Small Punch Tests to Evaluate the Tensile Properties of Highly Irradiated LYRA-10 RPV Model Steels

In the past few years, miniature testing techniques to evaluate the mechanical properties of structural materials of nuclear reactors have gained interest due to the limited number of irradiated surveillance specimens and strict safety regulations. One of such miniature testing techniques is the Small Punch Testing (SPT) method, which uses tiny discs to estimate mechanical properties such as tensile properties, fracture toughness and the ductile-to-brittle transition temperature of the examined material. As described in the ASTM E3205 standard: Standard Test Method for Small Punch Testing of Metallic Materials, empirical relations are used to correlate the yield strength and the ultimate tensile strength to the SPT parameters determined from the investigated material. The validity of these empirical relations at high fluence irradiation needs to be further studied and understood to assess the potential applicability of the SPT technique for the evaluation of the effect of high-fluence irradiation in reactor pressure vessel (RPV) steels and for the implementation of this testing method in surveillance programs of existing nuclear power plants. In this current work, SPT tests have been performed on six RPV model steels in the as-received and highly neutron irradiated state. These alloys were part of the joint NRG-JRC irradiation campaign LYRA-10 and resemble VVER and PWR RPV steels with tailored chemical compositions to study the synergetic effect of Ni, Mn and Si in the high fluence regime. The tensile properties of these materials prior and after irradiation are correlated with the SPT results and the shifts in SPT fitting parameter β_p0.2 as effect of irradiation and chemical composition are studied to evaluate the effectiveness of this technique for screening of irradiation-induced hardening.

NAZIRIS F. (Kiki);  ADAMECH Marek;  MARQUES PEREIRA Vivian;  MARTIN Oliver;  BAKKER Theo;  KOLLURI M.; 

2024-12-19

American Society of Mechanical Engineers (ASME)

JRC138136

978-0-7918-8847-6 (online),   

https://asmedigitalcollection.asme.org/PVP/proceedings-abstract/PVP2024/88476/V001T01A060/1209304,    https://publications.jrc.ec.europa.eu/repository/handle/JRC138136,   

10.1115/PVP2024-122633 (online),