Pressure Requirement on Module Leads to Simpler Design

• Simple modular box design with coolant flowing through the FW and then through the blanket- 4 m (poloidally) x 1 m (toroidally)

module- Be and CB packed bed regions aligned parallel to FW

- Li4SiO4 or Li2TiO3 as possible CB

• In general modular design well suited for CS application- accommodation of irregular first wall geometry - module size can differ for different port location to accommodate port size

June 16, 2004/ARR5

Ceramic Breeder Blanket Module Configuration• 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

- CB region > 0.8 cm

• 6 Be regions + 10 CB regions for a

total module radial thickness of 0.65 m

• He flows through the FW cooling tubes in alternating direction and then through 3-

passes in the blanket

June 16, 2004/ARR6

Example Brayton Cycle:350 MWE Nuclear CCGT (GT-MHR) Designed by U.S./Russia

Reactor

Power ConversionModule

Generator

Turbine

Recuperator

Compressor

Inter-Cooler

Pre-Cooler

ReactorCore

June 16, 2004/ARR7

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, P/P- Using blanket coolant to drive power cycle will increase cycle He P/P - With a separate cycle He, P/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 THX

• 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/ARR8

Two Example Brayton Cycle Configurations Considered

Brayton II:- A higher performance -

configuration with 4-stagecompression + 3 inter-coolers and 4-stage expansion + 3 re-heaters(shown on next slide)

- Considered by P. Peterson for flibe blanket

IP LPHP

Pout

Compressors

RecuperatorIntercoolers

Pre-Cooler

Generator

CompressorTurbine

To/from In-ReactorComponents or Intermediate

Heat Exchanger

1

2

3

4

5 6 7 8

9 10

1BPin

TinTout

η ,C ad η ,T ad

εrec

Brayton I:- A more conventional

configuration with 3-stage compression + 2 inter-coolers and a single stage expansion

June 16, 2004/ARR9

Brayton II

Generators

Recuperator

Tout Tout Tout ToutTinTinTinTinBrayton Cycle with 4-

Stage Compression + Inter-Coolers, and 4-Stage Expansion and

Re-Heaters

Pre-Cooler Inter-Coolers

4-Stage Compression

4-Stage Turbine Expansion

He Blanket Coolant

Re-Heaters

Heater 1A2A 2B 2C

2D

34A

4B

4C

4D

5A

5B

5C

5D6

1B 1C 1D

June 16, 2004/ARR10

Comparison of T-S Diagrams of Brayton I and Brayton II

4

5´7´

68

99´

10

1

2

3

2´

1B

T

S

Brayton I: • 3-stage compression + 2 inter-

coolers and a single stage expansion

Brayton II:• 4-stage compression + 3

inter-coolers and 4-stage expansion + 3 re-heaters

• More severe constraint on temperature rise of blanket coolant4A

6

1A

2A

3

1B

T

S

5A´

1C 1D

2C2B 2D

4B4C4D

5B´5C´5D´5D

2D´

June 16, 2004/ARR11

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

- CB region > 0.8 cm; Be region > 2 cm

- Ppump/Pthermal < 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

THX = 30°C - Minimum He temperature in cycle (heat sink) = 35°C

- ηTurbine = 0.93; ηCompressor = 0.89; εRecuperator = 0.95- Total compression ratio < 2.87

June 16, 2004/ARR12

Radial Build from Original Neutronics Optimization

Calculations

Radial Builds Thickness (m) q'''(MW/m3)Layer 1, FW Steel 4.00E-03 5.48E+01Layer 2, FW Cooling channel 2.00E-02 8.93E+00Layer 3, FW Steel 4.00E-03 4.99E+01Layer 4, Be #1 2.00E-02 2.17E+01Layer 5, CP #1 6.00E-03 2.36E+01Layer 6, SB #1 9.00E-03 4.70E+01Layer 7, CP #2 6.00E-03 2.15E+01Layer 8, Be #2 2.20E-02 1.65E+01Layer 9, CP #3 6.00E-03 1.87E+01Layer 10, SB #2 1.00E-02 3.67E+01Layer 11, CP #4 6.00E-03 1.68E+01Layer 12, Be #3 2.50E-02 1.25E+01Layer 13, CP #5 6.00E-03 1.44E+01Layer 14, SB #3 1.00E-02 4.04E+01Layer 15, CP #6 6.00E-03 1.29E+01Layer 16, Be #4 3.00E-02 9.22E+00Layer 17, CP #7 6.00E-03 1.07E+01Layer 18, SB #4 1.00E-02 3.71E+01Layer 19, CP #8 6.00E-03 9.54E+00Layer 20, SB #5 1.10E-02 3.38E+01Layer 21, CP #9 6.00E-03 8.41E+00Layer 22, Be #5 4.00E-02 5.77E+00Layer 23, CP #10 6.00E-03 6.64E+00Layer 24, SB #6 1.30E-02 2.13E+01Layer 25, CP #11 6.00E-03 5.84E+00Layer 26, SB #7 1.40E-02 1.85E+01Layer 27, CP #12 6.00E-03 5.06E+00Layer 28, Be #6 5.40E-02 3.25E+00Layer 29, CP #13 6.00E-03 3.77E+00Layer 30, SB #8 1.80E-02 1.04E+01Layer 31, CP #14 6.00E-03 3.27E+00Layer 32, SB #9 2.00E-02 7.49E+00Layer 33, CP #15 6.00E-03 2.81E+00Layer 34, SB #10 2.00E-02 6.60E+00Layer 35, CP #16 6.00E-03 2.42E+00Breeder+Multiplier+FW (per module) = 0.45 mBack wall + Manifold = 0.2 mTotal Blanket Module Thickness = 0.65 m

• 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/ARR13

Example Optimization Study of CB Blanket and Brayton Cycle• Cycle Efficiency (η) as a

function of neutron wall load () under given constraints

• For a fixed blanket thickness (blkt,radial) of 0.65 m (required for breeding), a maximum of 5 MW/m2 can be accommodated with: Tmax,FS<550°C; η~ 35%

Tmax,FS<700°C; η~ 42%

• The max. η corresponds to ~3 MW/m2:

Tmax,FS<550°C; η~ 36.5%

Tmax,FS<700°C; η~ 44%

• The max. η ~ 47% for ~3 MW/m2 for Brayton II.

• However, as will be shown, Ppump/Pthermal is unacceptably high in this Brayton II case.

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6

T,max Be

<750° ;C T,max CB

<950°C

,blkt radial=0.65 ;m T

HX=30°C

T,out div

=750°C

q''plasma

=0.5 /MW m2

( /Neutron Wall Load MW m2)

T,max FS

<550°CP

pump/P

thermal<0.05

3Brayton with-.+1- .comp exp

Brayton with4- .+4- .comp expT

, -max ODS FS<700°C

Ppump

/Pthermal

>>0.05

T, -max ODS FS

<700°CP

pump/P

thermal<0.05

June 16, 2004/ARR14

Corresponding He Coolant Inlet and Outlet Temperatures

0 /P P

0.02

0.05

0.07

0.1

Blanket T,He out

=650°C

300

400

500

600

700

800

1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6

( /Neutron Wall Load MW m2)

T,max FS

<550° C <700°C<700°C .+ . :Brayton comp exp stages3+1;3+1;4+4

Outlet

Inlet

T,max Be

<750° ;C T,max CB

<950° ;C THX

=30°C

Ppump

/Pthermal

<0.05;q''plasma

=0.5 /MW m2;,blkt radial

=0.65m

• Difference in blanket He inlet and outlet temperatures much smaller for Brayton II because of reheat HX constraint- Major constraint on

accommodating temperature and pressure drop limits

June 16, 2004/ARR15

Corresponding Maximum FS Temperature

• For lower (<~3 MW/m2), Tmax,FS limits the

combination of blanket outlet and inlet He coolant

temperatures

• For higher (>~3MW/m2), Tmax,CB and Tmax,Be limit

the combination of blanket outlet and inlet He coolant temperatures

Blanket T,He out

=650°C

400

450

500

550

600

650

700

750

800

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5

( /Neutron Wall Load MW m2)

FW Blkt Cooling Plate

T,max Be

<750° ;C T,max CB

<950° ;C THX

=30°C

Ppump

/Pthermal

<0.05;q''plasma

=0.5 /MW m2;,blkt radial

=0.65m

.+ . :Brayton compres expans stages

4+4

3+1

3+1

T,max FS

<550° C <700°C<700°C

June 16, 2004/ARR16

Corresponding Ratio of Pumping to Thermal Power for Blanket He Coolant

• An assumed limit ofPpump/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

0 /P P

Blanket T,He out

=650°C

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5

( /Neutron Wall Load MW m2)

T,max Be

<750°CT

,max CB<950°C

THX

=30°C

q''plasma

=0.5 /MW m2

,blkt radial

=0.65m

Brayton with4- .+4- .comp expT

, -max ODS FS<700°C

Brayton with3- .+1- .comp expT

, -max ODS FS<700°C

Brayton with3- .+1- .comp expT

, -max ODS FS<550°C

June 16, 2004/ARR17

Effect of Changing Blanket Thickness on Brayton Cycle Efficiency

• 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

• But is it acceptable based on tritium breeding?

0.3

0.35

0.4

0.45

0.5

0.55

0.6

2 2.5 3 3.5 4 4.5 5 5.5 6

Tmax,Be

<750°C;Tmax,CB

<950°C

Brayton with 3-comp.+ 1-exp.ΔT

HX =30°C;T

out,div= 750°C

q''plasma

=0.5 MW/m2

Tmax,ODS-FS

<700°C; Ppump

/Pthermal

<0.05

Neutron Wall Load (MW/m2)

Δblkt,radial

=0.65mΔ

blkt,radial=0.6m

June 16, 2004/ARR18

Effect of Changing the Plasma Surface Heat Flux on Brayton I Cycle Efficiency

• The efficiency decreases significantly with increasing plasma surface heat flux.

• 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)

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0.4 0.5 0.6 0.7 0.8 0.9 1 1.1

T,max Be

<750° ;C T,max CB

<950°C 3Brayton with- .+1- .comp exp

THX

=30° ;CT,out div

=750°C

=2 /Wall Load MW m2

T, -max ODS FS

<700°C

,blkt radial=0.65m

( /Plasma Surface Heat Flux MW m2)

Ppump

/Pthermal

<0.05

0.8 /up to q'' of MW m2

June 16, 2004/ARR19

Effect of Changing the Plasma Surface Heat Flux on Blanket He Temperatures

• The key constraint is the max. FS temp. limit in the FW (700°C).

• To accommodate the increase in plasma heat flux, the He coolant temperatures must be decreased, in particular the outlet He temperature

• Challenging to accommodate this design with a Brayton cycle for plasma heat flux much higher than 0.5 MW/m2

400

450

500

550

600

650

700

750

800

0.4 0.5 0.6 0.7 0.8 0.9 1 1.1

T,max Be

<750° ;C T,max CB

<950°C 3Brayton with- .+1- .comp exp

THX

=30° ;CT,out div

=750°C

=2 /Wall Load MW m2

T, -max ODS FS

<700°C

,blkt radial=0.65m

( /Plasma Surface Heat Flux MW m2)

Blanket inlet temperature

Blanket outlettemperature

+ .Blkt Div outlettemperature

June 16, 2004/ARR20

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 = 5-5.5 MW/m2 for Tmax,FS<700°C with corresponding η042043for 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 = 3-3.5 MW/m2 with η0365forTmax,FS<550°C and η044forTmax,FS<700°C.

• A max. η ~ 47% can be obtained for ~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

• 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 = 5-5.5 MW/m2 for Tmax,FS<700°C with corresponding η042043for 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 = 3-3.5 MW/m2 with η0365forTmax,FS<550°C and η044forTmax,FS<700°C.

• A max. η ~ 47% can be obtained for ~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

June 16, 2004/ARR21

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.

• 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/ARR22

Phase 1

Original Plan for Engineering Activities

Maintenance Scheme 1

Maintenance Scheme 2

Maintenance Scheme 3

Blkt/shld/div. 1

Blkt/shld/div. 1

Blkt/shld/div. 2

Blkt/shld/div. 3

Blkt/shld/div. 2

Blkt/shld/div. 3

Blkt/shld/div. 1

Blkt/shld/div. 2

Blkt/shld/div. 3

Detailed Design Study and Final Optimization

Optimize configuration and maintenance scheme

Machine Parameters and Coil Configurations

Evolve in conjunction with scoping study of maintenance scheme and blkt/shld/div. configurations

Phase 2

Phase 3

Optimization in conjunction with maintenance scheme design optimization

Optimize configuration and maintenance scheme

Optimize configuration and maintenance scheme

Overall Assessment and Selection

June 16, 2004/ARR23

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/SiCb) with insulated ferritic steel and He-cooled structure

2. He-cooled blanket with ferritic steel and He-cooled divertora) liquid breeder (Li)b) ceramic breeder

3. Flibe-cooled ferritic steel blanket (might need He-cooled divertor depending on heat flux)

June 16, 2004/ARR24

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)

• 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)

Yes, the divertor.

Yes, to calculate divertor heat loads and location.

The divertor.

• In response to Farrokh’s questions:- Are we missing analytical tools? - Are there technical areas receiving insufficient attention? - What should be the priorities for our research direction?

• In response to Farrokh’s questions:- Are we missing analytical tools? - Are there technical areas receiving insufficient attention? - What should be the priorities for our research direction?

June 16, 2004/ARR25

Extra Slides

June 16, 2004/ARR26

Blanket Module Structure

June 16, 2004/ARR27

Comparison of Brayton and Rankine Cycle Efficiencies as a Function of Blanket Coolant Temperature (under previously

described assumptions)

B

B B B B BJ

J

JJ J

J

H

HH

HH

H

F

FF

FF

F

11

1 1 1

0.2

0.3

0.4

0.5

0.6

100

200

300

400

500

600

700

800

900

1000

1100

1200

300 400 500 600 700 800 900 1000110012001300

Blanket Coolant Outlet Temperature (°C)

B

J

H

F

1

Brayton

Brayton

Blanket Cool. Inlet Temp.for Rankine Cycle:

200°C

250°C

300°C

350°C

400°C

• For CB blanket concepts, max. THe from past studies

~ 450-600°C

• 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