Alternative to pebble bed
The Pebble Bed Modular Reactor (PBMR) project is dead and that is official. South Africa, however, does have another major power card up its sleeve – its unexploited reserves of another fuel source, thorium, which can also consume uranium residues in nuclear power stations.
It hosts large resources of the thorium-LREE mineral monazite and there is renewed interest in this mineral for recovery of both rare earths and thorium. The country also has limited hydrocarbon resources and is looking to develop both renewable energy resources and nuclear energy with thorium being considered as a potential nuclear fuel, according to a report from Avalon Rare Metals Inc. after a rare earths conference in Cape Town in late February.
Thorium was discovered in 1829 by the Swedish chemist Jöns Jakob Berzelius and is the most common of a group of elements called the actinides. It is the 39th most abundant element in the earth’s crust at 7.2 parts per million (ppm).
Significant deposits of thorium are found in Australia, Brazil, Canada, Greenland, India, South Africa and the United States.
Government has decided not to invest any longer in the PBMR project, Public Enterprises Minister Barbara Hogan told the National Assembly on 16 September, according to government’s BUA news service
“Without going into too much detail right now, government, after careful deliberation, analysis and review and mindful of the fiscal constraints in these hard economic times, has had to make a decision to no longer invest in this project,” Minister Hogan said.
The scheme has swallowed up R7.4 billion of taxpayers’ money over the years,
The minister said government had to consider the fact that the PBMR has not been able to secure an anchor customer or another investment partner and that further investment in the project could well be in excess of an additional R30 billion. The project has been missing deadlines constantly, with the construction of the first demonstration model delayed further and further into the future.
Additionally, the opportunity afforded to PBMR to participate in the US Next Generation Nuclear Plant (NGNP) programme as part of the Westinghouse consortium was lost in May when Westinghouse withdrew from the programme.
Should SA embark on a nuclear-build programme in the future it will not be using the PBMR technology, which was still in the research and design phase.
Thorium figures encouraging
The use of thorium has been studied by local scientists and the basic economic costs appear encouraging.
Robbie Louw, a director of Promethium Carbon, a clean-development-mechanism project developer, told Engineering News that thorium may also be a solution to the world’s energy needs, as “we do not have as much uranium as we think we have”.
“If the price of uranium goes up and up, we’ll eventually have a problem in producing nuclear power.” Uranium is used in nuclear power reactors. The radioactive metal has seen a surge in price in recent times, up from $45/lb in January last year, to the current spot price of $85/lb, on the back of a feared supply shortage.
Not claiming his comparison to be an exact science, Louw says it requires 293 tons of natural uranium oxide (mining 800 000 t of ore), to produce one Gigawatt year of electricity. This process produces 39 t of spent fuel.
In contrast to this, it takes less than one ton of natural thorium oxide (mining 200 t of ore) to produce one Gigawatt year of electricity. Spent fuel totals 0,8 t.
Louw does acknowledge that the cost of building and operating a breeding reactor to create uranium (233U) from thorium to a large degree negates the cost benefits of using thorium – dependent again, though, on the spot price of uranium.
It was discovered in 1942 that it is possible to breed uranium from thorium which resulted in several exploratory projects from the mid-1950s through to the mid-1970s when it disappeared off the radar screen – that is, until recently.
India, for example, has decided to include thorium in its proposed large-scale nuclear power expansion, says Louw.
A 2005 International Atomic Energy Association (IAEA) report attributes this to the country’s limited resources of uranium at “very low grades (0,04%), but an easily available and vast source of monazite, containing 8% to 10% of thorium oxide in the beach sands”.
Louw says the report also indicates that thorium is three to four times more abundant on earth than uranium, while producing a lower radioactive waste.
The IAEA report notes that thorium fuels have not yet been introduced commercially as the world’s estimated uranium resources have proved to be sufficient for current needs. However, it adds that there has been growing interest globally to again consider thorium as a potential nuclear fuel.
Louw attributes the historical popularity of uranium over thorium to the by-products of uranium used in producing nuclear weapons.
Despite the seemingly positive cost comparison of thorium to uranium, thorium is of no real use today, which translates into an almost negligible price tag, says Louw.
“There is little use for thorium today. It was once used in welding tools, for example. Now it is just something to get rid of.”
Thorium occurs naturally with heavy minerals in South Africa.
Louw says it is possible to produce a thousand tons of thorium oxide a year from the tailings of current mineral-sands projects in South Africa.
“In this manner, there are large inventories of thorium in the world before we even have to start mining for it.” Louw describes his Steenkampskraal mine, near Vanrhynsdorp, in the Western Cape, “as the richest thorium mine in the world”. For the moment, though, it is lying dormant, awaiting the time when thorium will move into vogue.
“If the thorium price moves up near to where uranium is today, it can become a significant energy resource.”
Louw’s hopes may be enhanced later this month when the International Thorium Energy Organisation is holding a major conference in London from 17 to 20 October.