Integral reactor cavity seal/shield

This patent describes a nuclear reactor wherein a reactor pressure vessel having a lower portion and a removable head is surrounded by a structural wall to define a gap between the pressure vessel and the structural wall, a seal/shield assembly normally in place during operation and refueling of the reactor. The seal/shield consists of: a water-tight seal welded to the lower portion of the pressure vessel and the structural wall. The seal has an associated bellows for accommodating relative movement between the pressure vessel and the structural wall; and a shield defined by a substantially consolidated body of solid neutron-absorbing material fixed to and supported by the seal and generally coextensive therewith