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HTGR/VHTR Technology Maturation: A DOE Success Story
Dave Petti
Former National Technical Director Advanced Reactor Technology Program
Dave’s view of advanced reactors
• In terms of what limits each reactor system:
– LWRs are thermal hydraulic machines
– SFRs are physics machines
– HTGRs are materials machines
– MSRs are chemistry machines
2
Objectives of VHTR/NGNP R&D
• Key needs: Fuels, Graphite, High Temperature Materials Qualification
• Structure: Focus on needs of the technology
– Established TDO for focus and integration with the project/vendors
– NQA-1 (Quality Engineer embedded into R&D)
– Stayed away from politics
• Fuel program is 15 years old; graphite is ~10 years old and high
temperature materials work was mostly completed about 3 years ago –
original objectives remain valid today!
• Such longevity in a DOE program is rare.
Success breeds success! 3
TRISO Fuel Program Objectives (program started in 2003)
• Make fuel as good as the Germans
– Had never been done in the US
• Demonstrate UCO fuel performance under normal operation (1250°C; 19% FIMA)
– Bold performance envelope; many concerned about high temperature and high burnup
• Demonstrate UCO fuel performance under accident conditions (1600-1800°C in high temperature furnaces
– Never had fuel good enough in the past to do this type of testing
• Provide data to improve and validate models on fuel performance and fission product transport
Sounds easy but it was a lot of
hard work by the team (INL,
ORNL, BWXT and GA)!
• Irradiation: AGR-1 had no particle failures and AGR-2 had 0-1 failure (hard
to tell). Statistically inferred failure rates 10 to 20x better than designer
requirements
• Safety testing: Outstanding performance of UCO TRISO at high
temperatures. Results a factor of 5 to 8x better than designer requirements
• Tremendous amount of detailed PIE: meticulous work on fission product
mass balance to show that the fuel retains key fission products5
1.0E-10
1.0E-09
1.0E-08
1.0E-07
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
Kr-
85
m R
/B U.S. TRISO/BISO
U.S. WAR TRISO/BISO
U.S. TRISO/TRISO
U.S. TRISO-P
German (Th,U)O2 TRISO
German UO2 TRISO
AGR-1
AGR-2
U. S. Fuel German Fuel
U.S. German
Irradiation temperature ( C) 930 - 1350 800 - 1320
Burnup (%FIMA) 6.3 - 80 7.5 - 15.6
Fast fluence (1025 n/m2 ) 2.0 - 10.2 0.1 - 8.5 1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
-100 0 100 200 300 400
Re
leas
e f
ract
ion
Time at temperature (h)
Cs-1341800°C
1700°C
1600°C
NRC Topical Report
in Preparation this
FY on the
Performance
Demonstration of
UCO TRISO fuel
particle
TRISO Fuel Accomplishments: Irradiation, Accident Heating Tests and PIE
Structural
Behavior
Module
Past Failure
Mechanisms
Observed
in PIE
Physio-chemical
Properties
Thermo-
mechanical
Properties
Reactor Service Conditions:
Neutron Flux
Power Density
Fast Neutron Fluence/Damage
Temperature
Thermal
Response
Fission
Product
Release
Fission
Product
Transport
Properties
Failure
Evaluation(Weibull)
Fuel
Attributes
Pieces of
the Model:
the engine
Dimensionality, failure modes to be considered,key material properties
Corrosion
attack
rates of SiC
Constitutive
Relations:
the gasoline
Boundary
Conditions
and
Geometry:
the road
Transitioning models to BISON soon
Overview of Approachfor Particle Fuel Performance Modeling in PARFUME
6
Graphite Program
7
AGC - 3
AGC - 5
Database for previous nuclear graphite grades
900 ºC
1200 ºC
600 ºC
1500 ºC
AGC - 4
AGC - 6
Dose (dpa)
1 3 4.5 6
HTV
AGC - 1AGC - 2
Replaced by HDG-1
and -2: high dose
graphite irradiations
Graphite Accomplishments
• Established analytical measurement laboratories at INL and ORNL to
perform extensive material characterization of graphite. INL lab is being
upgraded to handle irradiated graphite
• Characterized thousands of graphite samples for AGC irradiations
• Detailed characterization of graphite billets from different vendors is
complete
• AGC-1 and 2 are complete. AGC-3 PIE is 90% complete
• AGC-4 irradiation is underway until next Fall. HDG-1 will follow and span CIC
• Lots of data to make strong statistical inferences about variations in material
performance and properties lot-to-lot and within a billet
8
Graphite Characterization Labs at INL and ORNL
Dimensional Change Data and Creep
Establishes graphite lifetime a key
unknown for designers!
9
High Temperature Materials Accomplishments
10
High Temperature Materials Characterization Lab at INL
High TemperatureMechanical and
Environmental Testingof Key Alloys
• Completed initial material screening tests to determine acceptability of candidate alloys for large metallic components in VHTR
• Established test loop to measure impact of impurities on IHX alloys and extended models for predicting He impurity interaction with IHX alloys up to 1000°C
• Developed data to demonstrate that LWR pressure vessel steel (A503/533) can be used in VHTR environment
• Extended code case for Alloy 800H from 760°C to 850°C
• Developed data to codify Inconel 617 for use in VHTR up to 950°C. Draft code case submitted to ASME