Abstract: A permanent pool seal and neutron shield 30 for providing an effective water barrier over the annular space 28 between a nuclear reactor vessel flange 24 and a surrounding annular ledge 22 includes annular deck sections 32 supported on spaced ribs 46.Flexible membranes 50,52 on the deck section peripheries accommodate relative movement. Openings 42, each with a removable plug structure which includes cover 44 and tapered can 60, provide vessel cavity 14 with ventilation and maintenance access. All cans 60 and similar containers 56 and 59 under the deck structure and flange 24 contain a shielding material 58 in the form of a boron-containing concrete. Supported below the cans is refractory insulating material 54.

Abstract: An arrangement for temporarily sealing the space between two substantially parallel, adjacent plates in which a flexible, partially inflatable seal is located between the plates to effect primary and secondary sealing interfaces along the upper and lower edges of the plates, respectively. The seal has a wedge-shaped upper portion, a tubular lower portion and a substantially solid intermediate shank. The tubular end of the seal is inflated so that it expands into contact with the lower edges of the plates, drawing the wedge-shaped upper portion of the seal toward the tubular portion, thereby forming primary sealing interfaces between the wedged-shaped portion and the upper edges of the plates. The contact of the inflated tubular portion with the lower edges of the plates forms secondary seal interfaces. The effectiveness of the seal can be tested by measuring the pressure in the chambers formed between each set of primary and secondary sealing interfaces.