Up to 150,000 gallons of water spilled from a broken pipeline Thursday at Hanford not too far from one of the most highly radioactive soil contamination sites known at the nuclear reservation.
However, the water did not reach the spilled radioactive waste about 150 yards away beneath the 324 Building or any other known soil contamination sites, said Peter Bengtson, spokesman for Department of Energy contractor Washington Closure Hanford.
The 324 Building just north of Richland has large hot cells where research was done with high level radioactive waste and materials. In 2010, Hanford officials discovered that cesium and strontium had leaked into the soil beneath the building from a newly discovered crack in the sump at the bottom of one of the building's hot cells.
Radioactivity has been measured at 8,900 rad per hour in the soil. Direct exposure for a few minutes would be fatal, according to Washington Closure.
Thursday, work was being done between that building and the 325 Building, which Pacific Northwest National Laboratory continues to use, at the site of the former 308 Building.
A ramp was being excavated down to the underground Training, Research, Isotopes, General Atomics, or TRIGA, reactor, which was used to look for defects in fuel elements and fuel jackets. The ramp is planned to be used to remove the reactor, which has been covered with shielding blocks since the 308A Building above it came down in 2011.
The excavator got too close to the water pipeline, breaking it and causing an estimated 100,000 to 150,000 gallons of water to spill before water valves were closed, Bengtson said.
However, the operator put the excavator bucket down over the top of the break to contain the spray and keep the water flow moving to the indentation in the ground that once was the basement of the 308 Building, where the water collected.
Within a couple of hours the water had drained into the sandy soil there, Bengtson said.
There are no known plumes of contamination beneath the 308 Building, he said.
However, monitoring wells will be watched to confirm the spilled water did not reach or spread any contamination.
The 324 Building has been left standing for now over the radioactive waste that spilled from one of its hot cells both to provide radioactive shielding and also to prevent rain water from reaching and possibly spreading the contamination.
The contamination is suspected to be the result of a large spill in the 1980s of cesium and strontium inside the hot cell that was being used to fabricate a heat source for German tests for a repository for radioactive waste, which emits heat.
The hot cell where the work was being done is the size of a room, but 30 feet tall and with 5-foot thick walls lined with stainless steel. Workers would stand outside the hot cell and use controls to operate manipulators inside the cells, watching what they were doing through leaded-glass windows to shield them from radiation.