Posiva’s solution for geological disposal of nuclear waste offers the best and most realistic possibilities to isolate high-level nuclear waste from the biosphere, i.e. the human habitat. The capsule shaft of Posiva’s final storage facility reaches a depth of more than 400 meters from ground level. The purpose of the capsule shaft is to lower the encapsulated nuclear waste rods to the bottom of the final storage site at the receiving station, where they will be temporarily stored before the final disposal.
”Our part of the project took about a year. We rein forced the shaft with a metal lining that protects the nuclear waste capsule when sub merged. This will prevent the capsule from hitting the rock wall or coming into contact with water. In practice, we installed a metal pipe of about 450 meters in the shaft, which was lined with acid-proof steel sheet,” says Olli-Pekka Parviainen, su pervisor of JIITEE Työt.
Due to minor water leaks, the shaft was also injected, that is, sealed. After the reinforcement of the capsule shaft, JIITEE Työt also carried out a project related to the electrification of the shaft, by pulling the electrical cables in the shaft so that electricians were only needed to connect the electricity.
Sitowise Group Oyj
the contract was implemented in 2019
reinforcement works, metal pipe installation and electric cable pulling.
”The project was extremely interesting because Posiva’s capsule shaft is the only one of its kind. The project was also challenging and we developed completely new ways of working for it. The reinforcementwork of the shaft was planned to be carried out from a hanging elevator, but the plan was changed. In the shaft there were shaft junctions about every hundred meters. We made a tower elevator that was dissembled and built up with the same distance. In this way, we were able to make the work more efficient than originally planned,” Parviainen describes.
According to Parviainen, JIITEE Työt always strives to develop working methods in order to streamline the work. The reinforcement work with Posiva’s capsuleshaft was carried out flexibly and even at night, so that the work did not get in the way of the other contractors working on the project.
The construction of the Posiva final storage facility is still ongoing, although JIITEE Työt’s shaft reinforcement project has already been completed. According to Jarno Säippä, who works as an internal consultant to Posiva through the Sitowise in the Shaft project, Finland is currently a pioneer in finding solutions to store geological waste deep below the earth’s surface. The capsule shaft, reinforced by JIITEE Työt, was a unique project.
” I don’t think there has ever been such consolidation work in the world before. The capsule shaft is 5.5 meters in diameter and there was only access to it every hundred meters during the project, which posed its own challenges for the work. Totalt approximately 2,000 pieces, 80 kilos of pre-bent steel plates,” says Säippä.
”The whole thing was challenging. By then, we had already done a similar work in the staff shaft, so we already knew a little about how to start strengthening the capsule shaft,” Säippä describes.
According to Säipä it went well to work with JIITEE Työt. At the beginning of the project, the employees of JIITEE Työt were introduced to the safety culture and operating methods of the construction site, after which the work could be started according to plan.
According to Säippä, the work was fluent throughoutthe project:
”We have close supervision on the construction site, because that’s what the excavation conditions require. The collaboration with JIITEE Työt worked really well, everything went smoothly, and the team was good. They took care of occupational safety and did what they promised during the time we had agreed.”
JIITEE Työt has also carried out other project work for Posiva after the reinforcement of the capsuleshaft, and according to Säippä a new project at the construction site is about to start again.
”Strengthening the capsule shaft was a really challenging project right from the design stage. JIITEE Työt had no previous experience with this reinforcement method, but the uniqueproject was still successful, Säippä sums up.
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