Patent Number: 063013193
Section: abstract

A method of temporarily sealing a reactor pressure vessel during an outage permits the water level in the vessel to be drawn down to a level which enables the interior surfaces of associated structures and equipment in the primary coolant loop to be inspected while dry when the vessel is submerged in a pool of water. A reactor pressure vessel internals lifting rig is used to position a temporary reactor pressure vessel head having an elliptical shaped dome with a circumferential flange retaining a pair of spaced apart, circumferential seal rings onto a reactor pressure vessel circumferential flange without marking or damaging the reactor pressure vessel flange. Advantageously, the weight of the temporary head (together with the static head of water, which must be supported by the elliptical design of the dome) is sufficient to cause the seal rings to seal against the reactor pressure vessel flange without the need for studs or other mechanical fasteners or the need to pump out leakage from the pool of water above the reactor pressure vessel. The flanges and the rings define a space which is tested for leak-tightness.