Yes, Pilgrim, a BWR has installed "permanent shielding" in their Drywell. We are in the process of an engineering analysis to do the same. In the mean time, ours is not installed, but the engineers have given the approval to "store" our shielding on the elevations of our Drywell to reduce the dose of just carrying the shielding from its' locations at shut down / start up. I know there are several PWR's that store the shielding inside Containment during operation, as long as it meets seismic requirements. I think Vogtle has been doing it for years.