Fast Reactor Development: Motivation, Challenges and Recent Advances Presented at NE50 - Symposium on the Future of Nuclear Energy Georgia Institute of Technology November 1, 2012 By Hussein S. Khalil Director, Nuclear Engineering Division Argonne National Laboratory
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Fast Reactor Development: Motivation, Challenges and Recent Advances
Presented at
NE50 - Symposium on the Future of Nuclear Energy Georgia Institute of Technology November 1, 2012 By
Hussein S. Khalil Director, Nuclear Engineering Division Argonne National Laboratory
Overview
Fast reactor characteristics and role in a closed fuel cycle
International development status of sodium cooled fast reactors (SFR)
Fast spectrum enhances actinide fission probability
Limits buildup of higher Pu isotopes and MA
Key for full recycle
Energy, eV
Norm
aliz
ed F
lux /
Leth
arg
y
Probability of fission per absorbed neutron
Motivation for Closing the Fuel Cycle
4
High-Level Waste Toxicity Normalized to Natural Uranium Ore
1.00E-01
1.00E+00
1.00E+01
1.00E+02
1.00E+03
1.00E+04
10 100 1000 10000Time (years)
1X
1XT
1Z
1G
2X
2Z
2G
3M
3T
ALWR spent fuel
No
rmal
ize
d H
azar
d
LWR
LWR + FR Strategies
Time, Years
Radiotoxicity of waste relative to mined U
Increase uranium utilization to >95%
– Related benefits from reduced need for uranium mining & enrichment
Improve waste management, through sharply reduced
– TRU content of waste
– Long-term (>100 y) and integrated heat emission by waste
Typical
Architecture
for Recycle
System
Requirements/challenges
– Favorable impacts: economic, safety, environmental, and proliferation risk
Key technical challenges
– Cost reduction, especially for FR
– Robustness of safety & reliability case
– Fuel fabrication and performance
– Minimal (<1%) TRU losses in recycle
– Durable, leach resistant waste forms
– Cost-effective fuel cycle safeguards
Key coolant characteristics – Low pumping power – Significant heat capacity – High thermal conductivity – Non-corrosive to structural steels – Large margin to coolant boiling (880°C) with low-pressure RCS
Can be exploited in SFR design to achieve passive (intrinsic) safety – Pool configuration for RCS enhances heat capacity – Negative reactivity from coolant temperature increase (+low stored heat in fuel) – Natural circulation flows in heat transport circuits
No coolant voiding or fuel damage in LOF or LOHS without scram accident
Nevertheless, coolant voiding and core compaction hypothesized (non-mechanistically) as reactivity addition mechanisms
High chemical reactivity with air and water must be controlled in design and operation
Sodium Cooled
Fast Reactor (SFR)
5
Nearly 400 reactor-years experience w/SFR in several countries – Experimental, prototype and demonstration units
Fast reactor R&D resumed in the US starting in 2003
– At much reduced scale, as part of the DOE Generation IV and Advanced Fuel Cycle programs
– Currently part of the DOE-NE Advanced Reactor Concepts (ARC) program
U.S. Fast Reactor Program following CRBR
9
Passive shutdown and decay heat removal
Schematic of Metal Fuel Pin (not to scale)
Injection Casting of Metal Fuel Slugs
10
Fuel Slug (U-Pu-10%Zr)
End Plug
Cladding (SS316, D-9 or HT-9) Sodium Bond
Gas Plenum
Pore morphology of irradiated U-10Zr
Fuel Periphery (dominantly a-phase)
10 μm
Fuel Center (dominantly g-phase)
100 μm
Metal Alloy Fuel
(U-Zr or U-Pu-Zr)
Over 40,000 U-Fs pins irradiated in EBR-II through early 1980’s
Approx. 17,000 U-Zr and 700 U-Pu-Zr fuel pins irradiated in 1984-1994
– U-Pu-Zr fuel reached peak burnup of ~20%.
7 metal fuel assemblies irradiated in FFTF
– Lead assembly achieved peak burnup of 16%.
– One assembly contained U-Pu-Zr, which achieved peak burnup of 10%.
Three MA bearing pins fabricated and irradiated to 6% burnup
– Initial composition: 68.2%U, 20.2%Pu, 9.1%Zr, 1.2%Am, and 1.3%Np
– Approximately 40% of the Am was lost during casting due primarily to volatile impurities in the Pu-Am feedstock
– Judicious selection of the cover gas pressure during the melt preparation and the mold vacuum level during casting is expected reduce the Am loss by ~200 times
– Extensive PIE revealed
• Similar U, Pu behavior as in non-MA bearing fuel
• Am follows Zr; precipitates in pores
• Np is sessile
11
Irradiation Experience with Metallic Fuel
Sample history of a typical driver fuel in EBR-II:
– 40 start-ups and shutdowns
– 5 15%-overpower transients
– 3 60%-overpower transients
– 45 loss-of-flow and loss-of-heat-sink tests
Excellent off-normal performance observed
– Transient accommodation
– Run-beyond-cladding-breach performance
– Transient overpower failure margins
– Pre-failure axial extrusion behavior
RBCB Test of Metal Fuel with 12% Burnup
RBCB Test of Oxide Fuel with 9% Burnup
12
Transient and Off-Normal Performance
Intrinsic Safety Demonstration
13
Time, s
-100 0 100 200 300 400
800
700
600
500
400
Outlet Temperature
Tem
per
atu
re, °
C
Time, s
-100 0 100 200 300 400
100
50
0
Primary Flow Rate Pe
rcen
t Time, s
-100 0 100 200 300 400
0.0
- 0.1
- 0.2
- 0.3
- 0.4
Reactivity
Do
llars
Time, s
-100 0 100 200 300 400
Power
Perc
ent
100
50
0
EBR-II Loss-of-Flow w/o Scram Behavior
Two major accidents were simulated in EBR-II tests conducted in Apr. 1986 LOF without scram from
full power LOHS without scram
from full power Tests demonstrated the passive safety potential of SFRs … Pool design provides
thermal inertia Low stored Doppler
reactivity due to high thermal conductivity of metal fuel
Negative feedback from core expansion
Fuel Temperature at Full Power
(Oxide Core)
Initial Coolant Temperature
Fuel Temperature at Full Power
(Metal Core)
Asymptotic Temperature
After LOF
Positive Doppler
Reactivity
Negative Expansion Reactivity
With metallic fuel, lower operating fuel temperature and hence smaller stored Doppler reactivity leads to a much lower asymptotic temperature
14
Benefit of Metallic Fuel in LOF w/o Scram
Current SFR R&D in the U.S.
15
Target significant cost reduction and enhanced assurance of safety & reliability – Commercial deployment by ~mid century
R&D areas – Advanced technologies (power conversion, ISI, refueling, …) – Improved materials – Safety research exploiting HPC capabilities
Research focused and integrated through conceptual
development a sodium cooled SMR concept (AFR-100)
– Reactor power of 250MWt/100MWe
– 30-year refueling interval; no on-site fuel storage
– Transportable from pre‐licensed factory
– Compact layout, with fission gas vented fuel (option) and advanced shielding materials
– High operating temperature
LMRs
16
4S 10 MWe SFR
Toshiba, Japan
PRISM 311 MWe SFR
General Electric, USA
• High power density hence compact core facilitates design of transportable reactor modules
• Efficient U conversion facilitates design for long refueling interval
• Outlet temperature enhances power conversion efficiency and expands output beyond electricity
• Intrinsic safety behavior may expand site options
ARC-100 100 MWe SFR
Adv. Reactor Concepts, USA
SMFR 50 MWe SFR
ANL-CEA-JAEA
Small Modular SFRs Benefits of SFR technology for SMR missions
Breed & Burn
Fast Reactor Concept
17
Fast-spectrum concept fueled with DU DU is converted to Pu w/irradiation Fissile material required only for the
first core, to initiate the conversion
Fission wave propagates from fissile “starter” through adjacent DU zone
Kinf vs. burnup for DU in a fast spectrum
Traveling wave reactor is a particular variant
Candle Concept
(Tokyo Inst. of Tech.)
17
Breed & Burn Concepts
Contemporary interest – CANDLE Reactor (Tokyo Institute of
Technology) – Traveling Wave Reactor (TerraPower) – Energy Multiplier Module (General Atomics) – National Lab and university studies
Drawbacks/development challenges – Low power density in DU assemblies – Large power swings – Reactivity management and control – Stability of power distribution – Demands on fuels and materials
Fuel recycle or “reconditioning” after discharge an option for all concepts
18
Annular layout with central DU zone
– Fission power shifts inward over time
Configured for extended (54 y) operation on the initially loaded fissile and DU assemblies