Benefits of Integrating Chemical and Mechanical Cleaning Process for Steam Generator Sludge Removal

Abstract

This paper discusses the benefits of performing in-bundle tubesheet sludge lancing in conjunction with chemical cleaning of PWR and PHWR steam generators in which a hard sludge pile is known to exist The primary benefits of in-bundle lancing are to: (I) increase the exposed area of the sludge pile by cutting furrows in the surface thereby enhancing sludge pile dissolution, (2) reduce the volume of solvents required since material removed by lancing does not have to be dissolved chemically, (3) improve rinsing and removal of residual solvent between iron and copper dissolution steps, and (4) allow for verification of process effectiveness by providing high quality in-bundle visual inspection. The reduction in solvent volumes can lead to a significant reduction in solvent costs and waste processing. A case study which includes an economic evaluation for a combined chemical/mechanical cleaning shows a potential cost savings of up to 300,000 (USD) over use of chemical cleaning alone.