Microbiologically influenced corrosion in the Fermilab Main Injector magnet low conductivity water system

In mid-November of 1997, numerous pinhole leaks in the new 304L stainless steel header piping of the Main Injector Magnet Low Conductivity Water System (MI LCW) were discovered. Metallurgical and biological analysis of the extensive corrosion damage in the welded areas of the piping revealed that microbiological organisms played a key role in the corrosion process. The resulting massive repair efforts included microbe eradication (through chemical biocides), damage assessment (through biological and metallurgical analysis, radiography, and internal remote video inspection), pipe cleaning (through custom designed mechanical cleaning devices), weld repair (through weld overlay), and microbiological control during system start-up (through ultra-violet radiation and heat treatments). Multiple contributing factors leading to the corrosion problems were identified, including poor welding practice (inadequate technical specifications and inspection), improperly treated fill water, and insufficient water flow for extended periods of time (several months) prior to system use. Lessons learned earned from these experiences will be of importance to the design of similar cooling systems in the future.