Abstract: A nuclear reactor having a remotely removable and replaceable thermal insulating shield for the head. Access permitting removal and replacement of the head is thus afforded.The thermal insulating shield includes a vertical frame of insulating material of polygonal transverse cross section encircling the head. A top panel of insulating material is mounted on the top of the frame pivotal by remote actuation between a horizontal position and a retracted position which may be vertical. In the horizontal position, the panels mate to provide thermal shielding for the head.

Abstract: An upwardly convex resilient annular strainer, fixed to the secondary core support base plate in a PWR, bends to remain in contact with the lower hemispherical head section of the pressure vessel as the gap between the internals and the lower hemispherical head section varies in size with reactor temperature to prevent debris from lodging in the gap where it could lead to reactor damage.

Abstract: A nuclear reactor having a remotely removeable and replaceable thermal and/or radiation insulating shield for the head. This shield is formed of interlocked integrated shielding units of thermal insulating material. Each unit has a vertical member and a horizontal member. Each unit has a lifting-and-lowering rod on its top and it may be raised vertically by a remotely operable clamp engaging the head. The interlocking surfaces of adjacent units are so formed that when any unit is raised or lowered vertically its interlocking surface readily slides along the interlocking surfaces of the units adjacent to it with which it is interlocked.