(FT/1-4Ra) Mechanical Properties of Reduced Activation Ferritic/Martensitic Steels after European Reactor Irradiations

C. Petersen1), J. Aktaa1), E. Diegele5), E. Gaganidze1), R. Lässer5), E. Lucon6), E. Materna-Morris3), A. Möslang3), A. Povstyanko2), V. Prokhorov2), J.W. Rensman4), B. van der Schaaf4), H.-C. Schneider1)
1) FZK, IMF II, P.O. Box 3640,76021 Karlsruhe, Germany
2) SSC RF RIAR, OMB&T, 433510, Dimitrovgrad, Russia
3) FZK, IMF I, P.O. Box 3640,76021 Karlsruhe, Germany
4) NRG, MM&I, P.O. Box 25, 1755 ZG Petten, The Netherlands
5) EFDA, CSU, Boltzmannstrasse 2, D-85748 Garching, Germany
6) SCK-CEN, Boeretang 200, 2400 Mol, Belgium

Abstract.  The timely development of First Wall and Blanket materials which are capable of withstanding many years the high neutron and heat fluxes, is for material scientists a critical path to fusion power. In an energy generating fusion reactor, structural materials will be exposed to very high levels of irradiation damage up to about 150 dpa. Regarding the radiation damage resistance of the considered Reduced Activation Ferritic/Martensitic steels like the European EUROFER and the Japanese F82H mod., as international reference material of this kind, broad European reactor irradiation programs cover several steps from up to 5 dpa for ITER Test Blanket Modules, till up to 80 dpa for First Wall and Blanket of a DEMO fusion reactor. The lower irradiation damage conditions until 15 dpa can be realized in European fission reactors like the HFR at JRC, Petten, but higher damages - in reasonable times - in fast reactors only. For this purpose the fast reactor BOR 60 of the State Scientific Centre of Russian Federation Research Institute of Atomic Reactors, Dimitrovgrad, has been utilized for irradiations up to 80 dpa. Results from the lower damage irradiations like SIENA, MANITU and HFR-Ib, up to 2.4 dpa had been reported in the past frequently. Recent results of mechanical properties, like Ductile to Brittle Transition Temperatures from instrumented impact-V tests with sub size specimens and stress and strain values from tensile tests with miniaturized specimens will be presented from specimens of the HFR Phase-IIb (SPICE) irradiation project up to 15 dpa at different irradiation temperatures between 250 and 450oC. The fast reactor irradiation project ARBOR 1 reached at temperature 340oC an irradiation damage of 33 dpa. In the post irradiation instrumented impact-V tests a significant increase in the Ductile to Brittle Transition Temperature as an effect of irradiation has been detected. During tensile testing the strength values are increased and the strain values reduced due to substantial irradiation hardening. Post irradiation heat treatments revealed novel and very encouraging results: After first thermal recovery tests with 550oC annealing for three hours it could be demonstrated on EUROFER specimens irradiated at 340oC up to 15 dpa, that nearly virgin conditions in Ductile to Brittle Transition Temperature and tensile behavior could be achieved.

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