High pressure thimble/guide tube seal fitting with built-in low pressure seal especially suitable for facilitated and more efficient nuclear reactor refueling service

A HP/LP seal arrangement for an elongated guide tube and an elongated thimble disposed therein, said guide tube and thimble extending outwardly from the core of a nuclear reactor to a seal table where said guide tube is welded to the seal table to provide a high pressure seal relative thereto, said seal arrangement comprising:

• a tubular seal fitting disposed in alignment with said guide tube with said thimble extending therethrough on the low pressure side of the seal table;
• first high pressure sealing means coupling one end of said fitting to an end of said guide tube to prevent leakage from within said guide tube;
• inwardly facing thread means disposed adjacent the other and outer end of said seal fitting;
• a nut having an opening through which said thimble extends and further having outwardly facing threading in mating engagement with said fitting thread means;
• said fitting having a seal seat spaced longitudinally inwardly from said thread means and facing said fitting outer end and further disposed annularly about the inner surface of said fitting;
• deformable ring seal means disposed about said thimble and between said nut and said fitting seal seat and having respective surfaces in engagement with the radially outwardly facing surface of said thimble, the radially inwardly facing surface of said fitting and said fitting seal seat to provide a low pressure seal between said fitting and said thimble;
• and
• second releasable high pressure sealing means coupling said thimble to the outer end portion of said guide tube.