Recovery work resulting from the 2011 accident at Japan’s Fukushima Daiichi Nuclear Plant, which is expected to take decades and cost at least $35 billion, is encountering problems, with a number of robotic probes failing after encountering more difficult conditions than expected, plant owner Tokyo Electric Power (TEPCO) said earlier this month.

The organisation’s head of decommissioning, Naohiro Masuda, said that the company needs to reassess its approach and “harness more creativity” in deciding how to proceed with the clean-up.

TEPCO has located an estimated 600 tonnes of melted fuel rods that will need to be removed. To do that, it needs to send robot probes into the wreckage, because radiation levels remain too high for human inspectors.

In fact, the radiation is proving too high for the Toshiba-built robot probes sent into the Unit 2 containment building, which have been failing much faster than expected.

One probe in early February stalled after reaching its exposure limit in just two hours, and two others have since failed. So far, none of the probes have been able to capture images of the damaged core, so more-creative approaches will be necessary, Mr Masuda said.

“We should ‘think out of the box’, so that we can examine the bottom of the core and see how the melted fuel debris has spread out.”