Actually, gas is a cleaner energy option than coal in SA, both in the combustion and the production thereof, for reasons I’ll attempt to make clear.
Radioactive emissions from coal-fired power plants are a concern, albeit a lesser one. The three biggest concerns re burning coal are CO₂ emissions, sulphide and oxides of sulphur, and particulates. The CO₂ emissions are obviously the result of burning the coal for energy. SA coal tends to have a high sulphur content and power station feed coal is typically not especially clean in this regard. SA has lots of steam coal but far less clean coal like coking coal and anthracite needed for smelting and steel production. The sulphides and oxides of sulphur go into the upper atmosphere and cause acid rain. The particulates, which include radioactive constituents, are very fine ash and mineral dust that don’t make for healthy air. Scrubbing power station emissions is possible but expensive and fraught with technical challenges.
The gas horizons identified for fracking in SA (Karoo) are two to three times as deep as those in the US and Canada. Moreover, they are in areas with perched water tables. What this means is that there’s far less risk of adverse consequences such as gas leakage or dropping of water tables in SA than what has been the case elsewhere. (This topic is among my father-in-law’s expertise and livelihood.) It’s true that the initial setup requires fairly large volumes of water that gets contaminated with chemicals but this can be managed by suitable containment and is a relatively small price to pay for the usable energy that can be extracted. The relative amount of water over the viable life of a gas well is in fact very small.
The radioactive aspect is also quite low risk. The article BM linked to speaks a lot about radon but doesn’t explain the risk adequately. Virtually all underground endeavours are at risk from radon, which is itself a product of radioactive decay. Radon is a noble gas (which means it’s chemically inert and doesn’t react with anything much) that is also radioactive. Its decay paths have relatively short half-lives and—this is its main hazard—its decay products are solids that are also radioactive and that settle or stick to surfaces. So, you breathe in small amounts of radon which decays rapidly, leaving radioactive solids in your lungs that decay further, eventually becoming lead (Pb), a protoplasmic heavy metal that kills cells. Insidious cycle, this: Cancer and cell poisoning.
But this hazard is also manageable through a sufficient residence period of the gas recovered from underground to allow any radon, if present in sufficient quantities, to decay to below acceptable levels. The solid radon decay products will settle in the residence tanks in a safe way because they aren’t high-energy gamma emitters.
The short of it is that fracking is actually a quite safe and reasonable intermediate solution to SA’s energy problems.