PELINDABA: Nuclear reactor is put to use for human good (01 September 2011)

The facility’s commercial cash cow is the leading medical isotope producer in the world, writes Sarah Wild

Published: 2011/09/01 07:02:28 AM

IT WAS once the apartheid regime’s best-kept secret, but now the South African Nuclear Energy Corporation’s (Necsa’s) flagship facility, Pelindaba, is open to the public — if you have letters of recommendation, have provided your ID number and car registration, had your fingerprints scanned , and gone through many other, not always visible, security checks.

A bubble of nuclear competence in the middle of Hartbeespoort’s hilly grasslands in Gauteng, Pelindaba is home to the Safari-1 reactor, the largest reactor of its kind in Africa and the leading medical isotope producer in the world.

"It’s SA’s fundamental atomic research installation," says Elliot Mulane, who began as a nuclear technician 11 years ago and worked his way up to being Necsa’s spokesman.

"You become specialised — it’s the main nuclear facility in the country." In SA, there is Koeberg, the nuclear power station in Cape Town, and Pelindaba, which houses the Safari-1 research reactor.

Standing 11m from the 20MW reactor as the overhead sign blinks "Reactor in Operation", Mr Mulane says this is the closest a member of the public can get to a nuclear reactor in the world.

The demineralised water encasing the reactor glows blue as neutrons and radiation are emitted from the low-enriched- uranium fuel rods at its centre.

In that science-fiction-esque blue water, a number of projects are taking place. The facility’s commercial cash cow — which falls under NTP Radioisotopes, a subsidiary of Necsa — is the production of molybdenum-99, for medical nuclear diagnostics.

Other activities include the doping of silicon, which is gaining importance as the world increasingly turns to technology. Microchips, which make up electronic components, include silicon, a semi-metal and a semi- conductor. But "doping" silicon with another element can improve its conductivity.

In Safari-1 — silicon, through exposure to neutrons in the reactor — becomes doped with phosphorous. "We dope 20 tons of silicon a year for international companies," Mr Mulane says.

Pelindaba also offers analytical services to mines, international laboratories and private companies. "If you want to open a mine — looking for asbestos, gold, copper, whatever, you use core sampling (a sample of the material from where the miners expect to mine).

"Neutrons in the reactor can activate the materials (in the soil), especially metals, and they become radioactive, and emit radiation at certain energies," Mr Mulane says.

Safari-1 contains fission reactions — radioactive elements, breaking down into other elements. A fission reaction releases energy and neutrons, and the neutrons cause chain reactions. These chain reactions take place in nanoseconds. Computers predict the reactor’s behaviour because "human reactions couldn’t do it".

Mr Mulane stresses the different safety measures that are in place. Safari-1 is a negative coefficient reactor, he says.

"If the reactor loses its ability to cool, it starts to suffocate in its own heat, and this retards the chain reactions."

Gazing down at the about two-storey-high reactor and casing, white-coated scientists and technicians walk past , each equipped with their own Geiger counter, to measure their radiation exposure. "They are never without it except outside the radiologically controlled areas … like your own personal toothbrush," Mr Mulane says.

The area is also monitored by the International Atomic Energy Agency (IAEA) and the National Nuclear Regulator.

Mr Mulane points to metal boxes on the pillars surrounding the reactor. "We do not interfere with them.

"They are independent (radiation) measures (that get sent) to the IAEA."

But then there is the big question: where does the radioactive waste go?

Mr Mulane points to yellow and red bins situated near the reactor. He says they are for low- level and intermediate waste, such as lab coats and gloves, as well as contaminated machinery. These barrels are buried at Vaalputs, in the Northern Cape.

Vaalputs has low rainfall, low seismic activity and is very sparsely populated — the nearest town is about 100km away, Mr Mulane says.
But the high-level waste has not been disposed of and remains on Necsa property.

"It’s the same at Koeberg," he says. "We’re holding on to the high-level waste because it’s a political issue and there is still value in it, should we decide to reprocess it.

"Globally, scientists are looking at waste options — transmuting (it into a different substance) or recycling: there is still energy in the fuel element. It could be reprocessed or re-used."

But perhaps the most exciting thing happening at Pelindaba at the moment — aside from the nuclear reactions taking place every day — is that scientists have developed a way to de-enrich highly enriched uranium (HEU). HEU is now illegal, since it is this form that is used for nuclear weapons. In fact, any enrichment over 20% is illegal through a recent international agreement.

But Dr Mapula Letsoalo, executive director of NTP Radioisotopes, says the conversion procedure has not come cheaply. "The whole production line (of molybdenum-99) has had to be changed because we’ve converted to LEU (low-enriched uranium). We have used most of the (stockpiles of) HEU, and whatever is left, we’ve converted to LEU," she says.

However, Mr Mulane argues that this gives SA a competitive edge: "It gives us an edge in the market because we use LEU, and we want (and expect to get) preferential treatment."