Steam Generator Chemical Cleaning

Abstract

Nuclear steam generator chemical cleaning has been under development for two decades, with the first large-volume (57,000 litres) steam generator tube bundle cleanings performed on the four steam generators at the Oconee Nuclear Station Units 1 and 2. Full-bundle steam generator chemical cleaning is under consideration for use at Bruce Nuclear Generating Station "A". Technical developments are underway for that cleaning. In 1978, an extensive development program was undertaken by the steam Generator Owners' Group (SCOG) under the management of the Electric Power Research Institute (EPRI) to develop generic chemical cleaning solvents to use in nuclear steam generators. Also at that time, Duke Power Company began to develop a process specific to the Oconee Nuclear Station. That process was for application to the B and W once-through steam generators at Oconee that were experiencing unacceptable pressure drop due to corrosion product build-up at the tube supports. The program for the Oconee units had three phases: system design, process qualification, and field application. The result of the Oconee operation was restoration of the steam generator pressure drop performance to as-new values. Corrosion monitoring performed during the operation verified that the corrosion of critical components, including the tube supports was within stringent allowable limits. This paper discusses the developments leading up to the initial full-scale cleaning operations at Oconee. It also reviews ongoing work relating to subsequent cleaning operations and further development to support application of the process to a variety of steam generators. The paper also references work specific to the Bruce "A" cleaning program.