As the first ever venture of its kind, the storage of spent nuclear fuel will begin in the early 2020s on Olkiluoto, an island that also houses a nuclear power plant. The historic repository is a tour de force of Teollisuuden Voima Oy (TVO), Posiva Oy, Saanio & Riekkola Oy (SROY, currently a part of AINS Group) and many other Finnish and foreign expert organisations, which have engaged in geological studies, design work and preparation of safety cases over the past four decades to assess long-term safety.
The repository project has its roots in the early 1980s, when TVO began to seek a solution for the storage of spent fuel from nuclear power plants. Saanio & Riekkola Oy participated in the project by identifying areas that were suitable in terms of their location and ground type. In 2004, the construction of the underground research facility ONKALO kicked off with the excavation of access tunnels. The tunnel has now reached its final depth.
The next stage for this unique large-scale project involves preparing for the construction of the repository premises and the submission of the operation permission application to the Finnish government. ‘SROY is in the process of conducting tests and experiments on the performance of the clay materials to be used in the repository space and the impact of excavation on the rock bed. In addition, we are involved in the preparation of the safety case. The goal is to start using the repository for storage in the early 2020s once the commissioning permission has been granted,’ explains Pirjo Hellä, leader of the long-term safety team at Saanio & Riekkola.
Collaboration is the key to success in the repository project
We have had to assess what will happen to the repository and radiation safety over then next hundreds of thousands of years, including during new ice ages.
SROY’s collaboration with TVO, Posiva Oy and several other Finnish and foreign expert organisations has produced a wealth of new information on how to ensure the functionality and safety of the 400-metre deep repository. For the actual commissioning, numerous instructions must be prepared to enable a rapid and appropriate response to various situations and events, such as water leaks.
‘We are currently compiling a safety case portfolio for the repository’s commissioning permission. In this portfolio, we describe the repository’s engineered barriers and factors influencing the long-term safety of the repository and their development, assess the ability of the repository, particularly its capsules, to contain the waste in the long term, and present the technologies used to protect the environment,’ explains Posiva’s Project Manager Barbara Pastina.
The preparation of the safety case, analysis of the repository location, design of the engineered barriers and assessment of the operations require multidisciplinary expertise and collaboration among various organisations. One example of the results produced by such close collaboration between SROY, Posiva and other expert organisations is the determination of requirements for the rock bed surrounding the repository. On the basis of these requirements, the repository could be placed in a location that is ideal in terms of the rock bed’s properties. The defined requirements and their management system ensure that the materials used in the repository function effectively together. Any deviations from the requirements and their impact are assessed as part of the safety case.
This is what repository operations at the Olkiluoto facility entail:
Before being placing in the repository, the spent nuclear fuel is cooled for several decades to decrease its radioactivity.
SROY’s solid expertise in underground construction and its meticulous rock bed studies, modelling of the geological development in the region, and skilled safety reporting activities played a major role in the Posiva project’s progress towards the construction permit being granted by the government.
After the period of intermediate storage, the spent fuel is encapsulated. The capsules are placed in the repository built in the rock bed 400 metres underground. The capsule, clay materials used to fill in and close the space, and the surrounding rock bed contain the spent fuel and isolate it from the environment. Even though the radioactivity of the material decreases with time, the spent fuel must be contained to ensure radiation safety.
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Building projects only succeed with good collaboration.
Read about our latest projects:
Hämppi parking facility, Tampere, Finland
The award-winning P-Hämppi is an engineering tour de force that meets all the user requirements for an underground parking facility with regard to usability and convenience. Upon completion, P-Hämppi became Europe’s most modern parking facility.
We acted as the principal consultant for the project. In addition, we were responsible for the project’s construction management; expert and local supervision; and geotechnical, rock, HVAC, traffic, and structural engineering, as well as the principal-designer activities in the initial stages.
The parking facility is designed for 900 vehicles.
Gross floor area: 200,000 m²
Cost: 70 million euros
Awards: The 2013 EPA European Parking Award, the Lighting Project of the Year 2013 Award, and the 2012 Pirkanmaan Y-teko Award in civil engineering
KOy Jousenpuisto parking facility, City of Espoo
The Jousenpuisto parking facility serves as the roof over the Urheilupuisto metro station’s platforms. The project was challenging because of the foundation conditions, connecting structures, and waterproofing requirements.
In addition, 2–8-storey residential buildings and a yard area will be built above the car park.
Cost: 30 million euros
Gross floor area: 30,000 m²
Tampere University Hospital renovation project 2020: AP parking facility, Tampere
Work on the parking facility is part of the hospital’s yard-area project. This, in combination with the D, N, and L buildings, will form a complex of new buildings. The two-storey parking hall is directly connected to the new buildings and is also used by taxis and, occasionally, ambulances.
The parking facility’s roof is made from post-tensioned structures and is designed to allow the construction of a tram line and stops over it.
The facility has 400 parking spaces.
Gross floor area: 18,000 m²
West Metro, Espoo and Helsinki
The construction of the West Metro, connecting Helsinki’s Ruoholahti to Matinkylä, in Espoo, involved designing eight separate and challenging station entities and 33 kilometres of train tunnel, including 15 complexes comprising escape routes, pressure-balancing ducts, and technical premises. Other noteworthy tunnel structures include 55 connecting tunnels, large-scale pump systems, a water reservoir for fires, track switch points, and maintenance tunnels and tracks.
The project was granted an honourable mention in the Tekla BIM Awards in 2016.
Cost: 1.186 billion euros
Gross floor area: 350,000 m²