PSI - Issue 42

S. Lindqvist et al. / Procedia Structural Integrity 42 (2022) 42–49 Author name / Structural Integrity Procedia 00 (2019) 000–000

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4. Conclusions Presently, there is no data, nor predictions, regarding the J-R curve development during a decreasing thermal transient. In this study, the effect of rapid cooling on J-R curves is investigated. Fracture toughness specimens of thermo-mechanically rolled ferritic steel plate 460MC were cooled from 300 ° C to the room temperature at a cooling rate of 2 ° C/s determined at the center location of the specimen. The cooling rate is faster close to the surface. The cooling rate was selected to be in the same range as during a loss of coolant accident. The following was concluded: 1. No brittle fracture in the upper shelf region was observed for the investigated material during the cooling transient. 2. Based on the results, when doing structural integrity analyzes of thermal transients in the upper shelf region, it is recommendable to use the lowest fracture toughness properties in the investigated temperature range, if no other information is available. Acknowledgements The writing of this paper was funded by project AMOS (Advanced materials characterisation for structural integrity assessment) part of SAFIR2022 (The Finnish Research Programme on Nuclear Power Plant Safety 2019 - 2022). References [1] Wallin KRW. Potential for a fast fracture occurring in the upper shelf area. VTT-R-04898-14. SAFIR2014. Project FAR. 2014. [2] Wallin K. Fracture toughness of engineering materials - estimation and application. EMAS publishing; 2011. [3] Ericksonkirk MT, Chokshi N, Woods R, Junge M, Malik S, Bessette D. Technical basis for revision of the pressurized thermal Shock (PTS) screening limit in the PTS rule (10 CFR 50.61), Summary report. NUREG 1806. vol. 1. 2007. [4] Cronvall O. Fast fracture analyses for boiling water reactor pressure vessel and its internals. Balt XI -2019 2019. [5] Lindqvist S, Sirkiä L, Karjalainen-Roikonen P. Tearing resistance under isothermic and decreasing thermal transients. VTT research report. VTT- R-06958-18. SAFIR2018. LOST (Longterm operation aspects of structural integrity). 2018. [6] Lara Melcher PJ, Castrodeza EM. Fracture toughness of SE(B) specimens of steel in the presence of splitting. 13th Int Conf Fract 2013, ICF 2013 2013;4:3332–41.