Tests Conclude Filters Safe for Vitrification Process
RICHLAND, Wash. - A team of engineers from the EM Office of River Protection (ORP) and contractor Bechtel National Inc. (BNI) joined industry and academia experts to develop a first-of-a-kind high-efficiency particulate air (HEPA) filter for the Hanford Waste Treatment and Immobilization Plant (WTP).
The filter helps protect the public and environment during operations. It’s at least five times stronger than a standard HEPA filter and meets or exceeds WTP standards and codes set by the American Society of Mechanical Engineers (ASME).
It could be of use across the DOE nuclear complex. EM is considering additional uses for the new filter at its sites due to its potential to survive smoke loading from facility fires, heavy dust loading, and pressure generated during severe events at nuclear facilities.
“These robust HEPA filters have the potential to greatly improve safety across DOE and the nuclear industry," said Bill Hamel, federal project director and assistant manager for the WTP.
The filter will be deployed in the WTP’s Low-Activity Waste (LAW) Facility, which is scheduled to be completed in spring 2018. The LAW Facility is vital to the direct-feed LAW approach to treat Hanford’s radioactive nuclear waste as soon as 2022.
The filters were developed after initial WTP testing showed standard HEPA filters used across the nuclear industry would not meet the plant’s stringent demands. Its process ventilation system operates at high temperature and humidity, making the standard filters susceptible to failure.
ORP and Bechtel collaborated with Porvair, a leading filter manufacturer that recently won Bechtel’s Large Business Subcontractor of the Year award, to design the new filters.
“The team developed a high-strength radial flow HEPA filter that expanded on a previous industry design to make a more robust filter for the Vit Plant (WTP)," said Peggy McCullough, Bechtel’s project director at the WTP. “The filter demonstrated positive results during testing, which is a significant accomplishment and energizes us as we drive towards making glass as soon as 2022."
HEPA filters are critical to the nuclear industry for their ability to filter airborne contaminants from ventilation and off-gas systems in accordance with state and federal requirements. The filters will be used in the plant’s three nuclear processing facilities: Pretreatment, LAW, and High-Level Waste. The filters are constructed of fragile fiberglass sheets, resembling paper, which are pleated and installed in a filter pack, similar to a thick furnace filter.
The filter recently passed tests performed under Nuclear Quality Assurance (NQA)-1 conditions by the Institute for Clean Energy Technology at Mississippi State University (MSU) to confirm it met safety requirements and codes in an environment that simulated extreme operating conditions. NQA-1 is the regulatory standard managed by ASME for nuclear quality assurance. The testing, which exceeded what is required for standard nuclear-grade HEPA filters, used various flow rates, steam, heat, and aerosols, and included conditions that could be caused by an extreme event.
The performance of the filter design was also validated by code compliance testing at MSU, Underwriters Laboratories, and the U.S. Army Edgewood Chemical Biological Center.
“From strategy to completion of testing, this is a collaborative success story," said McCullough.
Source: U.S. Dept. of Energy, Office of Environmental Management
