Method and arrangement for compression sealing an omega joint

An arrangement for joining an elongated housing to a nuclear reactor vessel nozzle by means of an omega seal, comprising:

• a vessel nozzle rigidly extending along a vertical axis from a reactor vessel and having a nozzle upper portion which includes a circumferential lip extending generally obliquely to said axis and defining a substantially upward-facing seal surface;
• an elongated housing coaxially situated above and having a housing lower portion resting against, the nozzle upper portion, said housing lower portion including a circumferential lip extending generally obliquely to said axis and defining a substantially downward-facing seal surface in confronting, spaced relation to the seal surface on the nozzle lip;
• whereby said lips form an omega seal structure including a gap between the seal surfaces, an annular cavity situated within the lips, and a compression surface along the outside of the lips;
• an omega seat of semi-rigid material substantially filling said cavity;
• a seal ring of semi-rigid material having an inner surface in intimate, conforming relation against substantially all of said compression surface, thereby covering said gap;
• seal carrier means for supporting the outer surface of the seal ring laterally and below said omega seal structure;
• and
• fixture means connected to the housing, for urging the seal carrier means against the seal ring, thereby compressing the seal ring against said compression surface such that a portion of the seal ring extrudes into said gap to form a seal between said lips.