Evaluation of permeated hydrogen through heat transfer pipes of the intermediate heat exchanger during the initial 950C operation of the HTTR

Sakaba, Nariaki ; Matsuzawa, Takaharu*; Hirayama, Yoshiaki*; Nakagawa, Shigeaki  ; Nishihara, Tetsuo ; Takeda, Tetsuaki

The permeation of hydrogen isotopes through the Hastelloy XR high-temperature alloy adopted for the heat exchanger pipes of the intermediate heat exchanger in the HTTR (High Temperature Engineering Test Reactor) is one of the concerns in the hydrogen production system, which will be connected to the HTTR in the near future. An evaluation of the hydrogen permeation between the primary and secondary coolant through the Hastelloy XR was performed using the hydrogen concentration data observed during the initial 950C operation of the HTTR. The hydrogen permeability of the Hastelloy XR was estimated conservatively high as follows. The activation energy E and pre-exponential factor F of the permeability of hydrogen were E = 62 kJ/mol and F = 3.610 cm(NTP)/(cm s Pa), respectively, in the temperature range from 735K to 940K. The results implied that some oxidized film had been formed on the surface of the heat exchanger pipes of the intermediate heat exchanger.