A new CANDU channel closure with a conical seal

A new channel closure is under development for future CANDU reactors. It takes up less radial space by using a conical all-metal sealing element that rotates and flexes for insertion and retraction. It seals using a face seal on both ends of the sealing element and is pressure energized over the entire working range of pressures. This seal element has many of the practical attributes of a bore seal such as was used in Gentilly-1, but is not limited by the tight tolerances and large strain range required to seal on the actual inner diameter of an end fitting. A major benefit of maintaining a constant bore diameter throughout an end fitting (with about 3 mm radial increase at the sealing area) is to permit refuelling without using a guide sleeve. The same seal design is readily adaptable to a larger end fitting diameter and could be used as part of a proposal to retube a CANDU reactor at mid-life without removing the end fittings. The sealing element has been tested over a wide range of test conditions appropriate to primary heat transport conditions of a CANDU reactor. A full-scale model of the new channel closure is under test. (author)