Posiva Oy

Barring a disaster—or a miracle, depending on your viewpoint—the Finnish government later this year will begin the final licensing of the world's first permanent storage facility for high-level nuclear waste. Located on Olkiluoto Island, just off Finland's southwest coast, the underground facility known as Onkalo will hold all of the country's existing waste and all that it expects to produce over the next century. It is designed to keep that waste secure for at least 100,000 years—in part by making humans forget it was ever there.

Onkalo is intended to house high-level waste (HLW), the most worrisome byproduct of nuclear power. It consists of spent nuclear fuel and some of the fuel's decay products, and it can emit dangerous types and levels of radiation for tens of thousands of years. Roughly 300,000 tons of it now exists; about 12,000 more tons are produced annually, and both numbers will increase significantly in the coming decades. To date, most HLW has been stored in water-filled pools at the nuclear plants where it was produced, or in temporary offsite facilities where the waste is bound in borosilicate glass and cast into ingots, which are then sealed inside shielding metal canisters. But these are impermanent and unsatisfactory solutions. Pools require constant maintenance and refilling, and both they and temporary facilities are physically insecure.

And there is the problem of time. HLW will remain dangerous for longer than civilization itself has existed. Future civilizations may not even have the ability to address the dangers—even if we could somehow warn them what they're dealing with.

The only viable solution seems to be facilities like Onkalo—deep underground bunkers carved from impermeable rock, in geologically stable zones, where the waste can be redundantly sealed and then permanently buried. The U.S. attempt to build such a bunker at Nevada's Yucca Mountain fizzled in a fit of political bickering. But in Finland, Onkalo marches on, with a plan to keep humans out of there long after the entrance is sealed.



Mega-Engineering

Onkalo's main access tunnels are almost complete, as are the vertical ventilation and personnel shafts. Digging has reached its ultimate depth of just under 1500 feet, and the hydrologic, geologic, and mechanical tests are underway. The final step is to dig the hundreds of horizontal burial shafts, arrayed like fish bones along the deepest access tunnels.

Workers are building above ground too. They're making transportation canisters for the waste that are designed to survive extreme impacts, temperatures, and pressures; also, thick-walled copper tubes inside which the waste will be sealed before burial. To ensure a perfect, uncontaminated seal, the canisters—weighing 26 tons when filled—will be welded shut by electron beams rather than the more common sacrificial-electrode method. These will be some of the most technically demanding electron-beam welds ever attempted.

Posiva, a joint venture of Finland's two nuclear power companies, is running all of these projects and footing the $3 billion price tag. Construction of Onkalo itself began in 2002, and the facility is expected to begin accepting nuclear waste in 2020. (Construction will continue on a reduced scale, however, as new storage tunnels will be dug as needed throughout the operating life of the facility.) Waste will be sealed in the copper coffins, placed into the storage shafts, and surrounded by a thick layer of bentonite, a natural clay almost impermeable to water. As each storage tunnel is filled, it will be sealed with a bentonite plug, and the plug will be backed by ultradurable concrete. Finally, when the whole site is at capacity—around the year 2120, after 5500 tons of high-level waste has been sequestered—the transport tunnels and vertical shafts will be backfilled with concrete and native rock, locking the scary stuff under a quarter-mile of granite.

Posiva Oy

Yet the most impressive thing about Onkalo may not be scale or engineering, but the fact that it is being built, period. Underground storage is a practical necessity and political poison. The U.S. spent decades working on its own facility at Yucca Mountain, Nev., only to see the project get killed—the victim of either prudence, the power of "not in my backyard," or exaggerated fears stoked by opponents of nuclear power, depending on your point of view.

Whatever your political views, the inescapable fact is that nuclear waste continues to pile up at American nuclear plants that are less secure and closer to major population centers than Yucca Mountain is. Meanwhile, the construction of new nuclear facilities continues apace, even in the U.S. Earlier this year, federal regulators granted licenses to construct two new plants in Georgia, the first such licenses in the U.S. since 1978. So our waste problem, and the world's, will only get worse.

Built to Be Forgotten

Onkalo is one of the most cautiously designed engineering projects the world has ever known. But in one respect it may prove to be radical. Unsurprisingly, Posiva put a lot of thought into selecting a location that would be ideal for keeping the waste in and preventing leaks. However, as Sandra Upson reported in a comprehensive 2009 IEEE Spectrum report, the spot was also chosen for its ability to keep future generations of humanity out.

The bedrock of Olkiluoto Island is boring, with no valuable metal ores or other enticements to encourage digging. The groundwater is unpleasantly salty, so it's not a good place to put in a well. The soil is bad for farming. Olkiluoto is at best unremarkable, and at worst unpleasant.

And that's why Finland thinks it's the perfect place to store nuclear waste. There may be no need to create elaborate ways to prevent unsuspecting people of the future from breaking into the waste repository, because nobody would ever want to visit this island in the first place.

In 2120 or so, Onkalo will be sealed, and if some engineers have their way, that will be it. No signs saying keep out, no skull-and-crossbones icons, no locks on the door. No door at all. Why draw unnecessary attention? Left alone, it won't be long—a few human generations at most—before nature buries the aboveground evidence, and after that there will be no reason for anyone to remember it was there at all.

The idea's simplicity is what makes it radical. Compare it to what is proposed for the Waste Isolation Pilot Plant, a test storage facility in New Mexico run by the Department of Energy since 1974, as described in a 2006 Los Angeles Times article by Charles Piller. To keep away future humans who may or may not speak English, the plan calls for a 2-mile-long berm, 98 feet wide and 33 feet tall, ringing the facility. Huge magnets and radar deflectors would be buried in the berm, intended to make its man-made nature and seriousness of purpose obvious to any future investigator. Forty-eight stone pillars, carved with warnings in seven languages, would be erected Stonehenge-style around the site. Three separate underground chambers (one of them inside Carlsbad Caverns, not far down the road) would house detailed plans of the tunnels. And thousands of noncorroding Frisbee-size discs, incised with images of human horror, will be buried all around for any inquisitive diggers to find.



The plan, of course, assumes that humanity's capacity for logic and instinct for self-preservation outweigh its natural curiosity—on evidence, a dubious assumption. Seriously, who wouldn't want to dig in a place so baroquely decorated, deathly warnings be damned? And besides, people constantly misinterpret one another's intentions—which has proved a real obstacle for designers seeking universal meaning. Take the 2003 project that challenged artists to come up with warning markers for Yucca Mountain. One suggestion was to engineer yucca plants to grow bright blue and cultivate them above the site, the idea being that they'd somehow demonstrate the mutative power of the waste buried below. Surely, though, it would be just as natural to assume the soil held some wonderful magical substance—and all you'd have to do is dig for it...

Relative to these proposed leaps of faith, Onkalo's designers seem brilliant for trusting in something else universal to the species—our tendency to forget. In any case, the final decision on how to keep Onkalo permanently closed won't need to be taken for a century. That's a long time for those of us living today, but just the first small step on the long journey we are asking this stony vessel to undertake.

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