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The leader in innovative technology applications

Metered Precoat System

A Proven Method

  • Extend filter/demineralizer run lengths
  • Eliminate precoat cracking
  • Simple operation
  • Avoid soluble impurity bypass
  • Easy plant retrofit
  • Applies uniform precoat with minimum precoat dosage
  • Reduce radioactive waste volume and improve water quality


Precision application of precoat materials on filter/demineralizer systems.


The Modified Precoat Process (MPP) is a mechanical system which enables the operator to apply a precoat slurry to the filter/demineralizer septa at a constant and much lower concentration over a longer period of time, thus producing a more uniform precoat with less potential for cracking. Longer process run lengths, increased septa life and improved water quality are the benefits that can be realized when using this improved precoating technique. The system was designed using a philosophy of maximum performance flexibility combined with operational simplicity.


Precoatable filter/demineralizer systems are commonly used in nuclear power generation plants to remove insoluble and soluble impurities from both primary and secondary loop process waters. Precoat mixtures of finely ground ion exchange resins and/or fibrous materials are slurried with water and hydraulically deposited onto a large number of porous filter septa contained in the filter/demineralizer pressure vessel. Industry experience and our laboratory testing indicates if the resin/fiber mixture is deposited on the filter septa over a very short period of time, a potential for uneven and/or cracking precoat layers occurs. This uneven and cracked precoat condition can allow passage of soluble impurities through the filter/demineralizer, as well as allowing insoluble impurities to penetrate the septa material itself, thereby creating an increase in septa plugging (high clean differential pressure). The effects of poor precoating performance are exacerbated when minimum precoat dosages are used. These phenomena will produce short process run lengths (which dramatically increases the volume of radioactive solid waste generated), reduce effluent water quality and decrease septa operating life.


The industry proven MPP is a system developed by RSI to reduce the volume of radioactive waste in nuclear power plants, while improving water quality and increasing filter/demineralizer septa operating life. This unique product has proven to be simple to install, easy to operate and will help you gain maximum performance from your filter/demineralizer system(s).