Abstract
Background
Environmental-assisted fatigue (EAF) is a major issue for the long-term survival of nuclear power plant fleets in the U.S. and worldwide. Multi-material welded regions (e.g., nozzles) and other high-stress regions of reactor coolant system (RCS) components are prone to EAF-related damage.
Objective
The discussed work describes a system-level finite element (FE) model of RCS components of a pressurized water reactor (PWR). This is with the goal of predicting the stress hotspots, strain residuals, strain amplitudes and the resulting fatigue lives.
Methods
The FE model was developed considering system-level loading conditions (under connected system thermal–mechanical boundary conditions). Thermal–mechanical stress analysis was performed considering thermal stratification and a design-basis reactor loading cycle. Based on the FE model results, the strain residuals, strain amplitudes and resulting fatigue lives of RCS components were predicted.
Results
The results show that some of the RCS components can have significantly different strain amplitudes, residual strain, and fatigue lives, despite having similar geometry and material. Higher residual strain can lead to accelerated cyclic hardening of material and the associated effect of EAF. The simulated component-level strain profile (under realistic multi-axial-multi-physics loading cycle) can guide the selection of appropriate test inputs for conducting laboratory-scale EAF tests, which is a focus of future works.
Conclusions
Despite similar geometry and material the RCS component can have significantly different strain profiles and resulting fatigue lives. The discussed approach can help to identify and prioritize the RCS components for conducting expensive nondestructive evaluation (NDE) inspections.
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Abbreviations
- CL:
-
Cold Leg
- DMW:
-
Dissimilar Metal Weld
- EAF:
-
Environmental Assisted Fatigue
- HL:
-
Hot Leg
- LAS:
-
Low Alloy Steel
- LTO:
-
Long Term Operation
- NDE:
-
Non-Destructive Evaluation
- NPP:
-
Nuclear Power Plant
- PRZ:
-
Pressurizer
- PWR:
-
Pressurized Water Reactor
- RCS:
-
Reactor Cooling System
- RPV:
-
Reactor Pressure Vessel
- SG:
-
Steam Generator
- SL:
-
Surge Line
- SMW:
-
Similar Metal Weld
- SS:
-
Stainless Steel
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Acknowledgements and Funding
This research was supported through the U.S. Department of Energy’s Light Water Reactor Sustainability program under the work package of environmental fatigue study with program manager Dr. Thomas. M. Rosseel and deputy program manager Dr. Xiang (Frank) Chen.
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Appendix
Appendix
Expansion coefficients for 316SS and 508LAS base, 316SS-316SS SW filler, and 316SS-508LAS DW filler and butter welds.
Temp (°C) | 316SS base metals | 508LAS base metals | 316SS-316SS SW filler (E316-16) welds | 316SS-508LAS DW filler (In 82) welds | 316SS-508LAS DW butter (In 182) welds |
---|---|---|---|---|---|
Expansion coeff (1/°C) | Expansion coeff (1/°C) | Expansion coeff (1/°C) | Expansion coeff (1/ °C) | Expansion coeff (1/ °C) | |
21.11 | 2.8385E-06 | 8.0805e-06 | 4.4273e-07 | 3.3078e-06 | 7.9477e-06 |
31.11 | 2.8385E-06 | 8.2561e-06 | 4.4273e-07 | 4.067e-06 | 7.8772e-06 |
41.11 | 3.4739E-06 | 8.7299e-06 | 8.7463e-07 | 4.7487e-06 | 7.8772e-06 |
51.11 | 4.6378E-06 | 9.1746e-06 | 2.2e-06 | 5.2931e-06 | 7.8772e-06 |
61.11 | 5.7242E-06 | 9.5914e-06 | 3.4306e-06 | 5.7206e-06 | 7.8772e-06 |
71.11 | 6.7361E-06 | 9.9815e-06 | 4.5703e-06 | 6.0495e-06 | 8.8574e-06 |
81.11 | 7.6763E-06 | 1.0346e-05 | 5.6232e-06 | 6.2969e-06 | 9.9318e-06 |
91.11 | 8.5479E-06 | 1.0686e-05 | 6.5934e-06 | 6.4781e-06 | 1.0949e-05 |
101.11 | 9.3536E-06 | 1.1003e-05 | 7.4849e-06 | 6.6072e-06 | 1.1855e-05 |
111.11 | 1.0096E-05 | 1.1298e-05 | 8.3017e-06 | 6.6965e-06 | 1.2624e-05 |
121.11 | 1.0779E-05 | 1.1572e-05 | 9.0479e-06 | 6.7574e-06 | 1.3251e-05 |
131.11 | 1.1405E-05 | 1.1826e-05 | 9.7275e-06 | 6.7998e-06 | 1.375e-05 |
141.11 | 1.1976E-05 | 1.2062e-05 | 1.0344e-05 | 6.8322e-06 | 1.414e-05 |
151.11 | 1.2496E-05 | 1.2281e-05 | 1.0903e-05 | 6.8621e-06 | 1.4445e-05 |
161.11 | 1.2967E-05 | 1.2483e-05 | 1.1407e-05 | 6.896e-06 | 1.4693e-05 |
171.11 | 1.3393E-05 | 1.267e-05 | 1.186e-05 | 6.9392e-06 | 1.4906e-05 |
181.11 | 1.3776E-05 | 1.2843e-05 | 1.2267e-05 | 6.9961e-06 | 1.5104e-05 |
191.11 | 1.4119E-05 | 1.3004e-05 | 1.2632e-05 | 7.0699e-06 | 1.5301e-05 |
201.11 | 1.4425E-05 | 1.3153e-05 | 1.2958e-05 | 7.1633e-06 | 1.5506e-05 |
211.11 | 1.4697E-05 | 1.3292e-05 | 1.325e-05 | 7.278e-06 | 1.572e-05 |
221.11 | 1.4938E-05 | 1.3422e-05 | 1.3512e-05 | 7.415e-06 | 1.5941e-05 |
231.11 | 1.5151E-05 | 1.3544e-05 | 1.3747e-05 | 7.5745e-06 | 1.6162e-05 |
241.11 | 1.5338E-05 | 1.3659e-05 | 1.396e-05 | 7.7563e-06 | 1.6372e-05 |
251.11 | 1.5503E-05 | 1.3768e-05 | 1.4155e-05 | 7.9594e-06 | 1.6558e-05 |
261.11 | 1.5648E-05 | 1.3873e-05 | 1.4336e-05 | 8.1823e-06 | 1.6709e-05 |
271.11 | 1.5777E-05 | 1.3974e-05 | 1.4506e-05 | 8.4232e-06 | 1.6816e-05 |
281.11 | 1.5891E-05 | 1.4073e-05 | 1.4671e-05 | 8.6799e-06 | 1.6872e-05 |
291.11 | 1.5995E-05 | 1.4172e-05 | 1.4833e-05 | 8.9497e-06 | 1.6878e-05 |
301.11 | 1.6091E-05 | 1.427e-05 | 1.4998e-05 | 9.2298e-06 | 1.6842e-05 |
311.11 | 1.6181E-05 | 1.437e-05 | 1.5168e-05 | 9.5171e-06 | 1.6783e-05 |
321.11 | 1.6269E-05 | 1.4473e-05 | 1.5348e-05 | 9.8083e-06 | 1.6728e-05 |
331.11 | 1.6358E-05 | 1.4579e-05 | 1.5543e-05 | 1.01e-05 | 1.672e-05 |
341.11 | 1.6450E-05 | 1.469e-05 | 1.5755e-05 | 1.0389e-05 | 1.6811e-05 |
350 | 1.6538E-05 | 1.4794e-05 | 1.5963e-05 | 1.0642e-05 | 1.7028e-05 |
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Mohanty, S. A System-Level Model for Estimating Residual Strain and Life of Nuclear Reactor Coolant System Components Under Connected-System-Thermal–Mechanical Boundary Conditions. Exp Mech 62, 1501–1517 (2022). https://doi.org/10.1007/s11340-022-00847-5
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DOI: https://doi.org/10.1007/s11340-022-00847-5