Abstract
The removal of fouling deposits from the secondary side of nuclear steam generators has become a very important goal of the utility industry. Research has shown that these deposits are primarily composed of magnetite and copper. The removal of the magnetite has not been a major problem; however, the removal of the copper part of the deposit has been difficult.
Of the known solvents available to the industry ammonia + oxidant appear to be the most feasible. To overcome the volatility of ammonia, ammonium salts were suggested as the base for the copper solvent. Several beaker tests were performed which showed that the ammonium salts of inorganic acids were very effective when used in a copper solvent formulation. These ammonium salt formulations dissolved and held in solution about ten to twenty times as much copper as the previously known copper solvents.
Two of the best ammonium salt formulations, ammonium carbonate and ammonium nitrate, were evaluated in “pot boiler” tests where they were compared to a chelant-hydrogen peroxide solvent. A “pot boiler” test is a large scale process definition test commonly used to evaluate solvents for nuclear steam generator cleaning.
These tests confirmed the effectiveness of the formulations by showing that one stage of the stabilized solution was about twice as effective as five stages of the chelant-hydrogen peroxide solvent.
