The radioactive water leaking from the site of the wrecked Fukushima Daiichi nuclear power plant in Japan is a stern reminder that we have not seen the end of the world’s largest nuclear crisis since the Chernobyl meltdown in Ukraine in 1986. After an earthquake and tsunami crippled the Fukushima plant in March 2011, it became clear that efforts to decontaminate the area would be long-lasting, technically challenging and vastly expensive. Now it turns out that the task has been too big for the owner of the plant, the Tokyo Electric Power Company (TEPCO). The Japanese government on 3 September announced a plan to take over the clean-up, but its intervention is overdue.

In the two and a half years since the accident, TEPCO has repeatedly failed to acknowledge the nature and seriousness of problems with safeguarding nuclear fuels in the three destroyed reactors at Fukushima. Each day, some 400,000 litres of water are being funnelled into the reactor cores to prevent the rods from overheating. Only in recent months has TEPCO admitted that some contaminated water is leaking into the reactor basement and, through cracks in the concrete, into the groundwater and the adjacent sea. Few independent measurements of radiation exposure are available, and it is worryingly unclear how these leaks might affect human health, the environment and food safety. But the problems do not stop there. There are now almost 1,000 storage tanks holding the used cooling water, which, despite treatment at a purification system, contains tritium and other harmful radionuclides. The leaks make clear that this system is a laxly guarded time bomb.

It is no secret that pipes and storage tanks sealed with rubber seams have a habit of leaking. TEPCO’s reliance on routine patrols to detect any leaks has been careless, if not irresponsible. That the company, in response to the latest incidents, intends to refit the tanks with sensors and extra safety controls just underlines the makeshift way in which the storage facilities were set up in the first place. Meanwhile, the fate of the constantly amassing polluted water is undecided. Proposals earlier this year to dump it into the sea understandably met with fierce opposition from local fisheries.

An international alliance on research and clean-up would help to restore shattered public trust.

Given the government’s past actions and information policies, one might doubt whether it would be any more competent than TEPCO at managing the situation and communicating it to the public. Over the weekend, it turned out that radiation doses near the leaking tanks are 18 times larger than first reported: leakage that started as a mere ‘anomaly’ has turned into a genuine crisis. Japan should start consulting international experts for help. The United States, Russia, France and the United Kingdom — to name but a few — all have know-how in nuclear engineering, clean-up and radiation health that would serve Japan well. An international alliance on research and clean-up would help to restore shattered public trust in the usefulness and effectiveness of monitoring and crisis-mitigation.

Nature special: Fukushima

The most important impacts of the leaks will be those on the sea off Fukushima and the larger Pacific Ocean, which must be closely monitored. After assessments by US and Japanese scientists in 2011 and 2012, two major questions remain unanswered. How much radioactivity is still entering the sea? And, given the high levels of radioactivity that have been measured in some species long after the accident, when will fish and seafood from the region be safe to consume? The leaks make it more urgent to find answers to these questions.

To make reliable assessments of any environmental effects, scientists need to be able to collect data on contamination of marine food webs with all long-lived radionuclides, and particularly with caesium-137, strontium-90 and plutonium-239. They also need to know the sources of contamination, and to study the transport of radionuclides in groundwater, sediments and ocean currents. Current Japanese Prime Minister Shinzo Abe and his government have promised to boost science; they should encourage and support researchers from around the world in collecting and sharing information. Chernobyl was a missed opportunity for post-accident research — in that sense at least, Fukushima could do much better.