EU RESULTS ON NEUTRON EFFECTS ON PFC MATERIALS

Among the low-Z materials, carbon and beryllium are primary candidates for use as plasma facing materials for the International Thermonuclea r Experimental Reactor (ITER), because of extensive experience in thei r application for first wall and divertor plate protection in existing tokamaks. In addition, their excellent plasma performance has been de monstrated. Carbon based materials have been chosen for protection of high heat flux components, whilst beryllium has been proposed as the f irst wall material for ITER. However, as next generation D/T plasma de vices, i.e. ITER, will produce intense neutron fluxes, substantial R&D is needed to elucidate the effects of neutron-induced damage on the m icrostructure and critical properties of these materials, e.g. thermal conductivity, swelling, and tritium trapping, because they could limi t the use of these materials in the next generation fusion devices. Ne utron induced changes in thermal conductivity, dimensional stability, mechanical properties as well as behaviour of tritium interaction are crucial problems which need to be better understood. The assessed neut ron flux of ITER will be around 3.5-9.0 x 10(14) cm(-2) s(-1) for the first wall, whilst the neutron flux for the divertor is around 1-3 x 1 0(14) cm(-2) s(-1), for which leads to a damage of around 10-20 dpa fo r the first wall and 3-6 dpa for the divertor for 1 full power year of operation. In the framework of European fusion R&D programs, an exten sive effort on neutron effects on plasma facing component (PFC) materi als is being undertaken. This paper presents the recent results of exp eriments performed to investigate the effects of neutron doses and il: radiation temperature on the thermal conductivity, mechanical properti es, dimensional stability and tritium inventory of various carbon base d materials as well as beryllium. The consequences are discussed. (C) 1998 Elsevier Science S.A. All rights reserved.