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Nuclear Plant Operator Uses RFID to Promote Safety

Southern Co. employs a unique type of active tag to track employees' locations at its training center, as well as teach them how to avoid excessive radiation exposure.
By Claire Swedberg
The system spent approximately a year in development, says Hans Schantz, Q-Track's CTO. The solution capitalizes on Q-Track's NFER technology, which employs very low radio frequencies (approximately 1 MHz) to measure location. When the tag transmits an RF signal, its electrical and magnetic waves are initially out of sync. With a system that operates at a higher radio frequency, RFID interrogators pick up a tag's RF signal after the electrical and magnetic waves have converged. But Q-Track's readers, because they operate at very low frequencies, can detect a tag signal's electrical and magnetic components with separate antennas, and measure the tag's distance from the reader based on the phase difference between the electrical and magnetic waves.

The plant required a system that could cover the 100- by 50-foot plant (that includes a ground floor and mezzanine level), with an accuracy of approximately 1 foot. The system also had to work around the types of obstacles generally found within a nuclear power plant—typically, water pumps and storage tanks.

Hans Schantz, Q-Track's CTO
To achieve such location accuracy, Q-Track installed eight receivers, each with three antennas. The receivers read each QT500 tag not by means of a unique ID number encoded to that tag, but rather by the specific radio frequency it emits (the system can accommodate up to 1,000 tags, with each tag's assigned frequency varying from the next by 1.5 kHz). The system recognizes the frequency of the specific tag's transmission, and links that signal with the name of the employee wearing that particular tag. During the training process, the Q-Track system can monitor the positions of up to 10 trainees simultaneously, receiving data transmitted from the tags to allow the software to calculate the radiation dose each worker receives, in simulation. Alarm points are set up in the system so that if a radiation threshold is being crossed, the device emits a loud warning signal to prompt the user to leave the environment.

At the plant simulation center, Hodnett said, Southern Co. instructs its trainees to "practice like you play." There is greater pressure on nuclear employees and contractors as refueling cycles drop, thus requiring workers to complete their tasks more quickly. "We want all radiation workers to receive the minimum dose," he told the audience. "The lower the person's dose, the better we all are." Plants feel further pressure, he added, as the workforce gets older; those who have already learned radiation skills are retiring, and new workers need to be trained.

According to Hodnett, radiation exposure is a significant concern. Each plant receives a rating based on the total dose per year that each worker receives. At Southern, he said, "Our goal is to be on the bottom of the list." But without the proper training, staff members may unnecessarily expose themselves to radiation. "If a worker is getting up towards the top limit, that bars them from doing certain activities in the plant, which creates scheduling difficulties."

The system, which commenced as a pilot in November 2008, is now a full deployment. Southern Co. also has the technology on display at its headquarters in Atlanta, to demonstrate to its own staff and visitors how it is being used for tracking trainees at Plant Vogtle.

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