High radiation levels have been detected deep under yet another cluster of old nuclear waste tanks at Hanford.
The radiation was recently found under the BX Tank Farms, where a dozen single-wall tanks were built to store uranium and plutonium processing wastes in the 1940s and ‘50s.
“We are using new detection equipment to get a handle on the situation,” said geophysicist John Brodeur.
The radiation, which includes long-lived cesium and uranium, is from one of the old tanks, BX 102.
It is a 530,000-gallon tank built in 1946 that leaked an estimated 70,000 gallons of its uranium-laden contents into the ground. The leak wasn’t detected until 1969, said Guy Schein, a U.S. Department of Energy “watch list” of problem tanks.
The BX leak has been partially studied before. It’s known that it spread a plume of radiation at least 300 feet to the northeast. But it wasn’t previously known that the leak went so far into the ground.
The contamination is “at least” 230 feet under the tank, where the bore-hole stopped, Brodeur said. It was found in May during tests in the 200 East area.
“Our guy in the field was logging the hole,” Brodeur said. “He found his (radiation) detector was swamped all the way to the bottom, just above the ground water.”
The radiation may have reached ground water at 255 feet, but additional work is necessary to verify that, Brodeur said.
“We have cesium to at least 140 feet. But the contamination levels are so high we don’t know what all the elements are yet because they are swamping our detection equipment,” Brodeur said.
His team plans to go back into the hole with a different type of detector - “something that can handle the very high (radiation) rates,” he said.
Brodeur works with a team of U.S. Department of Energy drilling experts from Grand Junction, Colo. They also found cesium contamination below a tank in the 200 West area in 1995.
The BX tanks in Hanford’s 200 East area are five miles closer to the Columbia River than the 200 West area where the earlier contamination was found.
The BX tanks contained uranium, far more mobile than cesium. That could make it easier for the radiation to move toward the Columbia.
Hanford managers already are doing a ground water study in the BX tank farm, said David Shafer, manager of DOE’s program to study the ground under the tanks.
It was started after Washington state officials “concluded there was sufficient reason to think waste from the BX farm had reached ground water,” Shafer said.
“We are most concerned about the implications for ground water,” he said.
, DataTimes ILLUSTRATION: Graphic: New underground radioactive leaks found