Fukushima NPP has a bigger problem than water release

The decommissioning of the plant also involves the removal of radioactive fuel debris.
Sejal Sharma
Representational image
Representational image


Japan is releasing wastewater from the Fukushima nuclear plant into the ocean after receiving a green light from the International Atomic Energy Agency (IAEA). TEPCO, the plant’s operator, started releasing the first batch of 7,800 tons from 10 of the group B tanks, among the least radioactive water at the plant, on August 24.

Over 1 million metric tons of water need to be released over the next 30-40 years. This water is stored in the 1,000 tanks that TEPCO has built. But this is not the biggest problem TEPCO has to tackle.

Removal of melted fuel debris

A significant amount of melted fuel debris is currently inside the nuclear reactors. A TEPCO spokesman told the Associated Press that about 880 tons of radioactive melted nuclear fuel remain inside the reactors. The company has tried using robotic probes to gather information, but the status of the melted debris remains largely unknown, and the amount could be even larger.

“At the time of the accident, Units 1 to 3 were operating and had fuel rods loaded in the reactors. After the accident occurred, the loss of emergency power prevented further cooling of the cores, resulting in overheating and melting of the fuel. Fuel debris refers to this melted fuel and other substances after they cooled and re-solidified,” said TEPCO.

TEPCO revealed how it will retrieve the fuel debris on its website. It says that in Units 1, 2, and 3, the fuel and the metal cladding that forms the outer jacket of the fuel rods have melted, then re-solidified and created fuel debris.

“To reduce the risk from this fuel debris, preparations are underway for retrieving it from the reactors. The current aim is to begin retrieval from the first unit (Unit 2) and to gradually enlarge the scale of the retrieval. The retrieved fuel debris will be stored in the new storage facility that will be constructed within the site,” said TEPCO.

Decommissioning the plant may take 50-100 years

The fuel debris is highly radioactive, and it will take years to remove it from the plant safely. A robotic study done by TEPCO in March this year provided the first visual confirmation that the melted nuclear fuel broke through a pressure vessel at Unit 1. The meltdown at Unit 1 is believed to be worse than at Unit 2 and 3 reactors. The International Research Institute for Nuclear Decommissioning estimates the building of Unit 1 reactor contains 279 tons of melted fuel debris, according to a report.

The removal of debris is expected to be mainly carried out by robots, so a trial removal using a giant remote-controlled robotic arm is set to begin in Unit 2 later this year, said the TEPCO spokesman.

It’s estimated that while the release of treated water from the plants will take 30-40 years, full decommissioning of the nuclear plant will take around 50-100 years.

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