Tatsuhiko Kodama began his 27 July testimony to Japan's parliament with what he knew. In a firm, clear voice, he said that the Radioisotope Center of the University of Tokyo, which he heads, had detected elevated radiation levels in the days following the meltdown of three reactors at the Fukushima Daiichi nuclear power station. But when it came to what wasn't known, he became angry. "There is no definite report from the Tokyo Electric Power Company or the government as to exactly how much radioactive material has been released from Fukushima!" he shouted.
Kodama's impassioned speech was posted on YouTube in late July and has received nearly 600,000 views, transforming him into one of Japan's most visible critics of the government. But he is not alone. Almost six months after an earthquake and tsunami triggered the meltdowns, other researchers say that crucial data for understanding the crisis are still missing, and funding snags and bureaucracy are hampering efforts to collect more. Some researchers warn that, without better coordination, clean-up efforts will be delayed, and the opportunity to measure the effects of the worst nuclear accident in decades could be lost. Kodama and a handful of Japanese scientists have become so frustrated that they are beginning grassroots campaigns to collect information and speed the clean-up.
Since the crisis began, the Tokyo Electric Power Company and the Japanese government have churned out reams of radiation measurements, but only recently has a full picture of Fukushima's fallout begun to emerge. On 30 August, the science ministry released a map showing contamination over a 100-kilometer radius around the plant. The survey of 2,200 locations shows a roughly 35-kilometer-long strip northwest of the plant where levels of caesium-137 contamination seem to exceed 1,000 kilobecquerels per square metre. (After the 1986 Chernobyl disaster in Ukraine, areas with more than 1,480 kilobecquerels per square metre were permanently evacuated by the Soviet authorities. In Japan, the high-radiation strip extends beyond the original forced evacuation zone, but falls within a larger 'planned evacuation zone' that has not yet been completely cleared.)
Japan's Nuclear and Industrial Safety Agency has also published new estimates of the total radiation released in the accident, based on models that combine measurements with what is known about the damage to the reactors. The latest figures, reported to the International Atomic Energy Agency in June, suggest that the total airborne release of caesium-137 amounts to 17% of the release from Chernobyl (see map). The government estimates that the total radiation released is 7.7 × 1017 becquerels, 5–6% of the total from Chernobyl.
Yet "there are still more questions than definite answers", says Gerald Kirchner, a physicist at Germany's Federal Office for Radiation Protection in Berlin. High radiation levels make it impossible to directly measure damage to the melted reactor cores. Perhaps the greatest uncertainty is exactly how much radiation was released in the first ten days after the accident, when power outages hampered measurements. Those data, combined with meteorological information, would allow scientists to model the plume and make better predictions about human exposure, Kirchner says.
Several measurements suggest that some evacuees received an unusually high dose. Five days after the crisis began, Shinji Tokonami, a radiation health expert at Hirosaki University, and his colleagues drove several hundred kilometres from Hirosaki to Fukushima City, taking radiation measurements along the way. The results indicate that evacuees from Namie, a town some 9 kilometres north of the plant, received at least 68 millisieverts of radiation as they fled, more than three times the government's annual limit (http://dx.doi.org/10.1038/srep00087).