HANFORD — Workers have found a nasty surprise beneath a Hanford building just north of Richland -- highly contaminated soil from an undiscovered leak.
"This is extremely high radiation. Nothing else compares in the river corridor," said Mark French, Department of Energy project director for environmental cleanup in the river corridor, the 75 square miles of Hanford along the Columbia River.
Radioactivity has been measured at 8,900 rad per hour, which would be about 10 times the lethal dose on contact, according to Hanford officials. The building where the leak was found is about 1,000 feet from the Columbia River.
However, there is no evidence that the contamination has reached the ground water, which could carry the contamination to the river, Hanford officials said. Wells are used to monitor ground water for contamination in the 300 Area, and more monitoring is planned.
The contaminated soil is beneath the 324 Building, which initially was used to examine fuel from Hanford's plutonium-production reactors and develop ways to chemically reprocess the fuel to remove plutonium for the nation's nuclear weapons program. Later, the building was used to help develop disposal methods for high-level radioactive waste, including vitrification, or glassification.
Work was done inside hot cells built to allow Hanford employees to work with highly radioactive materials without being exposed to radiation. Workers would stand outside the hot cells and use controls to operate manipulators inside the cells, watching what they were doing through leaded-glass windows.
The hot cells included drains with sumps, or low spots to collect liquids.
As workers were cleaning out hardened grout that had gotten into a drain beneath one of the hot cells, a crack was discovered in the steel lining of the sump, said Todd Nelson, spokesman for DOE contractor Washington Closure Hanford.
Radioactive monitoring equipment was driven into the ground and under the building to look for possible contamination. Radiation readings turned out to be so high that workers will not be able to scoop out a sample and assess it.
The level of contamination is a concern and a safe way will have to be found to clean it up, said Larry Gadbois, a scientist with the Environmental Protection Agency, the regulator on the project.
The good news is that the contamination was discovered before the hot cell was removed, French said. Now the building and the hot cell provide shielding that protect workers from the radioactivity.
Work will be done next to determine how wide and deep the contamination has spread and then revise the plan to remove the hot cell and soil, unless the contaminated area is determined to be small.
Records show that a large spill of cesium and strontium was reported in the hot cell above the cracked sump in 1986. Waste also could have leaked at other times as the building was being used from 1966 until at least 1996.
Hanford officials have described the cleanup and demolition of the building as the most difficult, complex and hazardous work that Washington Closure will do in the 300 Area, which had about 300 buildings before cleanup began.
Washington Closure began preparing the building for demolition as soon as it began work under its contract to clean up Hanford along the Columbia River in August 2005. The building has five hot cells, the largest of which has dimensions of 24-by-30-by-16 feet. Their concrete walls are 4 to 6 feet thick and they are lined with stainless steel. Each has numerous crawl spaces, ductwork, utilities, pipes, cranes and other systems cast into or attached to the facility.
The building will have to be torn down to remove the hot cells, which will be filled with concrete and then cut into blocks weighing20 tons to almost 1,000 tons each.
DOE is working toward a goal of having most cleanup completed along the Columbia River by 2015.