SA's nuclear safety is reassessed
The National Nuclear Regulator gave assurances last week that it was working to incorporate lessons learned from Japan’s Fukushima nuclear incident in domestic nuclear safety standards.
Environmentalists have argued that the incident in Japan revealed the shortcomings in global nuclear safety systems and regulation and there have been growing concerns about the threat of potential seismic activity in South Africa.
Speaking at a public seminar held by the Institute for Security Studies on July 27, Peter Bester, special nuclear projects co-ordinator at the nuclear regulator, said that after Fukushima, local operators had been instructed to conduct safety reassessments of nuclear installations in South Africa after Fukushima. The regulator was also in the process of reviewing its own regulatory standards and processes.
Earlier this year an earthquake clocking 9 on the Richter scale hit Japan and caused a tsunami that wreaked havoc at the country’s Fukushima Daiichi Nuclear Plant.
It was not the earthquake that caused the nuclear accident at Fukushima, but the failure of cooling systems in the reactor when power supplies to the plant were damaged as a result of the quake-induced tsunami.
The primary responsibility for safety rests with South Africa’s nuclear operators, Eskom and the Nuclear Energy Corporation of South Africa, which operate the Koeberg and Safari nuclear reactors, respectively.
Bester said the aim of the reassessments was to identify vulnerabilities in the design of the facilities, evaluate the safety margins for “beyond design events”, such as those at Fukushima, and identify any necessary modifications in design or technical features.
Among other things, the scope of the reassessments covered subjecting the plants to stress tests to see how they responded should important safety functions be lost and looking at the emergency management responses, he said.
In the case of Koeberg, which has two reactor units, the reassessments would also consider the potential of multi-unit impacts and whether the plant could withstand unexpected external events.
Bester said Koeberg had also established a team that had identified areas for improvement, which it had begun implementing. These improvements were being reviewed by the nuclear regulator as part of the installation plan to address any shortcomings in Koeberg’s design.
Despite assertions that the nuclear energy industry globally was subject to stringent safety standards, the Fukushima incident has highlighted the potential weaknesses of nuclear power plants in withstanding extreme scenarios not calculated for their design, Bester conceded.
But his arguments were countered by Rianne Teule of Greenpeace Africa, who argued that safety concerns arose not only from nuclear accidents but radioactive contamination from nuclear installations along the nuclear energy value chain, including uranium mining and nuclear processing plants.
She pointed out the difficulties the Japanese government had in containing the Fukushima incident’s radioactive impact and safeguarding the public.
Teule was highly critical of the environmental impact assessment now being conducted for the Nuclear 1 project, the next planned addition to the country’s nuclear fleet.
“It proposes emergency zones of 800 metres and 3 kilometres. Anyone who has been in the areas around Chernobyl or Fukushima would agree that such a proposal is misleading or simply outrageous.”
The unexpected sequence of events at Fukushima led to scenarios that had not been incorporated in nuclear safety assessments, Teule said.
She argued that South Africa “had no reason to think that its ability to ensure nuclear safety is better than in a highly technological country like Japan”. “South Africa does not have sufficient regulatory capacity to safeguard the public from nuclear risks posed by an additional 9 700MW [as outlined in the integrated resource plan of 2010] of nuclear power,” she said.
Although South Africa is not renowned for seismic activity, large earthquakes could happen here, according to geologist Chris Hartnady of consultancy firm Umvoto. He has previously warned of the potential risks of an earthquake to Koeberg. The Cape Town area is known to have had a 6.5-magnitude earthquake in 1809, he told the Mail & Guardian.
Eskom has stated that Koeberg was designed with this in mind and built to withstand the potential effects of a seismic event of this magnitude. Its design also used a newer generation of nuclear technology.
But the method developed to evaluate the risk of seismic activity that is favoured across the globe is being hotly contested in scientific circles.
Hartnady said the “probalistic seismic hazard analysis” took a catalogue of instrument-recorded quakes in an area and, using sophisticated modelling methods, extrapolated the likelihood of a maximum magnitude seismic event. But the method is unsuitable for regions such as Southern Africa, which does not have the requisite instrumental records, he said.
The analysis had given regions such as Mozambique maximum magnitude estimates of 6.4 on the Richter scale, but in 2004 the country experienced a magnitude 7 earthquake, which is roughly 2 000 times stronger. Given these concerns, there is an argument that nuclear power stations should be “overdesigned” to cater for the possibility of a maximum-magnitude event.
According to Hartnady, South Africa is part of the East Africa Rift System, which is steadily spreading southward—notably towards Thyspunt, the site in the Eastern Cape that is being targeted for Nuclear 1.