Recent Predictions on NPR Capsules by Integrated Fuel Performance Model

Transcription

1 Massachusetts Institute of Technology Department of Nuclear Engineering Advanced Reactor Technology Pebble Bed Project Recent Predictions on NPR Capsules by Integrated Fuel Performance Model Jing Wang Advisors: Prof. R. Ballinger & Prof. S. Yip Sponsor: Idaho National Engineering Lab. July 19, 2002 MIT Nuclear Engineering Department 1

2 Outline Overview of Integrated Fuel Performance Model Predictions on NPR Capsules 2 CANES

3 Integrated Fuel Performance Model 3 CANES

4 Pebble Bed Reactor and TRISO Fuel 4 CANES

5 Modules in the Integrated Model Fission gas release model Thermal model Mechanical analysis Chemical analysis Fuel failure model OPyC SiC IPyC Buffer PyC Fuel Kernel Simulation of refueling in the reactor core 5 CANES

6 Mechanical Analysis System: IPyC/SiC/OPyC Methods: Analytical or Finite Element Viscoelastic Model Mechanical behavior irradiation-induced dimensional changes (PyC) irradiation-induced creep (PyC) pressurization from fission gases thermal expansion Dimensional changes Creep Pressurization Thermal expansion Stress contributors to IPyC/SiC/OPyC 6 CANES

7 Benchmarking Stress Calculations on NPR Type Fuel MIT INEEL Stress (MPa) Fast Neutron Fluence (10^21nvt) Stresses in isotropic IPyC under constant temperature 1032 C 7 CANES

8 Weibull Strength Theory P = 1 e f σ 0 characteristic strength (MPa.meter 3/m ) m Weibull modulus ( σ / σ 0 ) m dv P f = 1 e ( σ / σ ) m mf σ mf mean fracture strength (MPa) applicable when microscopic cracks prevail 8 CANES

9 Fracture Mechanics Based Failure Model OPyC SiC IPyC σ t K I ( IPyC) K IC (SiC) = yσ t πa PO PI Irradiation applied when macroscopic crack presents 9 CANES

10 Simulation of Refueling through Non-isothermal MPBR Core reflector coolant control reflector fuel shutdown pressure vessel VSOP Model of MPBR core 10 CANES

11 Simulation of Refueling - cont d 1.6E E E+07 Power density (W/m^3) 1.0E E E E E E Irradiation time (days) A typical power history of a pebble in MPBR core 11 CANES

12 Integrated Fuel Performance Model MC Outer Loop 1,000,000 times Power Distribution in the Reactor Core Sample a pebble/fuel particle MC inner loop Randomly re-circulate the pebble t=t+ t Get power density, neutron flux 10 times Monte Carlo outer loop: Samples fuel particle statistical characteristics T distribution in the pebble and TRISO Accumulate fast neutron fluence FG release (Kr,Xe) PyC swelling MC inner loop: Mechanical model Failure model Mechanical Chemical Stresses FP distribution Strength Pd & Ag Implements refueling scheme in reactor core Y N Failed In reactor core Y N 12 CANES

13 Predictions on NPR capsules 13 CANES

14 Typical NPR Particle Parameters Mean Value Std. Deviation Distr. Type Kernel Diameter (µm) Triangular Buffer Thickness (µm) Triangular IPyC Thickness (µm) Triangular SiC Thickness (µm) Triangular OPyC Thickness (µm) Triangular Fuel Density (g/cm 3 ) Triangular Buffer Density (g/cm 3 ) Triangular IPyC σ 0 (MPa.meter 3/m ) (modulus) Weibull OPyC σ 0 (MPa.meter 3/m ) (modulus) Weibull SiC σ 0 (MPa.meter 3/m ) (modulus) Weibull SiC K IC (MPa. µm 1/2 ) Triangular 14 CANES

15 Example of Compact Irradiation History Temperature (C) Temperature history Elapsed Time (day) Temperature (C) Temperature history Full Power Days 2.5 Fast fluence history 80 Burnup v.s. Fast Fluence Fast Fluence (10^21nvt) Burnup (% FIMA) Ellapsed Time (day) Fast Fluence (10^21n/cm^2) NPR-1 A8 15 CANES

16 Fuel Failure Predictions Irradiation Conditions Fuel Compact ID Fast Fluence Irradiation Temp. Burnup (10 25 n/m 2 ) ( C) (%FIMA) NPR-2 A NPR-1 A NPR-1 A NPR-1A A IPyC Layer * % Failed 95% Conf. Interval (%) INEEL Calc. MIT Calc. NPR-2 A <p< NPR-1 A <p< NPR-1 A8 6 2<p< NPR-1A A9 18 5<p< SiC Layer * % Failed 95% Conf. Interval (%) INEEL Calc. MIT Calc. NPR-2 A4 3 2<p< NPR-1 A <p< NPR-1 A8 0 0<p< NPR-1A A9 1 0<p< (*: layer failure is considered as a through wall crack as measured by PIE. ) 16 CANES

17 Systematic Study on NPR-1 Capsule 17 CANES

18 NPR-1 R/B of Selected Fission Gases 18 CANES

19 Irr. Conditions for NPR-1 Compacts Compact ID A1 A2 A3 A4 A5 A6 A7 A8 EOL Fluence (10 21 n/cm 2 ) EOL Burnup (% FIMA) Avg. Irr. T (C) EFPD (Day) Irradiation Time (Day) CANES

20 Prediction of Failures /w Real Irr. History Compact ID A1 A2 A3 A4 A5 A6 A7 A8 IPyC Failure 47.38% 6.440% 14.99% 33.54% 26.61% 24.43% 15.64% 60.70% OPyC Failure 3.87% 0.262% 0.461% 1.91% 1.14% 1.00% 0.548% 6.13% Particle Failure 1.61% % 0.025% 0.857% 0.358% 0.272% 0.068% 2.74% 20 CANES

21 Prediction of Failures /w Ideal Irr. History Compact ID A1 A2 A3 A4 A5 A6 A7 A8 IPyC Failure 84.24% 16.71% 19.42% 33.85% 36.26% 30.26% 29.06% 91.71% OPyC Failure 13.1% 0.436% 0.549% 1.564% 1.85% 1.23% 1.11% 16.3% Particle Failure 8.32% 0.038% 0.074% 0.613% 0.790% 0.400% 0.337% 9.64% 21 CANES

22 Overall Failure of NPR-1 Capsule Irradiation Test Prediction (Real Irr. History) Prediction (Ideal Irr. History) No. Particles Contained No. Failed Particles 625 (a) Failure Probability 0.806% 0.846% 3.076% Peak Fluence at Initial Failure (10 21 n/cm 2 ) Peak Burnup at Initial Failure (% FIMA) % 59% 24% EFPD at Initial Failure Peak Temperature at Initial Failure (C) (a): From readings of the Kr 85m R/B 22 CANES

23 Kr 85m R/B of NPR-1 Capsule 1.0E E E-05 R/B 1.0E E E-08 Experiment Prediction-real 1.0E Irradiation Time (efpd) Prediction-ideal 23 CANES

24 Path Forward Develop Advanced Failure Model Follows PyC Cracking & Stress Distribution after initial PyC failure Develop and Incorporate Chemistry Model INEEL Inputs FP Migration Experimental Results Pd Interaction Results Other Input 24 CANES