Assessment of the lifetime of the beam window of the MEGAPIE target liquid metal container
Résumé
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 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 thickness of the wall by 3-4 percent. This should not be a critical issue. However, the corrosion induced grain boundary penetration will promote LBE embrittlement on the T91 steel in the beam window. Evaluated from the DBTT shift data and fracture toughness values of T91 specimens tested in LBE, the lower bound of the lifetime of the T91 beam window is considered as the time when the steel becomes brittle at the lowest operation temperature, 230DC. Taking a 30percent margin, it gives a dose limit of about 6 dpa, corresponding to 2.4 Ah proton charge received by the target. Considering the function of the AlMg3 safety container, the upper bound of the lifetime of the T91 beam window would be when the DBTT reaches the maximum operation temperature, 340DC. It would be 12 dpa or 4.9 Ah.