When steam is used to pass through the turbine of a nuclear reactor to be reused it has to be cooled and returned to water. This is why seawater is so crucial because seawater can be pulled into the piping system to cool the steam and then be sent back into the ocean. The use of seawater through the piping just once is due to it being cheaper and a lot simpler than other methods. However to use this system correctly the seawater has to be strained to stop blockage, excessive maintenance, and production downtime.
The main problem is that most strainers don’t allow both large and small particles to be strained and using multiple strainers can be used one after the other to catch both small and large debris but it requires more equipment, money, space, and labor. This is also especially difficult due to seawater being corrosive which causes the maintenance of the strainer and cooling equipment process to be continuous. Also if the filters get constantly clogged by large debris there is also a cost of having manual labor come in and clean them out regularly.
This issue has caused the development of the use of self-cleaning scrapers that have the very useful ability to filter both large debris and small particles getting the best of both worlds. The automatic scraper strainer from Acme Engineering, which is a manufacturer of industrial self-cleaning strainers, is a design using a motor to continually remove both very large and very small suspended particles from cooling water. The cleaning is done by using a spring-loaded blade and brush system that is fully run and managed by an automatic control system. The system’s rotation of 32 strokes per minute allows the brushes to dislodge particles that are resistant to the brush’s movement and solids that are usually tougher to get to using a simple strainer. The use of strainers like the one from Acme Engineering allows almost the complete elimination of manual maintenance along with equipment clogging and water fouling downstream allowing to help the minimization of production downtime.
The issue of corrosive seawater still presents itself as a problem for strainers even if the use of automatic strainers is implemented. This happens because the use of carbon steel or stainless steel deteriorates quickly when they are under constant exposure to salty and corrosive seawater. This can be reduced by using different materials that are more resistant to corrosive water but tend to be more expensive like duplex stainless steel or super duplex stainless steel which both have chromium content around 22-25%. Even with these more resistant materials, seawater will still lead to corrosion issues even after the new materials’ cost increases.
The option used by Acme is a Fiber-Reinforced Plastic which was designed as a polymer with fibers interlaced to add strength to the design. This material is more cost effective and is very corrosion resistant for the price due to it being more commonly used for piping systems after the strainers are used to transfer seawater. The use of Fiber-Reinforced plastic in the cooling process could reduce the costs down to 50% over the whole industry with only the actual inner parts being made of duplex stainless steel.
Overall the use of automated strainers can reduce maintenance costs, equipment clogs, and water fouling the Fiber-Reinforced Plastic can reduce the costs and corrosion of the strainers. This could be a revolutionary advantage to all nuclear plants using the seawater cooling process.
By: Vaughn Hafner