Iron oxides, which are the main constituents of corrosion products in the secondary circuit of pressurized water reactors, are known to play a role in various phenomena.

These corrosion products, primarily resulting from general corrosion and flow-assisted corrosion of carbon steel components located upstream of the steam generators (SGs), can be transported to the SGs. There, due to the diphasic operating conditions of the SGs, they may accumulate and contribute to deposit formation.

Depending on their location, deposits can lead to fouling of the free surface of the steam generator tubes, clogging of the broached holes in the tube support plates, or the formation of hard sludge at the bottom of the SG on the tube sheet. These phenomena typically result in reduced thermal transfer efficiency, disruption of diphasic fluid flow, and, in some cases, an increased risk of SG tube rupture. Such consequences are managed through costly maintenance operations, including chemical cleanings.

What is CORDEE?

The MAI CORDEE project aims to meet the high expectations of plant operators regarding the availability, safety, and performance of the secondary circuit. Its main objectives are :

  • To prevent steam generator performance loss by controlling deposit phenomena.
  • To improve material protection against corrosion during layup using Film Forming Substances.
  • To identify and validate alternative chemical conditioning strategies or technologies to replace hydrazine, a substance classified as carcinogenic, mutagenic, or toxic for reproduction.
  • To enhance our understanding of corrosion product speciation and improve the prediction of Flow-Assisted Corrosion.

The main value of the CORDEE project lies in optimizing maintenance operations and supporting the evolution of chemical conditioning in the secondary circuit through:

  • Predicting fouling kinetics, enabling the optimization of soft chemical cleaning intervals.
  • Improving material protection during shutdown periods by using Film Forming Substances.
  • Addressing the challenges associated with hydrazine use by qualifying safer alternative solutions.
  • Enhancing understanding of corrosion product speciation and improving the prediction of Flow-Assisted Corrosion.