31. 10. 2011
Il Piccolo
Stefano Giantin

«Krsko is earthquake-resistant»

It is safe. It is built in an earthquake-prone area. It boasts top-of-the-line security. It is filled with obsolete technology. The disaster in Fukushima set the spark to new disputes on the pros and cons of nuclear power, and of the Slovenian nuclear power plant of Krsko, too.

Built under Yugoslavia at about 130 km from Trieste, the power plant implements American technology from Westinghouse. In more than twenty years, there have been no significant failures, apart from one mishap in 2008: a leakage from the primary cooling circuit with no radioactive emissions that, despite international hue and cry, has been judged of “no safety significance” and ranked Level 0 of the INES scale. Since the Nineties, the technology and security systems of the plant underwent updating more than once.

So, why to be so scared? According to the Austrian geologist Heinz Hoegelsberger, a former consultant for Greenpeace and one of the long-standing opponents of the plant, Krsko is a time bomb that should shut down as soon as possible. “Building Krsko was political will. Regardless of geological data, the plant has been built in one of the most earthquake-prone areas of Slovenia. It was built in the wrong place”, denounces Hoegelsberger. “According to U.S. standards, Westinghouse shouldn’t have built near a fault”, he thunders, adding that it has been made possible by “erasing faults from geological maps. The building of Krsko comes along with criminal doings”.

Seismic risk is often minimized, yet it is apparently the sword of Damocles hanging over Krsko. Or, at least, that seems to be the convincement of its opponents. Theoretically, the plant should withstand seismic activity up to 5.8° on the Richter scale, but stronger earthquakes have been recorded in the area in the past. “It’s not only a matter of magnitude, but also of acceleration”, highlights Hoegelsberger, as “UNESCO calculated that waves with an acceleration of 0.31g may occur in the area once in 200 years, while the plant can withstand only to 0.30g”.

Leon Cizelj, Head of the Reactor Engineering Division of the Jozef Stefan Institute in Ljubljana, argues that when Krsko was built “two types of earthquakes have been considered. Following weaker seismic activity, up to 5.5° on the Richter scale, the plant would preserve its operational capacity. In case of a stronger earthquake, the objective of the builders was to keep the plant safe until its dismantlement. I think Krsko can withstand earthquakes up to 9° Richter, as strong as that in Fukushima”.

It is not only Cizelj, but the majority of experts believe that Krsko is reliable, despite the seismic risk. “The last strong earthquake near Krsko occurred in Brezice in 1917. There is no documentation of later earthquakes above 5.5° Richter in the area; the only record refers to an area in the vicinity of Zagreb, which is 50-60 km away, and where quakes reach magnitude 6-6,5° Richter”, says Peter Suhadolc, professor of Physics of the Earth at the University of Trieste.

Having been a member of the Committee set-up by the Austrian Senate in order to report on the situation in the plant, Prof. Suhadolc knows Krsko very well. In 1995, he examined the plant and issued a series of recommendations to improve its safety. Suhadolc makes clear a key point: “The plant was designed to withstand a force of 0.30 g, where g stands for the acceleration of gravity. Recently, the project has been revised to increase the resilience of the plant to 0.60 g. In my opinion, the plant is safe enough for the kind of earthquakes that can occur in the area”.

Mr. Cizelj draws the attention to the fact that “seismicity of Slovenia is much lower than of Japan. If the worst possible earthquake in Japan is expected to be 9° Richter, in Slovenia it would be 7°, which means that an earthquake would release 1000 times less energy”. The expert in nuclear safety thinks that “in Fukushima and Krsko we see the same approach to safety: if the Japanese plant withstood 9° Richter, with the disaster being caused by the tsunami that followed the shock, Krsko would resist to the same magnitude, even if 7° Richter is most we can expect there”.

Apparently, Wolfgang Lenhardt, Director of the Department of Geophysics of the Centre for Meteorology and Geodynamics in Vienna, should share Mr. Hoegelsberger’s fears, as he has been often depicted by Austrian newspapers as a fierce enemy of the Slovenian nuclear power plant. “They put words in my mouth,” comments Lenhardt, “the only reason for my concern refers to the quality of the construction and technical updates. We don’t have information”. So, how to banish all doubts? “I have been often asked, why shouldn’t I have faith? But faith is a matter of religion, scientists need facts”.

Mr. Cizelj makes efforts to reassure him: “According to the law, once in ten years Krsko must stand a test to verify if all safety measures have been implemented. Until now, the managing staff has accomplished to all the requirements set for this type of plant. Currently, for example, they are working on a backup generator”. Recommendations of the Austrian Government have also been taken into consideration. “A very good network for the monitoring of seismic activity has been put in place. On the whole, most relevant suggestions have been accepted, including that of improving the resilience of the plant from 0.30g to 0.60g”, explains Prof. Suhadolc.

The big fear of the past days seems to have no rational grounds, if fearing that an earthquake could trigger a nuclear disaster right in your backyard should actually call for reasonable arguments. However, one should also agree with Prof. Suhadolc concluding that “it is correct to be cautious and to verify. But there is no reason for alarm in Krsko”.

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