Control of the dissolved oxygen concentration is crucial for the use of liquid lead bismuth eutectic (LBE) as a coolant of advanced nuclear reactors. An electrochemical oxygen pumping (EOP) system was applied to a non-isothermal liquid LBE loop in order to evaluate its capability to control oxygen in 700 liters of flowing LBE. Oxygen pumps were fabricated using one end closed tube of yttria partially stabilized zirconia (YPSZ) as the solid electrolyte and LSCF (lanthanum strontium cobalt ferrite) as electrode. The oxygen transfer through the oxygen pump was regulated by controlling the applied electric current using a PID controller with feedback from a potentiometric oxygen sensor. The oxygen was added to or removed from the LBE by oxygen pumps depending on target oxygen concentration and a process value given by the oxygen sensor. At low oxygen concentrations, oxygen removal rates were limited by oxygen mass transfer. This limitation could be overcome by operating the pumps above the decomposition potential of zirconia. (C) 2019 The Electrochemical Society.