Swedish nuclear power plants are robust and resilient to most kinds of extreme events, but improvement measures are necessary for a few events. Swedish nuclear power plants are not fully dimensioned to withstand an accident scenario where several reactors are put out of commission at the same time as an extended sequence of events takes place. This assessment has been made by the Swedish Radiation Safety Authority in its analysis of the stress testing carried out by nuclear facilities in Sweden.
The Swedish Radiation Safety Authority has now reviewed the final reports from the stress testing by these nuclear power plants and CLAB, the interim storage facility for spent nuclear fuel.
“The stress tests are a key contribution to safety improvement work at Swedish nuclear power plants,” says Jan Hanberg, project manager for stress testing and head of section at the Swedish Radiation Safety Authority.
“We have identified several areas where additional analyses are necessary. However, our overall assessment is that Swedish facilities are robust and there is no reason for us to impose any restrictions on facility operations.”
One example of a strength feature is that all Swedish reactors have a filtered venting system to capture radioactive substances in the event of a severe accident. This considerably reduces the environmental impact of an accident. Accident filters were fitted after the nuclear power accident at Three Mile Island (Harrisburg).
Deviations from applicable requirements
In a number of cases, the stress tests indicate deficiencies in relation to, or alternatively, deviations from applicable requirements imposed on safety analysis.
“This shows the importance of the work relating to stress testing,” Mr Hanberg continues.
“In these cases, the Swedish Radiation Safety Authority will order the licensees to take action so that the facilities fulfil the applicable requirements. This for instance involves our wanting more in-depth analyses of the reactors’ resilience to earthquakes.”
Emergency response management needs improvement
On the other hand, if an accident occurs like the one in Japan where several reactors are affected at the same time, the stress tests show that the nuclear power plants’ emergency preparedness is not dimensioned for this kind of scenario.
“In this kind of scenario, one cannot rest assured that the joint resources of the entire facility will be sufficient, for example the firefighters, shared operational centre and personnel. The nuclear power plants also need to conduct further investigations into the performance of accident filters during an extended sequence of events similar to those that took place in Japan,” continues Mr Hanberg.
The stress tests also indicate a need for enhanced and backed-up systems for reserve power and an auxiliary external water supply at the facilities. Here, examples include an additional system independent of existing reserve power for the purpose of pumping in water for cooling the reactor core as well as several more mobile diesel generators.
Resilience to earthquakes needs further analysis
In Sweden, only the two newest reactors, Oskarshamn 3 and Forsmark 3, were originally designed to withstand earthquakes. All other reactors are now subject to requirements imposed on earthquake resilience. The Swedish Radiation Safety Authority has now assessed that analyses conducted on the part of older reactors need to be supplemented further so that it is possible to ascertain whether they are fully capable of withstanding a severe earthquake.
Also, ice storms have not been analysed in detail in the facilities’ reports:
“We will require the facilities’ licensees to analyse the consequences of ice storms and propose measures as necessary,” says Mr Hanberg.
For more information, please contact:
Jan Hanberg, Head of Section, Swedish Radiation Safety Authority. Mr Hanberg can be reached via the press officer on call; Tel. +46 8 799 40 20 after 11:00am.
Facts
The Swedish national report is to be submitted to the European Nuclear Safety Regulators Group (ENSREG) by 31 December.
In the spring, a specially appointed group of international experts, a ‘peer review team’, will review the respective countries’ national reports.
The results from stress testing will be presented to the European Council in June.
Read more:
Stress tests