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ORNL-developed instrument provides low-cost EMI protection

OAK RIDGE, Tenn., Oct. 16, 1995 — Researchers at the Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL) have developed a sophisticated receiver that detects electromagnetic interference (EMI), which causes problems for instruments in nuclear power plant control rooms.

EMI, caused by magnetic fields, can cause disruptions in some of the high-performance digital control systems in nuclear power plant control rooms and in industries using similar sophisticated instrumentation, according to Steve Kercel, principal inventor of the Magnetic Spectral Receiver.

The receiver provides low-cost, highly accurate magnetic field monitoring of diverse facilities where instrumentation is vital to the facility's operation. By knowing the exact levels of EMI present where sensitive instruments are to be used, design engineers can more accurately specify the amount of EMI resistance required to do the job. Typically, to be safe, engineers call for greater EMI resistance - or "hardness" - than is actually needed. This, however, is extremely wasteful because it substantially increases the cost.

"Experts have estimated that proper knowledge of the EMI ambient, or environment, would allow designers to save half the cost of digital instrumentation and controls packaging," said Kercel, whose receiver received an R&D 100 Award this year from R&D Magazine. This award recognizes the 100 most technologically significant new products of the year.

The Magnetic Spectral Receiver is about the size of a microwave oven and weighs 65 pounds. The instrument itself weighs about three pounds. Shielding and the package make up the remaining 62 pounds.

The ORNL receiver is one of the world's first devices that uses the wavelet transform, a processing system that provides analysis of transient, or very brief, effects that conventional receivers miss. Instead, these receivers include the transient peak as an EMI average, which doesn't tell the entire story.

"Conventional receivers respond to the average effects, not the peak effects," Kercel said. "These results can be misleading in the analysis of magnetic fields on control room instruments."

Another advantage of the Magnetic Spectral Receiver is cost. While conventional EMI receivers cost between $66,000 and $75,000, the ORNL unit would cost approximately $8,000 when produced in reasonable quantities, Kercel said. Part of the reason for the higher cost of other receivers is that they provide high precision, resolution and dynamic range; however, these capabilities aren't necessary for ambient surveys. Conventional EMI receivers also need constant monitoring by an attendant. The Magnetic Spectral Receiver, however, needs no attendant, which saves an appreciable amount in labor costs over the typical three-week monitoring period.

While the Magnetic Spectral Receiver is primarily intended for use in nuclear power plant control rooms, Kercel also expects it to find uses in other industries, such as textiles and semiconductor fabrication. In particular, the textile industry "suffers seemingly inexplicable failures of digital control equipment and suspect ambient EMI as the culprit," Kercel said. Companies in both industries have expressed interest in the receiver.

The same basic technology used in the Magnetic Spectral Receiver could be modified for use in many types of real-time environmental monitoring, surveillance, detection and signature identification applications where the wavelet processor identifies crucial features from the transient components of the signal. For example, by substituting a few standard parts, the receiver could be converted into a seismic monitor, Kercel said. The receiver could also be configured as a gunshot detector that would not be susceptible to other noises, such as thunder or vehicle backfires.

Other ORNL researchers who developed the award-winning receiver are William Dress, Robert Rochelle and Michael Moore.

ORNL, one of DOE's multiprogram national research and development facilities, is managed by Lockheed Martin Energy Systems, which also manages the Oak Ridge K-25 Site and the Oak Ridge Y-12 Plant. The research was funded by the Nuclear Regulatory Commission.