German TRISO Fuel Performance Envelope and Limits Normal Operations and Accident Conditions

Transcription

1 German TRISO Fuel Performance Envelope and Limits Normal Operations and Accident Conditions Michael J. Kania*, Heinz Nabielek**, Karl Verfondern Forschungszentrum-Jülich (FZJ), Germany * formerly ORNL and KAPL, USA June 23 ** formerly FZJ, Germany and DRAGON, UK IAEA, Vienna

2 German Fuel Development Program (978 to 995) Pebble Bed HTR Concept HTR Prototypes and Design Concepts [AVR, THTR, PNP & HHT, HTR-5, HTR Modul] Partnership between State & Local Governments and German Industry Production Scale Fuel Element Production Full-Scale Irradiation Testing - AVR Real-Time HTR ( ) - European Material Test Reactors (MTRs) Accident Condition Simulation International Cooperation [EU, UK, USA, China, Japan]

3 HTR Spherical Fuel Element Fuel sphere Fuel particle Fuel kernel

4 German UO 2 and (Th,U)O 2 TRISO Particle Designs Nominal Dimensions (μm) TRISO Particle Component LEU UO 2 HEU (Th,U)O 2 Fuel Kernel Diameter 235 U w/o Th/U Ratio n/a Buffer Layer thickness 95 9 IPyC layer thickness 4 4 SiC layer thickness OPyC layer thickness 4 4 TRISO coating design, combines inner and outer LTI PyC layers with a strong, stable SiC layer. This design not only improved clean manufacturing conditions, but also increased the mechanical strength and fission product retention over prior HTI-BISO coated particles.

5 Operating and Performance Requirements for PNP/HHT and HTR Modul Concepts Operating Parameter HTR Pebble Bed Concept PNP-3 HHT-Demo HTR Modul Duration [d] 6 26 Burnup [% FIMA] Fluence [E>6 fj, m -2 ] Central max. temp [ºC] (Cycled) Max. FE power [kw] Performance Requirements Matrix Contamination As-fabricated defects Irradiation-induced defects Accident Conditions

6 Specialized Fuel Particle Irradiation Tests R&D program HEU Program for Process Heat and Gas Turbine Applications LEU Program Variant Variant 2 Variant 3 Coated particle Test goal Particle performance Fission product transport in intact particles Release from kernel Chemical effects (Th,U)O 2 BISO (Th,U)O 2 TRISO UC 2 (UCO) TRISO+ ThO 2 TRISO BR2-P24 BR2-P25 BR2-P23 UO 2 TRISO HFR-P4 SL-P FRJ2-P22 FRJ2-P23 FRJ2-P24 FRJ2-P27 FRJ2-P25 FRJ2-P25 FRJ2-P25 FRJ2-P HFR-P3 HFR-P5

7 Reference Fuel Element Irradiation Tests R&D program Coated particle Fuel Test Elements HEU Program for Process Heat and Gas Turbine Applications LEU Program Variant Variant 2 Variant 3 (Th,U)O 2 BISO (Th,U)O 2 TRISO UC 2 (UCO) TRISO+ ThO 2 TRISO UO 2 TRISO Fuel element performance HFR-K R2-K2 R2-K3 R2-K2 HFR-K3 FE fission product transport - FRJ2-K FRJ2-K FRJ2-K3 FRJ2-K5 Large-scale demonstration AVR 4 AVR 8 AVR 5 AVR 2 AVR 3 AVR 9 AVR 2 Proof tests High burnup tests High temperature tests for hydrogen production etc. HFR-K5 HFR-K6 FRJ2-K5 HFR-EU HFR-EUbis

8 Irradiation Testing in MTRs (Accelerated) and AVR (Real-Time) MRT AVR Thermocouple Purge gas pipe Radiation shields Graphite cup Test fuel element

9 Accumulated Burnup vs. Irradiation Temperature LEU UO 2 TRISO Fuels HEU (Th,U)O 2 TRISO Fuels

10 Fast Fluence (x 25 neut/m 2, E> 6 fj) Accumulated Fast Fluence vs. Irradiation Temperature 8. SL-P/ HFR-P4/ & 2 HFR-P4/ HFR-K3/2 HFR-K5 HFR-K3/3 LEU UO 2 TRISO Fuels HFR-K6 4. HFR-K3/ Phase LEU UO 2 Limits FRJ2-P27/ AVR GLE 3 FRJ2-P27/3 FRJ2-P27/2 HTR Modul Limits. FRJ2-K5/ & 3 FRJ2-K5/2 & FRJ2-K3/ & Temperature ( o C) HEU (Th,U)O 2 TRISO Fuels

11 Performance of LEU UO 2 TRISO in MTR irradiation tests based on EOL 85m Kr R/B values MTR Irradiation Tests HTR Modul Proof Tests Irradiation Test/Capsule Beginning of Life 85m Kr R B BOL Equivalent Failed Particles 85m Kr R B EOL End of Life Equivalent Failed Particles Equivalent Failed Particles SL-P/ 5.8 x -7 ~5+.2 x -6 ~ x -4 HFR-K3/ 2 3 HFR-P4/ 3 FRJ2-K3/ 2 FRJ2-K5/ 2 3 FRJ2-P27/ 2 3 x -9 9 x - 2 x x x -9 2 x -9 8 x - 2. x x - 2. x -. x x x -8 ~ 2 x -7 x -7 3 x -7 ** 4.57 x -5 8 x -8 8 x x -5.6 x -8 7 x x -5.2 x -8 5 x -9 3 x -9.6 x -6. x -5.2 x -7.4 x -4 ~2 ~ x -4 Total for Entire LEU UO 2 Population (24,724) = ~ 7.56 x -5 Total for LEU UO 2 Population in 6-mm Diameter Fuel Spheres (59,88) =.87 x -5 Total for LEU UO 2 Population in Non-standard specimens (8,844) = ~ 2.25 x -4 Irradiation Test/Capsule HFR-K5/ 2 3 HFR-K6/ 2 3 Beginning of Life 85m Kr R B BOL 4.8 x x x -7 5 x - 3 x - 4 x -7 Equivalent Failed Particles ~ to 2 ~3 85m Kr R B EOL.6 x x x -7. x x x -7 End of Life Equivalent In-Reactor Failed Particles Estimated Failure Fraction (upper 95% confidence limit) 5.4 x x -5 Total Proof Test LEU UO 2 Population (6,64) = 2.57 x -5

12 Performance of HEU (Th,U)O 2 TRISO based on MTR irradiation tests EOL 85m Kr R/B values MTR HEU (Th,U)O2 Test Elements Irradiation test/ capsule or sphere Beginning of life Kr 85m R Equiv. B BOL failed particles Beginning of life Kr 85m R Equiv. B EOL inreactor failed particles Estimated failure fraction (upper 95% confidence limit) BR2-P25/ * R2-K2/ FRJ2-P23/ < -7 * < -7 * < -7 * < -7 * FRJ2-K/ 3, FRJ2-P25/ R2-K3/ Total for entire HEU (Th,U)O 2 population (26,664) Total for HEU (Th,U)O 2 population in 6 mm diameter fuel elements (82,72) Total for HEU (Th,U)O 2 population in nonstandard fuel specimens (43,95)

13 AVR test element EOL performance derived from 85 Kr fractional release during equilibration phase of accident simulation testing EOL Release from GLE 3 Spherical Elements Irradiated in AVR (with as-manufactured quality < 6 x -5 at 95% conf. Limit) AVR GLE3 Test Elements Isothermal Tests 6C to 8C AVR GO2 Test Elements.E-3.E-4 One UO 2 Particle Inventory Depressurized Accident Simulation Ramp Tests / 9C to 25C MTR and Module Proof Tests One UO2 Particle Inventory 85 Kr Fractional Release.E-5.E-6.E-7.E Burnup (% FIMA)

14 85 Kr release measurements during constantramp rate accident tests show no evidence of particle failure in AVR elements at EOL (Th,U)O 2 TRISO

15 In-reactor fuel performance comparison between HEU (Th,U)O 2 TRISO and LEU UO 2 TRISO fuels Standard HTGR spherical elements and fuel bodies with (Th,U)O 2 TRISO particles LEU UO 2 TRISO Irradiation testing MTRs Standard Non-stand HEU (Th,U)O 2 TRISO Irradiation testing No. fuel bodies 9 45 No. coated particles (N) 276,68 8,572 No. inreactor failed particles (n) AVR ,6 9 Expected failure fraction (=n/n) One-sided upper 95% confidence limit Total 88 75, MTRs Standard Non-stand ,72 43,95 AVR 9 94,32 Total 39 22,

16 Observations: In-Reactor Performance In-reactor failure levels: Results based on accelerated MTR and real-time AVR irradiation tests - LEU UO2: 2.x -5 (upper 95% C.L.- 9 failures out of 75,852 TRISO particles examined) - HEU (Th,U)O2: 6.5x -5 (upper 95% C.L. - 8 failures out of 22,99 TRISO particles examined) Compared to Performance Requirements: - ~X lower HTR Modul specification - 3X lower PNP/HHT specification Majority of particle failures observed in non-reference fuel specimens, at maximum or higher burnups and above maximum fluence requirements.

17 Accident Condition Simulation Testing conducted is specialized heating facilities KÜFA Heating Furnace A-Test Heating Furnace

18 with specialized fission product detection capabilities Gaseous FPs [Kr, Xe] Condensable FPs [Ag, Cs, Sr]

19 Temperature (C) Heating Scenarios for Demonstrating Accident Testing Performance Limits Isothermal & Constant Ramp Heating Tests HTR Modul D-LOFC Heating Curve C Time (h) Accident LEU UO 2 HEU (Th,U)O 2 Simulation Tests AVR Elements MTR Elements AVR Elements MTR Elements A-Tests - 8 KÜFA Isothermal - 6 C C/8 C C C HTR Module D-LOFC - 62 C - 7 C

20 Isothermal Heating Tests on LEU UO 2 TRISO AVR Elements (GLE 3) 85 Kr Fractional Release 37 Cs Fractional Release.E+ AVR 82/2, 8.6% FIMA, 6C.E+ AVR 82/2, 8.6% FIMA, 6C AVR 82/9, 8.9% FIMA, 6C AVR 82/9, 8.9% FIMA, 6C.E- AVR 88/5, 8.7% FIMA, 6/8C.E- AVR 88/5, 8.7% FIMA, 6/8C AVR 88/33, 8.5% FIMA, 6/8C AVR 88/3, 8.5% FIMA, 6/8C AVR 74/, 6.2% FIMA, 7C AVR 74/, 6.2% FIMA, 7C.E-2 AVR 76/8, 7.% FIMA, 8C.E-2 AVR 76/8 7.% FIMA, 8C AVR 88/4, 7.6% FIMA, 8C AVR 88/4, 7.6% FIMA, 8C 85 Kr Fractional Release.E-3.E-4.E-5 AVR 7/22, 3.5% FIMA, 6C 37 Cs Fractional Release.E-3.E-4.E-5 AVR 7/22, 3.5% FIMA, 6C.E-6.E-6.E-7.E-7.E Heating Time (h).e Heating Time (h)

21 Isothermal Heating Tests on LEU UO 2 TRISO MTR Elements 85 Kr Fractional Release 37 Cs Fractional Release.E+.E+ HFR-K3/, 7.7% FIMA, 6C HFR-K3/, 7.7% FIMA, 6C.E- FRJ2-K3/2, 8.% FIMA, 6C FRJ2-K3/4, 7.6% FIMA, 6/8C.E- FRJ2-K3/2, 8.% FIMA, 6C FRJ2-K3/4, 7.6% FIMA, 6/8C HFR-K3/3,.2% FIMA, 8C - # HFR-K3/3,.2% FIMA, 8C - # HFR-K3/3,.2% FIMA, 8C - #2 HFR-K3/3,.2% FIMA, 8C - #2.E-2.E-2 85 Kr Fractional Release.E-3.E-4.E-5 37 Cs Fractional Release.E-3.E-4.E-5.E-6.E-6.E-7.E-7.E E Heating Time (h) Heating Time (h)

22 Isothermal Heating Tests on HEU (Th,U)O 2 TRISO Elements AVR GO 2 and MTR Elements KÜFA Heating Tests.E+.E-.E-2 A-Test Heating Tests AVR 7/5, 7.% FIMA AVR 7/7, 7.3% FIMA AVR 69/3, 8.6% FIMA AVR 74/24,.2% FIMA AVR 74/2,.9% FIMA AVR 69/28,.% FIMA AVR 7/8, 6.8% FIMA AVR 74/7, 7.% FIMA R2-K3/,.3% FIMA AVR 7/26, 8.2% FIMA 85 Kr Fractional Release.E-3.E-4.E-5 KÜFA Tests.E-6.E-7.E Heating Temperature (C)

23 Temperature (C) Temperature (C) HTR Modul D-LOFC Simulation Tests on LEU UO 2 TRISO AVR Elements (GLE 3) 85 Kr Fractional Release 37 Cs Fractional Release.E+ 8.E+ 8.E- 6.E- 6.E-2 4.E Kr Fractional Release.E-3.E-4.E-5.E-6 AVR 85/8, 9.5% FIMA, 62C AVR 9/2, 9.33% FIMA, 62C AVR 9/5, 9.25% FIMA, 62C AVR 89/3, 9.6% FIMA, 62C AVR 9/2, 9.77% FIMA, 62C AVR 9/3, 8.97% FIMA, 7C 62C Heatup 7C Heatup Cs Fractional Release.E-3.E-4.E-5.E-6 AVR 85/8, 9.5% FIMA, 62C AVR 9/2, 9.33% FIMA, 62C AVR 9/5, 9.25% FIMA, 62C AVR 89/3, 9.6% FIMA, 62C AVR 9/2, 9.77% FIMA.E-7 2.E-7 AVR 9/3, 8.97% FIMA, 7C 62C Heatup 7C Heatup 2.E Heating Time (h).e Heating Time (h)

24 Fractional Release Temperature (C) HTR Modul D-LOFC Simulation Tests on MTR TRISO Element containing LEU UO 2 (GLE 4/).E+.E- HFR-EUbis/4, LEU UO 2 GLE 4/ (ITU Accident Simulation Testing) Kr-85 Release Cs-37 Release AG-m Release Temperature (C) 2 8.E E-3 2.E-4.E-5 8.E E-7 2 AVR GLE 4/ Element.E Heating Time (h) Tests conducted at ITU, Karlsruhe, Germany

25 Fractional Release Temperature (C) Fractional Release Temperature (C) Isothermal accident simulation tests on HTR Modul Proof Test Elements HTR Modul Proof Test HFR-K6/2, LEU UO 2 (ITU Accident Simulation Testing) HTR Modul Proof Test HFR-K6/3, LEU UO 2 (ITU Accident Simulation Testing).E+.E- Kr-85 Release CS-37 Release Temperature (C) 2 8.E+.E- Kr-85 Release Cs-37 Release Temperature (C) E-2.E E-3 2.E-3 2.E-4.E-4.E-5 8.E E-6.E E-7 2.E-7 2.E Heating Time (h).e-8 HTR Proof Test Elements 2, 3 Tests conducted at ITU, Karlsruhe, Germany Heating Time (h)

26 Release Fraction Temperature (C) Fractional Release Temperature (C) HFR-EUbis Isothermal Heating Tests HFR-EUbis/, LEU UO2 GLE 4/ (ITU Accident Simulation Testing) HFR-EUbis/3, LEU UO 2 GLE 4/ (ITU Accident Simulation Testing).E+.E- Kr-85 Release Cs-37 Release Ag-m Release Temperature (C) 2 8.E+.E- Kr-85 Release Cs-37 Release Ag-m Release Temperature (C) E-2.E E-3 2.E-3 2.E-4.E-4.E-5 8.E E-6.E E-7 2.E-7 2.E Heating Time (h).e-8 AVR GLE 4/ Elements Tests conducted at ITU, Karlsruhe, Germany Heating Time (h)

27 LEU UO 2 accident condition performance observed in 6C isothermal and HTR Modul D-LOFC accident simulation tests Accident Simulation Testing Isothermal Tests at 6 C - AVR GLE 3 - MTR - MTR GLE 4/2 - Subtotal HTR MODUL - tests 62 C* - test to 7 C during heatup phase (~587 C) - Subtotal All LEU UO 2 Accident Simulation Tests Total No. fuel bodies Total No. coated particles N 4,8 78,36 9,2 22,28 82, 6,4 98,4 Total No. failed* particles n 8 Expected failure fraction n/n One-sided upper 95% confidence limit 2.6 x x x -4.4 x x -5.6 x , x x -5 * range of C

28 Observations: Accident Condition Testing Accident Condition Testing Results: Full (%) retention of gaseous/solid fission products demonstrated up to 6 C for to 2 hours (Note: exception Ag). A-Test test data are unreliable - because of repeated autotemperature control failures Irradiated MTR elements experience higher temperatures and accumulate higher fast fluences. Some of these elements exhibited active diffusive release of solid fission products (Cs) from intact TRISO particles. AVR elements exhibit Cs surface contamination due to presence in the AVR of high-releasing elements from prior poor-quality fuel campaigns. 85 Kr fractional release typically lags Cs release because of holdup provided by intact PyC layers in TRISO fuels.

29 Comparison of performance statistics for reference HTR 6 mm diameter fuel elements containing HEU (Th,U)O 2 TRISO fuel with similar statistics on elements containing LEU UO 2 TRISO fuel. Standard HTGR spherical elements with (Th,U)O 2 TRISO particles Total No. fuel bodies Total No. coated particles N Total No. failed particles n Expected failure fraction n/n One-sided upper 95% confidence limit HEU (Th,U)O 2 TRISO Manufacture , Irradiation 5* 77,4* Accident 5 6, LEU UO 2 TRISO Manufacture 75 2,22, Irradiation 43 67,28** Accident 2 3, * Six MTR test elements with 82,72 particles plus nine AVR tests with 94,32 particles. ** Nineteen MTR Test elements with 276,68 particles plus 24 AVR tests with 393,6 particles.

30 Final TRISO fuel performance assessment statistics for manufacturing defects, irradiation and accident condition induced particle failures, and their one-sided upper 95% confidence limits for HEU (Th,U)O 2 and LEU UO 2. HEU (Th,U)O 2 LEU UO 2

31 It would be useful to compare to requirements.. Both (Th,U)O 2 TRISO and UO 2 TRISO fulfil the generic requirements on fuel performance in small modular HTRs -6 Failure Fraction ( ppm-level ) Demonstration at upper 95% Limit Thorium Uranium (Th,U)O 2 TRISO UO 2 TRISO Generic Requirement at 95% Level (after Hanson) Manufacture Irradiation Accidents Hanson, D.L., GT-MHR Source Term Overview, US-NRC, 28 January 23.

32 Conclusions Performance, meeting or exceeding HTR Modul requirements, for the modern LEU UO 2 TRISO fuel system was successfully demonstrated in 3 primary areas: Manufacturing In-reactor performance under normal operating conditions Accident condition performance Performance statistics for the HEU (Th,U)O 2 TRISO fuel system are in excellent agreement with those obtained for the LEU UO 2 TRISO fuel system. Thorium fuel system has the potential for higher burnup and higher accident temperatures, but may require additional testing to achieve (i.e. Accident condition testing).