Five years after the tsunami and resulting nuclear accident, scientists are still discovering radioactive elements in the waters off Japan. This indicates continued small leaks and raises concerns about the materials stored at the reactor site.
According to the Woods Hole Oceanographic Institution (WHOI), a worldwide network of independent researchers, citizens, small business foundations and large companies have been working together since 2011 to monitor the level of radioactive contiminants in the oceans following the 2011 Fukushima nuclear accident, which occurred 5 years ago to this day.
Ken Buesseler, a radiochemist at WHOI, is one of those scientists. He has taken samples off Fukushima at least once per year and has examined nearly 1,000 Pacific seawater samples for Fukushima radionuclides. His work reveals that although levels of radioactive substances in the ocean off Japan are thousands of times lower than during the peak release in 2011, the situation is still not yet under control.
“We are not seeing the steady decrease we would expect to see off Fukushima if all sources had stopped; rather, we are finding values are still elevated, which confirms that there is continued release from the plant,” explains Buesseler.
As cesium-134 has a half-life of just two years, researchers can tell when it comes from Fukushima. And the cesium-strontium ratio has been changing since 2011, indicating continued small leaks. His findings also raise concerns about the thousands of tonnes of strontium still stored in tanks at the nuclear power plant and accumulated in the buildings of soils – some of which is still leaking into the ocean.
“We think that when there is heavy rain, more cesium, strontium, and other isotopes from the nuclear power plant are carried into the ocean,” says Buesseler. “We are still investigating how that occurs –whether carried in the groundwater or from the run off of sediment – but clearly it is highest near the contaminated site of the Fukushima nuclear power plants.”
Image credit: IAEA Imagebank