Edward Dougherty Archives

By: Edward Dougherty

News & View, Volume 47 | Biofilms? MIC? What Are They? Has the heat conversion efficiency of your heat exchangers degraded? Is the flow of your cooling water system being impeded? Are you repairing or replacing equipment due to localized corrosion causing through-wall failure? Inefficiencies and equipment failures are big problems in any industrial process, but the cause of the problem may be smaller than you think. You might have a biofilm problem. Bacteria floating in a cooling or process water can become colonies on wetted surfaces and can form robust biofilms over remarkably short times. Biofilms are collections of living and dead cells that are enclosed in an extracellular polymeric substance matrix secreted by living organisms. The unchecked growth of biofilms can significantly decrease thermal efficiency on surfaces as the biofilm acts as an insulating layer. Highly localized chemical effects can also be created that lead to microbiologically influenced corrosion (MIC).

By: Ed Dougherty and Al Jarvis

for Bottom Tubesheet Filter/Demineralizers Initial Installation and Performance at Browns Ferry Nuclear StatioThe Browns Ferry Nuclear Station (BFNS) intends to implement an extended power uprate (EPU) at all three units beginning in 2018 for Unit 3 and Unit 1, and in 2019 for Unit 2. EPU implementation will increase the total thermal power of each unit by 494 MWth resulting in a total uprate of 20% from the originally licensed thermal power of 3293 MWth.

Each BFNS unit is currently designed with ten bottom tubesheet condensate filter/demineralizers (CF/Ds) in the condensate treatment system that require an application of a powdered resin precoat to perform the function of demineralization. The precoat material is applied as an overlay on top of vertical filter septa. The filter septa have an inner pleated area, and with a precoat overlay, perform the function of demineralization as well as particulate iron removal. In the absence of circulating water leakage into the condenser, the primary function of the CF/Ds is to remove particulate iron that collects in the condenser hotwell. The iron source is from the corrosion of carbon steel piping and components in contact with main steam and heater drain systems.