News Releases | Newsroom

Improved system developed to detect buried reactor fuel

02.10.2009

RICHLAND, Wash.—Workers at Washington Closure Hanford have developed a much safer way to detect and handle highly radioactive spent reactor fuel at cleanup sites along the Columbia River.

“Hanford may be the only place in the world where anyone is digging up spent reactor fuel, so we’ve had to develop our own methods for safely detecting and handling it,” said Mark Buckmaster, D Area Field Remediation project manager for Washington Closure. Washington Closure Hanford manages the River Corridor Closure Project at the U.S. Department of Energy’s 586-square-mile Hanford Site in southeastern Washington state.

DOE’s Hanford Site was home to nine plutonium-production reactors, which operated from 1944 through 1989. During reactor operations, contaminated equipment, worn-out reactor components and other wastes were buried in a series of unlined trenches and pits, called burial grounds, located near each reactor.

Nobody expected to find spent fuel in a burial ground – partly because it was so radioactive and partly because it was so valuable; it contained plutonium, which was Hanford’s sole product.

Existing records supported workers’ assumptions that no spent fuel had been disposed in burial grounds but would have been sent to reprocessing facilities where there the plutonium could be removed.

“So it was a surprise the first time we encountered spent fuel in a burial ground in 2004,” Buckmaster said. “Initially, we had to rely on visual observation and use of hand-held radiation detectors attached to long handles to locate the spent fuel fragments, extract them from the surrounding soil and isolate them from workers and the environment. The process was time- consuming and exposed site workers to additional radiation,” he said.

“Later, we developed another process that involved placing thin layers of contaminated soil in large sorting cells and using a pipe containing gamma detectors to identify radioactive hot spots. This process helped reduce the radiation exposure to workers. However, CRATER is a significant improvement,” said Buckmaster.

Ed Traverso led development of the CRATER for Washington Closure. CRATER, which stands for Compton Ratio Analysis for Testing Environmental Radioactivity, uses off-the-shelf components, assembled and mounted above the bucket of an excavator, which can be monitored with a Bluetooth-enabled, hand-held device.

Traverso said that within 15 seconds, the system can detect even small pieces of fuel at the bottom of a modified excavator bucket. “It also is capable of distinguishing between spent fuel and other high-radiation-dose materials, such as thermocouple wire used in the reactor cores, which have different disposal requirements,” Traverso said.

He added that a lot of people helped develop the new system, including two small-business subcontractors. Chesapeake Nuclear Services of Annapolis, Maryland, and Radiation Safety Associates of Hebron, Connecticut, built the prototype and developed the software to operate the system.

“The team came up with an innovative solution to a unique problem,” he said. Two of the CRATER instruments are onsite and in use and another two are on order.

Traverso said they will continue to make improvements, such as upgrading internal components to handle the near-zero temperatures experienced in December.

Since 2004, workers have discovered 74 pieces or fragments of spent fuel and more is expected. The system was tested at D Area, home to D and DR reactors, where more than half of the spent fuel identified to date has been found.

Most of the contaminated material dug up is not nearly as radioactive as spent fuel and can be sent to Hanford’s Environmental Restoration Disposal Facility for disposal. However, even small fragments of spent reactor fuel can be highly radioactive and highly dangerous. They will be packaged and stored for later disposal in a national repository.