The permeation of H isotopes through Hastelloy XR high-temperature alloy for heat transfer pipes was studied. The H permeation was evaluated using the actual H concentrations observed during initial 950C operation. The permeability of the Hastelloy was described by:

D (m3[STP]/msPa0.5) = 7.8 x 10-9 exp[-65.8(kJ/mol)/RT]

at 707 to 900K.

Hydrogen Permeation through Heat Transfer Pipes Made of Hastelloy XR during the Initial 950C Operation of the HTTR. N.Sakaba, H.Ohashi, T.Takeda: Journal of Nuclear Materials, 2006, 353[1-2], 42-51