Effect of Pt injection rate on corrosion potential and Pt distribution on stainless steel under simulated boiling water reactor conditions

Abstract

Online NobleChem is a technology to mitigate stress corrosion cracking in reactor internals and recirculation pipes of boiling water reactors (BWRs). For a more efficient reduction of the electrochemical corrosion potential (ECP) under hydrogen water chemistry conditions, noble metals (e.g. Pt) are injected into the feed water during power operation. They are claimed to deposit as very fine metallic particles on all water wetted surfaces and to stay electrocatalytic over long periods. To study the deposition and (re)distribution behaviour of Pt, a sophisticated high temperature water loop has been constructed, in which specimens can be exposed to simulated BWR water and Pt can be deposited in situ. The specimens are analysed by laser ablation–inductively coupled plasma–mass spectrometry and electron microscopy after the experiments. Results from two experiments with different Pt injection rates but similar total Pt amounts revealed a faster and more pronounced reduction of the ECP and slightly larger average Pt particle size using the higher Pt injection rate. A longer preoxidation of the specimens seems to increase the average Pt concentration on the specimen surface.

Keywords:

• NobleChem
• NMCA
• Platinum
• Stress corrosion cracking
• Boiling water reactor
• Deposition behaviour
• Hydrogen water chemistry

Acknowledgements

The financial support by ENSI and the contributions of the Swiss nuclear power plants KKL and KKM are gratefully acknowledged. Special thanks are also expressed to H. P. Seifert, B. Baumgartner, L. Nue (all PSI), G. Ledergerber (KKL) and C. Weber (KKM) for their excellent support of this project.