Life Extension and Long-Term Operation
Life extension of nuclear power plants (NPP) from 40 to 60 years has been approved for nearly 50% of the US fleet, and consideration is being given to extending that further to possibly 80 years. In order to obtain licenses for such extensions, it is necessary to develop a comprehensive understanding of the behavior of materials, some heavily irradiated by neutrons, as a function of extended age and environmental factors. ANATECH has been heavily involved in this work and in the Materials Reliability Program (MRP) being conducted by EPRI for the industry. As such, ANATECH has developed many of the material aging and degradation models and thus supports utilities in their relicensing efforts.
Reactor Internals
ANATECH has provided engineering services for the analysis of reactor internals in support of the EPRI Materials Reliability Program (MRP), including the Reactor Internals Issue Task Group (RI-ITG) and the Joint Owner’s Baffle Bolt (JOBB) programs. ANATECH provided the expertise and experience required to extract the appropriate experimental data to describe the service conditions of reactor internal components. That information was then used in the development of unique material constitutive models for irradiated stainless steel types 304 and 316. ANATECH constructed these models for use in a finite-element-based analysis environment for the functionality evaluation of PWR reactor internals under long-term reactor operation.
The material properties considered in the model included
- The elastic-plastic properties represented in the complete stress-strain curve (elastic modulus, yield strength, ultimate tensile strength, uniform elongation and total elongation) expressed as functions of initial cold work, irradiation dose, and temperature
- Irradiation creep
- Void swelling
- Material failure limits associated with the primary damage mechanisms considered to be potentially operative in stainless steel components in PWR environments.
These mechanisms included irradiation-assisted stress corrosion cracking (IASCC) and irradiation-induced loss of ductility. ANATECH’s technical contribution to this project was essential to address this technical issue and is a prime example of the how ANATECH applies unique, analytical approaches and methods to topical and emerging technical issues facing the nuclear industry.
