Contamination of cooling pond of NPP 'Paks' Unit 2 by radioactive materials after incident in Pool 1

Some results of measurements of radionuclide activity in cooling pond water and refueling pond of Unit 2 reactor, as well as the results of measurements of radioactive product deposits on the equipment of cooling pond, refueling pond and surfaces of fresh fuel assemblies are presented. Based on measurements the estimation of contamination of the fuel maintenance system by fission products, uranium and transuranium isotopes is performed, and also the hypothesis about oxidation of uranium dioxide in water as a main source of radioactive products polluting the cooling pond is formulated. In view of these factors the expected contamination of fuel rod surfaces by fissionable isotopes and expected activity of fission products in the primary coolant after reactor re-start is appreciated. The good coincidence of an expected realistic estimation of contamination by fissionable plutonium isotopes (∼0,7 x 10-8 kg/M2) and the value of contamination calculated using the results of direct measurements of fission product activity in reactor primary coolant after reactor start-up in August 2004 - (0,6...0,7) x 10-8 kg/M2 - have shown, that the model of uranium dioxide chemical transformation describes the behavior of radioactive products in spent fuel cooling pond of the NPP 'Paks' Unit 2 adequately. All results of measurements listed in the report were obtained by NPP 'Paks' personnel. (author)