New technique for in-plant high mass transfer rate electrochemical potential monitoring

Abstract

Corrosion monitoring is widely used in boiling water reactors for hydrogen water chemistry and for feedwater monitoring on the secondary side of pressurised water reactors. It is well known that water chemistry conditions can change during transport in sampling lines and also that electrochemical potential (ECP) results at low oxidant levels depend strongly on the mass transfer rate. Measurements at a low mass transfer rate may yield abnormally low corrosion potentials that are not representative of the system. In-pipe monitoring has been developed to overcome this problem, but such measurements require penetrations of the system pressure boundary. A new ECP sensor has been developed for measurements in high mass transfer rate conditions (corresponding to linear flowrates up to 3 m s⁻¹ at a mass flowrate of 100 kg h⁻¹). The sensor can be installed without penetrating the pressure boundaries of the system, using existing sampling lines. It comprises well known parts that have been used for in-plant measurements in several reactors for many years. The new technique is also able to detect small amounts of oxidants in the system by measurements in sampling lines. Local water chemistry and corrosion conditions can be accurately monitored.

Keywords:

• CORROSION MONITORING
• BOILING WATER REACTORS
• PRESSURISED WATER REACTORS
• ELECTROCHEMICAL POTENTIAL MONITORING