Public hearings were hosted in Centurion by the National Nuclear Regulator (NNR) on the merits and demerits of building the proposed smelter.

Earthlife Africa's Judith Taylor said the smelter would significantly add to radiation levels in the atmosphere.

"That site is an apartheid-era legacy which they now want to make use of. We do not need to process those metals which we are not sure are clear of radiation," she said.

"South Africa's poorest are already reeling, affected by effects of radiation. Exposure of the general public to radiation is growing exponentially," said Taylor.

However, Necsa group executive Van Zyl de Villiers said the smelter was being mooted to dispose of the voluminous contaminated waste at Pelindaba, in Pretoria.

"The purpose of the smelter is to melt down, which means separating metals -- steel and aluminium -- from the uranium," said De Villiers.

"The de-contaminated metal will be released and sold for re-use. The uranium is then concentrated in a controlled form which we can dispose of," he said.

"The melting technique would be efficient and environmentally friendly and had been specifically developed to de-contaminate bulk metals," said De Villiers.

The agency noted the opposition to the R20 million project, but called on the NNR to make a conclusion based on "facts and further risk analysis based on existing practices and scientific information".

De Villiers said fears of radiation needed to be presented to the NNR in a proper context.

"For one to say all radiation is bad for humans, I am surprised we are still alive because we are radiated from natural causes daily. In that case we should then stop radiation treatment and medical x-rays".

"We need to make a proper risk-benefit analysis rather than being selective with particular scare-mongering tactics," said De Villiers.

Around 14,000 tons of lightly uranium-contaminated ferrous and non-ferrous metals are stored at the Pelindaba site.

The material originated from the decommissioning of the uranium enrichment facilities at Pelindaba, according to Necsa.

It is part of Necsa's mandate to manage the material in accordance with internationally accepted norms.