ABSTRACT
Feed water chemistry in pressurised water reactors (PWRs) is important for mitigating corrosion and corrosion product transport. Recently, feed water chemistry has been given an increased focus and new approaches have been published. Many PWRs have experienced some chemistry-related corrosion concerns (such as danger of flow-accelerated corrosion, sludge burden, ingress of oxidants and reducible iron oxides into the steam generators), as well as some environmental concerns (in particular, hydrazine emissions during start-ups). In order to avoid capacity loss due to various corrosion effects, it is necessary to examine the possibilities of further improvements in secondary coolant chemistry. In particular, a slight increase in the feed water oxygen content is at present in focus to decrease flow-assisted corrosion and corrosion product transportation. It is well-known that the presence of small amounts of oxidants in high-temperature systems is difficult to detect and monitor. This paper describes electrochemical corrosion potential (ECP) measurements in PWR secondary systems and presents an improved monitoring technique to detect such low oxygen levels.
