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Prof. Dr.-Ing. Jarir Aktaa

jarir aktaa does-not-exist.kit edu

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Development and qualification of high-temperature design and crack assessment rules for RAFM steels and their welds

Nonlinear finite element analysis for the assessment of a crack in a TBM mockup
Nonlinear finite element analysis for the assessment of a crack in a TBM mockup

Reduced activation ferritic martensitic (RAFM) steels among others EUROFER97 and F82H are promising candidates as structure materials for first wall components of future fusion power plants.

During planed operation structural materials of in-vessel plasma facing components blanket and divertor are subjected to cyclic thermo-mechanical loading and high irradiation doses which yield different types of lifetime limiting failure mechanisms: ratcheting, creep, fatigue, and radiation induced loss of ductility and toughness.

Within our activities in the EFDA and F4E Technology Work program structural design criteria for components built from EUROFER97 will be developed and qualified. Our research is focused on high temperature rules, particularly those for preventing creep, fatigue, and creep/fatigue interaction, not yet considered and implemented in the current ITER Structural Design Criteria for In-Vessel Components (SDC-IC). Therefore we developed and formulated high temperature creep-fatigue design rules for the assessment of components built from EUROFER97 on the base of the current design codes well established for nuclear applications: ASME Boiler and Pressure Vessels Code and the French RCC-MR code. These rules have been extended to assess EUROFER97 welding joints (TIG, EB, laser diffusion welds) foreseen in the current designs of blanket and divertor. The extension has been done mainly by following the guidelines of the ASME Boiler and Pressure Vessels Code, code case N-47-29 for the consideration of welds.

For the assessment of cracks situated in components built from EUROFER97, particularly in areas operating at high temperature, rules based on elasto-viscoplastic fracture mechanics like those of the R5 code (British Standard) are considered. Accordingly the crack loading is determined in terms of the C(t)-integral which is an objective representative measure for the stress and strain rate fields ahead of the crack tip. For the determination of this integral the R5 code provides simplified formulae which might not be straightforward applicable to the cracks in structures built of RAFM steels due to the non-common viscoplastic behavior exhibited by these steels. Therefore our ongoing activities aim for the verification of the applicability of the R5 code rules to cracks in EUROFER97 structures and for the development and formulation of modified rules if required.

 


Publications

F. Siska, J. Aktaa, Fusion Engineering and Design, In Press, 2010.

J. Aktaa, M. Weick, C. Petersen, Journal of Nuclear Materials 386-388 (2009) 911-914.

F. Siska, J. Aktaa, Wissenschaftliche Berichte des Forschungszentrums Karlsruhe, FZKA-7450, Forschungszentrum Karlsruhe, Juni 2009.

J. Aktaa, Wissenschaftliche Berichte des Forschungszentrums Karlsruhe, FZKA-7449, Forschungszentrum Karlsruhe, Oktober 2009.

J. Aktaa, M. Weick, M. Walter, Wissenschaftliche Berichte des Forschungszentrums Karlsruhe, FZKA-7309, Forschungszentrum Karlsruhe, August 2007.

R. Sunyk, J. Aktaa, Wissenschaftliche Berichte des Forschungszentrums Karlsruhe, FZKA-7241, Forschungszentrum Karlsruhe, August 2006.