Lead (or lithium lead) would not work for ARC, because it is electrically conductive. It would not be possible to pump it in the strong magnetic field because of the back EMF generated. This is also why PbLi with vanadium structures was abandoned for DEMO: it proved impossible to make an insulating coating for the metal structures that would prevent the induced currents from flowing. Even slight cracks in the coating were found to be ruinous.