In the second operation phase, by using the closed loop for the regeneration of auxiliary molecular sieve bed, the tritium-containing waste water adsorbed in the auxiliary molecular sieve bed in the first operation phase can be transferred to water separator of helium purification regeneration system. The closed loop for the regeneration of auxiliary molecular sieve bed mainly consists in sequence of diaphragm compressor, electric heater, auxiliary molecular sieve bed, water cooler and water separator. Filled with helium from helium purification system, the closed loop for auxiliary molecular sieve regeneration operates at pressure of about 0.5–0.7 MPa. Driven by the diaphragm compressor, helium is heated by the electric heater and flows through auxiliary molecular sieve bed to desorb water at regeneration temperature of approximately 250–300 °C. The gas leaving auxiliary molecular sieve bed enters the water cooler of helium purification regeneration system where the cold water-cooled heat exchanger reduces gas temperature to approximately 10 °C. In this operation phase, a large quantity of tritium-containing waste water can be separated in the water separator of helium purification regeneration system. To avoid part of tritium-containing waste water emitting to the environment, auxiliary molecular sieve bed should not be vacuum degassed after regeneration.