ROKKASHO, Japan — More than 30 years ago, when its economy seemed invincible and the Sony Walkman was ubiquitous, Japan decided to build a recycling plant to turn nuclear waste into nuclear fuel. It was supposed to open in 1997, a feat of advanced engineering that would burnish its reputation for high-tech excellence and make the nation even less dependent on others for energy.

Then came a series of blown deadlines as the project hit technical snags and struggled with a Sisyphean list of government-mandated safety upgrades. Seventeen prime ministers came and went, the Japanese economy slipped into a funk and the initial $6.8 billion budget ballooned into $27 billion of spending.

Now, Japan Nuclear Fuel Ltd., the private consortium building the recycling plant, says it really is almost done. But there is a problem: Japan does not use much nuclear power any more. The country turned away from nuclear energy after the 2011 Fukushima disaster, and only nine of its 35 reactors are operational.

It is a predicament with global ramifications. While waiting for the plant to be built, Japan has amassed a stockpile of 47 metric tons of plutonium, raising concerns about nuclear proliferation and Tokyo’s commitment to refrain from building nuclear arms even as it joins the United States in pressing North Korea to give up its arsenal.