Outline of the Comprehensive Investigation into the Cause of Failure of a Pressure Tube in Pickering NGS A Unit 2

摘要

An intensive technical effort, utilizing the combined resources of Ontario Hydro and Atomic Energy of Canada Ltd., into the cause of the fast fracture of a Zircaloy-2 pressure tube in Pickering NGS Unit 2, is described. The cause of the failure was associated both with displacement of a pressure tube support spacer during commissioning and the development of much higher hydrogen concentrations in the Zircaloy-2 pressure tubes as a result of corrosion, than had been predicted. The evaluation concluded that the condition of the pressure tubes warranted replacement with the superior alloy, Zr-2.5 percent Nb, the pressure tube materials used in all CANDU reactors since Pickering NGS Unit 2. (Atomindex citation 17:062862)