Finland’s plan for eternal storage of nuclear waste

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.

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.

Finland’s Crazy Plan to Make Nuclear Waste Disappear, Popular Mechanics, By Tim Heffernan 11 May 12, The U.S. plan to bury nuclear waste in Yucca Mountain may be dead, but in Finland, engineers are going ahead with a plan to build an enormous bunker to house the dangerous stuff. And they have a radical solution to keep future civilizations away—hide the nuclear waste somewhere so unremarkable and unpleasant that nobody would ever think to go there. 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…..

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.

May 11, 2012 - Posted by Christina Macpherson | Finland, Reference, wastes

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