Seals for large ports on the Tokamak Fusion Test Reactor

Abstract

The Tokamak Fusion Test Reactor (TFTR) is a large fusion device being constructed at the Plasma Physics Laboratory of Princeton University. This unit is designed for bakeout at 250 °C, and for a base pressure of 10−8 Torr. The machine has a total of 57 large ports that are removable and are sealed with ‘‘Helicoflex’’ metallic gaskets. There are two seals on each port, a primary and a secondary, with flange bolts between seals. This arrangement balances the load on either side of the bolts, eliminating flange roll that could result from the high sealing forces. The dual seal arrangement also aids in leak detection and permits recovery from a failed primary seal by pumping between seals. All of the large ports have been leak-checked with a helium mass spectrometer leak detector, and all primary seals have been found to be leak tight.