The Clean Up
In one of the most unique and critical waste cleanups in the world, Refractron ceramic filter elements have demonstrated their superiority and effectiveness.
At the Idaho Nuclear Technical and Engineering Center, part of Idaho National Laboratory (INL), nearly 1 million gallons of radioactive waste were generated during decontamination activities following spent nuclear fuel reprocessing. Known as sodium-bearing waste, this liquid waste is contained in three underground storage tanks.
The U.S. Department of Energy is responsible for the cleanup and Refractron is proud of it’s crucial role in eliminating this environmental hazard in Idaho. As a trailblazer in ceramics technology, Refractron continues to push the boundaries of innovation with contemporary breakthroughs.
The Challenge – Why Refractron was Needed
The Integrated Waste Treatment Unit (IWTU) was established to convert 900,000 gallons of liquid radioactive waste into a granular solid for permanent storage.
The first-of-its-kind facility was designed and built from the ground up with extensive pilot plant testing in collaboration with multiple engineering firms. IWTU utilizes a dual fluidized bed reactor and steam reformer process to transform the liquid waste to a solid.
During pilot testing, filter bypass in the off-gas stream lead to agglomerates forming in the second fluidized bed, causing system shutdown. These failures not only incur high cleanup costs but also delay waste decontamination.
A Customized Design is Called For
Initially, Inconel 625 sintered mesh filters were installed in the 550°C system. However, after just 50 days in operation, the pressure drop (dP) started increasing exponentially. Inspection revealed significant corrosion in the usually corrosion-resistant Inconel 625, resulting in nickel deposition within the pore structure and subsequent plugging.
Efforts to regenerate the filters failed, prompting the search for a more durable filter material.
Along with Pall and Porvair, Refractron was chosen to design a ceramic filter element to fit their process. The engineering team at Refractron recommended testing a membrane-coated reaction-bonded silicon carbide (rbSiC) and a monolithic rbSiC filter element which are chemically inert, provide excellent creep resistance, and can withstand temperatures up to 1200°C, far exceeding their process requirements.
Compared head-to-head with Pall (ceramic) and Porvair (sintered metal fiber) elements, only Refractron’s rbSiC filter elements recovered to baseline dP with the infrequent nitrogen back pulses and in-process nitric acid cleaning. Refractron’s rbSiC filter elements were the clear winner and obvious choice by IWTU to complete the cleanup.
Craig L. Porter, P.E, - Chief Engineer at Jetseal Engineering & Techinical Services
“Refractron has been a responsive and high quality vendor in our quest to solve challenging hot gas filtering applications in the nuclear waste processing arena.
When faced with a need for a failsafe ceramic-based fuse that would fit within our existing envelope, Refractron was willing to develop a customized solution for us. It is great to work with such a technically capable company.”
Future State
Successful integration of the Refractron rbSiC filter elements indicated that these Refractron products would be capable of carrying the project to its completion in 7-10 years.
After four months of operation, IWTU approached Refractron to design a ceramic insert for the main filter body to act as failsafe, replacing the existing Inconel failsafe. This “fuse” is critical to avoid filter bypass in the event of a filter breakage.
Refractron’s engineers are designing a dual porosity ceramic filter integrated with a metal flange for testing in the pilot plant. This coarse substrate coated with a finer ceramic membrane coating will minimize additional dP while providing a final layer of defense against primary filter breakage.
Let Refractron Help You
Refractron’s expertise in manufacturing rbSiC ceramic filter elements for critical operations is integral in the cleanup of radiological waste.
Though not a “filtration company”, Refractron’s unique expertise in designing and manufacturing porous ceramics enabled it to tackle the challenge and partner with INL to create a customized solution.
Refractron leads the way in porous ceramics innovation for unique applications including those making semiconductor chips, processing chemicals, filtering hot gases, dewatering minerals, purifying water and carbonating beverages.
If you need a resilient porous ceramics tailored to a specific application, Refractron offers complimentary engineering assessments. Contact Refractron today to explore possibilities to enhance performance and reliability and lower operating costs.
Contributing Author: Tyler Roberts
Tyler Roberts is a Chemical Engineer at Refractron Technologies. Contact Tyler at (315) 879-0811 or troberts@refractron.com for a free assessment to see if we can help you with parts that will extend maintenance cycles, improve product quality and process reliability and reduce your operational costs.