The operator of the crippled Fukushima Daiichi nuclear power plant plans to conduct robotic probes and take samples from damaged reactors this year.
The works will be a key stage in the effort to dismantle the plant.
Reactors No.1, 2 and 3 suffered amalgamations following a major earthquake and tsunami in 2011.
The nuclear fuel melted and collapsed in the reactor containments. It mixed with the surrounding metal parts and formed solid fuel debris.
The Tokyo Electric Power Company plans to begin a robotic study of Reactor No.1 in mid-January. The investigation is expected to last about six months.
The robots will use ultrasonic devices to locate and measure the thickness of the deposits.
Utilities officials say they also hope to collect samples.
Preparations to recover fuel debris from Reactor No.2 are underway with a robotic device developed in the UK.
It is currently undergoing performance tests in Japan.
The Tokyo Electric Power Company plans to collect a few grams of debris with the robot by the end of the year. He hopes to gradually increase the amount to be recovered.
The safe removal and storage of extremely radioactive debris is considered one of the greatest challenges in the decommissioning process.