Steven A. Wright1, Ross F. Radel1, Tom Conboy, and

Gary Rochau1

Sandia National Laboratories1

6771 Advanced Nuclear Technology

505 845 3014, sawrigh@sandia.gov

Presentation to FHR Workshop

ORNL, Oak Ridge , Tennessee

October 20-21, 2010

BRAYTON POWER SYSTEMS FOR FLUORIDE SALT HIGH

TEMPERATURE REACTORS

Advanced Power Conversion Systems

• Contrast Differences Between

• Steam Rankine

– (Superheated, Supercritical, Saturated Vapor)

• Gas Brayton

– Helium Brayton

– S-CO2

• S-CO2 Development Status

G

G

Steam Rankine

Gas Brayton

Superheat

Supercritical

He

Supercritical CO2

η = 41-43% at 510-525C

200 bar, Pr = 2000 /1

η = 45% at 500C

250 bar Pr= ~3000/1

η = 43% at 900 C

70 bar Pr =3/1

η = 42% at 510-525 C

200 bar Pr = 2.6

η = 42% at 650 C

70 bar Pr=30/1 IHC

η = 48% at 650 C

200 bar Pr = 2.6

η = 55% at 650 C

250 bar Pr = 4.1

“Cond & Reheat”

CIT=295 KG

G

η = 37.5% at 380C

250 bar Pr= ~1200

Power Conversion Systems

For Advanced Reactors

Saturated

Vapor

η = 34% at 285C

160 bar Pr= ~1600/1

High Pressure Ratio

Means

Large Turbines

Many Stages

Low Density Steam

Large Condenser

Standard Brayton Brayton with Reheat

G

Steam Power Systems(Saturated, Superheated, & Supercritical)

Te

mp

(C

)

500 C 500 C

370 C

25 C

PWR

/BWR

SHSCWR

Entropy (kJ/kg-K)

Over Simplified

SCWR

FHR

LMR

GCR

Rankine

Cycle

Superheated

Supercritical

Saturated

Vapor

HP

Turb

LP

Turb

ReHeater

(Option)

Steam

Gen

Pump

Feedwater

Heaters

Large, Two-Phases, Well known, Work Well, and Commercially Available

G

Simple Brayton CycleHelium, Air, other Gases

200

400

600

800

1000

1200

19 20 21 22 23 24 25 26 27 28

entropy (j/g*K)

Te

mp

era

ture

(K

)

TurbComp

Recup

Gas

Cooler

HX

Simple, Small, Single Phase, Known Technology for Air, Immature Industry

G

Supercritical CO2 Brayton Cycle

250

350

450

550

650

750

850

0.5 1 1.5 2 2.5 3

Tem

pera

tuar

e (K

)

Entropy (kJ/kg-K)

Cond Brayton

ReComp SCO2 Brayton

ρ=0.1 kg/l, CO2

ρ=0.6 kg/l, CO2

ρ=0.2 kg/l, CO2

TurbCompComp

LT RecupHT Recup

Gas

Cooler

HX

Simple, Very Small, Likely More Efficient, Single Phase, Industrial Development Needed

G

All Brayton Cycles can use Reheat and Interstage Cooling

Heat SinkHeat Sink

200

400

600

800

1000

1200

19 20 21 22 23 24 25 26 27 28

entropy (j/g*K)

Te

mp

era

ture

(K

)

HXTurb

Comp

LT RecupHT Recup

Gas

Cooler

Turb Turb

Inter-

Cooler

Advanced S-CO2 Systems, Very Small, Highly Efficient, Single or Two-Phase,

Future Growth Path Industrial Development Needed

High Pressure Ratio

To Gain Efficiency

Power Conversion and Nuclear Reactor

Outlet Temperature Ranges

S-CO2 Power Conversion Operating Temperatures Matches all Advanced Reactor Concepts

LWR – compactness, condensing cycle appear promising

LWR- highly efficient with S-CO2 Condensing Power Cycles

300 400 500 600 700 800 900 1000 1100Temp C 300 400 500 600 700 800 900 1000 1100 …. 1500Temp C

Open Air Brayton

Brayton He

SCO2 BraytonElectrical Conversion

Technologies

Nuclear Reactors

With Superheat

Compactness 43% 50%

33%

~45%

40%

> 55% with

Steam Comb-Cycle

36% - 40%

Water Sodium He GasCO2

LWR SFR HTGRAGR

Steam Rankine

Reactor Technologies

46%Supercritical

Supercritical CO2 Brayton Cycles

• What is a Supercritical CO2 Brayton Cycle?

• Why is it Important and How is it Used?

• DOE Gen-IV S-CO2 Program

• Major Accomplishments

• Power Generation Example

• Summary & Conclusions

• Problems and Failures

• Unusual Behavior

• Advanced Cycles

What is a Supercritical CO2 Brayton Cycle?

How does it work?

Liquid like Densities with CO2

Very Small Systems,

High Efficiency due to Low Pumping Power

1

25

Compressor

CO2

h= h=

Motor Alternator Waste Heat

Gas Chiller

Turbine

h=

3

4

6

Heater

1

25

Compressor

CO2

h= h=

Motor Alternator Waste Heat

Gas Chiller

Turbine

h=

3

4

6

Heater Turbine

Rejects Heat

Above Critical Point

High Efficiency Non-Ideal Gas

Sufficiently High for Dry Cooling

High Efficiency at Lower Temp

(Due to Non-Ideal Gas Props)

High Density Means Very Small Power Conversion System

Non-Ideal Gas Means Higher Efficiency at Moderate Temperature

Cycle Efficiencies vs Source Temperature

for fixed component efficiency

0%

10%

20%

30%

40%

50%

60%

200 300 400 500 600 700 800 900 1000

Source Temperature (C)

Cy

cle

Eff

icie

nc

y (

%)

1t/1c rec He BraytonSCSF CO2 Brayton3t/6c IH&C He BraytonRankine cyclestoday's efficiency levels

SteamCO2

He

T 31 C (88 F)

S

Liq Vap

Critical Point

Critical Point

88 F / 31 C

1070 psia / 7.3 MPa

He Turbine

(300 MWe)

1 m

Steam Turbine (250 MWe)

S-CO2 (300 MWe)

60% Density of Water

20%

10%

Comp.

Key Features to a Supercritical Brayton Cycle

• Peak Turbine Inlet Temp is well matched to a Variety of

Heat Sources (Nuclear, Solar, Gas, Coal, Syn-Gas, Geo)

• Efficient ~43% - 50% for 10 - 300 MWe Systems

– 1000 F (810 K) ~ 538 C Efficiency = 43 %

– 1292 F (1565 K) ~ 700 C Efficiency =50%

• Standard Materials (Stainless Steels and Inconels )

• High Power Density for Conversion System

– ~30 X smaller than Steam or 6 X for Helium or Air

– Transportability (Unique or Enabling Capability)

– HX’s Use Advanced Printed Circuit Board Heat Exchanger

(PCHE) Technology

• Modular Capability at ~10-20 MWe

– Factory Manufacturable (10 MW ~ 2.5m x 8m)

AdvancedHeat Exchangers Meggit / Heatric Co.

Modular & Self ContainedPower Conversion Systems~ 1.5 m x 8 m

12’

Steam Turbine Turbine Building

Efficiency at Lower Operating Temps

Standard Materials, Small Size

Modular & Transportable

AFFORDABLE and FABRICABLE

S-CO2

Fabricated and Testing

1.5” Compressor

70 hp

Supercritical CO2 Cycle Applicable to

Most Thermal Sources

7

1

2

3

5

6

8

CompressorsTurbine

HT Recup4

Alternator Waste Heat

Chiller

LT RecupCO2

Solar

Fossil

Supercritical CO2

Brayton Cycle

INERI

NRCan CANMET &

SASK Power

DOE-NE

Gen IV

Nuclear

(Gas, Sodium, Water)

Naval

Sequestration Ready

SNL Solar Tower

EERE

Geothermal

S-CO2 Power Cycles for Reactors

NGNP

High Temperature

Gas Cooled Reactor

850-900 C

Sodium Cooled

Reactor

500-550 C

LWRs

Pressurized

Water Reactor

330 C

Potential SMR

Applications

2

3

6

8

CompressorsTurbine

HT

Recup

4 7

Alternator Waste Heat

Cooler

LT

Recup

CO2

5

2

3

6

8

CompressorsTurbine

HT

Recup

4 7

Alternator Waste Heat

Cooler

LT

Recup

CO2

5

2

3

6

8

CompressorsTurbine

HT

Recup

4 7

Alternator Waste Heat

Cooler

LT

Recup

CO2

5

2

3

6

8

CompressorsTurbine

HT

Recup

4 7

Alternator Waste Heat

Cooler

LT

Recup

CO2

5

2

3

6

8

CompressorsTurbine

HT

Recup

4 7

Alternator Waste Heat

Cooler

LT

Recup

CO2

5

2

3

6

8

CompressorsTurbine

HT

Recup

4 7

Alternator Waste Heat

Cooler

LT

Recup

CO2

5

2

3

6

8

CompressorsTurbine

HT

Recup

4 7

Alternator Waste Heat

Cooler

LT

Recup

CO2

5

2

3

6

8

CompressorsTurbine

HT

Recup

4 7

Alternator Waste Heat

Cooler

LT

Recup

CO2

5

He

He

S-CO2

850 C

650C

450C

800 C

600 C

~ 54 %

~ 46 %

~ 50 % Efficiency

(S-CO2 Brayton)

~ 44 % Efficiency

(S-CO2 Brayton)

Sodium

525C

~ 40 % Efficiency

(S-CO2 Recup Rankine

Condensing Brayton)

315C

LWRs

SFRs

GCRs

Inventory Control

Volume

PCHE

Gas

Chiller

(0.5 MW)

TAC - B(not installed)

TAC - A

Flow Meters

PCHE Recup

(up to 1.6 MW)

260 kW Heater

High Temp

PCHE Recuperator

2.2 MW

Electrical Immersion Heaters

130 kW each, ASME

810 K / 1000 F @ 2600 psia

PCHE Gas Precooler

0.5 MW

Turbo-Alternator-Compressor

Main Compressor, 124 kWe

Turbo-Alternator-Compressor

Re-Compressor, 122 kWe

Motor/Alternator Controller

High Temp

PCHE Recuperator

2.2 MW

Electrical Immersion Heaters

130 kW each, ASME

810 K / 1000 F @ 2600 psia

PCHE Gas Precooler

0.5 MW

Turbo-Alternator-Compressor

Main Compressor, 124 kWe

Turbo-Alternator-Compressor

Re-Compressor, 122 kWe

Motor/Alternator Controller

Supercritical S-CO2

Brayton CycleDOE-Gen IV

Key Technology

Turbo- Alternator Compressor Design with Gas Foil

Bearings ( 24” Long by 12” diameter)

Tie Bolts (Pre-stressed)

Turbine

Compressor

Laby Seals

Journal BearingThrust Bearing

Stator

Water Cooling PM Motor Generator

Low Pressure Rotor Cavity

Chamber (150 psia)

Gas-Foil Bearings

5

6

h = .85

Waste Heat

Coolers

531 kW

3

23

7

h= 0.66

Re-CompTurb-2

M-CompTurb-1 Alt-1Alt-2

1

T=305 K

P=7690 kPa

T=324 K

P=13842 kPa

T=389 K

P=13727 kPa

T=698 K

P=13612 kPa

T=750 K

P=7885 kPa

T=810 K

P=13499 kPa

4

8T=418 K

P=7820 kPa

T=335 K

P=7755 kPa

Heaters

783 kW

Heaters

2232 kWHeaters

610kW

126 kW 126 kW213 kW178 kW

87 kW 51 kW

h= 0.71 h = .85

5.77 kg/s 5.77 kg/s 3.46 kg/s

2.3 kg/s

3.15 kg/s

2.58 kg/s

Gen IV Split-Flow Re-compression

S-CO2 Brayton Cycle Design Goal

Tie Bolts (pre-stressed)

Gas Foil Journal

& Thrust Bearings

Motor/Alternator Stator

Gas Foil

Journal

Bearing

H2O Cooling Channels

for PM Alternator

Low Pressure (250 psia)

Chamber for PM Alternator

TurbineCompressor

Permanent Magnet

Tie Bolts (pre-stressed)

Gas Foil Journal

& Thrust Bearings

Motor/Alternator Stator

Gas Foil

Journal

Bearing

H2O Cooling Channels

for PM Alternator

Low Pressure (250 psia)

Chamber for PM Alternator

TurbineCompressor

Permanent Magnet

Tie Bolts (pre-stressed)

Gas Foil Journal

& Thrust Bearings

Motor/Alternator Stator

Gas Foil

Journal

Bearing

H2O Cooling Channels

for PM Alternator

Low Pressure (250 psia)

Chamber for PM Alternator

TurbineCompressor

Permanent Magnet

S-CO2 Development Status (Brayton Loop)

• S-CO2 Brayton Loop Summary– First Operations (July 2009)

– Split Flow with Dual Turbo-Compressors (Dec. 2010)

– Recuperator Installed in February 2010

– First Power Production (March 2010, 430 F)

– Startup Up Issues Due to Low Temperature High Density Fluids

• Startup Procedures and Methods Developed and Successful

– Two Heaters added (total of 0.52 MW) (Oct-Dec 2010

– High Temperature Recuperated Added (Oct-Dec 2010)

– Commercialization Strategy for 10 MW Demo System Development Initiated

• Future Activities– Increase Heater Power and Facility Cooling Capabilities

– Increase Turbine Inlet Temperature (Design 1000 F)

– Ship to SNL Facility (Sep 2011)

– 10 MWe demonstration, Concept Design and Funding Path Developed

– Research on Mixed Fluids

– Research on Condensing Cycle

Inventory Control Volume

PCHEGas

Chiller

(0.5 MW)

TAC - B(not installed)

TAC - A

Flow Meters

PCHE Recup(up to 1.6 MW)

260 kW Heater

Summary and Conclusions• Steam Rankine Power Systems Can be Directly Applied to FHR Reactors

– Commercially Available (Now)

– Efficiency up to ~ 45% at 500 C

– Corrosion Issues

– Fluoride Salt Steam Compatibility Issues?

– Superheated are Larger than Supercritical which are larger than S-CO2 power systems

• S-CO2 Brayton Cycles– S-CO2 Appears Most Suited to Advanced Reactors

– Very Good Efficiency (400C -650 C) Temperature Range (43-48% at 500C and 650 C)

– Peak Temperatures (750-800 C)

– Small due to low pressure ratio and high fluid density

– Advanced S-CO2 Systems have very high efficiency (up to 55%)

• Condensing, CO2-Gas Mixtures change Critical T, Interstage Heating with Condensing

– Remain Small

– Very Good Materials Compatibility

– Reactor Experience in AGRs and MagNox Rx in Great Britain

– Inexpensive fluid

– Single Phase

– Power Systems are Simple (due single phase nature)

– Less Sensitive to Pressure Drop

– Need Development and Not Proven on Commercial Industrial Scale

• Helium Brayton– Commercial Testing in 1950s, Didn’t meet efficiency Goals

– Potential for High Efficiency at High T (> 900 C) , 48%

• But pressure drop, gas costs, leakage, generally reduce efficiency to 43%

– IHC Lowers Improves efficiency at Lower Temp (650 C) eff~43%

• But complexity and Size make Economics questionable