Mixed Bed Resins in Nuclear Power Plants

Mixed Bed Resins in Nuclear Power Plants

Table of Contents

Mixed Bed Resins are unique tiny plastic beads that have addressed the various industrial applications by doing heavy work. They are specialized in each industry, and there are multiple types of products in the world of resin. Using resins in nuclear power plant operations is one of the industries in that resins do a fantastic job of supporting the relevant project.

Someone can raise two basic questions regarding the resins used in the nuclear industry.

  • Where to use resins in nuclear power plants, and its importance?
  • Are there any specially modified resins to use in nuclear power plant applications?

Let’s move with the article to find complete answers to the above questions and gather more details.

Where are we to use resins in nuclear power plants?

With non-purified water, power plants can shoot up with lots of problems; corrosion and scaling in equipment can be an issue for their safety and maintenance, radioactive contaminations also can be occurred, problems with cooling towers & boilers, etc. Therefore nuclear power plants need highly purified water for different applications throughout total operations. Water treatment in a nuclear plant is a critical process. Resins play a significant role in it.

Resins are used in the nuclear power operation premises.

  • makeup water treatment plants
  • cooling tower makeup water plants
  • cooling tower blowdown
  • condensate polishing plants
  • stator cooling treatment
  • reactor cooler purification
  • spent fuel pool purification
  • Radioactive waste purification

It simply purified water used throughout the nuclear plant. Let’s have a simple overlook in a few sectors mentioned above.

Boiler makeup water treatment.

Steam generation is required high-quality pure water to reduce the usage of boiler chemicals with more undersized boiler blowdown frequency. Lower frequencies result in low operating costs. Purified water helps to reduce the corrosion, scaling, and fouling of heat transferring surfaces in boiler systems.

Several water treatment methods can combine; IX-Demineralization plants, UF systems, RO systems or Nanofiltration systems, and IX mixed bed systems.

A mixed bed Ion exchange system is always used as a final polishing step in the boiler water makeup system. This systems are ideal for removing residuals from ppm range to ppb level. MB resin with uniform particle sizes used in IX MB systems reduces leakages, results longer run lengths, efficient regeneration, and performs a low-pressure drop.

Cooling towers make up water plants.

Due to drift, evaporation, and blowdown water losses, cooling towers need a constant water supply. Adequately designed water treatment plants combined with different technologies are required for the cooling towers due to the type of water source and type of cooling towers. On many occasions, Ultrafiltration, iron exchange for pretreatment, and RO or Nano Filtration systems are combined to treat raw water.

The ion exchange resin systems remove high TDS (total dissolved solids), high contaminant levels, and organic carbon. The ion exchange system helps reduce scaling in the RO unit used in the next step, and also it helps to remove hardness in water by using Strong acid cations and weak acid cations (WAC).

Cooling tower blowdown.

Recycling of cooling tower blowdown minimizes the consumption of makeup water. Blowdown has elevated levels of contaminants, so it can’t reuse without treatment. Using robust, foul-resistant, and reliable water purification and filtration systems will be an optimal solution in cooling water operation processes. Ultra Filtration (UF), Ion exchange (IX) plant, RO, or Nanofiltration (NF) plants will increase the treatment of contaminated cooling tower blowdown in nuclear power plants.

Strong Acid Cation (SAC) resins in the IX unit help to protect RO / NF unit from cation polymers present in the upstream coagulation system. WAC cations remove organic species in cooling tower blowdown wastewater.

Condensate polishing systems in nuclear power plants.

It is a must to remove radioactive isotopes and corrosive products. Ion exchange resins used in this system are non-re-generable but have high stability and capacity. Low chloride regeneration processes result in the lowest chloride content and highest purity resins in the nuclear power industry. Nuclear-grade resins perform the highest oxidative stability. The highest loading capacity of any nuclear-grade ion-exchange resins provides the most extended lifetime.

The ion exchange unit contains mixed bed resins in the form of hydrogen ions and hydroxyl ions. Nuclear grade resins perform high oxidative stability, capacity, and longer life span than the others.

Radioactive (Rad) wastewater treatment.

Effluent water with radioactive isotopes needs to dispose of efficiently and safely. Radwaste in the solid phase will be gathered separately, and treated water can reuse. Radioactive components mixed in regeneration, effluent water of condensate polishing, non-reusable wastewater, etc. It is a challenge to remove all radioactive particles prior to disposal.

Radwaste can be concentrated by evaporation and Reverse osmosis (RO) systems. Combination of IX and IX mixed Bed plants, residual contaminants, and radioactive particles that were released after filtration. Uniform particles help to minimize the pressure drops and long life span, and the high capacity of resins will allow the effective elimination of contaminants. In IX systems SAC and SBA have high operating capacities, and separate beds help ionize and dissolve some Rad colloidal with varying pH levels.

Are there any specially modified resins to use in nuclear power plant applications?

We discussed where we could use resins in nuclear power plants.

Resin manufacturers improve their resin qualities to achieve the targets used in water treatment at nuclear power plants. These resins must have higher exchange capacity, high stability in oxidative environments & osmotic pressures, longer run time, and improved version for fouling.

As mentioned, resins are used in different applications within nuclear plants, so the selection of resins must be susceptible.

Nuclear grade resins.

There are four types of standard resins.

  1. Strong Acid Cation resins
  2. Weak Acid Cation resins
  3. Strong Base Anion resins ( Type -1 & Type –11 )
  4. Weak Base Anion resins

Resin companies specially prepare nuclear grade deionizing resins. Nuclear grade resins are a mixture of hydrogen form strong acid cations and hydroxyl form type I strong base anions into the ratio of 2:3, respectively. SAC resins have a functional group as a sulfonic group, and H+ ions are electrostatically bonded to that group. SBA resins have Quaternary Amine, Type I functional group, and OH ions electrostatically bonded to it. These forms can vary according to the selected application. E.g., Softening resins are in the form of Na+ ions.

Resins are small, spherical, plastic beads combination of styrene cross-linked with divinylbenzene. Gel type and macro-porous type resins are common. High resistivity and high capacity of nuclear grade resins support water treatment in nuclear power plants. During water purification and polishing in water treatment plants at power stations, IX units are designed as separated columns and mixed bed columns. SAC and SBA resins are used in two separate vessels in the two-bed system. But in a mixed bed, SAC and SBA resins are mixed and used as one resin bed in one column.

Conclusion

Water treatment is a powerful feature throughout nuclear power stations. Purifying water to ultra-pure water is a challenge, but the water treatment field has won it with the help of new technologies. Ion exchanging technology is one of the efficient, cost-effective, and user-friendly techniques commonly used in water purification in nuclear power stations.

Designers use IX units as a two-bed system or a mixed bed system. Resins play an excellent role in removing target contaminants in influent and effluent water.

SAC and SBA are the common resin types used in IX units.

Nuclear grade resins are ready to mix SAC and SBA products in a 2:3 ratio.

These resins follow a similar procedure to remove ions as other resins.

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