The Underestimated Role of the Oxygen on RCS Component Failures

(LCC13 AR)

PWR chemists may claim that there is no oxygen in the Reactor Cooling System because hydrogen injection suppresses the oxidising species generated by radiolysis. This is why, at EDF, the RCS has no oxygen monitoring. In fact, this assessment is true only if free flowing conditions are considered. The RCS contains many flow-restricted or occluded zones where some chemistry deviations can occur, one being the presence of oxygen.

This report aims to keep the plant chemists alert regarding oxygen tracking, ingress, venting, scavenging, monitoring. It also shows some examples of field failures that occurred because oxygen presence was not anticipated in the environment. This report helps plant engineers understand why they should stay alert regarding oxygen control. The report shows there are several ways to limit oxygen ingress or to scavenge oxygen in the RCS. The oxygen specification may seem stringent, however the failures presented in this report support a non-deviation application of the RCS oxygen specification.