A Technique for Assessing the Abrasion Resistance of Steam Generator Internal Tube Oxide

Abstract

The outcomes of previous primary side mechanical cleanings of CANDU steam generators (SG) have varied significantly between different stations suggesting that differences in mechanical properties of the ID oxide may be partly responsible. To assess the root cause/reasons for such differences, a rotational wire brush tool to mechanically abrade oxide from the primary side of steam generator tubes was developed. Coupled with a collection system, the technique permits a layer by layer characterization of the oxide characteristics. The tool was applied to a Pickering Unit 2 SG cold leg and Unit 8 SG hot leg tube sections. The abrasion characteristics and the chemical and radiochemical profiles of the two oxides were found to be quite different. Additional samples from other CANDU stations will be studied in the next two years. The overall goal is to relate the mechanical and chemical characteristics of SG tube oxide to the future performance of mechanical cleaning.