How safe are Czech nuclear plants?

Czech nuclear power plants get mixed marks from a global watchdog, but this does not mean much regarding tough new stress tests

Opravdové potíže nastanou, až se první dukovanský blok bude blížit konci životnosti. Bude to právě v době, kdy Německo plánuje odstavit svoje poslední reaktory. foto: ČEZČeská pozice

Opravdové potíže nastanou, až se první dukovanský blok bude blížit konci životnosti. Bude to právě v době, kdy Německo plánuje odstavit svoje poslední reaktory.

When Germany pushed through its demand for stress tests of European nuclear reactors in the wake of the accident at Japan’s Fukishima plant, speculation rose that the Czech Republic’s oldest plant at Dukovany might fare better than the more modern Temelín complex.

That speculation was based on the World Association of Nuclear Operators’ (WANO) ranking of power plants. But the WANO ranking would be a misleading tool, as Czech Position’s information suggests that the European stress tests will be a lot stricter.

Of course, it’s expected that the stress tests will be carried out by national authorities, in this case the State Office for Nuclear Safety (SÚJB) with nothing revolutionary to be expected as a result.  The Czech nuclear world is a small and cozy one where everyone is fully aware of the respective strengths and weaknesses of certain power plants. They all share a common goal in promoting nuclear power, and the most that could be expected would be that a list of remedial repairs would be ordered to correct any problems. The reactor containers could be good for another 20 years and the reactors themselves could have a lifespan of around 60.

But the Dukovany complex in the Vysočina region is beginning to show its age. Its reactors went into operation between 1985  and 1988. Experience from other aging reactors suggests that the reactor containers could be good for another 20 years and the reactors themselves could have a lifespan of around 60. That could mean that Dukovany’s four reactors might be approaching their phase out in 2025, the same time that neighboring Germany is looking to shut down its last nuclear reactors.

That would probably result in neither Germany nor nuclear-free Austria having much sympathy for the idea of extending the life of the Czech reactors. Fukushima suffered its accident toward the end of its active life, and while the reactors’ age was not the cause it is usually a contributing factor in such critical incidents.

Currently, though, age does not seem to have had any impact on Dukovany’s performance. The opposite seems to be the case as the plant benefits from the long-term experience of its engineers.

 A comparison between Dukovany’s four pressurized water reactors and the two more recent and modern reactors at Temelín show the older models to be far more reliable. In the world ranking of the best performing nuclear reactors drawn up by WANO, Dukovany’s reactors frequently come out near the top. In the last published evaluation, Dukovany’s fourth reactor scored 99.87 points out of a possible 100. Worldwide, there were only 15 reactors with a better rating.

Recent problems at the plant may have taken the shine off those figures. A crack appeared in one pipe and, soon after that was fixed and the reactor restarted, it had to be shut down again for a few days when a valve failed. With another reactor closed down for routine inspection, the plant was only producing at half its full capacity.

The WANO reliability and performance records, while giving an indication of how a nuclear power plant is operating, cannot be taken as an indication of how safe it is. Such safety rankings and assessments are not in the public domain. For that, the future stress tests will be the best test and indication.

Temelín didn’t make the top 50

The same argument holds true for the Temelín reactor in South Bohemia.  Even though it does not appear even in the ranking of the best performing 50 reactors in the world, it can only be concluded that the plant is unreliable, not that it is dangerous. One expert actually worked out from the frequent shut downs and agency reports that the plant’s annual electricity output is around 55 percent of its full capacity. ‘We expect better quality repairs, a reduction in errors and less time spent on assembly as a result of the center.’

Temelín’s operator, state-controlled power giant ČEZ,  is aware of the flaws at the plant. Plant spokesman Marek Sviták assured Czech Position that it is operating well within its security limits with the radiation safety norms set very high. But with the drawn-out unplanned outages continuing, the operator has opened a practical training center on site where employees can learn how to carry out repairs.  

“We expect better quality repairs, a reduction in errors and less time spent on assembly as a result of the center, which should have a marked impact on the time taken for outages, ” Sviták said.

While the earthquake and tsunami that prompted the stress tests are unlikely in the Czech context, those tests do look like being a lot tougher than anything that has gone before. A crucial test for all power plants, whatever their age,  will be of the cooling systems and backup power supplies. Their capacity to resist a terrorist attack should also come under the spotlight.  There are mixed views on the latter point in Europe, with the tests likely to lose all sense if subject to French pressure for changes in the criteria.

At this point it should be noted that the Dukovany reactors do not have the classical type of containment in a watertight reinforced concrete envelope but has a “fourth barrier” against leaks of radioactivity in the form of a vacuum bubbler system. This would be of little use in the case of a terrorist attack.

For the German  EU energy commissioner,  Günther Oettinger, the stress tests are not that difficult to promote, although they will create problems for European power networks. Some nuclear reactors at the bottom end of the WANO rankings, and apparently the target of French pressure, could fail the tests.    

The second major nuclear accident at Fukushima occurred in part because of human error where human error should have been impossible. Having said that, there is no real path but ahead for the nuclear sector. If that involves tougher tests for countries that want to close their nuclear plants and those that want to continue building more, so be it. In the latter case they will just have to submit to more and tougher oversight.