Current projections see the ore reserves of First Quantum Minerals’ Pyhäsalmi mine (IM, December 2014, pp10-17) running out in 2019. However, after 60 years of operation the mine, situated in Pyhäjärvi, Finland, might be given a new lease on life as a centre for particle physics and a load-following power plant. When the mine’s operations come to an end, the mining area will be closed in accordance with the approved closure plan, notes an article in the latest volume of Metso’s RESULTS minerals & aggregates magazine. According to the current plan, the costs will be roughly €30 million.
“What matters most is that when the underground mining operations end, an alternative livelihood is found for the city – we are, after all, the largest local employer. From an emotional point of view, too, it would be preferable to find some sensible future use for the mine rather than letting the mine shaft fill up with water and sealing it up for safety,” says Pyhäsalmi’s Managing Director, Kimmo
Various possibilities for the mine’s continued use are being actively planned now, while mining operations continue. The most ambitious plan is the European Laguna consortium’s particle physics project. The Pyhäsalmi mine would serve as a detector site for neutrino beams from CERN’s European particle physics laboratory in Switzerland.
“Pyhäsalmi is the number one option on account of its location and depth. Filtering out other cosmic radiation requires at least 1.3-kilometer-thick rock [cover] or 4 km of water. Our location 2,300 km from Switzerland is also ideal,” says Luukkonen.
For the CERN project, a facility that is 60–70 m wide, 100 m long and 40 m high would be constructed at a depth of nearly 1.5 km. A massive chamber containing liquid argon cooled to -185°C would be installed within a concrete and refined-steel structure to detect neutrino beams sent through bedrock from the CERN laboratory in Switzerland.
Last spring, rock sampling and drilling of several kilometres was carried out at the mine as part of a neutrino site investigation. If the project goes forward, a pilot detector will be built in Pyhäsalmi in the near future at a cost of €45–50 million.
As a parallel project, a pumped-storage hydroelectric power plant is being planned for Pyhäsalmi. It would serve as a carbon-free energy source, producing load-balancing energy for the national grid. Essentially, space would be excavated at the bottom of the mine, from where water would be pumped, mostly at night, up to the open-pit mine and led through turbines down into the mine to produce electricity when needed.
“Thanks to the height difference, the power plant would be able to produce a high amount of energy with a small amount of water. We are discussing the plan’s execution with four regional energy companies,” says Luukkonen.
The load-following power plant would be implemented in three phases, each of which would generate 200 MW of electricity. In phase I, 350,000 m3 of water would keep the power plant running at a capacity of 200 MW of electricity every day for six hours.
Recycled pyrite and even agricultural production are also possibilities. The mine’s tailing ponds have already been used to recover pyrite. Reprocessing from the 90-ha ponds could be continued if the operations could be made profitable. All in all, the processing could result in the recovery of some 2 Mt of pyrite.
“Underground cultivation of vegetables and mushrooms in the mine is another possibility. LED lighting and even temperatures guarantee a growth rate that is three to five times faster than in above-ground greenhouses,” Luukkonen points out.
