Safety and energy efficiency
The plant units have been developed in a systematic and methodical manner over the decades. TVO utilises the annual outages and specific modernisation projects for systematic modernisation of the OL1 and OL2 plant units. Solutions based on the most advanced technology are introduced throughout the lifespan of the plants in order to improve availability, productivity and safety. At present, plant modifications are being designed and implemented in preparation for the extension of the operating licence of the plant units in 2018. The ongoing modifications will further improve the ability of the plant units to survive events caused by exceptional natural phenomena which may involve the simultaneous loss of the functional capability of several plant units and safety systems.
As a result of the modernisation efforts, the electrical capacity of the plant units has increased based on improved energy efficiency. TVO has over the years participated in the voluntary Finnish Energy Efficiency Agreement for Industries. TVO has been a party to the Energy Efficiency Agreement Scheme of the Finnish Government and various sectors and industries since 2008. The associated Action Plan for Energy Production describes the implementation of actions designed to make the use of energy more efficient and to improve the efficiency of primary energy use as well as the total performance of energy production. TVO's goal for the ongoing agreement period of 2017–2025 is to achieve total savings of 150 GWh, and energy efficiency actions needed to achieve this are implemented in the annual outages in 2017 and 2018. The energy efficiency goal corresponds to the average annual consumption of some 7500 detached houses that use electrical heating.
Refuelling and maintenance outages annually
Olkiluoto nuclear power plant is kept in a good condition at all times by means of annual refuelling and maintenance outages carried out in turns at the plant units. The annual outages take place every spring, usually starting with the refuelling outage where uranium fuel is replaced in the reactor and the necessary repair and maintenance activities are carried out, including any preparations required for the maintenance outage of the following year. Refuelling outages usually last about one week.
The annual outage then continues at the other plant unit where various major maintenance activities and modifications are implemented, in addition to refuelling. The normal duration of a maintenance outage is 2-3 weeks. Extensive modernisation and renovation projects have been implemented during maintenance outages at intervals of ca. 5 years.
The annual outages were carried out at the Olkiluoto nuclear power plant between 22 April and 23 June 2018. The maintenance outage at OL1 took 40 days and 18 hours, while the refueling outage at OL2 lasted 13 days and 18 hours.
At Olkiluoto 1, the key works carried out during the maintenance outage included replacement of recirculation pumps and the associated frequency converters, renewal of the neutron flux calibration system, forward pumping of high pressure bleed and replacement of high pressure preheaters as well as replacement of tube bundles and ejectors in turbine condensers. The refuelling outage of OL2 included also maintenance work, repairs and tests scheduled for performance once a year, in addition to refuelling.
In addition to TVO's own personnel, 1,646 employees of external contractors were involved in the outage works.