Molten fuel rods at the Fukushima nuclear plant may have eaten two-thirds of the way through a concrete containment base, the plant's operator says.

The statement from TEPCO is based on a new simulation of the March meltdowns.

It says its latest calculations suggest the nuclear fuel inside the number one reactor has melted entirely.

Simulations predict the molten fuel has eaten through 65 centimetres of concrete in a containment base below, stopping just 37 centimetres short of an outer steel casing.

It is also believed that the molten core has eaten part of the way through the concrete bases of the number two and three reactors.

The findings indicate the facility came much closer to a cataclysmic meltdown than previously thought.

The operator's assessment comes about six months after international nuclear experts warned that molten fuel could eat through containment vessels below the reactors.

Meanwhile, TEPCO has scrapped the construction of a new nuclear power station in Japan's north.

It is the first time a new plant has been abandoned since the Fukushima disaster.

The Higashidori nuclear power plant was to have been an advanced boiling water reactor with a capacity of nearly 1.5 million kilowatts.

But TEPCO decided to abandon the construction, which was to have been finished in five years' time.

The company is blaming the cost of compensating victims of the meltdowns at its Fukushima plant, which is expected to run into tens of billons of dollars.