A world first
Special. New. Educational. Requiring know-how and precision. Surprising. Interesting. There are many ways to describe the big ten-year project. At Posiva, these attributes refer to the construction of ONKALO which commenced in summer 2004, opening a path to a totally new research world.
Posiva's construction controller Kimmo Lehtola and research manager Kimmo Kemppainen have overseen the ONKALO underground research facility project right from the initial blast.
"This has been a special project alright. We have seen the full palette of rock construction techniques being put into use. This has given us the perfect opportunity to learn new methods in rock construction", says Mr Lehtola.
"At the start of construction, I was enough of a novice myself that I did not have the imagination to envision the finished/completed ONKALO. After excavating the first 300 metres, we understood that we needed to take another look at the plans. The first change was implemented quite soon", says Kemppainen.
However, the mission of ONKALO remained unchanged during the construction project. It has provided Posiva with essential information about rock construction and the prevailing conditions in the Olkiluoto bedrock.
Technology catering for construction needs
Over the past ten years, ONKALO has taught many lessons to those involved in the project, and to the Posiva organisation as a whole. If boring-drilling experts are required during an excavation, ONKALO builders are first in line in terms of talent.
"Over the years, I have learned new things about construction development, as well as construction as a whole and contractual matters", says Lehtola.
The ONKALO project has also led to the development of new technologies. When an ONKALO-customised rock reinforcement bolt was needed for construction, we developed it in tandem with a trusted partner.
One should be ready for surprises, as this is the first time a research facility has ever been built to cater for the needs of a final disposal project related to spent nuclear fuel. Even though the plans had been carefully drawn up and were kept updated, the precision nature of the work (requiring simultaneous construction and research processes) and the maximising of industrial safety made for a particularly challenging scheduling process.
"It is easy for outsiders to say that should be able to plan more reliably. We must keep in mind that we are the first operator in the world to do almost all these things and we really want to thoroughly explore all of our findings. For example, almost every rock hole takes a surprising amount of time to survey ", says Kemppainen.
New efforts with the same levels of enthusiasm
Even though the ONKALO vehicle access tunnel has been excavated at its planned depth (455 m), Lehtola and Kemppainen will have more tasks related to the underground research facility.
Research is still being performed at ONKALO and preparations are being made for large-scale testing.
"The researcher is the last one to switch off the lights", says Kemppainen.
Lehtola's tasks this year include ONKALO shaft reinforcement, amongst other things. New shafts will be built later.
"Were I again given the challenge of building ONKALO to the same scope, I would do it again just as enthusiastically", says Lehtola.