1. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL An Overview of the DOE Advanced Gas Reactor Fuel Development and Qualification Program David Petti Technical Director AGR Program

2. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL 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 Fuel Safety Limits Fuel Kernel (UCO, UO 2 ) Coated Particle Outer Pyrolytic Carbon Silicon Carbide Inner Pyrolytic Carbon Porous Carbon Buffer Severe Accident Behavior Containment And Barriers And Defense in Depth Mechanistic Accident Source Term PARTICLES COMPACTS FUEL ELEMENTS

3. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL 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

4. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL Key Differences between German and US fuel are related to coating not performance Coating rate used to make PyC (affects 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 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 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 caused failures US German Weak interface Strong interface Columnar SiC Small grained SiC Isotropic PyC Anisotropic PyC

5. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL 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  m 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

6. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL 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)

7. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL Why Do Additional AGR Fuel Work? - Comparison of Fuel Service Conditions Germans qualified UO 2 TRISO fuel for pebble bed HTR-Module –Pebble; 1100°C, 8% FIMA, 3.5 x 10 25 n/m 2, 3 W/cc, 10% packing fraction Japanese qualified UO 2 TRISO fuel for HTTR –Annual compact; 1200°C; 4% FIMA, 4x10 25 n/m 2, 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, 4-5x10 25 n/m 2, 6-12 W/cc, 35% packing fraction –UCO TRISO fuel in compact form

8. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL Coated Particle Fuel Fabrication Fuel Qualification Analysis Methods Development & Validation Coated Particle Fuel Fabrication Fuel Qualification Analysis Methods Development & Validation Fuel Performance Modeling Post Irradiation Examination & Safety Testing Fuel Supply Program Participants INL, ORNL BWXT, GA NGNP/AGR Fuel Program Elements Fission Product Transport & Source Term Fuel and Materials Irradiation

9. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL Overview of AGR Program Activities PurposeIrradiation Safety Tests &PIE Models AGR-1 AGR-2 AGR-3&4 AGR-5&6 AGR-7&8 Early lab scale fuel Capsule shakedown Coating variants German type coatings Fuel and Fission Product Validation Fuel Qualification Proof Tests Failed fuel to determine retention behavior Production scale fuel Performance Demonstration AGR-1 AGR-2 AGR-3&4 AGR-5&6 AGR-7&8 Update & Fuel Performance And Fission Product Transport Models Validate Fuel Performance And Fission Product Transport Models feedback

10. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL AGR-1 Related Activities Fab baseline & variant particles Characterize Particles Fab & Characterize Compacts Ship to INL Inspect & insert into capsules Complete test train fab Complete, install & checkout gas control system Complete checkout & install fission product monitor Complete cubicle cleanout Safety analysis and training Begin AGR-1 Irradiation Critical dimensions & HM loadings to size gas gap Ready to Insert AGR-1 Certified Data Package Confirmatory analysis, update pretest prediction, finalize test plan Characterization Data Complete QA Hold

11. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL AGR-1 Baseline and Coating Variants (on 350 µm diameter UCO kernels) CGF = 0.3 T = 1265°C  =1.91 g/cc 1500°C 1.5% MTS ~1425°C ~1.5% MTS OPyC Layer: Same as IPyC baseline All continuous coating Note: Choice of Variant 3 selection to be based on TCT recommendation supported by batch characterization data. Goal: PyC with low anisotropy and low permeability And acceptable Surface connected porosity CGF = 0.3 T = 1290°C  =1.85 g/cc CGF = 0.45 T = 1265°C  =1.92 g/cc CGF = 0.3 T = 1265°C  =1.91 g/cc Baseline 2 capsules in AGR-1 Variant 1 Increase Coating Temp Variant 2 Increase Coating Gas Fraction Variant 3a Deposit SiC with Ar 1500°C 1.5% MTS 1500°C 1.5% MTS 1500°C 1.5% MTS CGF = 0.3 T = 1265°C  =1.91 g/cc Goal: fine grained SiC Variant 3b Interrupted between IPyC & SiC

12. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL Optimize Sintering Conditions Production Line 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 1890 o C. 69302 (AGR-1) 59307 59308 LEUCO for AGR-1 Improved carbon dispersion 1890 4 Hours 1890 4 Hours 1890 1 Hour

13. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL AGR-1 Fabrication LEUCO coated particles Fuel Compact Loose kernels Sintered kernels

14. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL All required characterization capabilities have been established Density Dimensions Microstructure/ Ceramography Sphericity BET Surface Area Anisotropy Permeability Crystallite/Grain Size Porosity Uranium Dispersion Heavy Metal Contamination Missing Buffer Fraction Defective SiC Fraction Defective OPyC Fraction Impurities Kernel Buffer IPyC SiC OPyC Particle Compact – Completed – In Progress – Not applicable/required

15. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL 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 3In Process

16. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL AGR-1 Experiment Block Diagram Vessel Wall Capsules In-core He Ne He-3 Silver Zeolite Particulate Filters H-3 Getter Grab Sample FPMS

17. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL AGR-1 Capsule Design Features 6 Capsules with individual temperature control and fission product monitoring Fuel compacts –3 fuel compacts/level –4 levels/capsule –Total of 12 fuel compacts/capsule –Encased in graphite containing B 4 C 3 thermocouples/capsule Thermal melt wires for temperature back-up Fast and thermal flux wires Hafnium & SST shrouds ATR Core Center Graphite Fuel Compact Gas Lines Thermocouples Flux Wire Hf Shroud SST Shroud Stack 1 Stack 3 Stack 2

18. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL 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 0.18 MeV) Minimum fast neutron fluence > 1.5 x 10 25 n/m 2 (E>0.18 MeV) U-235 enrichment 19.7 wt% Packing Fraction 35% (about 1410 particles/cc) Gas Line Thermocouple Fuel Stack Hafnium Shield SST Holder Capsule Spacer Nub

19. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL 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

20. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL 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

21. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL Fission Product Monitors: Assembled equipment for checkout and calibration

22. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL AGR Fuel Program High Level Schedule

23. US Department of Energy (DOE) Advanced Gas Reactor (AGR) Fuel Development and Qualification Program UT-BATTELLE ORNL 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