FAC damage is normally found between about 90 – 230°C. However, damage at higher temperatures and occasionally lower temperatures has been seen. Although not common, low temperature degradation can result in shutdowns and costly maintenance activities.

Described are three reports of damage in the condensate system in Pressurized Water Reactors (PWR). At another PWR, damage was found downstream of a blowdown demineralizer. In all cases, the piping contains flowing deoxygenated, neutral water at about 50°C. Also, experience with non-FAC degradation was reported at one unit.

Also described are two sets of damage to systems in a Boiling Water Reactors (BWR). In both cases, there was a low concentration of dissolved oxygen. Damage to BWRs may be less common, but similar damage rates have been observed.

Based on this work, it is recommended that plant operators perform susceptibility analyses and if necessary inspections in areas where there is neutral water with a low concentration of dissolved oxygen. PWR units that run their polishers full-time are especially vulnerable.

Jeffrey S. Horowitz has been an independant consultant to EPRI for over twenty years. He is a principal technical contributor to the CHEC® family of computer programs. He has also worked in several other areas of nuclear safety analysis. Jeffrey is a fellow of the American Nuclear Society and the American Society of Mechanical Engineers.