US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
An Overview of the DOE Advanced
Gas Reactor Fuel Development
and Qualification Program
David Petti
Technical Director
AGR Program
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
Coated Particle Fuel Performance Is at the
Heart of Many of the Key Pieces of the Safety
Case for the NGNP
Normal Operation
Source Term
Containment
And
Barriers
And
Defense in
Depth
PARTICLES
Outer Pyrolytic Carbon
Silicon Carbide
Inner Pyrolytic Carbon
Porous Carbon Buffer
Mechanistic
Accident
Source Term
COMPACTS
Coated Particle
Severe
Accident
Behavior
Fuel Kernel
(UCO, UO2)
Fuel Safety
Limits
FUEL ELEMENTS
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
Why Additional Fuel Work is Needed
Comparison of German and US EOL Gas Release
Measurements from Numerous Irradiation Capsules
Only German fuel had excellent EOL performance
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
Key Differences between German and US fuel are
related to coating not performance
US
• Coating rate used to make PyC (affects
German
•
•
•
•
permeability and anisotropy of layer; US is
low which reduces permeability and
increases anisotropy; German is high which
reduces anisotropy and increases
permeability)
Nature of the coating process. US used
Isotropic PyC
interrupted coating. Germans used
uninterrupted coating. Interrupted coating
and tabling led to metallic inclusions (from
the tabling screens) in the SiC layer creating
weak particles
Nature of the interface between SiC and
IPyC (German fingered interface is strong
Strong interface
and US is weak which causes debonding)
Microstructure of SiC (German is small
grained and US is large columnar grained;
difference is largely due to temperature used
during SiC coating step)
US had significant iron contamination of
compact matrix which attacked the SiC and
Small grained SiC
caused failures
Anisotropic PyC
Weak interface
Columnar SiC
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
NGNP/AGR Fuel Program Priorities,
Requirements and Approach
•
•
The gas reactor in the US must demonstrate high integrity in-reactor and accident
performance at any operating envelope envisioned the VHTR to have a chance of being
commercialized. The fuel is the sine qua non of the VHTR.
Qualify fuel that demonstrates the safety case for NGNP
– Manufacture high quality LEU coated fuel particles in compacts
– Complete the design and fabrication of reactor test rigs for irradiation testing of
coated particle fuel forms
– Demonstrate fuel performance during normal and accident conditions, through
irradiation, safety testing, and PIE
– Improve the understanding of fuel behavior and fission product transport to improve
predictive fuel performance and fission product transport models
•
•
•
Build upon the above baseline fuel to enhance temperature capability
Lowest risk path to successful coated-particle manufacturing is to “replicate” the proven
German coating technology to the extent possible in an uninterrupted manner on the
AGR particle design (350 mm UCO), incorporating the lessons learned from prior U.S.
fabrication and irradiation experience
Irradiations of more that one type of fuel (variants) are required to provide improved
understanding of the linkage between fabrication conditions, coating properties and
irradiation performance
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
Qualification of TRISO fuel requires
two important conditions to be
demonstrated
•
•
Production of high quality fuel at a manufacturing scale with very few
manufacturing defects (~ 1E-05) - this is the difficult part
– Disciplined control of coating process
– Statistical demonstration (nature of the CVD process) of irradiation and
accident behavior
– Currently cannot establish satisfactory fuel product specification to cover
all aspects of fuel behavior
» Some process specifications are required. Thus, we are qualifying the
coater and the process.
Satisfactory performance for the service/performance envelope. The historical
database suggests this is attainable.
– Normal conditions (temperature, burnup, fast fluence, packing fraction and
power density)
– Accident conditions (hundreds of hours @ 1600°C with no fission product
release)
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
Why Do Additional AGR Fuel Work? Comparison of Fuel Service Conditions
•
•
•
•
Germans qualified UO2 TRISO fuel
for pebble bed HTR-Module
– Pebble; 1100°C, 8% FIMA, 3.5 x
1025 n/m2, 3 W/cc, 10% packing
fraction
Japanese qualified UO2 TRISO fuel
for HTTR
– Annual compact; 1200°C; 4%
FIMA, 4x1025 n/m2, 6 W/cc; 30%
packing fraction
Eskom RSA is qualifying pebbles to
German conditions for PBMR
Without an NGNP design, the AGR
program is qualifying a design
envelope for either a pebble bed or
prismatic reactor
– 1250°C, 15-20% FIMA, 4-5x1025
n/m2, 6-12 W/cc, 35% packing
fraction
– UCO TRISO fuel in compact
form
Packing Fraction
50
Power Density
(W/cc)
Temperature
( C)
30
10
10
German
1250
1100
2
NGNP
25
10
3.0
5.0
Burnup (% FIMA)
Fast Fluence
(x 10 25 n/m2)
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
NGNP/AGR Fuel Program Elements
Fuel Supply
Post Irradiation
Examination &
Safety Testing
Coated Particle
Fuel Fabrication
Fuel and Materials
Irradiation
Fuel Qualification
Fission Product
Transport &
Source Term
Analysis Methods
Development &
Validation
Fuel Performance
Modeling
Program Participants
INL, ORNL BWXT, GA
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
Overview of AGR Program Activities
Purpose
Early lab scale fuel
Capsule shakedown
Coating variants
German type coatings
Irradiation
Safety Tests &PIE
AGR-1
AGR-1
feedback
Production scale fuel
Performance
Demonstration
AGR-2
Failed fuel to determine
retention behavior
AGR-3&4
AGR-3&4
Fuel Qualification
Proof Tests
AGR-5&6
AGR-5&6
Fuel and Fission
Product Validation
AGR-7&8
AGR-7&8
AGR-2
feedback
Models
Update &
Fuel
Performance
And Fission
Product
Transport
Models
Validate
Fuel
Performance
And Fission
Product
Transport
Models
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
AGR-1 Related Activities
Fab baseline & variant
particles
Characterize
Particles
Fab & Characterize
Compacts
Critical dimensions & HM
loadings to size gas gap
Confirmatory analysis,
update pretest prediction,
finalize test plan
Characterization
Data
Complete
Complete
test train fab
Safety analysis
and training
Certified Data
Package
QA
Hold
Ship to
INL
Inspect & insert
into capsules
Ready to
Insert
AGR-1
Complete, install &
checkout gas control system
Complete cubicle
cleanout
Complete checkout & install fission
product monitor
Begin
AGR-1
Irradiation
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
AGR-1 Baseline and Coating Variants
(on 350 µm diameter UCO kernels)
All
continuous
coating
Baseline
2 capsules in
AGR-1
Variant 1
Increase
Coating Temp
Variant 2
Increase
Coating Gas
Fraction
Variant 3a
Deposit
SiC with Ar
Variant 3b
Interrupted
between
IPyC & SiC
Goal: PyC with
low anisotropy
and low permeability
And acceptable
Surface connected
porosity
CGF = 0.3
T = 1265°C
r =1.91 g/cc
CGF = 0.3
T = 1290°C
r =1.85 g/cc
CGF = 0.45
T = 1265°C
r =1.92 g/cc
CGF = 0.3
T = 1265°C
r =1.91 g/cc
CGF = 0.3
T = 1265°C
r =1.91 g/cc
Goal:
fine grained SiC
1500°C
1.5% MTS
1500°C
1.5% MTS
1500°C
1.5% MTS
~1425°C
~1.5% MTS
1500°C
1.5% MTS
OPyC Layer: Same as IPyC baseline
Note: Choice of Variant 3 selection to be based on TCT recommendation supported by batch
characterization data.
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
Optimize Sintering Conditions
Production Line
69302 (AGR-1)
LEUCO for AGR-1
1890 4 Hours
59307
59308
Improved carbon dispersion
1890 4 Hours
1890 1 Hour
Kernel improvement is primarily due to better carbon dispersion during
kernel forming, and less grain growth most likely due to the shorter sintering
time at 1890oC.
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
AGR-1 Fabrication
Sintered kernels
Loose kernels
LEUCO coated particles
Fuel Compact
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
All required characterization capabilities have been
established
Impurities
Defective OPyC
Fraction
Defective SiC
Fraction
Missing Buffer
Fraction
Heavy Metal
Contamination
Uranium
Dispersion
Porosity
Crystallite/Grain
Size
Permeability
Anisotropy
BET Surface Area
Sphericity
Microstructure/
Ceramography
Dimensions
Density
Kernel
Buffer
IPyC
SiC
OPyC
Particle
Compact
– Completed
– In Progress
– Not applicable/required
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
14March06 Status
Product
TRISO
Batch
Fabrication
TRISO
Batch
Characterization
Blend to
Form
Composite
TRISO
Composite
Characterization
Compact
Fabrication
Compact
Characteriza
tion
Baseline

 - pass

 - pass

In Process
Variant 1

 - pass

 - pass
In Process
Variant 2

 - pass

In Process
Variant 3
In Process
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
AGR-1 Experiment Block Diagram
Vessel Wall
He
Ne
He-3
FPMS
Particulate
Filters
Capsules
In-core
H-3
Getter
Silver
Zeolite
Grab Sample
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
AGR-1 Capsule Design Features
•
•
•
•
•
•
Thermocouples
Graphite
6 Capsules with individual
temperature control and
fission product monitoring
Flux Wire
Fuel compacts
– 3 fuel compacts/level
Stack 1
– 4 levels/capsule
– Total of 12 fuel
ATR Core
Stack 2
compacts/capsule
Center
– Encased in graphite
Stack 3
containing B4C
3 thermocouples/capsule
Hf Shroud
Thermal melt wires for
temperature back-up
SST Shroud
Fast and thermal flux wires
Fuel Compact
Gas Lines
Hafnium & SST shrouds
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
Experiment Conditions
•
Minimum compact average burn-up > 14 %
FIMA (134.5 GWd/t)
•
Maximum capsule burn-up > 18 % FIMA
(172.8 GWd/t)
•
Maximum fast neutron fluence < 5 x 1025
n/m2 (E>0.18 MeV)
•
•
•
Gas Line
Fuel Stack
Thermocouple
SST Holder
Minimum fast neutron fluence > 1.5 x 1025
n/m2 (E>0.18 MeV)
Hafnium Shield
U-235 enrichment 19.7 wt%
Packing Fraction 35% (about 1410
particles/cc)
Capsule
Spacer Nub
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
Experiment Conditions
•
Maximum temperature
<1400 ºC
•
Time average peak
temperature of  1250 ºC
•
Time average volume
average temperature of
 1150 +30/-75 ºC
•
Particle power not to
exceed 400 mW/particle
•
Only graphite (with
boron carbide) may
contact fuel specimens
NT11
+2.285e+03
+2.228e+03
+2.171e+03
+2.115e+03
+2.058e+03
+2.001e+03
+1.945e+03
+1.888e+03
+1.832e+03
+1.775e+03
+1.718e+03
+1.662e+03
+1.605e+03
2
3
1
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
Welding of mockups of an AGR-1 capsule and brazing
of tubes to the end cap
These two mockup capsules are straight
within about .010 inch
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
Fission Product Monitors: Assembled
equipment for checkout and calibration
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
AGR Fuel Program High Level Schedule
UT-BATTELLE
ORNL
US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program
Summary
• AGR Fuel Development and Qualification needed to support NGNP
• Highest priority is to demonstrate the safety case for NGNP
• Fuel is based on reference UCO, SiC, TRISO particles in thermosetting
resin (minimum development risk consistent with program objectives)
• Based on Lessons Learned from the past - German coating is the
baseline. Limit acceleration level of the irradiations.
• ‘Science’ based--provides understanding of fuel performance. Modeling
is much more important than in the past US programs.
• Provides for multiple feedback loops and improvement based upon
early results
• Improves success probability by incorporating German fabrication
experience
UT-BATTELLE
ORNL