RFID Ensures Worker Safety at Nuclear Plant Archive

Since there are four rooms with complex spatial arrangements of shelves, as well as multiple entry and exit points, Areva NP ruled out a system based on portal controls. It opted instead to employ a real-time location system (RTLS) from Ubisense. The company began implementing the project in April 2008, installing 34 interrogators mounted 1 meter (3.3 feet) above the upper edge of the shelves, at various locations around the four rooms. Ubisense completed the deployment in September, according to Terry Phebey, the company's VP of sales in Europe and Asia.

Each worker or guest in the archive wears a Ubisense tag that measures approximately 3 centimeters long by 3 centimeters wide by 1 centimeter thick (1.2 inches long by 1.2 inches wide by 0.4 inch thick) and contains an active, ultra-wideband (UWB) RFID transponder that sends out a 6 GHz to 8 GHz signal in short pulses. The 10-gram (0.4-ounce) tag can be worn on a belt or slipped inside a badge. Batteries in the tags last for about 12 months. The readers in the four rooms record the signals and calculate the locations of each tag and its wearer using time-of-arrival and angle-of-arrival data. A worker's position in the archive can then be visualized on a screen accessible to rescue teams.

According to Phebey, tests of the system showed that in some cases, it lost sight of workers when they were actually between shelves. To overcome this problem, Ubisense added a few additional interrogators and designed the system to infer that a worker is between two shelves if he or she moves between them but has not yet been detected moving out of the area.

Areva NP's German division invested roughly €130,000 ($180,300) in the application, Phebey says. However, it has not yet calculated a return on investment since the application is currently focused on workers' safety.

"The application is valuable, and it works without problems," Seydel states. "In the event of a fire, we are able to make sure all workers are safe."