An integrated approach for the evaluation of BWR vessel internal corrosion

Intergranular stress corrosion cracking (IGSCC) of boiling water reactor (BWR) piping has been studied extensively since 1975 when cracks were discovered in eight operating BWR plants. This type of cracking has been known to occur when sensitized stainless steel material near welds is loaded or strained in the presence of the water environment containing dissolved oxygen. The three ingredients or necessary conditions for IGSCC initiation are sensitized microstructure, tensile stress, and oxygenated high-temperature water. The BWR internals and vessel attachments were made using the same materials and fabrication methods as the BWR piping systems that have experienced severe IGSCC in the past. These major structural components are difficult to inspect because of access limitations and would be very expensive to repair or replace.