SA DOES not face the same threats to nuclear technology as Japan, says former South African Nuclear Energy Corporation head Rob Adam, referring to the Fukushima Daiichi nuclear crisis in Japan last year.

A magnitude-nine earthquake in March last year, about 70km from the coast of Japan, triggered a tsunami which damaged cooling mechanisms and generators in three of Daiichi's reactors. This fuelled concerns globally over the safety of nuclear technology, with Germany undertaking to close all its nuclear plants by 2022.

"The circumstances are different. Japan's reactors are boiling water reactors built in 1971. That is 40 years behind what SA is contemplating," said Mr Adam.

Eskom's nuclear power spokesman, Tony Scott, agreed. "They used boiling water reactors, whereas we use pressurised water reactors. About 70% of all new nuclear stations in the world use the pressurised system."

The main question is whether SA's proposed nuclear infrastructure - and the existing Koeberg power station - would be at risk from earthquakes and tsunamis.

Aon Benfield Natural Hazard Centre director Andrzej Kijko said last month that SA had a low seismicity rate because it was considered an intraplate region.

"The seismicity of SA is generally characterised by a low level of activity, but is poorly understood and capable of producing rare, but destructive events," said Prof Kijko.

The Eastern Cape was the least seismically active area, while Gauteng and Western Cape were more active, he said.

Earthquakes do occur in SA, but the largest number are in gold and platinum mining areas.

"The largest historically and instrumentally known natural (of tectonic origin) earthquake took place in the Ceres-Tulbagh area in September 1969," said Prof Kijko. "It is important to note that the occurrence of this event near the City of Cape Town (about 90km) was taken into consideration in the construction of Koeberg nuclear power plant."

"Earthquakes of this magnitude are a regular occurrence in Japan," but are exceptional in SA, Mr Adam said.

Besides, Japan's reactors had a "relatively good response to the quake. It was the tsunami that stopped the cooling mechanism.

"The possibility (of a tsunami) happening off the coast of SA is nonexistent," he said.