New advanced amine for secondary systems in pressurized water reactor plants

Comanche Peak Nuclear Power Plant (CPNPP) augmented morpholine chemistry in the secondary system with dimethylamine (DMA) chemistry after discovering the benefits from Italian fossil plant experience. As a result of the operational success with DMA, CPNPP began searching for other amines with similar properties that may provide greater benefit. The amine discovered to have the most favorable potential benefits was found to be 1, 8-Diazabicyclo [5.4.0] undec-7-ene (DBU), which is a strong base with a pKa of 13.4. Corrosion and compatibility testing was performed in reference to existing amines and followed the pattern of the qualification testing performed for implementation of DMA. This work will describe the candidate testing that led to the selection of DBU and the qualification testing for operation at CPNPP. Testing was performed on carbon steel for BOP considerations and Alloy 600 steam generator tubing material. Also described is an unexpected finding from the testing. One test regime indicated a corrosion protection benefit of DBU beyond a simple pH effect which may be the result of surface modification or surface reaction with the carbon steel oxide. (author)