Session: CS-19-03 European Project FRACTESUS for mini-CT Master Curve - 1

Paper Number: 107254

107254 - Master Curve Evaluation Using Miniature C(t) Specimens as Part of a Round Robin Program Within the Fractesus Project 

Surveillance testing is the basis for all reactor pressure vessel (RPV) integrity and lifetime assessments to evaluate the validity of the RPV embrittlement trend curve used for a specific reactor.  Most of the standard surveillance programmes, do not contain sufficient number of surveillance specimens for beyond the original design life of 40 years. Thus, testing methods based on small / sub-sized specimens are considered.  Experimental programmes have proven that miniature compact tension (4*9.6 *10 mm³) specimens, mini-CT, can successfully be used for fracture toughness characterization in the transition regime and can be applied for reference temperature (T₀) determination based on the master curve method. However, application of miniature testing techniques on irradiated materials in hot cells comes along with several technical challenges such as remote controlled machining, application of the extensometers, manipulator sensitivity, accurate sample geometry measurement etc. In addition, the optimal test temperature range for obtaining valid  K_IC  values for the mini-CT specimen is narrow and consequently sufficient number of specimens should be tested  to guarantee a reliable valid T₀-value.

Within the FRACTESUS project, European and International efforts are joined to establish the foundation of small specimen fracture toughness validation and demonstration to achieve change in code and standards allowing to address the various national regulatory authority concerns. As part of the third work package (WP), high-fluence fracture toughness data, on well characterized RPV materials, will be produced to serve as input for the guidelines of future testing. 

To assure the robustness of the testing procedures to the difference in testing machines or operators, a round robin (RR) exercise on un-irradiated materials is organised among the partners of WP3. This work presents the preliminary results of the mini-CT fracture toughness data on un-irradiated RPV SA503 Cl. 3 material which was independently tested by three institutes: CIEMAT, KIT and NRG. All three institutes determined T₀ according to the ASTM E1921 standard and the results are compared and discussed in this work.

Presenting Author: Frideriki Naziris NRG

Presenting Author Biography: Frideriki Naziris works as a material consultant at NRG since 2020. She mainly focuses on the cange of mechanical properties of materials due to irradiation damage.

Authors:

Frideriki Naziris NRG
Rebeca Hernandez CIEMAT
Timo Metzler KIT
Ermile Gaganidze Karlsruhe Institute of Technology
Inge Uytdenhouwen SCK CEN, Nuclear Materials Science Institute
Murthy Kolluri NRG