The conundrum of what to do with nuclear waste is not easily solved.

Seven decades into the age of nuclear power, the major world powers who ushered in the nuclear era like the United States have yet to solve the problem with any conviction.

However, the small nation of Finland is on the verge of completing a giant underground facility designed to store the country’s growing stockpile of radioactive waste.

The result is a sprawling cement sarcophagus, which burrows about 1,400 feet underground and is built to last between 100,000 and a million years.

In the past few decades, countries like the US, the UK, Germany, Japan and Sweden have all tried to build underground storage facilities.

Meanwhile, in Australia, former Prime Minister Bob Hawke has campaigned for the Outback to be used as a nuclear waste storage center for the world.

But such plans have all hit political roadblocks and Finland is the only country that has a permanent nuclear-waste repository under construction, The Atlantic reports.

Globally, there are about 300,000 tons of spent nuclear fuel stored in temporary facilities — much of them at reactor sites — that are beginning to show their age, and accidents are surprisingly common.

If all goes according to plan in the next five to 10 years, Finland will begin filling up its underground labyrinth with the unwanted waste, marking the world’s first long-term storage solution for the radioactive by-product.

Dubbed the Onkalo Nuclear Waste Repository, the facility is being built on an island off Finland’s western coast with the front entrance nestled in an untouched forest.

Construction began in 2004 and when it is completed, it will consist of 30 to 40 miles of tunnels within an area of about one square mile.

The repository is designed so that once the waste is deposited, authorities won’t have to do much else, according to nuclear policy researcher Matti Kogo.

“The idea is to more or less forget it. It’s based on passive safety,” he told PRI in July. “There aren’t any plans to put any kind of warning signs or anything like that. There won’t be anything.”

The simplicity of Onkalo’s design is its strong suit. The near-seamless local bedrock that it is carved into — a type of rock called gneiss — is geologically stable and keeps water out, while bentonite clay will absorb any water that does manage to seep in.

Researchers have used extensive modeling “to assess the performance of final disposal and the effects it has on the rock environment in terms of long-term safety,” the project’s website says.

It’s the culmination of more than 40 years of research and development, and the facility is currently going through the final phases of construction and preparation. A practice run for the disposal procedure is set for 2022. If that goes well, researchers expect the first silos of waste to be dumped in about 2024.