The methods used to determine earthquake risk at Thyspunt in the Environmental Impact Study are scientifically flawed according to leading seismology experts.

A serious reassessment of the earthquake hazard to Koeberg, which lies about 8km from the offshore Milnerton Fault is also required according to geotectonics expert Chris Hartnady.

Koeberg is only 8 km from the Milnerton Fault that caused a huge earthquake 200 years ago.

Hartnady, an international expert on geotectonics recently told the Cape Times: “I do not agree that there is ‘no risk’ … A ‘great’ earthquake, of 8 and above, is quite conceivable on the Milnerton Fault.”

After the nuclear crisis in Japan, triggered by an earthquake of 8.9, the authorities here have assured South Africans that Koeberg is not an earthquake risk.

Koeberg has been designed to withstand an earthquake with a magnitude of 7. The Milnerton Fault caused an earthquake in 1809 with an estimated magnitude of between 6.3 and 6.5.

But Hartnady, a specialist in seismic risk assessment, believes these assurances are wrong. His says the methods used to work out what is “likely” are outdated.

Hartnady says the engineers who built the Fukushima nuclear plant had a “misplaced confidence” in this regional earthquake risk assessment, which was believed to be 7.9. They had probably arrived at this figure “simply by adding an arbitrary 0.4 to the largest known historical event, a 7.5 earthquake in November 1938”.

He believes the authorities should focus their reassessment on the pools where the spent fuel, still highly radioactive, is stored on site.
The spent fuel, essentially radioactive waste, in Japan has given rise to massive problems after the storage pools were damaged by the tsunami.

Last week, the cabinet approved a new 20-year electricity plan which sees 23 percent of all new electricity generation coming from nuclear. Thyspunt near Jeffreys Bay seems to be the preferred site to build the next nuclear power station in South Africa.

But if the methods used to calculate the quake risk to Koeberg are outdated, it appears that the methods used recently to calculate the quake risks for the new nukes are not only outdated, but “incomplete and scientifically flawed”, according to seismology expert Andreas Späth.

In his critique of the environmental impact assessment’s quake risk, he says the methods used to conclude that none of the sites posed a risk were “disingenuous”.

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