Gas handling for the Tokamak Fusion Test Reactor during the DT phase of operation: System overview

The original design of the Tokamak Fusion Test Reactor (TFTR) and tritium handling are described. Modifications to these designs inspired by operational experience gained from running TFTR since 1982 with deuterium-deuterium (D-D)-fueled experiments are also presented. The presently installed gas handling systems work well for the D-D phase of operation, but they do not have the level of sophistication needed for tritium injection, tritium-contaminated-gas exhaustion, and gas detritiation for deuterium-tritium (D-T) operations. The pumping and gas-handling systems were designed prior to the operation of TFTR to handle the tritiated process streams anticipated during the DT phase. Since then, it has been found that certain changes and refinements to this design would make tritium handling simpler and safer. Most (90%) of the process gas (deuterium fuel) is pumped by the cryopanels in the neutral beams during operations. This nearly pure elemental hydrogenic gas is radiologically 25,000 times more safe to handle than the corresponding amount of tritium oxide. It has been decided to transfer the hydrogenic species from the neutral beam cryopanels into special containers for off-site shipment as elemental tritium rather than as oxide. This reduces the exposure of oil-lubricated pumps from large contact with tritium-laden gas and reduces the risk of exposure to tritium oxide. Conditioning of the torus will be processed by impurity cryopumps, designed to pump only the nonhydrogenic species (impurities) and reduce the total amount of tritium used during conditioning.