Storage needed
Lise Pretorius
Thursday, 10 Nov 2011
SA will next year start the process to build a 9600MW nuclear fleet, which together with Koeberg’s current 1800MW capacity will result in 13,4% of the country’s electricity being supplied by nuclear power by 2030.
It is expected that SA’s nuclear facilities will generate dependable power to consistently meet demand, with hardly any carbon emissions and at a cost of 35c/kWh — substantially cheaper than Eskom’s current 52c/kWh.
But this decision brings to light the contentious issue of what will happen to the nuclear waste that is produced by the power stations.
The current storage solutions for radioactive waste at Koeberg are temporary, and with a new fleet on its way, decisions must be made now about permanent storage. “We cannot go into the construction of a new fleet unless decisions are made on what will eventually happen to the spent fuel ,” says Eskom’s nuclear-power manager Tony Stott.
The 2008 National Radioactive Waste Disposal Institute Act provides for the establishment of a National Radioactive Waste Disposal Institute. However, the institute has yet to be established. The management of SA’s radioactive waste disposal will be one of the institute’s tasks.
The department of energy’s deputy director-general of electricity, nuclear & clean energy Ompi Aphane says the institute will be off the ground early next year, after the board is appointed and a programme of actions drafted.
At present nuclear waste is managed according to its classification of having low, intermediate or high radioactivity. According to Eskom, low-level waste that may be contaminated with small amounts of radioactivity is sealed in metal drums and temporarily stored on site at Koeberg. Intermediate-level waste, which is more radioactive, is mixed with concrete, which is then sealed in concrete drums. Both these waste categories are then shipped to Vaalputs — SA’s storage facility for low and intermediate waste — 500km north of Koeberg. It is buried there for permanent storage. Vaalputs is currently managed by the SA Nuclear Energy Corp (Necsa ), but will be taken over by the new institute.
A more pressing issue for the institute will be the storage of highly radioactive waste, called spent fuel.
According to Eskom it takes 10000 years for the radioactivity of this waste to decay to levels that would have been there if uranium had been left undisturbed in the ground.
For now, spent fuel at Koeberg is stored on site in high density borated steel storage racks in pools. About 70 fuel elements (a collection of tubes that houses the enriched uranium) are replaced each year, producing a spent fuel element that is stored on a rack.
This waste is stored in pools because the water both cools the waste and insulates radiation. Necsa CEO Rob Adam says this “cooling off” phase could last 20-30 years.
However, these measures are temporary. Stott says though there is storage space for “quite a few more years”, depending on how the station is operated, there will not be enough storage space for the remaining life of Koeberg, and certainly not if its life is extended (Koeberg has been operating for 27 years of its 40-year life span).
Necsa also produces nuclear waste at its research facility at Pelindaba in the North West province, though much less than Koeberg .
The spent fuel it produces is first stored in pools, then moved to piped storage where it’s put under pressure into a steel casing within a concrete container.
Pelindaba and Koeberg are the only facilities that are licensed to store spent fuel in SA.
Stott says the department of energy may have to build and licence a new interim storage facility, but SA needs a long-term final facility.
In fact, all over the world the question of permanent storage is being asked. Finland is building a permanent storage facility, and France is in the research phases.
Aphane says it will be the institute’s task to decide on this. There are two options for SA. The first is to reprocess the spent fuel — extracting the energy left in the fuel and leaving about 5% of the original waste, says Adam. The tonnage that has to be stored permanently is therefore a lot less.
This technology is already commercially available in France, and the Russians are also working on it. “We are not there yet in terms of deciding where to cut into the nuclear fuel cycle,” says Aphane. “We will have to confront this issue if we decide to go this route locally.”
The second option is to store the original radioactive waste in deep geological fissures, typically granite and about 100m-200m deep. Potential sites have not yet been identified.
“These are two diametrically opposed approaches,” says Aphane. “One is to try to eliminate the waste substantially to close the cycle, but with the other the volumes don’t matter if you have a place to store it.”
The tenders for SA’s nuclear fleet should be finalised by July next year, says Adam. Each of these new facilities (which should be up and running by 2023 according to Adam) will be licensed with temporary storage facilities such as those at Koeberg.
But decisions about permanent storage must be taken in conjunction with developing nuclear power stations. Stott says it could take up to 20 years to research, develop and construct such a facility.
Financial Mail
10 November 2011