PSI - Issue 22

Maksym Zarazovskii et al. / Procedia Structural Integrity 22 (2019) 305–312 Maksym Zarazovskii and Yaroslav Dubyk / Structural Integrity Procedia 00 (2019) 000 – 000

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4. Conclusions According to the RPV brittle fracture criterion, the open issues are divided onto two groups related to computational aspects of Fracture Mechanics, and Fracture Toughness definitions. As for the computational part:  Estimations within EPFM have shown that the J-integral inherent absence of convergence in case of reloading and at the Bi-metallic interface.  Modelling of WRS needs to be justificated within EPFM, before they are considered as the part of good-practice methodology of RPV integrity assessment.  Currently best-practice is postulating of WRS as additional force/pressure. Based on the current “state of the art” RPV cladding integrity assessment is not related to the good practice. As for the Fracture Toughness part:  The PNAE G-7-002-86 (1989) FT curves for WWER-1000 RPVs are lower envelope of corresponding data. Modern WWER codes have more conservative FT curves which is unreasonable from the practical point of view.  Artificially created upper shelf of FT curve must be excluded at all as it contradicts to the FT nature.  Currently, MC approach is inapplicable for the WWER-1000 RPV integrity assessment.  CTB shift ideology must be improved (in terms of initial CTB and data scatter accounting) or replaced on the usage of actual CBT data and its scatter (obtained directly from Charpy V-notched impact tests).  Chemical factor must be included in the radiation embrittlement assessment as for deterministic RPV brittle strength assessment as well as for probabilistic ones.  VERLIFE’s radiation embrittlement chemical factor for probabilistic RPV brittle fracture assessment contradicts with the results of welds SS of WWER-1000 RPV and cannot be used in the practice. References Arai, K., Okada, H., Yusa, Y., 2018. Formulation of three-dimensional J -integral for finite strain elastic-plastic fracture problems under any load histories (monotonic and cyclic loads). PVP2018-84241 ASME 2018 Pressure Vessels and Piping Conference , ASME, Prague. ASTM E1820. Standard Test Method for Measurement of Fracture Toughness . Brumovsky, M., 1993. Large-scale testing of VVER reactor pressure vessel materials - verification of fracture mechanics calculations. Proceedings of the Joint IAEA/CSNI Specialists' Meeting on Fracture Mechanics Verification by Large-Scale Testing , pp. 331-349. IAEA-TECDOC-1627. 2010. Pressurized Thermal Shock in Nuclear Power Plants: Good Practices for Assessment. Deterministic Evaluation for the Integrity of Reactor Pressure Vessel . IAEA, Vienna. Lei Y. 2005. J -integral evaluation for cases involving non-proportional stressing. Engineering Fracture Mechanics 72, 577 – 596. Lei, Y., 2016. Validation of contour integral functions ( J and C(t) ) in ABAQUS v6.11-v6.14 for combined mechanical and residual stresses. Procedia Structural Integrity 2, 2566 – 2574. MRKR-SKhR-2004. 2004 . Procedure for Calculating the Resistance to Brittle Fracture of the Reactor Vessels in Nuclear Power Plants with WWER During Operation . ROSENERGOATOM, Moscow. MT-D.0.03.391-09. 2009. Procedure for Assessing the Strength and In-service Life of WWER Reactor Pressure Vessels . Energoatom, Kyiv. Nosov, S. I., Chirkin, A. V., 1988. Evaluation of the properties of the root part of welded joints in 15Kh2NMFAA steel. Welding International 2, 112 – 114. Onizawa, K., Nishikawa, H., Itoh, H., 2010. Development of probabilistic fracture mechanics analysis codes for reactor pressure vessels and piping considering welding residual stress. International Journal of Pressure Vessels and Piping 87(1), 2 – 10. Orynyak, I., Zarazovskii, M., Radchenko, S., 2015. Methodological features of WWER RPV metal critical temperature of brittleness prediction on the base of the data scatter and the chemical composition. PVP2015-45679, ASME 2015 Pressure Vessels and Piping Conference , ASME, Boston, Massachusetts, USA. Orynyak, I., Zarazovskii, M., Radchenko, S., Kozlov, V., 2013, To Determination of the WWER RPV Steels Crack Resistance Characteristics. PVP2013-97742, ASME 2013 Pressure Vessels and Piping Conference , ASME, Paris. PM- Т.0.03.120 -08. 2009. Typical program for properties control of WWER-1000 RVP metal by surveillance specimens . Energoatom, Kyiv. PNAE G-7-002-86. 1989. Code for Strength Calculations of Components and Piping in Nuclear Power Plants . Energoatomizdat, Moscow. Probert, M., Coules, H., Truman, C., 2018. Effects of crack introduction history on fracture initiation in residually stressed components. PVP2018 84412, ASME 2018 Pressure Vessels and Piping Conference , ASME, Prague. Timofeev, B. T., Karzov, G. P., Blumin, A. A., Anikovsky, V. V., 1994, Fracture toughness of 15X2HMFA and its welds. Int. J. Pres. Ves. & Piping 74, 165 – 172. VERLIFE. 2008. Unified Procedure for Lifetime Assessment of Components and Piping in WWER NPPs .