Finnish reactors pass stress tests

01 November 2011

Stress tests at Finland's nuclear power plants show that no major modifications are needed, utilities Fortum and Teollisuuden Voima Oyj (TVO) have told the Finnish nuclear regulator.



Loviisa 1 and 2
Loviisa (Image: Fortum)

Shortly after the accident at the Fukushima Daiichi plant in Japan in March, the European Council decided to implement a Europe-wide re-assessment of safety at nuclear power plants. As a result, in June, the Finnish radiation and nuclear safety authority, Stuk, instructed the country's two nuclear utilities - Fortum and TVO - to conduct the specific safety evaluation. The Finnish Ministry of Employment and the Economy had earlier also requested that Stuk conduct safety assessments of their plants. The EU stress test and the assessment requested by the ministry essentially addressed the same safety issues.



Having already reported to the ministry on the results of its requested assessment, Fortum and TVO have now submitted reports to Stuk detailing the findings of the EU stress tests. These addressed the safety of Fortum's Loviisa plant and TVO's Olkiluoto plant in conjunction with an earthquake, flood, exceptional weather phenomenon and a loss of cooling functions of the reactor or used fuel ponds, which may involve the simultaneous loss of several safety systems. It also looks at the operations of the utilities in the event of a severe accident and how the plants are technically equipped against such accidents.


Fortum said that the stress test showed that the Loviisa plant's "design basis and safety in incidents reviewed were found to be at a good level and the safety margins sufficient." It added that Loviisa "has prepared for incidents that exceed the design basis with systems and procedures that create the prerequisites to manage severe accidents without significant release of radioactivity into the environment."


According to Fortum, "The assessment made in spring 2011 by Stuk noted that Finnish nuclear power plants meet the set safety requirements and that there was no need for immediate corrective measures. The stress test conducted now indicates that the assessment remains unchanged."


However, Fortum noted that the assessment had "identified some possibilities to improve safety even further: for example, securing sea water cooling with air cooling; and securing the fuel pond cooling in case of exceptionally long lasting accident situations."


The company said that these additional measures require further analysis, which will be submitted to Stuk on 15 December "in accordance with the further national evaluation."


According to Fortum, these "possible safety improvements and plant modifications could be implemented within the normal power plant investment program, and that they will not affect the operability of the power plant."


TVO tests


Meanwhile, TVO said the stress tests at its Olkiluoto plant had "not identified any hazards characteristic of the Olkiluoto plant site that would result in immediate modification needs at the plant units." However, it said that the assessment process "has been useful for TVO" and that "preparedness for the loss of power supply and sea water cooling will be further improved in the future."


TVO said, "A great increase in sea level, like the tsunami experienced in Fukushima, has been judged an improbable problem" at Olkiluoto. In addition, a rise in sea level due to climate change "will not pose a risk to the plant site during the foreseeable operating life of the plant." It added that seismic events "do not constitute a significant hazard in Finland either."


While "no safety deficiencies have been identified" at the interim storage of used fuel, TVO said that it would carry out a comprehensive probabilistic safety analysis on used fuel storage by the end of 2013. This, it said, was being done "proactively in preparation for future regulatory requirements."


TVO said that several plant upgrades are either being considered or are at the design or implementation stage for units 1 and 2 at Olkiluoto. These include improving the security of water supply to the two reactor buildings, as well as improving water supply through the fire water system to both the fuel pools and the reactor pressure vessels. At Olkiluoto unit 3, currently under construction, "no modification needs were identified in the applied design bases."


Researched and written

by World Nuclear News