CHARACTERIZATION AND DISSOLUTION STUDIES OF BRUCE UNIT 3 STEAM GENERATOR SECONDARY SIDE DEPOSITS

摘要

The physical and chemical properties of secondary side steam generator deposits in the form of powder and flake obtained from Bruce Nuclear Generating Station A (BNGS A) Unit 3 were studied. The chemical phases present in both types of deposits, collected prior to the 1994 chemical cleaning during the pre-clean water lancing compaign, were magnetite (Fe_3O_4), metallic copper (Cu), hematite (Fe_2O_3) and cuprous oxide (Cu_2O). The major difference between the chemical composition of the powder and the flake was the presence of zinc silicate (Zn+2SiO_4) and several unidentified silicate phases containing Ca, Al, Mn, and Mg in the flake. The flake deposit had high hardness values, high electrical resistivity, low porosity and a lower dissolution rate in the EPRI-SGOG (Electric Power Research Institute-Steam Generator Owner's Group) chemical cleaning solvents compared to the powder deposit Differences in the deposit properties after chemical cleaning of the Unit 3 steam generators and after laboratory cleaning were noted. The presence of silicates in the deposit inhibit magnetite dissolution.