Presentation for the Infocast Advanced SMR Sumposium, March 2011

1. SmAHTR – the Small
Modular Advanced High
Temperature Reactor
Presented to
Infocast SMR Symposium
Washington, DC
March 28, 2011
By
Sherrell Greene
Director, Research Reactors Development Programs
Oak Ridge National Laboratory
greenesr@ornl.gov, 865.574.0626

2. Presentation overview*
• Fluoride salt
• Fluoride salt-cooled high temperature reactors (FHRs)
• SmAHTR FHR design objectives
• Preliminary SmAHTR concept
• SmAHTR concept optimization and design trades
• Principal SmAHTR development challenges
* S. R. Greene, J. C. Gehin, D. E. Holcomb, et al., Pre-Conceptual Design of a
Fluoride-Salt-Cooled Small Modular Advanced high-Temperature Reactor
(SmAHTR), ORNL/TM-2010/199, Oak Ridge National Laboratory, December 2010
2 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

3. What the heck is “fluoride salt” ?
Liquid and “Frozen” 2LiF-BeF2 salt
• “Fluoride salt” is a “halide salt”
• Halide salts are ionic compounds formed from the
combination of a halogen and another element –
commonly, but not exclusively, alkali metals or
alkaline earths
• Examples: LiF, BeF2, KF, NaF, ZrF4, RbF, and
3 Managed by UT-Battelle
mixtures of same
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

4. Fluoride salt-cooled High Temperature
Reactors (FHRs) combine the best
attributes of other reactor types to
provide unique performance benefits
Molten Salt Liquid Metal
Reactors Reactors
• Halide salt coolant • Low pressure
• Metallic materials • Integral primary
• Heat exchangers system
• Passive decay
Gas Cooled Light Water
heat removal
Reactors Reactors
• TRISO fuel • Water / Air-
• Graphite tolerant coolants
• Brayton Power • Excellent coolant
Conversion heat transport
Fluoride Salt Reactors
• Very high temperature
• Low pressure
• Compact system
• Excellent heat transport
4 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

5. FHRs incorporate many attractive
attributes for high-temperature
applications
Coolant
High
Low
(Reactor
High
Working
Volumetric
Low
Primary
Reac>vity
Concept)
Tempa
Heat
Pressurec
With
Air
&
Capacityb
Waterd
Water
(PWR)
" 
" 
Sodium
(SFR)



"
Helium
(GCR)

" " 
Salt
(AHTR)




a FHR system working temperature functionally limited by structural materials capabilities
b High coolant volumetric heat capacity enables ~constant temperature heat addition / removal (η = 1
C
– TC/TH ~ Carnot cycles), compact system architectures, and reduces pumping power requirements
c Low primary system pressure reduces cost of primary vessel and piping, and reduces energetics of
pipe break accidents
d Low reactivity with air and water reduces energetics of pipe break accidents
5 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

6. FHRs are promising candidates for
traditional and non-traditional
applications
• Electricity production
– Large centralized
– Small remote site
• High and Very High-Temperature Process Heat
production
– Large centralized
– Small remote site
• Incremental energy demand growth scenarios
• Compact power applications
6 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

7. FHRs coupled with Brayton power
conversion systems can be highly
efficient electricity generators
FHRs
LWRs
7 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

8. Potential FHR operating temperatures
match many important process heat
applications
LiF-BeF2 (67-33)
nge
re Ra
LiF-NaF-KF (46.5-11.5-42)
Tem peratu
iquid
ide Salt L
NaF-BeF2 (57-43) Fluor
Melts Boils
H2 Production & Coal Gasification
Steam Reforming of Nat. Gas & Biomass Gasification
Cogeneration of Electricity and Steam
Oil Shale/Sand Processing
Petro Refining
0 100 200 300 400 500 600 700 800 900 1000 110 1200 1300 1400 1500 1600 1700
Temperature (C)
8 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

9. SmAHTR and AHTR are products of
ORNL’s investigation of the Fluoride
salt-cooled High-temperature
Reactor (FHR) design space
• Reactor power level AHTR
• Physical size
• System complexity
125 MWt • Operating temperature
• Fuel and core geometry
• Materials 3400 MWt
• Economics
• Applications
9 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

10. SmAHTR design objectives target
both electricity and process heat
production
• Initial concept operating temperature of 700 ºC with
future evolution path to 850 ºC and 1000 ºC
• Thermal size matched to early process heat markets
• Integral, compact system architectures
• Passive decay heat removal
• Truck transportable
• Multi-reactor systems with integral thermal energy
storage
10 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

11. SmAHTR is an “entry-level” very-
high-temperature reactor (VHTR)
Overall System Parameters
Parameter
Value
Power
(MWt
/
MWe)
125
/
50+
Primary
Coolant
LiF-­‐BeF2
Primary
Pressure
(atm)
~1
Core
Inlet
Temperature
(ºC)
650
Core
Outlet
Temperature
(ºC)
700
Core
coolant
flow
rate
(kg/s)
1325
OperaQonal
Heat
Removal
3
–
50%
loops
Passive
Decay
Heat
Removal
3
–
50%
loops
Power
Conversion
Brayton
Reactor
Vessel
PenetraQons
None
11 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

12. SmAHTR is small… B&W mPower
(400 MWt / 125 MWe)
NuScale
(160 MWt / 45 MWe)
SmAHTR 23 m
(125 MWt / 50 MWe)
18.3 m
9m
3.6 m 4.3 m 4.5 m
12 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

13. SmAHTR is a cartridge-core,
integral-primary-system FHR
(1 of 3) (1 of 3)
Downcomer
Skirt
13 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

14. SmAHTR primary system mechanical
design enables rapid component
servicing and refueling
IHX removal DRACS Core Removal Reflector
removal Removal
14 Managed by UT-Battelle
for the U.S. Department of Energy Note: downcomer skirt not shown S. R. Greene, 28 Mar 11

15. Cylindrical annular compacts are
current SmAHTR reference fuel concept
Op>on
2
SmAHTR
Fuel
/
Core
Parameter
Op>on
1
(Reference)
Op>on
3
Solid
Cylindrical
Annular
Cylindrical
Compact
Stringers
Compact
Stringers
Flat
Fuel
Plates
in
Fuel
Assembly
Design
in
Hex
Graphite
In
Hex
Graphite
Hex
ConfiguraQon
Blocks
Blocks
UCO
fuel
kernel
diameter
(microns)
425
500
500
Number
fuel
columns
or
assemblies
19
19
19
Number
fuel
pins
/
plates
per
column
72
15
9
or
fuel
element
Number
graphite
pins
or
plates
per
19
4
9
column
or
fuel
element
IniQal
Fissile
Mass
(kg)
195
357
398
Total
Heavy
Metal
(kg)
987
1806
2015
Enrichment
19.75%
19.75%
19.75%
Avg.
Power
Density
(MW/m3)
9.4
9.4
9.4
Refueling
Interval
(yr)
2.5
4.0
3.1
15 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

16. Three identical in-vessel primary heat
exchangers remove operational heat
Intermediate Heat Transport Loop Parameters
Parameter
Value
Number
of
Primary
Heat
Exchangers
(PHX)
3
Number
PHX
needed
for
full
power
opera>on
2
PHX
PHX
Design
Concept
Single-­‐pass,
tube-­‐in-­‐shell
Primary
Coolant
LiF-­‐BeF2
Primary
Inlet
Temperature
(ºC)
700
Primary
Outlet
Temperature
(ºC)
650
Primary
flow
rate
(kg/s)
350
(x
3)
Secondary
Coolant
LiF-­‐NaF-­‐KF
Secondary
Inlet
Temperature
(ºC)
600
Secondary
Outlet
Temperature
(ºC)
690
Secondary
flow
rate
(kg/s)
247
(x3
)
16 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

17. Three identical in-vessel heat
exchangers remove post-scram decay
heat
In-vessel Passive Decay Heat Removal System Parameters
In-­‐vessel
DRACS
HX
Parameter
Value
PHX Number
DRACS
in-­‐vessel
heat
exchangers
3
Number
DRACS
loops
needed
for
full
2
power
opera>on
DRACS
Salt-­‐to-­‐Salt
Design
Concept
Single-­‐pass,
tube-­‐in-­‐shell
Primary
Coolant
LiF-­‐BeF2
Secondary
Coolant
LiF-­‐NaF-­‐KF
17 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

18. SmAHTR DRACS utilizes salt-to-air,
natural convection heat rejection
Ex-vessel Passive Decay Heat Removal System Parameters
Ex-­‐vessel
DRACS
HX
Parameter
Value
Salt-to-
FLiNaK Air Number
DRACS
3
Radiator
Number
DRACS
needed
for
full
power
2
opera>ons
DRACS
Salt-­‐to-­‐Air
Design
Concept
Ver>cal
finned
tube
radiator
Primary
Coolant
LiF-­‐NaF-­‐KF
Air
Air
Flow
Area
(m2)
4
In-
vessel In-­‐vessel
HX
–
to
–
air
HX
riser
height
(m)
8
DRACS FLiBe
HX Total
chimney
height
(m)
12
~
18 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

19. SmAHTR is good match with Brayton
power conversion technologies
• Options
– Standard closed
– Supercritical closed
– Open air (similar to ANP & HTRE)
• Issues to consider
– Physical size & weight
– Multi-unit clustering
– Heat exchanger pressure differentials
– Efficiency and scalability to higher temperatures
– Tritium leakage
– Compatibility with dry heat rejection
• Trade study underway
19 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

20. SmAHTR thermal energy storage “salt
vault” enables clustering of multiple
reactors
• Liquid salt vault acts as
thermal battery
• Salt vault buffers
– reactors from load
– reactors from each other
• Salt selection and salt
vault size can be
optimized for differing
applications
– 125 MWt-hr storage @ 500
–600 ºC requires ~ 13
meter cubic salt tank
20 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

21. Preliminary transient analysis confirms
robust SmAHTR design
1178°C Transient: All cooling pumps trip, 20 s
coast-down, 10 s delayed scram
~1230°C
650°C 700°C
• Peak fuel temperatures during
normal operations are acceptable
• Peak transient fuel temperatures for
loss-of-flow with delayed scram are
acceptable
• Smooth transition to natural
circulation decay heat removal
21 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

22. Materials R&D will pace evolution to
higher operating temperatures
System Element @ 700 ºC @ 850 ºC @ 1000 ºC
Graphite Internals Toyo Tanso IG110 or 430 Toyo Tanso IG110 or 430 Toyo Tanso IG110 or 430
Reactor Vessel Hastelloy-N • Ni-weld overlay on 800H • Interior-insulated low-
• Insulated low-alloy steel alloy steel
• New Ni-based alloy
Core barrel & Hastelloy-N • C-C composite • C-C composite
other internals • New Ni-based alloy • SiC-SiC composite
• New refractory metal
Control rods and • C-C composites • C-C composites • C-C composites
internal drives • Hastelloy-N • Nb-1Zr • Nb-1Zr
• Nb-1Zr
PHX & DRACS Hastelloy-N • New Ni-based alloy • C-C composite
• Double-sided Ni cladding • SiC-SiC composite
on 617 or 230 • Monolithic SiC
Secondary (salt- Coaxial extruded 800H • New Ni-based alloy ?
to-gas) HX tubes with Ni-based • Coaxial extruded 800H
22 Managed by UT-Battelle
layer tubes with Ni-based layer
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

23. An integrated S&T strategy is needed
to deliver on FHR promise
• Fuels:
– Continue and optimize on-going TRISO fuels S&T
• Materials:
– High-nickel alloys, graphite, C-C composites, and SiC
– Optimized salts
• Components
– Heat exchangers
– Pumps
– Valves
– Instrumentation
• Open and closed Brayton Cycle power conversion
23 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

24. Summary
• FHRs are a new class of reactor that leverages best features of
traditional reactors
• SmAHTR is a small, “entry-level” VHTR concept
– explores the small modular FHR design space
• SmAHTR design objectives target :
– process heat production and electricity generation
– ease of transport and deployment
– long-term evolvability to higher efficiency electric generation and higher
temperature process heat applications
• Present concept demonstrates feasibility and promise
• Present concept is not optimized
– Fuel / core geometry (fixed, pebble-bed, etc.)
– Power density
– Mechanical design
– Salt vault
24
– Conduct of operations
Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

25. Backup
25 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

26. The potential benefits and challenges
of FHRs stem from fundamental
materials characteristics
High
coolant
High
coolant
volumetric
melQng
heat
capacity
temperature
26 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

27. FHR salt coolant heat transfer
technologies were successfully
demonstrated in MSRE for > 26,000 hr
Molten Salt Reactor Experiment
(1965 – 1969)
MSRE LiF-BeF2 Secondary Coolant Loop 600 ˚C LiF-BeF2 / Air Blast Radiator
27 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

28. Four fuel assembly concepts are under
consideration (3 fixed core and pebble-bed)
Solid cylindrical
compact stringers
Annular cylindrical
compact stringers
Hex-plate
fuel assemblies
Pebble Bed
• Cylindrical fuel assembly O.D. = 34 cm
• Plate fuel assembly O.D. = 43 cm
28 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11

29. SmAHTR employs a two-out-of-three
approach for operational and decay
heat removal
29 Managed by UT-Battelle
for the U.S. Department of Energy
S. R. Greene, 28 Mar 11