The ABC has obtained documents confirming the operator of Japan's crippled Fukushima nuclear plant grossly underestimated how devastating a tsunami could be to the facility.

After lodging a Freedom of Information request, the ABC has obtained Tokyo Electric Power company's (TEPCO) tsunami and earthquake plan for its Fukushima plant.

Submitted in 2001, it is contained on just a single page, which was accepted by Japan's nuclear regulators.

The document, which was never updated, predicted the highest wave to hit the plant after an earthquake would be 5.7 metres high.

The tsunami that hit the Fukushima complex on March 11 was 15 metres high.

The document also predicted that the strongest earthquake that could rattle the facility would come from a magnitude 8.6 tremor.

The one that hit on March 11 was magnitude 9.

On Tuesday at TEPCO's annual shareholders' meeting, officials admitted to the more than 9,000 shareholders that it underestimated the size of a possible tsunami.

The nuclear crisis has wiped more than $30 billion from the company's value and seen it post the biggest loss in Japanese history outside the financial sector, sparking anger from ordinary Japanese, including its own shareholders.

Inside the meeting a group of 400 anti-nuclear shareholders banded together to demand TEPCO abandon nuclear power.

Outside protesters shouted anti-nuclear slogans and accused the company of cover-ups and incompetence, and of mishandling the nuclear meltdowns at its Fukushima plant.

"We'll fight at this meeting for TEPCO to shut down all nuclear power plants," shareholder Yui Kimura said outside the meeting.

"We also don't want the company building any new reactors."

A group of Fukushima residents led by Ikuko Hebiishi also protested at the meeting.

"I want to tell TEPCO shareholders about the tough time Fukushima people are having right now," Ms Hebiishi said.

"It's very stressful living under the cloak of radioactive contamination. I also want shareholders to support the scrapping of nuclear power plants in Japan."

Another shareholder, Yui Kimura, says the tsunami plan document shows TEPCO is incompetent and unable to operate nuclear power plants.

"They've caused trouble not just for Japan but also for the world. We must abandon nuclear power," she said.