1. Reminder of the physico-chemical properties of water

In PWRs, water is used as a moderator and coolant in the primary circuit, and as a thermodynamic fluid in the secondary circuit, to transform heat into mechanical energy by means of a Carnot cycle involving the liquid and its steam. The performance of the thermal machine thus created will depend essentially on the physical properties of the water. However, the physico-chemical properties will play a direct role in corrosion processes, and it is therefore essential to characterize them under PWR operating conditions, i.e. at temperatures of up to 325°C and pressures of the order of 150 bar (the critical temperature of water is 375°C).