Two decades after a sodium leak and fire shut it down and nearly six decades after it was first conceived, the Monju prototype fast-breeder reactor in Tsuruga, Fukui Prefecture, suffered another blow Wednesday when the Nuclear Regulation Authority called for it to be turned over to another operator.

To date, over ¥1 trillion has been poured into Monju — a plant that has never produced commercial electricity. Despite remaining inactive, safety measures alone cost ¥50 million a day.

Anti-nuclear activists have hailed the NRA’s unusually critical language as an important step toward scrapping the reactor, which was supposed to burn plutonium mixed with uranium.

Fukui politicians who heavily support Monju, including the prefecture’s governor and the mayor of Tsuruga, doubt that another operator can be found. They also worry that scrapping it would create local concerns as well as safety issues.

“What does it mean when the NRA says that it can’t leave Monju’s operations to the (government-backed) Japan Atomic Energy Agency? There aren’t any other organizations it can be left to,” Tsuruga Mayor Takanobu Fuchikami told reporters after the decision.

Fukui Gov. Issei Nishikawa also criticized the decision, saying such advice was “lacking in kindness.”

“Monju’s system should be rebuilt as a research facility, as part of Japan’s national strategy,” Nishikawa said.

Monju, conceived in the 1950s, has faced nothing but technical trouble, domestic and international controversies, and scandals.

Originally slated to go live in 1970, monju did not reach criticality until 1994. It was shut down following a December 1995 leak and fire involving liquid sodium. The incident was at that time Japan’s worst nuclear-related accident.

Further delays and scandals meant that by 2005, when Monju was taken over by JAEA after its predecessor organization was disbanded, officials hoped it would be commercially viable by around 2050.

But after it was revealed in 2012 that JAEA had failed to inspect nearly 10,000 reactor components in and after 2010, the NRA ordered Monju not to engage in preparatory work until it was satisfied safety had been improved.

Despite the technical difficulties and official denials, fears Japan might somehow use Monju to produce nuclear weapons were also heightened after statements from senior Japanese officials, including Prime Minister Shinzo Abe.

In 2002, Abe, while serving as deputy chief Cabinet secretary, said Japan could legally possess nuclear weapons so long as they were small and strategic. That same year, Ichiro Ozawa, then the leader of the Democratic Party of Japan, suggested plutonium at Japanese nuclear power plants made it possible for Japan to produce 3,000 to 4,000 warheads.

Activists are urging the government to give up on the project.

“Monju should be permanently shut down. If the Japanese government is capable of immediately and permanently scrapping Monju, we can gain some trust that it intends to have a logical, functional basic energy policy,” said Aileen Mioko Smith, executive director of Kyoto-based anti-nuclear group Green Action. “If it continues the status quo by flogging a horse that has been dead for 20 years, it bodes badly for Japan’s energy future.”