Four and a half years after the Fukushima disaster, and as Japan tentatively restarts nuclear power elsewhere, the legal challenges are mounting for the crippled plant’s operator.

They include a judge’s forced disclosure of a 2008 internal document prepared for managers at Tokyo Electric Power Co warning of a need for precautions against an unprecedented nuclear catastrophe.

Also, class actions against Tepco and the government now have more plaintiffs than any previous Japanese contamination suit and, overruling reluctant prosecutors, criminal charges have been leveled against former Tepco executives for failing to take measures to prevent the 2011 meltdowns and explosions.

Radiation from the worst nuclear disaster since Chernobyl in 1986 forced 160,000 people from their homes, many never to return, and destroyed businesses, fisheries and agriculture.

The criminal and civil legal cases do not threaten financial ruin for Tepco, which is now backstopped by Japanese taxpayers and faces far bigger costs to decommission the Fukushima plant and clean up the surrounding areas.

Rather, the cases could further increase opposition to nuclear restarts - which consistently beats support by about two-to-one - as Prime Minister Shinzo Abe’s government pushes to restore nuclear to Japan’s energy mix to reduce reliance on imported fossil fuel.

“The nuclear plant disaster has upended our way of life,” evacuee and former beekeeper Takahisa Ogawa, 45, testified recently in a court in Iwaki, near the Fukushima power station. “We’ve lost the support we counted on.”

PROVING NEGLIGENCE

Ogawa and other plaintiffs are seeking 20 million yen ($160,000) each in damages from Tepco. More than 10,000 evacuees and nearby residents have brought at least 20 lawsuits against the utility and the government over the handling of the disaster at the Fukushima Daiichi nuclear plant 220 km (130 miles) north of Tokyo.

The biggest class action, with 4,000 plaintiffs, seeks to dramatically increase Tepco’s liability by proving negligence under Japan’s civil law, rather than simply proving harm and seeking compensation, said lead attorney Izutaro Managi.

Japan recently approved increasing the amount of compensation payments through a government-run fund to 7 trillion yen ($56 billion).

Prosecutors twice declined to charge former Tepco bosses over their handling of the disaster, citing a lack of evidence, but a citizens’ panel overruled them last month. It’s unlikely the three former executives, who will be summoned to give evidence in court, will be convicted as it is hard to prove criminal acts in this type of case, said Nicholes Benes of The Board Director Training Institute of Japan.

A first trial is not expected to start until next year at the earliest.

The legal actions against Tepco are “serious for the industry” as it seeks to gradually bring some of Japan’s 43 idled nuclear reactors back online, said Tom O’Sullivan, an independent energy consultant and former investment banker.

“With potentially up to 25 reactors coming online, board members of other electric power companies must be quite nervous about what could happen if something goes wrong,” he said. “Most reactors have been switched off for four years so switching them back on is going to be potentially problematic, not to mention the risk of natural disasters.”

“UNAVOIDABLE”

It’s unclear what bearing the various lawsuits against Tepco might have on one another, but a common thread is that it should have anticipated the possibility of a devastating quake and tsunami and taken steps to reduce the impact.

The company maintains that the severity of the 9.0 magnitude quake and 13-meter wave could not have been predicted.

But the document introduced as evidence in the shareholders’ suit after a judge forced Tepco to produce it, appears to challenge that. The “Tsunami Measures Unavoidable” report, dated September 2008, was filed with the Tokyo District Court in June, but has not been widely reported.

The unnamed authors prepared the report for a meeting attended by the head of the power station and marked the document “to be collected after discussion.” It’s not clear whether senior executives in Tokyo saw the report at the time.

The report called for Tepco to prepare for a worse tsunami than it previously assumed, based on experts’ views.

“Considering that it is difficult to completely reject the opinions given thus far of academic experts on earthquakes and tsunami, as well as the expertise of the (government’s) Headquarters for Earthquake Research Promotion, it is unavoidable to have tsunami countermeasures that assume a higher tsunami than at present,” says the report.

“This is prime evidence that Tepco recognized the need for tsunami measures,” said Hiroyuki Kawai, lead attorney in the shareholders’ suit. “This will have an important impact on the lawsuit.”

Tepco, in a court filing, counters that the document “does not mean there was a risk that a tsunami would strike and did not assume any specific tsunami countermeasures.”

Asked to comment further on the internal report and the range of legal problems facing the company, Tepco spokesman Kohji Sakakibara told Reuters, “We cannot answer these questions because they pertain to lawsuits and because they suppose a hypothetical determination of negligence. However, the company is making appropriate assertions in the lawsuits and expects that in the end the courts will render fair judgments.”

The shareholder lawsuit, filed in March 2012, seeks to establish responsibility for the disaster and demands 5.5 trillion yen ($44 billion) in damages from current and former executives. A verdict is not expected for at least a year.

“This is likely to become a long battle where lawsuits go on for several decades or half a century,” said Shunichi Teranishi, a professor emeritus of environmental economics at Hitotsubashi University in Tokyo, comparing it to the Minamata mercury poisoning disaster in the 1950s, where lawsuits continue to be filed to this day.