Catalytic purification of reactor KS-150 heavy water moderator of organic impurities

The method is described of purifying D2O by catalytic combustion of organic substances down to carbon dioxide and water in a water bath at elevated temperature while oxygen is added. The laboratory experiments were conducted using an apparatus consisting of an evaporator, a drop separator, a steam preheater under which an oxygen dosing device was located, a catalyst body, a condenser and a fraction collector. Cherox 40-00 and Cherox 40-04 with 0.4% of palladium were used as catalysts. No deterioration of the properties of the catalyst was observed during the experiments. The organic substance content was determined as the chemical oxygen demand by the dichromate or by the permanganate method. The variations were determined of the amount of burnt organic substances in D2O with the temperature and the amount of added CO2 and pure O2, and of the D2O purity with the catalyst volume load. The experiments showed the following optimal combustion conditions: temperature 200 to 350 degC, catalyst volume load up to 20,000 vol. units of steam per vol. unit of catalyst per hour, and oxygen amount approx. ten times the stoichiometric demand. The advantages of the method include ease, low cost, full combustion of organic substance in D2O and no deuterium losses. (J.P.)