Chernobyl Exclusion Zone radioactive longer than expected
Radioactive Material Isn’t Disappearing From the Environment as Quickly as Predicted
By ALEXIS MADRIGAL
Dec. 20, 2009 Chernobyl, the worst nuclear accident in history, created an inadvertent laboratory to study the impacts of radiation — and more than twenty years later, the site still holds surprises. Reinhabiting the large dead zone around the accident site may have to wait longer than expected. Radioactive cesium isn’t disappearing from the environment as quickly as predicted, according to new research presented here Monday at the meeting of the American Geophysical Union. Cesium 137’s half-life — the time it takes for half of a given amount of material to decay — is 30 years, but the amount of cesium in soil near Chernobyl isn’t decreasing nearly that fast. And scientists don’t know why. It stands to reason that at some point the Ukrainian government would like to be able to use that land again, but the scientists have calculated that what they call cesium’s “ecological half-life” — the time for half the cesium to disappear from the local environment — is between 180 and 320 years. “Normally you’d say that every 30 years, it’s half as bad as it was. But it’s not,” said Tim Jannick, nuclear scientist at Savannah River National Laboratory and a collaborator on the work. “It’s going to be longer before they repopulate the area.” … The results of this study came as a surprise. Scientists expected the ecological half-lives of radioactive isotopes to be shorter than their physical half-life as natural dispersion helped reduce the amount of material in any given soil sample. For strontium, that idea has held up. But for cesium the the opposite appears to be true. The physical properties of cesium haven’t changed, so scientists think there must be an environmental explanation. It could be that new cesium is blowing over the soil sites from closer to the Chernobyl site. Or perhaps cesium is migrating up through the soil from deeper in the ground. Jannik hopes more research will uncover the truth. “There are a lot of unknowns that are probably causing this phenomenon,” he said. …
