SIMULATION OF FUEL BEHAVIOURS UNDER LOCA AND RIA USING FRAPTRAN AND UNCERTAINTY ANALYSIS WITH DAKOTA

Transcription

1 SIMULATION OF FUEL BEHAVIOURS UNDER LOCA AND RIA USING FRAPTRAN AND UNCERTAINTY ANALYSIS WITH DAKOTA IAEA Technical Meeting on Modelling of Water-Cooled Fuel Including Design Basis and Severe Accidents, 28 October - 1 November 2013, Chengdu, China Dr. Jinzhao Zhang Fuel Modelling & Safety Analysis jinzhao.zhang@gdfsuez.com CHOOSE EXPERTS, FIND PARTNERS

2 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct TABLE OF CONTENT Introduction/Objectives FRAPCON and FRAPTRAN Fuel Rod Codes Independent Validation of FRAPCON and FRAPTRAN Uncertainty/Sensitivity Analysis Method FRAPTRAN Simulation and Uncertainty Analysis of CIP3-1 FRAPTRAN Simulation and Uncertainty Analysis of IFA Conclusions and Perspectives

3 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct INTRODUCTION Modelling of fuel behaviours during Loss of Coolant Accident (LOCA) and Reactivity Initiated Accident (RIA) are important: High burnup LOCA/RIA tests: Halden, NSRR, CABRI Better understanding of complex phenomena : fuel fragmentation, relocation, dispersal, cladding ballooning, burst, oxidation, and hydriding Revision of LOCA/RIA acceptance criteria: USNRC, IRSN Need improved fuel rod codes and uncertainty analysis methods As the Owner s Engineer of all 7 Belgium plants, Tractebel needs to: Qualify the fuel rod codes FRAPCON/FRAPTRAN for simulation of high burnup fuel behaviours during LOCA/RIA conditions; Develop a safety evaluation method for margin assessment regarding to the new LOCA/RIA safety criteria; Develop a method for independent verification of the safety analyses for demonstrating the compliance with the new LOCA/RIA safety criteria.

4 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct INTRODUCTION FRAPCON & FRAPTRAN fuel rod codes are being used for Independent verification of fuel rod design provided by fuel vendors; Independent verification of vendors LOCA/RIA safety analysis and reloads fuel safety evaluation; Generation of fuel rod input data for neutronics code; Feasibility studies for power uprate, burn-up extension and power modulation; Operational and licensing support. Qualification of the fuel rod codes by independent validation Assessing the applicability of both codes to specific applications Participation in international benchmarks Application of statistical uncertainty and sensitivity analysis method

5 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct INTRODUCTION Objectives of this presentation Demonstrate the capability of FRAPCON/FRAPTRAN to simulate the LOCA/RIA fuel behaviours of interest, based on OECD fuel rod benchmark cases CABRI RIA test CIP3-1, and Halden LOCA test IFA Identify relevant input parameters that influence the phenomena of interest Evaluate the impact of the fuel rod fabrication data, model and test uncertainties on the results of interest To be used for further code qualification and method development

6 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct FRAPCON & FRAPTRAN FUEL ROD CODES Fuel rod performance and transient analysis codes developed by PNNL Used by USNRC and an international user group For both steady-state and transient conditions, including LOCA/RIA Major models and capability Fuel thermal models including thermal conductivity degradation; Mechanical models including FRACAS-I rigid pellet and 1D thin wall model, or the optional finite element analysis (FEA) model for the cladding stress-strain analyses; Fission gas release (Massih or FRAPFGR), rod internal pressure (RIP) and void volumes models; Cladding oxidation and hydrogen content models; Simplified thermal hydraulic (TH) model («Coolant» and «Heat» Options)

7 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct FRAPCON & FRAPTRAN FUEL ROD CODES Developmental code assessment FRAPCON3.4 code assessment database: 133 fuel rods FRAPTRAN1.4 code assessment: 43 integral assessment cases The parameters of interest Fuel temperatures, FGR, cladding corrosion, cladding deformation and burst time Assessment of bias and sensitivity on major models

8 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct INDEPENDENT VALIDATION Contribution to IAEA FUMEX-III Selected cases on PWR and BWR fuel rods at high burnups Super-ramp cases : PK1-6, PW3 & PW5 Accidental conditions : NSRR BWR RIA fuel rods FK1-3 Normal operation : AREVA idealised case Focusing on capability for verification of design/safety criteria Fission gas release and rod internal pressure Fuel temperatures Stress and strain states for pellet to clad mechanical interaction (PCMI/PCI) Comparison with available measurement data, and Comparison of available models and sensitivity studies

9 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct INDEPENDENT VALIDATION Contribution to OECD RIA benchmark FRAPTRAN simulation of selected 4 RIA tests with high burnup fuel rods at different coolant temperatures CABRI sodium loop test CIP0-1 CABRI water loop test CIP3-1 (blind calculation) NSRR capsule tests : VA-1 & VA-3 All measurement data are not yet available Comparisons code to code and between different users Focusing on capability for verification of RIA acceptance criteria Fuel average enthalpy Fuel temperatures Cladding temperature

10 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct INDEPENDENT VALIDATION Simulation of OECD LOCA benchmark cases FRAPTRAN simulation of 3 Halden LOCA tests (PWR rods) IFA IFA IFA Focused on the relevant thermal and mechanical responses of fuel and cladding during LOCA Fuel temperatures fuel fragmentation and relocation cladding ballooning and burst (rupture) oxidation Objectives Check the ability of the codes to predict or reproduce the measurements to identify the improvements to be made in the codes

11 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct UNCERTAINTY ANALYSIS METHOD Regulatory requirements and industrial trends 1970 s : Conservative evaluation model (EM) : Best estimate code calculations for LOCA accident analysis RG1.157 : Best-estimate Calculations Of Emergency Core Cooling System Performance (May 1989). Development of LOCA analysis methodologies with deterministic or statistical unvcertainty analysis: BELOCA (Westinghouse), DRM (Framtome), ASTRUM (Westinghouse) 2005 present: best estimate code calculations plus uncertainty analysis (BEPU) for LOCA and non-loca accident analysis RG 1.203: Transient And Accident Analysis Methods (December 2005) Application of deterministic or statistical uncertainty analysis method in fuel rod design and RIA analysis

12 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct UNCERTAINTY ANALYSIS METHOD Propagation of input parameter uncertainties The sampled N input uncertainties are propagated through code calculations Y = f(x)

13 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct UNCERTAINTY ANALYSIS METHOD Non parametric order statistics Determination of the Wilks estimator (top rank) with minimum number of calculations (N ) one-sided tolerance limit 1 γ N = β double-sided tolerance limits 1 γ N N (1-γ) γ N-1 = β

14 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct UNCERTAINTY ANALYSIS METHOD Use of DAKOTA tool from Sandia National Lab DAKOTA = Design Analysis Kit for Optimization and Terascale Applications

15 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD RIA BENCHMARK CASE CIP3-1 The CIP3-1 blind test case RIA test to be performed in the CABRI reactor with pressurised water loop At a pressure of 155 bars, an inlet temperature of 280 C, and an inlet velocity of 4 m/s. The CABRI core power during the CIP3-1 test is assumed to be a 10 ms pulse. The used rodlet has been refabricated from a high burnup PWR fuel rod UO2 rod cladded with ZIRLO at a maximum local burnup close to 75 GWd/t The rodlet has a length of about 702 mm, with a plenum of about 2 cm3, and a He filling pressure of 20.5 Bar. FRAPCON3.4/FRAPTRAN1.4 simulation of CIP3-1 FRAPCON calculation of the base irradiation of the fuel rod and the rodlet based on the specifications, with nominal rod data and operating conditions. FRAPTRAN transient calculation for the rodlet based on specified bet estimate testing conditions default model options (in particular, the «Coolant» option for the T-H model)

16 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD RIA BENCHMARK CASE CIP3-1 Objective to assess the ability of Reactivity Initiated Accidents (RIA) fuel rod codes to reproduce the results from experiments performed in different conditions in NSRR and CABRI test reactors with a certain degree of adequacy. Preliminary uncertainty/sensitivity analysis is performed To consider the impact of the uncertainties in fuel rod data, operating conditions and model options on the code simulation results To provide certain confidence on the code simulation results In line with the BEMUSE and PREMIUM project sof OECD/NEA/CSNI /WGAMA and the UAM project of NSC/EGUAM.

17 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD RIA BENCHMARK CASE CIP3-1 Identification and definition of input uncertain parameters Input uncertainty parameter Mean Standard deviation Lower bound Upper bound Distribution Thermal conductivity model Normal Thermal expansion model Normal Fission gas release model Normal Fuel swelling model Normal Cladding creep model Normal Cladding corrosion model Normal Cladding hydrogen uptake model Normal Multiplicative factor on the temperature history during base irradiation 1 0, ,9929 1,0071 Normal Multiplicative factor on the power history during base irradiation 1 0,02 0,96 1,04 Normal Multiplicative factor on the power pulse 0, ,0186 0, ,96695 Normal Coolant inlet enthalpy (J/kg) during the transient Normal Cladding outside diameter (m) 0,0095 0, , , Normal Cladding inside diameter (m) 0, , , , Normal Dish radius (m) 0, , , ,0026 Normal Fuel density (%) 95,5 0, ,5 Normal Pellet diameter (m) 0, , , , Normal Cladding roughness (µm) 0,6355 0, ,001 1,27 Normal Fuel roughness (µm) 1,6005 0, ,001 3,2 Normal Cold plenum length during base irradiation (m) 0, , ,0278 0,0301 Normal

18 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD RIA BENCHMARK CASE CIP3-1 The Upper/Lower Bound Values (Double-sided tolerance, N=93)

19 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD RIA BENCHMARK CASE CIP3-1 Impact of the uncertainty distribution and sample numbers

20 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD RIA BENCHMARK CASE CIP3-1 Sensitivity on the importance of uncertainty parameters

21 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD HALDEN LOCA TEST IFA Halden LOCA Experimental set-up Fuel rodlet (0.5 m) installed in test rig LOCA activated by blowdown valve Fuel power controlled by reactor power Surrounding rods simulated by electrical heater Measurements of interest: Cladding temperatures (TCC1 & 3) Used as boundary condition Inner flow channel temperature (TCC3) Fuel rod pressure (PF1) Cladding elongation (EC2) Test of interest IFA-650.5: PWR rod at 83 GWd/t, ~72µm oxide, Fill pressure at 70bar, peak cladding temperature at 1100 C

22 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD HALDEN LOCA TEST IFA Test reseults Cladding temperatures increase after the end of blowdown until scram (max 1040 C) Rod internal pressure reaches maximum ~171 s after LOCA Balloning Burst was detected at 750 C, ~178 s after the start of blowdown Rod internal pressure reduces very slowly after burst small crack?

23 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD HALDEN LOCA TEST IFA Simulation with FRAPCON/FRAPTRAN Pre-irradiation with FRAPCON Transient simulation by FRAPTRAN with imposed cladding outside temperatures Focus on the fuel rod responses of interest: rod internal pressure, ballooning, burst, ECR Modelling assumptions FRAPCON simulation of the refabricated rodlet at normal operation conditions Modification of the FRAPCON restart file used for initialization of FRAPTRAN model Refabricated rodlet pressure and gas content Use of FRAPTRAN Heat option for thermal mechanical calculations only Cladding temperature history imposed as the coolant temperature on the base of TCC1 measurements High heat transfer coefficients (HTC) imposed identical cladding and coolant temperatures

24 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD HALDEN LOCA TEST IFA Chosen models Fuel clad deformation: FRACAS I Rigid pellet model (default) Clad ballooning/burst: BALON2 failure model with empirical stress & strain limits (default) Fission gas release: Massih model (default) High temperature oxidation: Cathcart-Pawel model (C-P) Plenum gas temperature model modification The original rod gas plenum temperature model gave unsatisfactory results: too high temperature and rod internal pressure Modifications made to allow specification of an external plenum volume held at a defined constant gas temperature A arbitrary gas temperature of 127 C assumed for the whole transient Major source of uncertainties as the plenum gas temperature varies with time! Possible further improvement to the code by Imposing evolution of plenum gas temperature during transient, or Improving the gas plenum temperature model to calculate the plenum gas temperature

25 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD HALDEN LOCA TEST IFA Imposed cladding temperatures in two zones

26 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD HALDEN LOCA TEST IFA Evolution of best-estimate rod internal pressure Ballooning Burst

27 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD HALDEN LOCA TEST IFA Uncertainty analysis Objectives Identify the most important input parameters influencing the result of interest Evaluate the impact of the fuel rod data, model and test uncertainties on the uncertainties of the calculation results Identification of uncertainty parameters in three categories Fuel rod fabrication data Models Operation or test boundary conditions Selection of important uncertainty parameters Some parameters added for confirmation of importance Distributions and ranges taken as usually presented in literature Material properties not included

28 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD HALDEN LOCA TEST IFA Uncertainty analysis: parameter range and distribution

29 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD HALDEN LOCA TEST IFA Uncertainty analysis Method and assumptions Monte-Carlo simple random sampling of all parameters with 93 FRAPCON/FRAPTRAN runs Use of first order: Min/Max are the lower and upper bounds (5/95 and 95/95, doublesided) Use of Pearson s and Spearman s correlation coefficients for sensitivity analysis Identification of the most influential parameters on the results of interest

30 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD HALDEN LOCA TEST IFA Uncertainty analysis: DAKOTA UA/SA process Fabrication Clad inner diameter Pellet outer diameter Resintering Cladding roughness Models Fuel thermal conductivity FGR model Fuel thermal expansion Corrosion model Boundary conditions Plenum temperature Cladding temperature Steady state power Transient power DAKOTA Clad inner diameter Pellet outer diameter Resintering Cladding roughness Fuel thermal conductivity FGR model Fuel thermal expansion Corrosion model Steady-State Power Cladding roughness Transient power Plenum temperature Cladding temperature FRAPCON input Restart file FRAPTRAN input Responses: - ECR, - strain, - pressure, DAKOTA UA/SA Results: - Lower/upper bounds - Correlations

31 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD HALDEN LOCA TEST IFA Uncertainty analysis: evolution of rod internal pressure

32 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD HALDEN LOCA TEST IFA Uncertainty analysis: evolution of average fuel temperature

33 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD HALDEN LOCA TEST IFA Uncertainty analysis: evolution of cladding radial strain

34 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD HALDEN LOCA TEST IFA Uncertainty analysis: evolution of Cathcart-Pawel ECR

35 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD HALDEN LOCA TEST IFA Sensitivity analysis Pearson s linear correlation coefficients Designate the linear correlation between one input and one output. Absolute values less than 0.25 indicate week correlation. Absolute values between 0.25 and 0.75 indicate moderate correlation. Absolute values above 0.75 indicate strong correlation. Example: Fuel temperatures before burst at node 6 (close to burst position) Instant = 180 s, node 6 Av. Fuel T. Center T. Clad inner diameter 0,88 0,89 Pellet outer diameter -0,71-0,73 Resintering 0,42 0,43 Cladding roughness 0,10 0,09 Fuel thermal conductivity -0,97-0,98 Relative power during transient 0,94 0,96 Relative power during base irradiation 0,89 0,91 FGR model 0,54 0,57 Fuel thermal expansion 0,99 0,99 Steady state corrosion model 0,80 0,82 Plenum temperature 0,17 0,18 Cladding temperature 1,00 0,99

36 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD HALDEN LOCA TEST IFA Sensitivity analysis Example: Rod internal pressure/burst time before burst at node 6 (close to burst position) RIP/burst time impacted significantly by plenum gas temperature and cladding temperature RIP impacted also by fuel thermal expansion model Cladding elongation and radial strain impacted by more parameters and models Instant = 180 s, node 6 Internal P. Elongation R. strain Burst time Clad inner diameter -0,34 0,93 0,85-0,32 Pellet outer diameter 0,22-0,26 0,01-0,11 Resintering -0,02-0,01-0,04-0,05 Cladding roughness -0,24-0,23-0,20 0,16 Fuel thermal conductivity 0,72 0,49 0,59 0,00 Relative power during transient 0,31 0,98 0,75-0,17 Relative power during base irradiation -0,35 0,89 0,81 0,06 FGR model -0,04 0,14 0,13-0,07 Fuel thermal expansion -0,91-0,80-0,85 0,10 Steady state corrosion model -0,38 1,00 1,00 0,19 Plenum temperature 1,00 1,00 1,00-0,99 Cladding temperature 1,00 1,00 1,00-1,00

37 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct OECD HALDEN LOCA TEST IFA Sensitivity analysis Example: Cladding oxidation at node 6 (close to burst position) Before transient (ECR650.5): impacted only by cladding diameter, initial power and steadystate corrosion model After transient (ECR650.5e): impacted also by cladding transient temperature Node 6 ECR ECR e Clad inner diameter -0,99-0,81 Pellet outer diameter -0,57 0,00 Resintering 0,05 0,09 Cladding roughness -0,05 0,00 Fuel thermal conductivity 0,06-0,11 Relative power during transient 0,02 0,08 Relative power during base irradiation 1,00 0,99 FGR model -0,10-0,25 Fuel thermal expansion -0,05-0,01 Steady state corrosion model 1,00 1,00 Plenum temperature -0,13 0,29 Cladding temperature 0,10 1,00

38 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct CONCLUSIONS FRAPCON & FRAPTRAN predict quite well fuel thermal behaviour during RIA (by comparing with other codes) Adequate for design/safety criteria verification FRAPCON & FRAPTRAN mechanical models need to be improved to predict cladding deformation and PCMI failures during RIA Further benchmark needed (OECD RIA benchmark phase II) The failure of fuel rod is sensitive to the initial conditions and the following parameters/models: Initial gap thickness; Initial cladding spallation; Void volume; Fission gas release Uncertainty and sensitivity analysis needed (OECD RIA benchmark phase II)

39 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct CONCLUSIONS With the measured cladding temperatures and imposed plenum gas temperature as boundary conditions, FRAPTRAN is able to simulate the Halden LOCA test IFA-650.5, in particular: Fuel pellet temperature; Rod internal pressure; The ballooning and burst. Further model improvement needed The important parameters influencing the calculation results of interests during LOCA are identified: Plenum gas temperature; Cladding temperature; Cladding inner diameter; Initial power and steady-state corrosion for oxidation Uncertainty analysis needed

40 IAEA TM Fuel Modelling in Accidental Conditions, Chengdu, China 29 Oct PERSPECTIVES FOR FUMAC The accurate simulation of physical phenomena during LOCA/RIA is essential for further uncertainty analysis Improvement of models for FGR, plenum gas temperature, axial gas transportation, cladding ballooning and burst, fuel relocation and dispersal? Detailed measurements and/or their uncertainties in LOCA/RIA tests are important for fuel modelling and uncertainty analysis applications Focus on a few, but well instrumented tests (e.g., Halden LOCA tests)? Thermal Hydraulic models needs to be improved to better simulate the test and transient conditions during LOCA/RIA Coupling with a qualified system or sub-channel T/H code?