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