Assessment of the lifetime of the beam window of MEGAPIE target liquid metal container

The lifetime of the beam window of the T91 liquid Pb-Bi container in the MEGAPIE target is discussed based on the present knowledge of lead bismuth eutectic (LBE) corrosion, embrittlement and radiation effects in relevant conditions. In the MEGAPIE target, since the high hydrogen production will likely reduce the oxygen content to a low level, LBE corrosion may reduce the wall thickness up to 2%. In addition, the corrosion induced grain boundary dissolution will promote LBE embrittlement on the T91 steel in the beam window. The DBTT data and fracture toughness values of T91 specimens tested in contact with LBE suggest a lower bound of the lifetime of the T91 beam window to be limited to a dose of 6 dpa, corresponding to 2.4 Ah proton charge to be received by the target in about 20 weeks in the normal operation condition.