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Home  /  PRODUCTION  /  Plant units  /  Safe operation  /  Development of plant units


TVO’s operations are subject to licenses, permits, and supervision by the authorities. The Radiation and Nuclear Safety Authority (STUK) supervises nuclear and radiation safety.

TVO is not alone in thinking about safety issues. Other nuclear power companies, organizations, research institutes, and public authorities are looking for ways to develop the safety of nuclear power and safety culture at nuclear power plants. For example, WANO supports the gathering of operating experience feedback and its utilization by its members.

TVO develops the Olkiluoto nuclear power plant in accordance with the principle of continuous improvement. Modernization and modifications have been implemented throughout the plant’s lifetime, and many improvements have been made to its safety features. Particular attention has been paid to ensuring the adequate cooling of spent fuel under all circumstances. A severe accident management system that can prevent any major releases in the very unlikely case of a severe accident has also been installed to both plant units.

Plant modifications to further improve safety

The nuclear power plant is currently undergoing modifications, with more in the planning stages. The purpose of these modifications is to prepare for the extension of the operating license of the plant units in 2018. The modifications will further improve the plant’s ability to survive various events caused by exceptional natural phenomena, which, in the worst case, could involve the simultaneous loss of the operability of several plant units or safety systems. Also underway is a project to improve the company’s safety culture and related procedures.

TVO will replace the emergency diesel generators as part of an ongoing major modernization project. The emergency diesel generators ensure the power supply of the plant in the possible but unlikely loss-of-power situation. The new emergency diesel generators have both seawater and air cooling.

Preparations for the replacement project of the emergency diesels were started already in early 2000s. The project is the largest individual plant modification project ever in Olkiluoto. TVO procures the emergency diesel generators from Wärtsilä Finland Oy. The agreement on the delivery of the emergency diesel generators and their auxiliary systems to the Olkiluoto nuclear power plant was signed in May 2013. The implementation of the replacement project started in 2016 and is estimated to continue until 2020.

The replacement of the recirculation pumps is one of the most significant modernisation efforts in the history of TVO. The replacement of the recirculation pumps will further improve plant response during operating transients and help ensure that the safe and reliable operation of the plant units can continue in the future. In 2015, TVO signed a contract with Westinghouse Electric Sweden (WSE) on the replacement of the recirculation pumps at Olkiluoto 1 and 2. The project covers a total of 12 recirculation pumps and is valued at more than EUR 40 million.