The wrecked Fukushima nuclear plant in Japan may have released more than twice the amount of radiation estimated by the government, a study by European and U.S.-based scientists said.

Tokyo Electric Power Co.’s Fukushima station, which was wrecked in the March 11 earthquake and tsunami, may have emitted 35,800 terabecquerels of radioactive cesium 137 at the height of the disaster, according to a study in the Atmospherics Chemistry and Physics journal. Japan’s nuclear regulator in June said 15,000 terabecquerels of cesium 137 was discharged.

Cesium 137 is a source of concern for public health because the radioactive isotope has a half-life of 30 years. The amount discharged is about 42 percent of that released at Chernobyl in 1986, the worst civil atomic disaster in history, according to the atmospheric study.

“I haven’t read the article,” Takumi Koyamada, spokesman at Japan’s Nuclear and Industrial Safety Agency, said when asked about the finding. “I can’t comment on it.”

The study led by Andreas Stohl, an atmospheric scientist at the Norwegian Institute for Air Research, was released on the website of Atmospheric Chemistry and Physics Discussions.

Japanese government officials and the utility known as Tepco haven’t updated figures on radiation from the Fukushima Dai-ihi station. The plant north of Tokyo may have started releasing radiation before the tsunami arrived about 45 minutes after the magnitude-9 quake struck, according to the study, contradicting official assertions. (Bloomberg)

“There is strong evidence that the start of the release occurred early, already during or shortly after the automatic emergency shutdown of the reactors triggered by the big earthquake,” the authors said. This “may indicate some structural damage to the reactor units during the earthquake.” 

(Bloomberg)