Earthquake and nuclear: what security? | 14 / 11 / 2019 | Désintox | ARTE

[izentrop]

The earthquake that took place at the beginning of the week in Ardèche made fear the worst for the nuclear power plants of the region. The network "Sortir du nucléaire" has also alerted in a series of tweets about "the casual attitude" of EDF. And highlights that the Cruas power plant was built to withstand 5,2's "enhanced earthquake" while the quake reached 5,4 on the Richter scale.

A disturbing but misleading message.

The increased earthquake risk of a plant is calculated from a "reference" earthquake, which is the strongest known earthquake in the region. For the Cruas plant, the reference earthquake occurred in 1873. He was from 4,7. To arrive at the increased value, we add 0,5. In the case of Cruas, we arrive at 5,2.
But things are more complicated than that.
First, this earthquake plus safety is determined in the event that the epicenter of the earthquake is placed exactly below the plant. Which, fortunately, was not the case on Monday November 11.

Second, and most importantly, "Getting out of the nuclear" has mixed the brushes in the scales of magnitude. The Ardèche earthquake was announced between 5,1 and 5,4 in local magnitude. The earthquake plus safety, it is expressed on another scale: in magnitude of surface waves. And it's not the same thing at all.
"If we follow this scale to compare the two values, the Teil earthquake was of a magnitude in surface waves of 4,5 in its epicenter," says an expert at Désintox.
To arrive at the earthquake of reference, there is still, fortunately, a margin.

[Christophe]

Below 7 we do not have fun!

Good without laughing, since it only concerns the energy / power released at the epicenter, without correction of distance from the human installation 1ere, I understood the scam of the Richter Scale in 5ieme ...

[sen-no-sen]

The increased earthquake risk of a plant is calculated from a "reference" earthquake, ie the strongest earthquake known in the region

Small remark concerning the industrial or civil risk in its majority: each time we consider a "reference earthquake", a "reference flood" (centennial etc ...) as if nature had to stick to a curious spell. a limit decided by "experts".
A Fukushima the engineers had estimated that the wave would not exceed 6m ... and it is a wave of 10-12m which is presented during the tsunami.

[Christophe]

Good without laughing, since it only concerns the energy / power released at the epicenter, without correction of distance from the human installation 1ere, I understood the scam of the Richter Scale in 5ieme ...

Rectification, as there is now a Surface Richter Scale, my remark makes less sense ... I replied before reading everything

[Bardal]

The increased earthquake risk of a plant is calculated from a "reference" earthquake, ie the strongest earthquake known in the region

Small remark concerning the industrial or civil risk in its majority: each time we consider a "reference earthquake", a "reference flood" (centennial etc ...) as if nature had to stick to a curious spell. a limit decided by "experts".
A Fukushima the engineers had estimated that the wave would not exceed 6m ... and it is a wave of 10-12m which is presented during the tsunami.

As far as Fukushima is concerned, the tsunami risk has been known for a long time, for a very long time, and for 15 meter heights regularly reached in the region. So much so that all the hills surrounding the bay had been marked with engraved posts, indicating that below the indicated limit it was strongly advised not to settle because of the danger of tsunami; the local archives keep track of known tsunamis, repeating themselves at fairly regular intervals every forty years (ie the probability of a disaster during the life of the plant was very high). See here https://www.lemonde.fr/japon/article/20 ... 92975.html .

Tepco had also been advised to raise the dyke supposed to protect its power stations, which it declined for economic reasons, as it refused to follow EDF's advice to install an anti-hydrogen device on the island. these plants, for the same reasons.

It is not the respect of a "reference earthquake" which is at the origin of Fukushima, it is on the contrary the non-respect of the lessons of recent history, and the rapacity of capitalist companies ...

These warning signs still exist, if some skeptics want to check, and they are actually at a height of fifteen meters.

[sen-no-sen]

It is not the respect of a "reference earthquake" which is at the origin of Fukushima, it is on the contrary the non-respect of the lessons of recent history, and the rapacity of capitalist companies ...

I agree, but a member of the network going out of the nuclear power will be able to argue that taking into account the risk on the French nuclear power plants is not based either, for economic reasons, on the recent history (case of the 11 / 09 / 2001 or a hypothetical dam break).
Moreover, the ASN has ordered the strengthening of the protective dyke of the Tricastin power station following the Fukushima incident, under the understanding that all the provisions would not have been implemented against a construction disaster. .

EDF has made 2017 reinforcements of the portion of the dike concerned to ensure earthquake resistance plus safety [1]. On this basis, the ASN had agreed to restart the reactors in December 2017.

EDF has planned additional work on this dike so that it can withstand the extreme earthquake [2] defined after the Fukushima accident. The decision adopted by the ASN 25 June 2019 requires the realization of this reinforcement at the latest end 2022. In anticipation of this work, it also frames some of the actions to be carried out by EDF, in particular:

https://www.asn.fr/Informer/Actualites/Tricastin-renforcement-de-la-digue-protegeant-la-centrale-nucleaire

Here we are talking about nuclear but the problem also affects the civil construction sector, especially with regard to flood risk.

[GuyGadebois]

It is not the respect of a "reference earthquake" which is at the origin of Fukushima, it is on the contrary the non-respect of the lessons of recent history, and the rapacity of capitalist companies ...

Exact. It is the profitability, the savings and the short-term profit that we saw working in Fukushima with the results we know.
With regard to EDF, Areva and others, the same values ​​are at work, which is hardly reassuring, especially with the systematic use of inadequate and incompetent subcontracting.

[izentrop]

FYI: Historic history of earthquakes on the Cévennes fault in the same region.
http://www-dase.cea.fr/actu/dossiers_sc ... index.html

[izentrop]

All is said https://www.irsn.fr/FR/Actualites_press ... 112019.pdf

The fault on which the Teil earthquake occurred was not known to be active in the period
recent, while potentially active faults are identified within 10 km of distances (by
example the Marsanne fault). This shows the interest of studying faults even in a context with seismicity
moderate like that of metropolitan France.
The Teil earthquake is a very superficial earthquake that created a surface rupture with an offset
centimeter. The trace of this rupture could be quickly identified thanks to satellite data, which
guided the geologists who were able to measure the deformations on the ground. This is a first in France
for this type of use of satellite data. Indeed the Annecy earthquake in 1996 of
magnitude Mw of 4,6 also created a centimeter rupture at the surface, but the techniques of the time did not
not allow to quickly have this type of data.

Impact on nuclear installations
Three nuclear sites are located within a 50 km radius around the epicenter. The closest is that of
the Cruas nuclear power plant. The distance to the nearest rupture zone is approximately 12 km. Account
given the magnitude and the shallow depth of the earthquake, the attenuation of the seismic movement is
important. Thus at 20 km, the seismic stations of the national observation networks recorded
accelerations of a few thousandths of g (value of the acceleration of gravity), in particular of 0,006 g
near the Tricastin power station. At Cruas, the instruments installed on the site recorded a
maximum acceleration of 0,045 g in free field (another measurement carried out at the plant premises has
resulted in a shutdown and verification procedure for the installations).

With regard to the Cruas nuclear power plant, the "response spectrum" in force is that used for
the third reactor safety review. It is calibrated at 0,26 g. This spectrum was used for the
reassessment of the seismic behavior of the entire installation during the third safety review.
It should be noted that for the Cruas nuclear power plant, seismic elastomeric supports were
interposed during construction between the foundations and the main buildings.
For the Tricastin nuclear power plant, the "response spectrum" in force is that used
for the third reactor safety review. It is calibrated at 0,285 g. This spectrum was used for the
reassessment of the seismic behavior of the entire installation during the third safety review ...