Investigation of the impact of the physical and chemical factors during correction treatment of NPP unbalance water to ensure compliance of conditioned radioactive waste with regulatory requirements

The paper considers the results of a study of the decomposition of surfactants in the unbalanced waters of nuclear power plants by corrective treatment with hydrogen peroxide followed by heating. It proposes a method of determining the type and concentration of surfactants in aqueous solutions based on the method of high-performance liquid chromatography in tandem with mass spectrometry (HPLC-MS). The dependences of the purification efficiency of the solution on the initial concentration of surfactants, time and temperature as well as on the presence of an additional contaminant (potassium permanganate) are investigated. It is shown that in order to meet the requirements of regulatory documents with a conservative approach the efficiency of surfactant purification should be at least 81% when evaporating the cubic residue before cementing to 150 g/l and at least 95 % when evaporating to 450 g/l. Decomposition of complexing agents is shown to occur during processing in the temperature range of 80-100 degrees Celsius when hydrogen peroxide is dosed into aqueous solutions. The surfactant concentration reaches a value of 62 % at temperatures of 80 C and above which corresponds to the surfactant content in the cube residue not exceeding the value of 1 % (without conservative approach) after 4 hours of treatment. Dosing of potassium permanganate into the purified water allows to achieve virtually 100% purification from surfactants, without resorting to heating the water to boiling point. The efficiency of purification from surfactants to the level of complexing substances in the cubic residue in the range below 1 % is achieved by dosing potassium permanganate 70 minutes after the start of the experiment, and when heated to 100 C – in less than 40 minutes. The results obtained can be used to substantiate the safety of radioactive waste management technologies used in nuclear energy.