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Student-built test facility could lead to safer nuclear facilities

A team of New Mexico State University engineering technology students has designed and built a prototype test facility that could be a step toward more reliable air filtration systems for certain types of nuclear facilities.

NMSU engineering technology students Jeff Nelson of Albuquerque, left, and Roberto Briones of Las Cruces, right, tighten a bolt on a filter test facility designed and built as a senior class project. Faculty member Craig Ricketts looks on. (NMSU photo by Darren Phillips)

Besides giving the students a challenging senior class project, "there is a crying need for this facility," said faculty member Craig Ricketts.

The prototype is designed to test high-strength HEPA (high-efficiency particulate air) filters for use in nuclear facility ventilation systems. High-strength filters are used in German nuclear facilities but are not part of the U.S. national Code on Nuclear Air and Gas Treatment, Ricketts said.

Ricketts, a member of the committee that helps write that code section for the American Society of Mechanical Engineers (ASME), is among those who feel strongly that high-strength HEPA filters should be used in critical applications such as nuclear fuel processing facilities or any facility where plutonium is handled.

"In the event of an accident, these filters are all that stands between the radioactive materials inside and the surroundings outside of these facilities," he said.

In high-strength HEPA filters, the filter medium is reinforced with a fiberglass cloth so the filters could withstand greater pressure changes in the case of an explosion or a loss-of-coolant accident subjecting the filtration system to steam pressure.

The fiberglass reinforcement doubles the cost of a filter, but the main hurdles are regulatory ones, Ricketts said. For filters to be certified as nuclear-grade, the performance standards must be written into the code, and that cannot be done unless there are test facilities to qualify the filters.

Thanks to the students' work over the past semester, there now is a prototype for such a facility - "the only one of its kind in the world," Ricketts said.

Rather than "scale up" the design of test facilities used for standard HEPA filters, which is basically what the Germans have done, Ricketts' class designed a test facility that pumps water through a filter during a test instead of blowing airborne water spray through it.

"You get the equivalent pressure but the investment cost is lower, the operating costs are lower and the energy demands are lower," he said. "You need something that is relatively compact and inexpensive, but it's important to test the filters under wet conditions."

The students' prototype test facility has two components, one that subjects the filter to pressurized water and one that tests the filtration efficiency of the filter in air flow before and immediately after the water test.

The students were able to use parts from a surplus fire simulation test facility that Professor Emeritus Phil Smith of the NMSU Mechanical Engineering Department had developed to test air-cleaning systems subjected to high temperatures and soot. With these available parts and a $500 budget, the students designed and built "a $25,000 test facility," Ricketts said. "The students were very resourceful."

Ricketts will make two presentations on the project to professional organizations later this summer in Cincinnati, hoping to build support for use of high-strength filters in critical nuclear applications.

The 15-member class of seniors in mechanical engineering technology organized itself into seven teams of two to three students each - a management team and teams responsible for piping, structural, filtration efficiency and other specific aspects of the project.

"It was a real-life experience working as a big group on one project," said Matt Serna of Las Cruces, a member of the management team. "And being a manager gives you a head start because most students don't have management experience."

Serna, who graduated May 13 as the College of Engineering's top student and is soon to take a job with Raytheon Corp. in Tucson, said the students met once or twice a week for six or seven hours to work on the project.

"The project taught teamwork," said Jeff Nelson of Albuquerque, also a member of the management team. "We ran into a lot of problems during the design and fabrication process, but eventually it came together."

"Hopefully it will result in a better design of HEPA filters," he added.