Meso-Scale Modeling of Irradiated Concrete in Test Reactor A. Giorla - - PowerPoint PPT Presentation

Meso-Scale Modeling of Irradiated Concrete in Test Reactor

• A. Giorla1
• M. Vaitov´

a2

• Y. Le Pape1
• P. ˇ

Stemberk2

1Oak Ridge National Laboratory, 2Czech Technical University, Prague

November 5, 2015

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 1 / 35

Outline

1

Why numerical modelling?

2

Elleuch’s experiment

3

Numerical model

4

Preliminary sensitivity analysis

5

Conclusion

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 2 / 35

Outline

1

Why numerical modelling?

2

Elleuch’s experiment

3

Numerical model

4

Preliminary sensitivity analysis

5

Conclusion

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 3 / 35

Motivation

NPP licence renewal - condition of bological shield RIVE of aggregate - first order degradation mechanism Irradiation effect on concrete assessment - experiments

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 4 / 35

Differences between PWR and Test Reactor

PWR Test Reactor / Gamma facility fast neutron flux (n.cm−2 s−1) 1 to 2 ×1010 5 × 1011 to 2 × 1014 fast neutron fluence (n.cm−2) < 6 × 1019 < 1020 gamma flux (kGy h−1) 5 to 20 0.02 to 200 gamma dose (MGy) 50 to 200 0.1 to 1000 gamma heating rate (W g−1) 0.02 0.04 to 1.3 temperature (◦C) <≈ 65 (design) 40 to 250 internal RH (-) strong gradient

• ften pre-dried

mechanical boundary conditions structural restraints free materials concrete mortar time scale (years) 60 to 80 < 1 year

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 5 / 35

Exposure time difference

short time experiments higher flux of irradiation to get total fluence(dose) role of creep PWR Test Reactor / Gamma facility fast neutron flux (n.cm−2 s−1) 1 to 2 ×1010 5 × 1011 to 2 × 1014 fast neutron fluence (n.cm−2) < 6 × 1019 < 1020 gamma flux (kGy h−1) 5 to 20 0.02 to 200 gamma dose (MGy) 50 to 200 0.1 to 1000 time scale (years) 60 to 80 < 1 year

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 6 / 35

Temperature difference

higher flux of irradiation to get total fluence(dose) cooling of the samples temperature gradient PWR Test Reactor / Gamma facility fast neutron flux (n.cm−2 s−1) 1 to 2 ×1010 5 × 1011 to 2 × 1014 gamma flux (kGy h−1) 5 to 20 0.02 to 200 gamma heating rate (W g−1) 0.02 0.04 to 1.3 temperature (◦C) <≈ 65 (design) 40 to 250

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 7 / 35

RH difference

moist walls pre-dried samples different gradients PWR Test Reactor / Gamma facility internal RH (-) strong gradient

• ften pre-dried

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 8 / 35

Scale difference

material mechanical boundary conditions different gradients T, RH PWR Test Reactor / Gamma facility mechanical boundary conditions structural restraints free materials concrete mortar

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 9 / 35

Meso-scale model

Understand experiments Transpose the experimental data to assess the actual structure

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 10 / 35

Model

Expansion and degradation of concrete Function with parameters of environmental conditions and composition of material Calibrate model with known experiment - environmental conditions, concrete composition

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 11 / 35

Outline

1

Why numerical modelling?

2

Elleuch’s experiment

3

Numerical model

4

Preliminary sensitivity analysis

5

Conclusion

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 12 / 35

Experimental data

Experiment dimensional changes mechanical properties components of concrete and concrete itself Data for simulation material parameters of cement paste and aggregate (strength, modulus of elasticity, thermal expansion coefficient etc.) environmental conditions: relative humidity, thermal and fluence history

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 13 / 35

Elleuch’s experiment

Environment temperature history - setting, thermal treatment, storing, irradiation neutron fluence relative humidity exposure period Materials cement paste - aluminous cement aggregate - serpentine mechanical properties physical properties

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 14 / 35

Experimental data

Conditions dependent on the position in the rig temperature neutron fluence

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 15 / 35

Outline

1

Why numerical modelling?

2

Elleuch’s experiment

3

Numerical model

4

Preliminary sensitivity analysis

5

Conclusion

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 16 / 35

Modeling Strategy

Finite Elements

Conditions

Microstructure

Mechanisms Results

• Fluence
• Temperature
• Humidity
• Macro. expansion
• Micro. damage

Aggregates

• Radiation-induced

expansion/softening

• Thermal expansion
• Brittle failure

Cement paste

• Drying shrinkage
• Thermal expansion
• Brittle failure
• Creep

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 17 / 35

Modeling Strategy

Implementation in AMIE C++ finite element library initially developed at EPFL Random generation of concrete microstructures Robust creep-damage algorithm . 2D simulations Relatively small computational time (≈ 20 h) More crack percolation than in 3D? ITZ is neglected

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 18 / 35

Cement paste

Visco-elastic

Logarithmic creep curve (recoverable/irrecoverable creep strains) Depends on T, RH (no drying creep)

. Quasi-brittle

Non-local damage model (no mesh sensitivity) Linear softening post-peak behavior

. With imposed deformations

Thermal expansion (∝ T, reversible) Drying shrinkage (∝ 1-RH, irreversible)

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 19 / 35

Aggregates

Elastic

Homogeneous circular inclusions Young’s modulus is reduced by irradiation No failure in the aggregates (cement paste breaks first)

. With imposed deformations

Thermal expansion (∝ T, reversible) Radiation Induced Volumetric Expansion (RIVE) (irreversible, using [Zubov and Ivanov, 1966] sigmoid) ǫΦ = κ ǫmax

• eδΦ − 1
• ǫmax + κ eδΦ

Parameters calibrated by [Le Pape et al, 2015] Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 20 / 35

Microstructure

F¨ uller PSD based on the experimental mix design (fine and coarse) Particles are randomly placed from largest to smallest Particles smaller than element size are ignored Very large aggregate size compared to sample size

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 21 / 35

Environmental conditions

100 200 300 400 500 Time [d] T emperature Fluence Humidity Cure Pre-drying Irradiation Cool-off Expansion measurements

5 different irradiations duration 3 different temperature/fluence Simulate the experimental protocol Use intermediate data to calibrate unknown material parameters

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 22 / 35

Example of simulation result

Stages of damage process:

1

Debonding of large aggregates

2

Crack bridging between large aggregates

3

Debonding of small aggregates

. Very high damage in the cement paste Loss of sample integrity Overestimation of damage (homogeneous aggregates)

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 23 / 35

Reference results

Good agreement between simulation and experiments Slightly lower expansion

Less aggregates

Scatter in expansion

Temperature, flux

Anisotropic expansion for very high fluences

Experimental sample is not representative

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 24 / 35

Outline

1

Why numerical modelling?

2

Elleuch’s experiment

3

Numerical model

4

Preliminary sensitivity analysis

5

Conclusion

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 25 / 35

Preliminary sensitvity analysis

Additional shrinkage in cement paste? Role of creep? Role of aggregate loss of stiffness? Role of damage model?

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 26 / 35

Additional shrinkage of cement paste

Elleuch [1972] measured shrinkage of the cement paste during irradiation. High variations, and no apparent correlation with neutron fluence Provides upper/lower bounds of expansion

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 27 / 35

Role of creep and aggregate stiffness

No apparent effect (in these conditions) . No creep Constant aggregate stiffness

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 28 / 35

Role of creep and aggregate stiffness

No apparent effect (in these conditions) . No creep Relatively short-term experiment No mechanical restraint Most of the damage occurs in the first 2 months of irradiation Aluminous cement paste has a much slower creep than OPC

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 28 / 35

Role of damage model

Stress-strain relation of concrete strongly depends on loading rate .

Strain Stress

εt εy

ft Strain Stress

εt

ft Fast, 2.1·10-2 mm/s Slow, 1.3·10-7 mm/s Strain Stress adapted from [Baˇ zant and Gettu, 1992] Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 29 / 35

Role of damage model

Strong effect on the damage pattern . . Similar expansion Damage:

Starts later Higher final value More spread Sample integrity

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 30 / 35

Outline

1

Why numerical modelling?

2

Elleuch’s experiment

3

Numerical model

4

Preliminary sensitivity analysis

5

Conclusion

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 31 / 35

Summary

Conclusions Numerical model for neutron radiation-induced expansion and damage in concrete Validation upon experimental data of the literature [Elleuch et al, 1972] RIVE is the primary cause of loss of strength and stiffness in the material Current model provides a higher bound of the damage . Perspectives Further investigation of the role of creep Strong coupling between temperature and RIVE Effect of mechanical restraint on the expansion and damage propagation Effect of polyphasic aggregates Development of structural models based on series of meso-scale simulations .

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 32 / 35

Questions?

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 33 / 35

References

[1]

• Z. Baˇ

zant and R. Gettu Rate effects and load relaxation in static fracture of concrete. ACI Materials Journal, 89(5):456–468, 1992. [2]

• L. Elleuch, F. Dubois, and J. Rappeneau. Effects of neutron radiation on special concretes and their components. Special Publication of The American

Concrete Institute, 43:1071–1108, 1972. [3]

• K. Field, I. Remec, and Y. Le Pape. Radiation Effects on Concrete for Nuclear Power Plants, Part I: Quantification of Radiation Exposure and

Radiation Effects. Nuclear Engineering and Design, 282:126–143, 2015. [4]

• A. Giorla, M. Vaitov`

a, Y. Le Pape, and P. ˇ

• Stemberk. Meso-scale modeling of irradiated concrete in test reactor. Nuclear Engineering and Design, 259:

59–73, 2015. [5]

• H. Hilsdorf, J. Kropp, and H. Koch. The effects of nuclear radiation on the mechanical properties of concrete. Special Publication of The American

Concrete Institute, 55:223–254, 1978. [6]

• A. Hummel Vom Einfluss der Zementart, des Wasserzementverhaltnisses und des Belastungalters auf das Kriechen des Betons. Zement-Kalk-Gips, 5:

181–187, 1959. [7]

• Y. Le Pape, K. Field, and I. Remec. Radiation Effects in Concrete for Nuclear Power Plants - Part II: Perspective from Micromechanical Modeling.

Nuclear Engineering and Design, 282:144–157, 2015. [8] V.G. Zubov and A.T. Ivanov Expansion of quartz caused by irradiation with fast neutrons . Soviet Physics Crystallography, 11(3):372–374, 1966. Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 34 / 35

List of Acronyms

AMIE Automated Mechanics Integrated Environment EPFL Ecole Polytechnique F´ ed´ erale de Lausanne ITZ Interfacial Transition Zone OPC Ordinary Portland Cement PSD Particle Size Distribution RIVE Radiation Induced Volumetric Expansion RH Relative Humidity

Giorla, Vaitov´ a et al (ORNL, CTU) Meso-Scale Modeling of Irradiated Concrete November 5, 2015 35 / 35