The two spent-fuel pools at Eskom’s 1 800 MW Koeberg nuclear power station, in the Western Cape, will be full by 2018, increasing the urgency on the State-owned utility to begin pursuing alternative storage options.
Koeberg has, over the past 32 years, accumulated a total of 2 229 spent-fuel assemblies, which are currently all stored on site. A total of 1 065 used-fuel assemblies are currently stored in the Unit 1 spent-fuel pool, while 1 052 reside in the Unit 2 pool. In addition, 112 assemblies have been transferred into dry storage casks, which are also kept on site.
The pools each measure 1 326 m3, with a length of 12.6 m, a width of 8.5 m and a depth of 2.4 m and each pool has the capacity to hold 1 150 spent-fuel assemblies.
Depending on refuelling requirements, Eskom adds about 56 fuel assemblies every 18 months, which means the pools will reach their storage limits in 2018.
Group executive for generation Matshela Koko tells Engineering News Online that Koeberg is currently pursuing a project of moving the used nuclear fuel from the spent-fuel pools into dry storage casks, which will be stored on the Koeberg site for an interim period.
It is envisaged that the used fuel will be moved in phases from 2017 to 2025, with complete fuel assemblies loaded into the casks. In other words, a fuel assembly would be moved, under water, from the spent-fuel pools into a dry storage cask, following established protocols. The cask would then be transferred from the fuel building to a storage location.
The first cycle of casks is to be delivered to the Koeberg site from October 2017 onwards, with the loading of used fuel into the casks to follow soon after the delivery. The process will be preceded by a National Nuclear Regulator (NNR) licensing process.
Koko reports that the contract for the first cycle of casks has been awarded to Holtec, of the US, which has been contracted to design, supply and deliver casks, as well as provide licensing support for the casks. “As part of a localisation drive, Holtec will train local skills to conduct the fuel loading, or casking activities. The procurement of further cycles of casks will be done through a competitive tender process.”
The first cycle of casks will be stored in an existing ‘Cask Storage Building’, but Eskom was also making preparations for a so-called Transient Interim Storage Facility (TISF), to be built on vacant land within the Koeberg site.
The facility will comprise a concrete pad covering an area of approximately 12 800 m2, onto which up to 160 dry storage casks can be placed, and an auxiliary building to store associated equipment.
Koko insists that the TISF will meet the requirements of the NNR and will be built and managed according to International Atomic Energy Agency (IAEA) safety standards. “The concept design is currently in progress and according to the current schedule, the TISF will be established by 2019,” he added, noting that the capital costs will only be confirmed on completion of the procurement process.
Construction of the TISF will commence in 2018, and will take about 12 months to complete.
Besides the work under way on the TISF, there are also plans for a Centralised Interim Storage Facility (CISF), which is proposed for establishment by the National Radioactive Waste Disposal Institute (NRWDI) by 2025.
Vaalputs, in the Northern Cape, is currently considered to the mostly likely location for the CISF, owing to the fact that there is already infrastructure in place for the storage of low and intermediate level waste. However, the NRWDI has not yet become operational and any co-location of the CISF at the site would still require approval.
“It is anticipated that the CISF will be established by 2025; however the option remains to increase the temporary on-site storage capacity for used fuel at Koeberg almost indefinitely. Hence, there is a high level of confidence in the measures undertaken for management of used fuel now and into the future,” Koko says.
However, with Eskom looking to extend the life of Koeberg to 60 years and with South Africa considering the development of a further 9 600 MW of new nuclear capacity more will need to be done to clarify the country’s approach to the management and disposal of spent fuel.
At this stage, South Africa’s preferred route would be deep geological repository disposal, but there is not such capacity in place. At present Vaalputs is licensed only for the storage of low- and intermediate-level waste and high-level waste will only be disposed of at Vaalputs if approved for that purpose.
“Reprocessing and recycling remains an alternative option to direct disposal, and can be undertaken at a later date, dependent on economic feasibility,” Koko concludes.