Chemical Might Keep Radiation Out of Riverby Associated Press
Seattle Times, March 23, 2007
RICHLAND -- Hanford nuclear reservation scientists will soon begin using a substance found in bones and teeth to stop radioactive contamination from reaching the Columbia River.
After seven years of studies and successful tests last year, workers this spring will begin injecting calcium phosphate into the ground to prevent radioactive strontium from a defunct reactor from seeping into the river, state and federal officials said.
Calcium phosphate is in bones and teeth. It binds to strontium and forms a crystal that holds the radioactive element in place until the radioactivity naturally decays.
"It should keep it bound up for hundreds of years while the strontium decays away," said John Fruchter, Pacific Northwest National Laboratory program manager for the project.
Within 90 years, about 90 percent of the radioactivity is gone, and within 270 years, radioactivity is within drinking water standards.
Plans are to inject a 300-foot-long chemical barrier about 40 feet underground near the banks of the river where groundwater is contaminated with strontium.
When the N Reactor was operating to produce electricity and plutonium for the nation's nuclear-weapons program, water used to cool the reactor was contaminated with strontium.
Contamination remains in the soil between the reactor and the river and is carried by groundwater.
Radioactive strontium is particularly dangerous to humans. Chemically similar to calcium, it is deposited in the bones, where it can release radiation for years.
Strontium's similarity to calcium offered a promising cleanup solution, but only after scientists figured out a way to inject the chemical into the earth through wells without the phosphate and calcium binding up.
If the chemicals were combined in solution, they would bind up in the pipe rather than spreading out each of 10 wells along the river, said geologist Mike Thompson.
Instead, the calcium is mixed with citrate, which prevents it from binding with the phosphate immediately.
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