4 Water chemistry

In any power cycle using high-temperature water as the heat transfer medium, water chemistry has a major influence on materials degradation, and it is necessary to understand those water properties that influence material degradation processes. In particular, for any supercritical water-cooled reactor concept the properties of supercritical water directly affect general and localized corrosion (such as environmentally assisted cracking) of system materials and the transport of corrosion products to and from the core. The deposition of corrosion products on surfaces can affect heat transfer to the coolant leading to higher metal temperatures, which can also affect bulk degradation mechanisms such as creep. This chapter starts by examining the question “What is supercritical water?”. The discussion then turns to feedwater chemistry, the release and transport of radioactive material out of the core, and water radiolysis. Preliminary water chemistry specifications are then presented. The chapter ends with a brief introduction to molecular dynamics simulations of the structure of SCW at surfaces, which serves as an introduction to Chapters 5 and 6 Chapter 5 Chapter 6 .