“Measurement of void swelling in thick non-uniformly irradiated 304 stainless steel blocks using nondestructive ultrasonic techniques”
Void swelling is of potential importance in PWR austenitic internals, especially in components that will see higher doses during plant lives beyond 40 years. Proactive surveillance of void swelling is required to identify its emergence before swelling reaches levels that cause high levels of embrittlement and distortion. Non-destructive measurements of ultrasonic velocity can measure swelling at fractions of a percent. To demonstrate the feasibility of this technique for PWR application we have investigated five blocks of 304 stainless steel that were irradiated in the EBR-II fast reactor. These blocks were of hexagonal cross-section, with thickness of ~50 mm and lengths of ~218-245 mm. They were subjected to significant axial and radial gradients in gamma heating, temperature and dpa rate, producing complex internal distributions of swelling, reaching ~3.5% maximum at an off-center mid-core position. Swelling decreases both the density and elastic modulii, thereby impacting the ultrasonic velocity. Concurrently, carbide precipitates form, producing increases in density and decreases in elastic modulii. Using blocks from both low and high dpa levels it was possible to separate the ultrasonic contributions of voids and carbides. Time-of-flight ultrasonic measurements were used to non-destructively measure the internal distribution of void swelling. These distributions were confirmed using non-destructive profilometry followed by destructive cutting to provide density change and electron microscopy data. It was demonstrated that the four measurement types produce remarkably consistent results. Therefore ultrasonic measurements offer great promise for in-situ surveillance of voids in PWR core internals.
- Research Organization:
- Idaho National Lab. (INL), Idaho Falls, ID (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- DE-AC07-05ID14517
- OSTI ID:
- 1169232
- Report Number(s):
- INL/CON-14-33001
- Resource Relation:
- Conference: Fontevraud 8 - Contribution of Materials Investigations and Operating Experience to LWRs’ Safety, Pe,Avignon, France,09/14/2014,09/18/2014
- Country of Publication:
- United States
- Language:
- English
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Assessment of void swelling in austenitic stainless steel PWR core internals.
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