This spring's nuclear disaster at the Fukushima Daiichi power plant released almost double the amount of radiation the Japanese government has claimed, according to a new analysis. The authors say the boiling pools holding spent fuel rods played a role in the release of some of the contaminants, primarily cesium-137 - and that this could have been mitigated by an earlier response. Researchers at the Norwegian Institute of Air Research ... say the amount of cesium-137, a long-lived isotope that persists in the atmosphere, was about twice as high as the Japanese government's official estimate. The researchers also say about 20 percent of the total fallout landed over Japan, but the vast majority fell over the Pacific Ocean. (The effects of this fallout on fisheries and aquatic wildlife are still being determined.) Cesium-137 emissions peaked three or four days after the quake and tsunami, remaining high until March 19, according to this new study. That's the day authorities started spraying water on the spent-fuel pool at reactor unit 4, the researchers note. This indicates that emissions were not only coming from the damaged reactor cores, but also from the spent-fuel pool of unit 4 and confirms that the spraying was an effective countermeasure," they say. This contradicts Japanese government reports claiming the pools released no radiation.