LLNL research at Marshall Islands could lead to resettlement

Feb 11, 2010

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 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 Bikini Island and Rongelap and Utrok Atolls. Pretest estimated yield for the Bravo test was about five megatons. The much larger yield resulted in vaporization of more coral reef and island than expected and the debris-cloud reached a much higher altitude than anticipated.

High-altitude winds were to the east at the time of detonation and carried the radioactive debris toward Rongelap Atoll. Utrok Atoll also received fallout from the Bravo test but at much lower air and ground-level concentrations than at Rongelap Atoll. Other atolls received Bravo fallout at levels below that of Utrok.

Today, scientists in Lawrence Livermore's Marshall Islands Dose Assessment and Radioecology Program work to minimize exposure through ingestion and other pathways for the Marshallese now living on or wishing to return to their islands. The program continues research begun nearly 30 years ago to characterize radiological conditions on affected islands and develop strategies to minimize radiological exposure to a people who want to resettle. The program also supports Marshallese efforts to implement radiation protection programs for residents wishing to track their exposure to radionuclides from fallout contamination that still lingers on the islands.

Previous assessments showed that 137Cs accounts for about 98 percent of the total dose for returning resident at the various atolls. About 85 percent to 90 percent of the dose (depending on the atoll) is from consumption of locally grown foods such as coconut meat and fluid, copra meat and milk, Pandanus fruit and breadfruit. About 10 percent of the dose is due to external gamma radiation from 137Cs in the soil. Isotopes of strontium, plutonium and americium account for less than 5 percent of the estimated dose.

The research appears as the cover article in the journal, Health Physics.

Explore further: New insights found in black hole collisions

Related Stories

Bikini corals recover from atomic blast

Apr 15, 2008

Half a century after the last earth-shattering atomic blast shook the Pacific atoll of Bikini, the corals are flourishing again. Some coral species, however, appear to be locally extinct.

Researchers track Chernobyl fallout

Oct 01, 2008

When a reactor in the Chernobyl nuclear power plant exploded in 1986 in what was then the Soviet republic of Ukraine, radioactive elements were released in the air and dispersed over the Soviet Union, Europe and even eastern ...

Freshwater supplies threatened in central Pacific

Aug 15, 2007

An international team from The Australian National University, Ecowise Environmental, the Government of the Republic of Kiribati, the French agency CIRAD and the Pacific Islands Applied Geoscience Commission has been studying ...

Recommended for you

New insights found in black hole collisions

Mar 27, 2015

New research provides revelations about the most energetic event in the universe—the merging of two spinning, orbiting black holes into a much larger black hole.

X-rays probe LHC for cause of short circuit

Mar 27, 2015

The LHC has now transitioned from powering tests to the machine checkout phase. This phase involves the full-scale tests of all systems in preparation for beam. Early last Saturday morning, during the ramp-down, ...

Swimming algae offer insights into living fluid dynamics

Mar 27, 2015

None of us would be alive if sperm cells didn't know how to swim, or if the cilia in our lungs couldn't prevent fluid buildup. But we know very little about the dynamics of so-called "living fluids," those ...

Fluctuation X-ray scattering

Mar 26, 2015

In biology, materials science and the energy sciences, structural information provides important insights into the understanding of matter. The link between a structure and its properties can suggest new ...

Hydrodynamics approaches to granular matter

Mar 26, 2015

Sand, rocks, grains, salt or sugar are what physicists call granular media. A better understanding of granular media is important - particularly when mixed with water and air, as it forms the foundations of houses and off-shore ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.