Development of water leak detection method in fusion reactors using water-soluble gas

Hiroki, Seiji ; Tanzawa, Sadamitsu; Arai, Takashi; Abe, Tetsuya 

A water leak detection method using krypton as a water soluble tracer has been proposed for fusion reactors with fully circulating the in-vessel cooling water. This method is targeted for applying to the ITER. The water leaks are effused into the vacuum vessel evacuated with a cryopump and the water dissolved Kr is detected with a quadrupole mass spectrometer. When two leak valves with 1 m distance are attached to the test pipe with 30 C heating, two distinct / = 84 peak current rises caused by the water leak are successfully detected with the time interval of 39 sec. On the other hand, the water accession length as a function of the traveling time is calculated by considering a natural convection flow caused by the 30 C heating, where the traveling time is 44.6 sec for the 1 m length. This means that the observed positional accuracy is 12.6%, based on the calculation. This method can be applied to the ITER condition.