The first-ever ‘tomb’ for nuclear waste, located nearly 1,500 feet below the surface, will soon be sealed off from humans for 100,000 years to break down safely.
Finland‘s $4 billion Onkalo project consists of a six-mile network of underground tunnels designed to store the country’s 6,500 tons of uranium waste generated by a nearby nuclear power plant.
The nation is a leader in nuclear power, with its reactors boasting an average lifetime capacity factor of over 90 percent.
Finland’s waste management organization, Posiva, launched the initiative in 2019, explaining that nuclear waste would be stored in water-tight canisters.
By 2026, Posiva plans to bury 3,250 copper canisters of waste, each measuring 17 feet long and containing about two tons of spent reactor fuel.
The canisters will be transported to 230-foot-long deposition tunnels and surrounded by bentonite clay for permanent storage.
Each one will then be lowered into a vertical borehole within the repository’s disposal tunnels, which feature about 30 to 40 boreholes each.
Once all the boreholes in a tunnel are filled with canisters and isolated with bentonite clay buffers, the tunnels will be backfilled with clay and sealed.
Finland ‘s $4 billion Onkalo project is located on on Olkiluoto Island
The underground facility features six miles of tunnels, which will soon be home to the country’s 6,500 tons of uranium released by a nearby nuclear power plant
The fuel, which contains plutonium and other byproducts of nuclear fission, will remain radioactive for tens of thousands of years.
However, encased in two-inch-thick copper, surrounded by bentonite clay, and embedded in ancient granite, the waste poses no risk of contamination to future generations, according to Posiva.
Originally a research facility, Onkalo became the first-of-its-kind nuclear waste repository after Posiva proposed using it to permanently house high-level radioactive material.
‘Many countries using nuclear power have final disposal facilities for low- and medium-level waste, but final disposal of high-level spent nuclear fuel has not yet been launched anywhere,’ Posiva stated on its website.
Currently, spent nuclear fuel is typically stored in large, secure tanks at dedicated facilities.
Another method involves encasing the waste in glass and burying it approximately 500 feet underground, a process known as Deep Geological Disposal.
While effective, this method carries risks due to the long timescales and the potential for unforeseen geological changes that could compromise containment over thousands of years.
Posiva claimed that its tunnel system and containers are engineered to withstand earthquakes, future glaciations for up to a million years, and stress caused by continental ice.
For over four decades, Posiva studied and tested the bedrock near the Olkiluoto nuclear power plant, ensuring that even if one or more containment barriers were to fail, radiation would not seep into the environment.
Onkalo consists of a spiral-shaped access tunnel, vertical shafts, central tunnels, final disposal areas, technical rooms, welfare facilities and even a café-canteen for personnel.
Posiva, a waste management organization, built a tunnel to house spent nuclear fuel to prevent radioactive material from harming the environment
The canisters will be lowered into a vertical borehole in a the repository’s disposal tunnels, which have about 30 to 40 holes
When all the holes contain a canister and the canisters have been isolated with bentonite clay buffers, the whole tunnel is backfilled with clay and sealed
The tunnels are too narrow to carry the canisters to the final depository, so they will be brought to a service area using a lift from an encapsulation plant on the surface which houses the spent fuel canisters until they’re ready to be placed in the tunnel.
The canisters will then be picked up by robotic vehicles and taken to deposition holes in an area where they’ll be stored for the next 4,000 generations.
At the time that the spent fuel will be disposed, Posiva said only one-thousandth of its original radiation levels will remain, but this small amount is still highly radioactive.
‘A small portion of the radioactive materials contained by the fuel have an extremely long life, which necessitates their isolation from nature,’ Posiva said.
‘For this reason, the final disposal canisters are designed to remain tight and impervious in their final deposition place long enough for the radioactivity of spent fuel to decrease to a level not harmful to the environment.’
The tunnel is located 1,480 feet below ground on the west coast of Finland and will be sealed off for 100,000 years starting in 2025
The canisters are made of copper and are filled with bentonite to prevent it from releasing into the surrounding bedrock
The copper and cast-iron canisters will be wrapped in bentonite clay and deposited in 1,410 feet of 1,800-year-old bedrock – otherwise known as a natural release barrier
The organization said that even after the initial tunnel is sealed off next year, it will continue to expand and excavate more deposition areas and central tunnels, allowing final disposal operations to continue until the 2120s.
As each tunnel is completed and filled with the spent fuel, it will be sealed off and when the final disposal is made, the access connections to the ground level including the vehicle tunnel, shafts and test holes will be shuttered.
The researchers explained that the radiation levels will decrease to one-hundredth of their original amount within the first year.
The researchers tested the final disposal starting in 2019, when two canisters were installed in deposition holes buried deep in the tunnel.
Each hole is separated by bedrock and is about 26 feet deep and 5.7 feet in diameter.
It was filled with bentonite – a soft, plastic clay formed from volcanic ash and sedimentary rocks – and sealed off with a concrete plug.
Posiva built a facility above the tunnels to hold the spent fuel canisters and then will deposit them into the tunnels using a lift
Researchers then activated 500 sensors that monitored whether the radioactive material seeped into the bedrock.
The bedrock at Olkuluoto’s final disposal area was thoroughly studied to look for any weakness zones, chemically unstable sections and water flow routes that would carry radioactive material to the surface.
Their findings showed that the material wouldn’t harm the environment when placed in the canister, prompting the company to begin construction on the tunnels the following year.
Posiva started its final test on August 30 to confirm the tunnel was ready for final disposal and said at the time that it would take several months to complete the entire process.
DailyMail.com has reached out to Posiva for comment and to confirm the official date the tunnel will be sealed.
This article was originally published by a www.dailymail.co.uk . Read the Original article here. .