Japan was unprepared for a nuclear accident on the scale of the one at the Fukushima plant, the government said in a report to be submitted to the IAEA. The report says poor oversight may also have contributed to the crisis.
The authorities have pledged to make Japan's nuclear regulator (NISA) independent of the industry ministry, which also promotes nuclear power.
This comes after NISA doubled its initial estimate of leaked radiation in the first week after the disaster. The nuclear safety agency now says 770,000 terabecquerels escaped into the atmosphere following the March 11 disaster—more than double its earlier estimate of 370,000.
Although the amount is just 15% of the total released at Chernobyl in 1986, it suggests contamination of the surrounding area is worse than first thought.
More than 80,000 local residents living within a 12-mile radius of the plant have been evacuated from their homes. Nearly three months into the crisis, the Fukushima Dai-Ichi plant is still leaking radioactive material. Chief Cabinet Secretary Yukio Edano says more evacuations are being considered. Monitoring shows the lie of the land and wind patterns may be causing a buildup of radiation in other areas.
The government admitted that it was unprepared for a severe accident, in a report by Japan's nuclear emergency taskforce, to be handed in to the IAEA later this month.
The report confirms three reactors went into meltdown earlier than thought when the earthquake and tsunami knocked out cooling systems and backups.
Earlier, NISA said that in reactor 1, molten nuclear fuel dropped to the bottom of the pressure vessel within 5 hours of the quake—10 hours earlier than initially estimated by Tepco.
NISA also said a meltdown damaged reactor 2 after 80 hours and reactor 3 after 79 hours of the disasters.