A Japanese court is due to rule next month on a claim that Tokyo Electric Power is responsible for a woman's suicide, in a landmark case that could force the utility to publicly admit culpability for deaths related to the Fukushima nuclear disaster.

In July 2011, nearly four months after the massive earthquake and tsunami that triggered a series of catastrophic failures at the Fukushima Daiichi nuclear plant, Hamako Watanabe returned to her still-radioactive hilltop home, doused herself in kerosene and set herself on fire.

She left no suicide note, but her husband Mikio says plant operator Tokyo Electric is directly responsible.

"If that accident hadn't happened, we would have lived a normal, peaceful life" on their family farm some 30 miles from the plant, said Watanabe, now 64, who discovered her charred body.

A district court in Fukushima is expected to rule in late August on Watanabe's lawsuit, which Tokyo Electric (Tepco) is contesting. The outcome could set a precedent for claims against the struggling utility, said Watanabe's lawyer Tsuguo Hirota.

The triple meltdowns at the plant forced more than 150,000 people from their homes. About a third, including Watanabe, remain in temporary housing.

The utility has settled a number of suicide-related claims through a government dispute resolution system, but declined to say how many or give details on how much it has paid.

Japan has made public 25 disaster-related death cases that were settled through the resolution system, some for nearly $160,000. Causes of death were not always specified. They include those from natural causes, such as elderly patients who died in evacuation centers. A Mainichi report this week said arbitrators were encouraged to automatically halve requested damage to expedite the process.

Tepco said it could not comment on pending cases, including Watanabe's.

Watanabe has so far declined to settle outside of court and has broken off contact with relatives who urged him to drop his suit. His oldest son left his job after co-workers harassed him, accusing him of using his mother's death for personal gain. Watanabe is seeking nearly $900,000 in damages.

"No matter what verdict I get in August, I just want my wife to rest in peace," said Watanabe.