11.03.2011 

Vladimir Asmolov: “In the course of Japanese earthquake of over 8 magnitude the local NPPs proved their seismic resistance”.

Rosenergoatom Concern OJSC First Deputy Director, Doctor of Engineering Vladimir Asmolov commented on the events in Japan.

Three large NPPs are situated on the north-east coast of Honshu island, where Tokyo is located. One of the plants is Fokushima where 10 boiling vessel light-water reactors are operated. Two power units of the kind operate at Anagava plant. And to the south from Tokyo there is one more NPP with similar power units.

It was reported that one of the power units had lost its external power supply, two power units had been stopped by the automatic protection system, and the rest of the units had been stopped in normal mode. There were no reports available concerning other events at other Japanese NPPs (totally 55 power units).

Generally, a nuclear plant is the most protected facility from the point of view of any external influences. 

Modern NPPs are rated for the influence of tsunamis, tornado, plane crashes, and earthquakes. The main danger for NPP is the energy overrun of the borders of the four plant physical safety barriers. These barriers, even the first of them, must not be destroyed at so-called strength level earthquake.

Meeting the unified international approaches, Japanese nuclear plants were constructed with an account of the country seismic conditions, where earthquakes, among them strong ones, happen quite often. All the Japanese NPPs were constructed with a strength level earthquake of 8 magnitude and the maximal strength level earthquake of 9 magnitude by Richter scale. On March 11, the strength of the earthquake in the epicenter (that appeared to be not at NPP site, but in the sea), amounted to 8.9 magnitude. At that activity output, even in case the earthquake reaches its maximal strength level, is impossible –in this case the plant may only be damaged from the economic point of view.

If we compare with Spitak earthquake in 1998 in Armenia, then at Armenian NPP site it was about 6.5 magnitude, nevertheless the plant, executed in seismic design, withstood, and during the week, when all Armenian power was turned off, remained the only source of power.


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