Patent Number: 
Section: claims

1. An apparatus for watertight sealing of a steam generator nozzle, comprising:an attachment ring adapted to be fitted in an interior of said nozzle, said attachment ring comprising:a plurality of retaining tabs extending from an interior of said attachment ring towards a center of said attachment ring;a plurality of receiving slots formed between said retaining tabs; anda nozzle dam landing formed in the interior of the attachment ring below the retaining tabs;a nozzle dam adapted for insertion into said attachment ring and abutment against said nozzle dam landing, said nozzle dam comprising:two top disc segments;a plurality of radial protrusions extending from the two top disc segments of the nozzle dam and fixed with respect to the two top disc segments, said radial protrusions adapted to pass through said receiving slots of said attachment ring and directly interlock between and directly abut against said nozzle dam landing and said retaining tabs for fixing said nozzle dam in said attachment ring upon rotation of the nozzle dam in the attachment ring; anda seal covering at least a bottom side of the nozzle dam for effecting a watertight seal between the nozzle dam and the attachment ring. 2. An apparatus in accordance with claim 1, wherein the nozzle dam and seal form a nozzle dam assembly. 3. An apparatus in accordance with claim 2, wherein:the seal forms a hinge connecting the two top disc segments, enabling the nozzle dam. 4. An apparatus in accordance with claim 3, further comprising:a center locking mechanism for locking the two top disc segments together in an unfolded state of the nozzle dam. 5. An apparatus in accordance with claim 1, further comprising:a rotation limiting mechanism provided on the nozzle dam to prevent over-rotation of the nozzle dam in the attachment ring. 6. An apparatus in accordance with claim 1, further comprising:a locking mechanism for locking the nozzle dam into the attachment ring. 7. An apparatus in accordance with claim 6, wherein the locking mechanism comprises a locking pin or a locking tab. 8. An apparatus in accordance with claim 1, further comprising:cladding fitted into the interior of said nozzle;wherein said attachment ring is fixed in said cladding. 9. An apparatus in accordance with claim 1, wherein:the attachment ring is machined from cladding provided in the interior of the nozzle. 10. An apparatus in accordance with claim 1, wherein the seal extends over the bottom side of the nozzle dam at over at least a portion of the nozzle dam edge. 11. An apparatus in accordance with claim 1, wherein the seal extends over the bottom side of the nozzle dam and beyond the edges of the nozzle dam. 12. An apparatus in accordance with claim 1, wherein the seal comprises an inflatable seal. 13. An apparatus in accordance with claim 12, wherein the seal is pressurized remotely after interlocking of said nozzle dam in said attachment ring. 14. An apparatus in accordance with claim 13, further comprising:a computerized pressurization control and monitoring station for controlling and monitoring said remote pressurization of said seal. 15. An apparatus in accordance with claim 13, wherein said seal comprises a segmented seal having a diaphragm extending over the bottom side of the nozzle dam and pneumatic seals extending around a circumference of the nozzle dam. 16. An apparatus in accordance with claim 15, wherein two pneumatic seals are provided with an annulus arranged therebetween. 17. An apparatus in accordance with claim 15, wherein said segments of said seal are adapted to be pressurized and monitored independently by a pressurization control and monitoring station. 18. An apparatus in accordance with claim 15, wherein the diaphragm comprises a mechanical seal which is activated by flow of water.