Patent ID: 8670514

Claim:
A pressurized water reactor nuclear steam supply system steam generator pressure vessel having a secondary side for separating steam from condensate comprising: a generally horizontal deck plate within the secondary side of the pressure vessel defining an access opening extending between an upper surface of the deck plate and an undersurface; a removable plate for covering the access opening; a pin holder attached to either one of the deck plate or the removable plate; an elongated mechanical pin retractably attached to the pin holder for moving in a generally horizontal plane between a closed position and an open position; a receiving socket attached to the other one of the deck plate or the removable plate for engaging the mechanical pin in its closed position; a locking mechanism for securely locking the pin when the pin is in the closed position, throughout steam generator operation, the locking mechanism including a lock nut; and wherein the pin has a first peripheral end that engages the receiving socket and a second peripheral end wherein at least a portion of a surface of the pin between the first peripheral end and the second peripheral end is threaded to engage the lock nut.