LIVERMORE, Calif. - Through Laboratory soil cleanup methods, residents of Bikini, Enjebi and Rongelap Islands - where nuclear tests were conducted on the atolls and in the ocean surrounding them in the 1950s - could have lower radioactive levels than the average background dose for residents in the United States and Europe.
The National Nuclear Security Administration's Lawrence Livermore National Laboratory scientists Bill Robison and Terry Hamilton calculated the radiation doses for people resettling Bikini, Enjebi, Rongelap and Utrok Islands. The two found that when it rains, a portion of the soluble cesium-137 (137Cs) - an isotope of cesium - is transported to the groundwater that lies about three meters below the soil surface. The groundwater eventually gets mixed with the ocean waters so the 137Cs is lost from the soil and is not available for uptake by growing vegetation on the island. The rate of this loss process is much faster than the loss by radiological decay.
In addition, treatment of food crops with potassium reduces the 137Cs concentration in edible fruits to about 5 percent of pretreatment concentrations. Potassium treatment and removal of the top 15 centimeters of soil around houses and community buildings prior to construction of new buildings to reduce external exposure where people spend most of their time - referred to as the combined option - could be used as a remediation strategy before resettlement, Robison said.
"If this approach is taken, the natural background dose plus the nuclear-test-related dose at Bikini, Enjebi and Rongelap would be less than the usual background dose in the United States and Europe," Hamilton said.
The United States conducted 24 nuclear tests at Bikini Atoll with a total yield of 76.8 megatons (MT). The Castle series of tests produced about 60 percent of this total yield and included the 15-megaton Bravo test that was the primary source of radioactive contamination of Bikin
|Contact: Anne Stark|
DOE/Lawrence Livermore National Laboratory