Hydrodynamic study of the effectiveness of the APCITROX decontamination technology

In the VVER-type pressurized water reactors, the so-called AP-CITROX method (AP: alkaline permanganate, CITROX: citric and oxalic acids) is widely used for the chemical decontamination of the austenitic stainless steel piping of steam generators (SGs). During the period of 1993-2000 in the blocks 1-3 of the Paks NPP chemical decontamination of ten SGs were carried out, even in 2 or 3 consecutive cycles. Based on the above decontamination procedures a database of characteristic parameters was compiled. Some new findings are presented obtained in the experiments focused on the optimization of the linear flow rate at which the decontamination factor of the heat exchanger tubes increases remarkably without detrimental changes in the passivity of the surfaces. (R.P.)