The debate about nuclear power has escalated with the approach of the final deadline on Monday for appeals against Minister of Environmental Affairs and Tourism Mohammed Valli Moosa’s approval of a pebble bed modular reactor in the Western Cape.
After the deadline, the national nuclear regulator must decide whether to issue a licence for the construction of the reactor that would be built next to the conventional nuclear power plant at Koeberg, 30km outside Cape Town. Koeberg is a licensed nuclear site with the necessary infrastructure and engineering personnel. A new plant could plug directly into the national electrical grid.
“It makes more sense than starting from a virgin site,” said Andrew Kenny of the University of Cape Town’s Energy Research Centre, speaking in his private capacity.
But anti-nuclear lobbyists argue that the site is not as safe as the environmental impact assessment claims.
Geologist Nik Wullschleger said the history of seismic activity in the region cast doubt on the stability of the site. A report released after a geological survey in 1974 recorded more than 50 earthquakes and tremors in the southwestern Cape since 1620.
Earthquakes
Six of these are estimated to have measured a magnitude of five or greater on the Richter scale. One quake, in 1809, was estimated to have an epicentre “relatively close to Cape Town”.
“Apart from the damage and destruction to buildings in and around Cape Town,” the report stated, “surface fissures appeared between Milnerton and Killarney of up to 10cm wide, 2km long and deeper than 3m, accompanied by sand volcanoes … water spouted from the sand volcanoes to a height of 2m. The actual magnitude of the earthquake must have been at least close to 6,5 [on the Richter scale].”
More recently, the Ceres-Tulbagh quakes of 1969 and 1970 measured 6,3 and 5,7 on the Richter scale.
The 1969 quake caused extensive damage, deaths, “sand boils”, waterspouts and cracks in the ground.
But Koeberg was designed to withstand the “worst earthquake that is likely to happen in the next million years” said Kenny, and the pebble bed reactor would withstand even worse stresses.
Wullschleger countered, by saying that though engineers could construct dams and bridges for those “one-in-so-many-year” floods because climate systems were well understood and more predictable, they could not yet predict seismic events with the same accuracy. “Earthquake risk cannot be quantified the same way because you may have an idea of the past, but you cannot predict the future,” he said.
“Even if some unimagined earthquake should damage the reactor, nothing much would happen.” said Kenny. “If the reactor vessel were tilted or even ruptured and the fuel elements dislodged, fission would stop and the resulting radiation would be small.
“Japan is in a far worse earthquake zone and hasn’t had a single accident at a nuclear plant due to an earthquake,” he said.
The reactor’s radioactive fuel consists of granules of uranium encased in graphite spheres the size of snooker balls. Each of the uranium particles is also coated in extremely tough layers of heat-resistant carbon and silicon carbide.
These graphite pebbles must be positioned precisely for the fission reaction to occur and cannot overheat, which poses the threat of a “meltdown” that plagued the older reactor technology.
The environmental impact assessment does call for a geologist to supervise site excavation and to look out for signs of geological instability such as liquefaction, where waterlogged soil or clay becomes liquid because of seismic shock, or from shifting rock layers.
Waste disposal
The pebble bed reactor has a lifespan of 40 years, during which time high-level radioactive spent fuel will be stored on the site. But the highly dangerous exhausted fuel may remain there after the power station is decommissioned because the government has struggled to determine a waste disposal policy.
Vaalputs in the Northern Cape has been proposed as the site for the burial of nuclear waste and is already used to dispose of low- and intermediate-level waste, such as contaminated protective clothing. But some of the radioactive elements may take several billion years to decompose into harmless material. Buried waste would need to be stored in stable conditions with no rock movement or rising water levels to damage the containers as their load loses its deadly character.
Vaalputs is regarded as geologically stable, sufficiently arid, remote and dry with low volumes of groundwater, making it suitable for the burial of waste. But Wullschleger points out that the disposal site may not remain arid while its deadly cargo becomes more benign.
Climate
The Earth’s climate see-saws between hotter and colder conditions. Not too many centuries ago Africa was a tropical forest from top to toe. Though the Northern Cape is now dry and desolate, it may well enjoy abundant rainfall again within even a few thousand years, an instant in the time high-level nuclear waste would need to lose its deadly radioactivity. Rising groundwater levels could spread the deadly radioactive material far and wide.
Lobbyists are also concerned with the health risks for the community of Atlantis, near Koeberg.
“The environmental impact assessment gives a circuitous logic,” said Leslie London, a professor at the University of Cape Town’s public health department. “It says that because there is no evidence to suggest there is a problem [of radioactivity causing health problems in the area], there is no need to look.
“Koeberg is a major installation, but there is no data on the communities living around it. One can’t say there is no risk when no one in fact knows.”
London calls for an independently funded study of the rate of cancer and birth defects in Atlantis. The industry should not sponsor the research, he argued because “history shows that such research findings are often skewed”.
Radiation readings around Koeberg over the years have been negligible. Naturally occurring radiation from granite rock used in construction of some of the Cape’s buildings and roads outstrips Koeberg’s readings by several thousand times.