pipe wall thinning due to microbiologically influenced corrosion 1

[ed2009]

The piping wall thinning is caused by microbiologically influenced corrosion (MIC) in high pressure service water system in nuclear power plant. The pipe was designed in accordance with ASME B31.1. Is ASME B31G applicable to do the evaluation to assess the strength of remaining pipe wall thickness? As ASME B31.1 appendix IV-1 indicates the B31G may provide additional guidance.

Your time and help would be appreciated.

 

[bimr]

Your are dealing with pits which typically will not be large enough to effect the structural integrity of the pipe. Suggest that you hydrostatically test the piping. Add a disinfectant.

 

[MJCronin]

This is a problem that has been around for decades in the US Nuclear Power industry. I worked on this issue in 1993

In the USA, detailed methodologies for pitting detection and preferred mitigation techniques were well developed by EPRI and the USNRC

http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/33/031/33031184.pdf

1. USNRC Generic Letter 89-13, Service Water Problems Affecting Safety-Related Equipment; July 18, 1989.

2. EPRI TR-102063, Guideline for the Examination of Service Water Piping
3. EPRI TR-109633, Guideline for the Evaluation and Treatment of Corrosion and Fouling in Fire Protection Systems


The issue of MIC induced corrosion was folded into USNRC concerns about "flow induced corrosion" which had been discovered just a couple of years before the Service/Raw water MIC issues became of note. There was a pipe rupture failure in an elbow in the feedwater system at the Surry Nuclear Power Station about 1989.

Several plants simply decided to replace decades old carbon steel systems with high-nickel materials resistant to MIC.

https://www.rolledalloys.com/shared...-Alloy-N08367-Service-Water-Piping-Review.pdf

Consulting firms developed training programs and technical papers (and careers ?)on this specific subject

https://www.structint.com/competency/training/training-corrosion-microbiologically-control

So, I don't think an informal pitting evaluation and a quick hydro test will cut the mustard ....

In what country is this Nuclear Plant located and why is MIC pitting now a new issue ?





MJCronin
Sr. Process Engineer

 

[ed2009]

Thank you very much for great help and time.

 

[zdas04]

MJCronin,
Great post, thank you.

MIC was already on the radar in Navy Nuclear Power in 1972 when I went through Nuc School in Vallejo. I don't think I've ever read anything better on the subject than was available (mostly in confidential documents) in 1974 when we refueled in Bremerton.

I don't think the world's understanding of this issue has improved since the 1960s, but the proposed "solutions" seem to keep getting dumber. I have cut into pipelines for repairs several times and had to deal with concentrated biocides falling into welder's laps, the solution to MIC failures is often just dumping in more biocides. That solution has occasionally worked on liquid-filled lines, but two phase and mostly gas lines rarely have the flow energy to transport the chemicals to the colonies.

[bold]David Simpson, PE[/bold]
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[davefitz]

It might not be completely applicable to nuclear industry SS pipes, but the condenser industry also had to deal with MIC , and resulted in general guidelines related to allowable flow velocity ranges . For SS piping, a flow velocity range of 7-12 fps was sufficient to prevent microbiological attachment, and extended outages with null velocity were to be addressed by draining the condenser. This is the opposite of copper alloy tubedc condensers, which require a max velocity less than 7 fps to avoid erosion corrosion at the tube entrances ( vena contracta effect).

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick