Modeling of Fuel Performance and Fission Product Release Behavior

Transcription

1 Mitglied der Helmholtz-Gemeinschaft Modeling of Fuel Performance and Fission Product Release Behavior IEK-6, Research Center Jülich, Germany IAEA Training Course on HTGR Technologies, Beijing, China, October 22-26, 2012

2 Release pathes and retention mechanisms Slide 2

3 Fuel Performance Slide 3

4 TRISO fuel performance code PANAMA Particle failure detected by gas release Only SiC layer considered ( soap bubble ) ipyc and opyc ignored Failure mechanisms: - pressure vessel failure (SiC) SiC thinning by corrosion, strength fluence dependent - thermal decomposition (SiC) Failure occurs if stress induced in SiC exceeds its strength Subsequent gas release from bare kernel (Booth model) Slide 4

5 TRISO mechanical performance modeling Pressure buildup p in the free volume V free of the buffer layer n n Xe n Kr n CO p RT n V free Martin 2002 Induced stress in a single thin layer (e.g. SiC): r p 2 t SiC SiC Failure occurs when induced stress exceeds strength UTS Slide 5

6 PANAMA model pressure buildup p F d F f V f O / V k f Bu R T V m Pa Gas pressure inside particle depending on: Temperature T, burnup Bu, oxygen production O f, void volume V f, yield of stable gases F d D = reduced diffusion coefficient of Kr, Xe in UO 2 Nabielek 1974 Allelein 1983 Slide 6

7 PANAMA input parameter SiC strength Strength = material property following Weibull statistics unirradiated: σ oo = 834 MPa, m oo = 8.02; irradiated: σ o = 687 MPa, m o = 5.98 Degradation of SiC strength with fast neutron fluence Slide 7

8 PANAMA model CO production Number of oxygen atoms produced UO 2 vs. (Th,U)O 2 Slide 8

9 PANAMA model CO production in UO and 1100 o C Pressure buildup Failure fraction Slide 9

10 PANAMA model SiC corrosion by FP d d 0 * 1 t 1 d t 0 / d exp 179,500 R T m / s Montgomery 1981 Slide 10

11 Fuel performance FRJ2-K13/4 heating at 1600/1800 o C Slide 11

12 Fuel performance AVR 76/18 heating at 1800 o C Slide 12

13 Failure fraction Postcalculation particle failure AVR 90/2 1 E+0 AVR 90/2 1 E-1 1 E-2 1 E-3 1 E-4 1 E-5 1 E-6 1 E-7 Tirr=700 Tirr=1000 Kr-85 measurements 1 E Heating time (h) Temperature Slide 13

14 Failure fraction Postcalculation particle failure AVR 89/13 1 E+0 1 E-1 AVR 89/13 1 E-2 1 E-3 1 E-4 Tirr=700 Tirr=1000 Kr-85 measurements Temperature 1 E-5 1 E-6 1 E-7 1 E Heating time (h) Slide 14

15 Failure fraction Fuel performance AVR 91/31 (transient to 1700 C) 1 E+0 AVR 91/31 1 E-1 1 E-2 1 E-3 1 E-4 Tirr=700 Kr-85 measurements Tirr=1000 Temperature 1 E-5 1 E-6 1 E-7 1 E Heating time (h) Slide 15

16 Failure fraction Temperature ( C) Postcalculation particle failure HFR-K6/3 1 E+0 1 E-1 HFR-K6/ LEU UO 2 1 E ,580 cp 634 efpd 1 E % FIMA 1 E (25) n/m 2 T s = 940 o C 1 E T c = 1140 o C 1 E T H = o C 1 E-7 1 E-8 Tirr=940 Tirr=1140 Kr fract. release measurements Temperature Heating time (h) Slide 16

17 Failure fraction Temperature ( C) Postcalculation particle failure HFR-EU1bis/1 1 E+0 1 E-1 HFR-EU1bis/ LEU UO cp 249 efpd 9.3% FIMA 2.4(25) n/m 2 T c = 1250 o C T H = o C 1 E-2 1 E-3 1 E-4 1 E-5 1 E E-7 1 E-8 Tirr=1250 Kr fract. release measurements Temperature Heating time (h) 500 Slide 17

18 Fuel performance prediction HFR-EU1 T irr = 1100 o C Slide 18

19 Failure fraction CRP-6 prediction particle failure HFR-EU1 Assumptions 1.E+00 US INL Particle Failure Fraction LEU UO cp 600 efpd 20% FIMA 1.E-02 1.E-04 US GA RF France Japan UK 6.0(25) n/m 2 T c = 1025 o C 1.E-06 German Korea 1.E-08 1.E-10 Slide 19

20 PANAMA V&V conclusions Failure mechanisms are principally well understood supported by improved fuel performance models More experimental work on material properties (SiC) necessary Observation of no particle failure in 1600C heating tests principally confirmed by PANAMA postcalculations Observation of extremely low failure fraction in recent KÜFA-II tests CRP-6 benchmark excellent demonstration that PANAMA works properly and in agreement with other codes Slide 20

21 Ideal gas law vs. Redlich-Kwong Ideal gas law Harrison 1969 Redlich-Kwong equation Ideal gas law in agreement with Redlich-Kwong over HTGR-relevant burnup range; beyond differences still negligibly small Slide 21

22 Influence of prestressing with ipyc and opyc UO 2 TRISO T irr = 1100 o C Problem 1: Uncertainty in PyC shrinkage and creep data Problem 2: Detection limit of 2x10-5 in particle failure Slide 22

23 Uncertainties in kernel/layer thicknesses Frequency distribution for 1,000,000 particles Slide 23

24 TRISO particles with different gas pressures Example: particles after 1100 o C irradiation to 20% FIMA variation kernel: 502.2±10.6 μm; buffer: 94.3±13.0 μm Slide 24

25 Failure with/without kernel/buffer statistics Failure fractions slightly increase with kernel/buffer statistics Slide 25

26 Failure with/without buffer/sic statistics Failure fractions strongly increase with buffer/sic statistics Slide 26

27 SiC corrosion by fission product attack Slide 27

28 Calculated SiC thinning distances Slide 28

29 PANAMA potential for improvement Equation-of-state Ideal gas law Redlich-Kwong (insignificant) Prestressing by pyrocarbon layers (realistic, but then less conservative) Statistical distribution of particle geometric data (more realistic at the extreme ends of fuel performance) Review SiC corrosion relationship (very conservative) Slide 29

30 I Fission Product Transport Slide 30

31 Fission product diffusion code FRESCO-II Numerical solution of Fickian equation of diffusion in discrete steps of time and space Effective diffusion coefficients Pebble version for irradiation and heating test Main input - geometrical and thermodynamical conditions - initial fission product distribution - particle failure function (bare kernels) - sorption isotherms Slide 31

32 FRESCO-II fission product transport behavior Slide 32

33 log10 D(m 2 s -1 ) FRESCO-II input parameter diffusion coefficient Effective diffusion coefficient D eff Qi Do, i exp D T,, c,... i RT Original Verfondern FIT 95% one-sided UCL 99% one-sided UCL Diffusion coefficients in SiC [IAEA 1997] E4/T(K) Cesium in SiC Slide 33

34 FRESCO-II input parameter diffusion coefficient Diffusion coefficients in UO 2 in matrix material [IAEA 1997] Slide 34

35 Silver according to van der Merwe Slide 35

36 Initial uranium distribution in fuel element Uranium inside fuel kernel = 1 Σ(fractions outside) Slide 36

37 Particle failure function Several options: Observations (postcalculation) SIEMENS trumpet curve PANAMA calculation Statistical evaluation of experimental data trumpet curve for normal operation PANAMA for accident conditions In the model: defective/failed particle = bare kernel Slide 37

38 CRP-6 accident condition benchmark Case 1: bare kernel a) 1200 o C b) 1600 o C Case 2: bare kernel + buffer + IPyC a) 1200 o C b) 1600 o C Case 3: TRISO coated particle a) 1600 o C b) 1800 o C c) d) crack in 1800 o C e) crack in 1600 o C, 1800 o C Case 4: like case 3, with irradiation 500 d, 1000 o C 10% FIMA, 2(+25) fast neutron fluence Case 5: like case 4, with irradiation of 10 cycles of 100 d, o C ( o C) Slide 38

39 Fractional Release Cesium Release from particle kernel 1.E+00 1.E-01 1.E-02 Bare kernel Release of Cs E-03 Kernel + buffer + PyC 1.E-04 1.E-05 1.E-06 1.E-07 TRISO particle with without irradiation 1.E Heating Time [h] Slide 39

40 Fractional Release Cesium Release from particle kernel 1.E+00 8.E C Release of Cs E-01 Bare kernel 4.E-01 Analytical solution 1200 C 2.E-01 Kernel + buffer + PyC 0.E Heating Time [h] Slide 40

41 Fractional Release Fission product release at 1600/1800 o C 1.E+00 1.E-01 1.E-02 Ag-110m (e) Cs-137 SiC E-03 Sr-90 1.E-04 1.E-05 Cs E-06 1.E-07 Cs-137 no irradiation Fission gases through-coating failure 1.E Heating Time [h] Slide 41

42 CRP-6 benchmark code comparison Fractional release of 137 Cs from Participant bare kernel bare kernel + buffer + ipyc TRISO Case 1a (1200 o C) Case 1b (1600 o C) Case 2a (1200 o C) Case 3a (1600 o C) Case 3b (1800 o C) France Germany Korea South Africa US/GA US/INL US/NRC US/SNL Analytical solution Minato: Slide 42

43 Fractional Release FP release during 10-cycle-irradiation 1.E+00 1.E-01 1.E-02 1.E-03 Ag-110m 1.E-04 Sr-90 1.E-05 1.E-06 1.E-07 1.E-08 Temperature o C Irradiation Time [h] Cs-137 Slide 43

44 Fractional Release FP release during 1600 o C heating phase 1.E+00 1.E-01 1.E-02 1.E-03 1.E-04 1.E-05 1.E-06 1.E-07 1.E-08 Cesium Strontium Silver Silver 1000 Cesium case 4a Cesium case 3a Irradiation Time [h] Slide 44

45 Fractional Release Postcalculation HFR-K3/3 heated at 1800 o C 1.E+00 blue= 110m Ag; red= 137 Cs; green= 90 Sr; black= particle failure 1.E-01 Ag-110m Fuel sphere with UO 2 LTI TRISO particles prior irradiation to 10.6% FIMA 1.E-02 1.E-03 1.E-04 1.E-05 1.E-06 1.E-07 1.E-08 Sr-90 Cs-137 Failure fraction Heating Time [h] Slide 45

46 Postcalculation Cs profiles in fuel sphere Fuel sphere disintegration technique Slide 46

47 Postcalculation cesium release AVR 89/13 AVR fuel sphere UO 2 LTI TRISO particles Transient heating 2 x irradiation to 9.1% FIMA 2.6(+25) n/m 2 Slide 47

48 Postcalculation silver release AVR 89/13 AVR fuel sphere UO 2 LTI TRISO particles Transient heating 2 x irradiation to 9.1% FIMA 2.6(+25) n/m 2 Slide 48

49 Postcalculation HFR-P4/3-7 heated at 1800 o C UO 2 LTI TRISO particles Heating at 1600 o C irradiation to 13.9% FIMA 7.5(+25) n/m 2 Slide 49

50 Fractional release Temperature ( C) Postcalculation cesium release HFR-K6/3 1 E+0 1 E-1 HFR-K6/3 Cesium LEU UO 2 1 E ,580 cp 634 efpd 1 E % FIMA 1 E (25) n/m 2 T s = 940 o C 1 E T c = 1140 o C T H = o C 1 E-6 1 E-7 1 E-8 Release from CP (940) Release from FE (940) Cs-137 fract. release measurements Failure fraction Temperature Heating time (h) Slide 50

51 Postcalculation cesium release HFR-K6/3 Slide 51

52 Fractional release Temperature ( C) Postcalculation cesium release HFR-EU1bis/1 1 E+0 HFR-EU1bis/1 Cesium E E LEU UO cp 1 E efpd 9.3% FIMA 1 E (25) n/m 2 T c = 1250 o C 1 E-5 Release from CP (1250) 1500 T H = o C 1 E-6 Release from FE (1250) Cs-137 fract. release measurements 1000 Release from FE (1 fail) 1 E-7 Release from FE (10 fail) Release from FE (100 fail) 500 Temperature 1 E Heating time (h) Slide 52

53 Postcalculation silver release HFR-EU1bis/1 LEU UO cp 249 efpd 9.3% FIMA 2.4(25) n/m 2 T c = 1250 o C T H = o C Slide 53

54 FRESCO input parameter: sorption isotherms Slide 54

55 Influence of sorption effect on core release Core heatup scenario in 750 MW(th) THTR-300 Slide 55

56 FRESCO-II V&V Conclusions Diffusion coefficient essential input parameter, reference data showing mostly conservative coverage of experimental data Use of average data appropriate for postcalculations; for predictions wise to use upper 95% conf. design data CRP-6 benchmark excellent demonstration that FRESCO works properly and in agreement with other codes New heating tests with proof test fuel with extremely low release of Cs and Kr largely overpredicted with FRESCO Slide 56

57 FRESCO-II potential for improvement Temperature profile in sphere Fractional release from kernel (diffusion Booth model) Buildup of inventory during normal operation Particle failure function (limited # of steps unlimited) Introduction of third-type particle (failed SiC, intact PyC) Slide 57

58 Inventory buildup during irradiation Current approach: isotope buildup acc. to decay constant such that full inventory be available at EOI New approach: TNT model to consider all potential sources and sinks of an isotope Cs-137 I-131 Slide 58

59 TNT model TNT = Topological Nuclide Transmutation New approach Apply graph theory: nuclide objects are vertices (nodes) and transmutation rates are egdes (arrows) => generic programming Advantages Minimum nuclide system is set up based on initial nuclide vector defined by the user Solver exploits the topology information by working along the real nuclide chain Based on peer-reviewed code libraries (e.g. boost, Eigen) Reduced code complexity by using object-oriented programming techniques Slide 59

60 Code development for HTGR HTR Code Package 1969: V.S.O.P. (Reactor design and operation) 1985: PANAMA (Particle failure) 1983: FRESCO-II (Fission product release) 1987: DIREKT (Thermal hydraulics) 1987: TINTE (Accident scenarios) 2010: MGT-3D 2007: MGT (Multi-Group TINTE) Slide 60

61 HCP overall concept Slide 61

62 HTGR primary loop codes non local heat sources VSOP core design, reactor operation MGT-3D reactor dynamics, accident simulation nuclide densities, FE history, decay heat Neutron flux, nuclide densities TNT detailed burnup studies nuclide densities STACY fuel performance, FP diffusion, FP deposition and transport Slide 62

63 HCP Module: STACY FP-Release rate from one FE (NOC and accident Conditions) Fickean diffusion of FPs in defective and intact CPs / FEs Recoil SiC-Layer thinning Release from FEs and transport under accident conditions FP-Transport in Core due to convection Deposition on reflector surfaces Fuel Performance CP damage rates SiC-Layer thinning due to thermal decompostion Deposition / penetration metallic surfaces (primary loop) Some features have been implemented multiple times in the separate codes Not complete to describe all phenomena under NOC and accident conditions Slide 63

64 Overall conclusions Main uncertainties introduced by input rather than model requiring measurements for actual materials Experimental data from 1600 o C (1620) heating tests confirm, in principle, model assumptions/data used at FZJ Two CRP-6 benchmarks have shown good agreement with other international code developments Recent observations of extremely low Cs release and no particle failure (HFR-K6) at T>1600 o C and comparatively high release at T=1600 o C (HFR-EU1bis) show need for more heating tests Slide 64

65 Thank you for your kind attention Phone: Slide 65