Implementation of Small Punch Testing and Automated Ball Indentation in the Process of Irradiated NPP Materials Degradation Evaluation

Abstract

In the terms of nuclear power plant operational life management, current trend of components lifetime extension requires precise and credible information of structural material degradation. Present-day standard conventional methods of mechanical testing are usually based on the use of large specimens and higher consumption of testing material, whose availability and volume is often limited. For determination of material properties, sampling of the necessary volume of material is in most cases connected with affecting the integrity or even destruction of the assessed component. Moreover, several components are not usually covered surveillance programs, e.g. reactor pressure vessel internals. Innovative testing methods of Small Punch Testing (SPT) and Automated Ball Indentation Test (ABIT) are based on the determination of material properties from miniaturized testing specimens and their semi-destructive approach is very promising for the possibility of present data base of irradiated materials testing results enlargement and enable the option of component in-situ testing (ABI testing). Paper describes the process of implementation of Small Punch Testing and Automated Ball Indentation Testing techniques in the evaluation of mechanical properties of irradiated NPP structural materials degradation. Presentation depicts all necessary steps carried out at the Hot Cell facility of UJV Rez, a. s. (Integrity and Technical Engineering Division) for the employment of these innovative testing techniques to the portfolio of accredited mechanical tests performed within the frame of surveillance programs of WWER type reactors — e.g. preliminary design, modification of the testing equipment, fractography analyses etc. Detailed comparison between the results of standard conventional testing techniques and SPT and ABIT for both initial unirradiated and irradiated state for the material A533B (JRQ) is included for determination of suitability of used methods for testing of materials within the surveillance programs of WWER type reactors.