EMBRITTLEMENT BEHAVIOR OF DIFFERENT INTERNATIONAL LOW-ACTIVATION ALLOYS AFTER NEUTRON-IRRADIATION

The embrittlement behaviour of ferritic/martensitic steels, after irra diation in the Petten High Flux Reactor (HFR), was investigated by Cha rpy-V tests with subsize specimens. The main objective, apart from stu dying the effects of particularly low doses, was to compare the irradi ation response of low activation alloys from various countries with di fferent levels of Cr, minor alloying elements and impurities. Specimen s were irradiated at temperatures ranging between 250 degrees C and 45 0 degrees C to dose levels between 0.2 and 2.4 dpa. The evaluation cle arly showed a tendency to a much reduced embrittlement problem for the advanced reduced-activation alloys; it could not, however, be attribu ted to lower Cr-contents. Instead, the role of helium, already suspect ed in our earlier work, could be correlated with the characteristic bu rn-up of different boron levels in the steels. This correlation transl ates for a fusion reactor environment into a non-saturating deteriorat ion of alloys even without any boron, due to helium-yielding high ener gy neutron reactions with the base elements. Though the effect seems t o be less detrimental for the more homogeneous distribution of the hel ium in the matrix. (C) 1998 Elsevier Science B.V. All rights reserved.