A question has haunted Toshiko Nishimura since she saw her husband’s swollen body in a hospital 21 years ago.

“What did he die for?”

Her husband, Shigeo, was a deputy chief of the general affairs department at Power Reactor and Nuclear Fuel Development Corp. (PNC).

His duties changed significantly after a fire and sodium leak occurred at PNC’s Monju prototype fast-breeder reactor in Tsuruga, Fukui Prefecture, on Dec. 8, 1995.

Shigeo was put in charge of the internal investigation of the suspected cover-up over the accident.

PNC, now the Japan Atomic Energy Agency (JAEA), entered the plant twice on the day after the incident and took video recordings of the damage.

However, the company only released the second video to the public, and that footage was heavily edited to cover up the extent of the accident.

On the morning of Jan. 12, 1996, Toshiko made a cup of coffee for her husband as usual, but he left for work without drinking it.

That evening, Shigeo appeared at a news conference to explain the sodium leak. Through his investigation, he and others knew the truth about the videos, but he gave false statements to the media about when the video footage came to the knowledge of PNC managers.

After the news conference, Shigeo is believed to have jumped to his death from the eighth floor of a hotel where he was staying. He was 49.

Toshiko, now 70, could not believe her husband would kill himself. Just days before his death, during the New Year break, their son announced his wedding plans.

Shigeo left a letter to his wife, but it did not mention the reason for the suicide.

PNC could not provide a satisfactory explanation to Toshiko, so she asked police officers, hospital workers, hotel staff and people at other places.

In 2004, she took legal action against the Japan Nuclear Cycle Development Institute, the successor of PNC, thinking that the testimonies of workers would give a clear account of what Shigeo was going through before his death.

But no details were revealed, and she lost the case.

She also joined an “anti-Monju movement” because she “could not forgive Monju for continuing to run at the sacrifice of human life.”

The Monju reactor, plagued by numerous problems, has proved a costly failure in the government’s plans for a nuclear fuel recycling program.

In 2015, the Nuclear Regulation Authority, Japan’s nuclear safety watchdog, condemned the JAEA as “unqualified to run Monju safely.”

In September this year, the government decided to conduct a fundamental review of the prototype fast-breeder reactor. And on Dec. 21, the government officially announced the reactor would be decommissioned, and a new project would begin to build a fast reactor for its nuclear fuel recycling program.

“The decommissioning will be a milestone,” Toshiko said. “One less burden is on my shoulder now.”

Toshiko, meanwhile, is still involved in a lawsuit at the Tokyo District Court, demanding the return of her husband’s personal belongings that he left at the hotel.

She says she wants to tell Shigeo, “Monju was not worth dying for.”