Hydrogen isotope permeation from cooling water through various metal piping

In order to investigate the behavior of hydrogen isotope on the water–metal boundary, deuterium permeation experiments from heavy water vessel through various metal piping, such as pure iron (Fe), nickel (Ni), stainless steel (SS304), and pure iron with 10 μm gold plating, were performed at 573 K and at 15 MPa. During the experiment, surfaces of metal piping except gold plating one were oxidized at the heavy water boundary and then deuterium would generate by the oxidation reactions. This deuterium could be detected by mass spectrometer, which monitored the inside gases of the piping under continuous evacuation. The result showed clearly that the deuterium permeated through Fe, Ni, and SS304 piping was detected as mainly deuterium gas (D2) under continuous evacuation, though that through gold plating one could not be detected effectively. The D2 permeation rate through Fe, Ni, and SS304 piping reached equilibrium conditions with oxide generation at D2O–metal boundary, although concluding the transfer mechanism will require further testing and modeling activities.