Mr Grossi said the 11 March 2011 accident had galvanised the international community. He took stock of the work the IAEA and its member states have done to strengthen nuclear safety since the accident.
He noted, however, that that the agency is still helping tackle the “ongoing challenge of the water” at the site in northern Japan.
Water used to cool the melted-down cores and groundwater from close to the damaged facility contains some radioactive materials. It is being collected, treated and stored in tanks on the plant grounds, but space is running out and the government is exploring ways to deal with the waste water – which already totals more than one million tonnes with the volume increasing by more than 100 tonnes every day.
The IAEA has urged Japan’s government to urgently decide on how to dispose of the water. Five disposal methods are being considered by the government: ground injection, controlled discharge into the sea, discharge as steam, discharge as hydrogen, and solidification for underground burial.
Japan’s industry ministry has said it will be safe to release water into the ocean, stressing that on an annual basis the amount of radiation measured near the release point would be very small compared to levels to which humans are naturally exposed.
Releasing treated water into the sea in a controlled manner is common practice at nuclear power plants and is generally considered the most viable option for Fukushima-Daichi because it could be done quickly and would cost the least.
Japan’s Nuclear Regulation Authority has long said that releasing the treated water into the sea is the most reasonable option, but people in Fukushima prefecture, especially fishermen, fear it will damage the region’s reputation, the Japan Times reported.
Mr Grossi said the IAEA had put in thousands of manhours and compiled thousands of pages of data and knowledge, pointing to a 2015 report that represents the findings of the first four years following the accident.
He said that at Fukushima-Daiichi, the equipment reacted just as it was designed to do. It stopped, the control rods were inserted into the reactor core, and the cooling system kicked in. About an hour later, however, a giant tsunami swept across the mainland, overwhelming Japan’s coastal defences and the station’s safety perimeter.
Though the ensuing damage caused nuclides to be released into the environment, scientists have found no evidence that this caused radiation-induced health effects.
“An important lesson of Fukushima is that regulators must be strong, independent and adequately resourced,” he said. “A robust, normative safety framework with the IAEA at its centre is critically important. Our work has not only led to concrete improvements in the safety of nuclear sites; it has created a sustained and robust global safety culture.”