Earthquake hazard from nuclear power plants
The problem of the earthquake hazard of nuclear power plants was brought to the attention of a broad world public by the Fukushima nuclear disaster .
Older types of systems such as those at Fukushima-Daiichi are, in terms of their basic design, less well designed to withstand the effects of strong earthquakes than are more recent ones. However, there are also differences in the technical design against earthquakes between countries with lower earthquake activity such as in Europe and countries with high activity such as Japan . The Japanese nuclear power plant in Kashiwazaki survived a quake with a magnitude of 6.8 Richter scale in 2007 and was much closer to the epicenter than at Fukushima, with around 2,800 seismically-related damage findings for all seven units, but no serious release of radioactivity .
Precautions for stabilization
Block 7 of the Kashiwazaki power plant is an advanced boiling water reactor , the reactor building of which is anchored underground to almost half of the total height of the building in order to be resistant to earthquakes - a z. B. in Europe, but also in Fukushima-Daiichi not used construction method, which was largely practiced with the other Kashiwazaki blocks. In its floor area, the reactor building is also firmly anchored in the rock, a vise effect that minimizes the building's sway, especially when the earthquake accelerates horizontally (ground movement). On the other hand, a disadvantage of the rock foundation is that it transports the earthquake accelerations the most: For Kashiwazaki 7 with 490 to 650 meters per second, compared to only 330 m / s in clay (stone) and 150 to 200 m / s in sand. This disadvantage is compensated in Kashiwazaki insofar as the rock only attacks the bottom of the reactor building, the overlying layers of the subsoil consist of clay and - in the uppermost soil layer - sand, which has a rather stabilizing effect with regard to acceleration forces.
Distance from the epicenter
Regarding the distance of the location to the epicenter of the earthquake, it can generally be said, regardless of the example of Kashiwazaki, that this distance can reduce the strength of the ground movement. In certain cases, however, larger local deposits of softer sediments can lead to greater soil movement than at the epicenter.
Internal robustness
The internal structures of the power plant, such as tanks, pumps, pipes, fittings , can also be technically designed in terms of their fastening so that they can withstand the vibrations of an earthquake better (which does not necessarily mean stronger fixation, but also better mobility in the case of pipelines, for example ). A current example from France shows, however, that this is still inadequate in some cases: in more than half of the French nuclear power plants, it was found in 2013/14 that the earthquake robustness of certain valves was still insufficient despite an official requirement from 2010.
literature
- ENSI : Experience and research report 2011, in it the chap. Structural behavior of the Kashiwazaki nuclear power plant during the earthquake of 2007, as well as (in Appendix A) the expert group for strong earthquakes
- ENSI: Experience and research report 2007, in it the chap. Instructive incidents in foreign nuclear facilities
Individual evidence
- ↑ Media report from the ASN supervisory authority ( Memento of the original from February 22, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
