Survey of domestic and foreign PWR experience with morpholine in chemistry control by all-volatile treatment. Final report

Most pressurized water reactors (PWRs) in the US use ammonia for pH control and hydrazine for oxygen scavenging in secondary cycle all-volatile treatment (AVT) chemistry programs. Selected high-molecular-weight amines have more favorable liquid-vapor distributions and thus offer possible advantages for liquid-phase pH control over ammonia, which is very volatile and poorly ionized in the steam generator environment. Several PWRs in the US and Europe, plus many CANDU-type plants, use morpholine in AVT chemistry control for that purpose. Domestic and foreign experience with morpholine is discussed in this study, which specifically excluded French PWR experience with morpholine. Morpholine was reported to be an effective pH control agent in AVT chemistry control. The only negative feature reported associated with its use is a slightly elevated cation conductivity level, presumably from organic acids formed from decomposition of morpholine. 16 tabs