Microbially-influenced corrosion in low carbon stainless steel (SS-304L) by viable but non-culturable (VBNC) bacteria of spent nuclear fuel pool

Abstract

Microorganisms can pose significant challenges in causing corrosion of low carbon stainless steel (SS-304L) in closed dynamic systems such as spent nuclear fuel (SNF) pools This study investigates the corrosion behaviour of SS-304L in the presence of biofilm-forming bacteria and ‘viable but non-culturable’ (VBNC) bacteria present in SNF pool water. Electrochemical measurements such as, open circuit potential (E_OCP), pitting potential (E_pit), and corrosion rate were measured. Confocal and metallurgical microscopy, were used to provide insights into biofilm morphology and localized corrosion features. Confocal scanning laser microscopy analysis showed variation in biofilm morphology and distribution. The uniform biofilm growth by the four SNF bacterial isolates exhibited corrosion inhibition property. Electrochemical measurements, such as E_OCP and E_pit, revealed the putative role of VBNC bacteria in the corrosion of SS-304L. Electrochemical impedance spectroscopy study also showed the role of biofilm mediated corrosion inhibition property. Biochemical characterization of extracellular polymeric substance of biofilms revealed very high protein content, which provided an interesting hypothesis regarding SS-304L corrosion prevention. The formation of biofilm protective layer and the probability for localized corrosion by SNF pool water bacteria are described. This study elucidates the complex interplay between microbial biofilms and plausible corrosion in the SNF pool environment that has critical implications to the nuclear power industry.