Jaderná energie na jihu Afriky

South Africa has two nuclear reactors generating 6% of its electricity.

• Its first commercial nuclear power reactor began operating in 1984.
• Government commitment to the future of nuclear energy is strong.
• Budget funding for the construction of a demonstration Pebble Bed Modular Reactor was given in 2004.
• Electricity consumption in South Africa has been growing rapidly since 1980 and the country is part of the Southern African Power Pool (SAPP), with extensive interconnections. A 400 MW power line serves Namibia. Total generating capacity in the region is 49.8 GWe, of which 41.3 GWe is South African, mostly coal-fired, and largely under the control of the state utility Eskom. Over 200 billion kWh is sent out each year, 87% from coal-fired plants and 6% from nuclear.

Eskom supplies about 95% of South Africa's electricity and more than 60% of Africa's. By 2008 regional electricity demand is expected to exceed supply capacity, and SA power exports are already being curtailed.

South Africa's main coal reserves are in the north-east, while much of the load is on the coast near Cape Town and Durban. Moving either coal or electricity long distance is inefficient, so it was decided in the mid 1970s to build some 2000 MWe of nuclear capacity at Koeberg near Cape Town.

The Koeberg plant was built by Framatome and commissioned in 1984-85. It is owned and operated by Eskom and has twin 900 MWe reactors the same as those providing most of France's electricity.

While there had been no intention to build further power stations of this type, the government announced early in 2006 that it was considering building a further conventional reactor, possibly at Koeberg, to boost supplies in the Cape province.

In February 2007 it was announced that further conventional plants would be built in the Western Cape province, with the first - of about 1 GWe - being on line by 2014 and probably using French or Westinghouse technology.

The Nuclear Energy Corporation of South Africa (Necsa) expects nuclear capacity to increase to about 27 GWe, supplying 30% of electricity, by 2030, including 12 new large PWR units and an initial set of 24 PBMRs.

PBMR

Since 1993 Eskom in collaboration with others has been developing the Pebble Bed Modular Reactor (PBMR) and is ready to build the lead unit of this design.

The PBMR draws on well-proven German expertise and aims for a step change in safety, economics and proliferation resistance. Production units will be 165 MWe and will have a direct-cycle gas turbine generator and thermal efficiency of about 41%. Some 450,000 fuel pebbles recycle through the reactor continuously (about six times each) until they are expended, giving an average enrichment in the fuel load of 4-5% and average burn-up of 80 GWday/t U (eventual target burn-ups are 200 GWd/t). The pressure vessel is lined with graphite and there is a central column of graphite as reflector. Control rods are in the side reflectors and cold shutdown units in the centre column. Performance includes great flexibility in loads (40-100%), with rapid change in power settings. Each unit will finally discharge about 19 tonnes/yr of spent pebbles to ventilated on-site storage bins.

Construction cost (when in clusters of eight units) is expected to be modest and generating cost competitive.

In 2003 environmental approval was given for construction of the demonstration PBMR unit at Koeberg and the fuel plant at Pelindaba near Pretoria. In October 2004 the South African government budgeted to allow development of the first PBMR to proceed. This was seen as conditional approval for the demonstration unit at Koeberg.

The Brayton cycle turbine design has been simplified from 3-shaft vertical to single shaft horizontal configuration.

This change plus a successful procedural appeal on the environmental clearance resulted in the Department of Environment Affairs recommending a new environmental assessment, which was commenced in August 2005 and remains unfinished.

PMBR Ltd has been seeking a further international equity partner in the venture. After the demonstration pilot plant is in operation, the South African government has said that it wants to order 24 or more units totalling at least 4000 MWe. One quarter of South Africa's electricity is envisaged from PBMRs.

A shareholders' agreement for the PBMR project was struck in 2005 among Eskom (41%), the South African Industrial Development Corporation (14%), the SA government (30%) and the US company Westinghouse (15%), now owned largely by Toshiba. These shares were expected to move to 5%, 15%, 30% and 4% respectively by 2012, with 46% being held by another investor. However in August 2006 the agreement expired due to a delay in a licensing issue, and PBMR Ltd reverted 100% to Eskom. A new agreement is envisaged and Pebble Bed Modular Reactor (Pty) Ltd's current investors are the South African government, the Industrial Development Corporation (IDC), Eskom and Westinghouse..

In April 2005 the PBMR company awarded a US$ 20 million contract to Uhde, a local subsidiary of Germany's Thyssenkrupp Engineering, to build a plant at Pelindaba near Pretoria to manufacture the fuel pebbles for the planned demonstration PBMR. The fuel plant is expected to be completed by 2010.

In the USA, the company is planning to submit a design certification application for the reactor in 2008, and to bid for a nuclear-powered thermochemical hydrogen production plant at the Idaho National Laboratory.

Uranium mining

Uranium production in South Africa has generally been a by-product of gold or copper mining. In 1951 a company was formed to exploit the uranium-rich slurries from gold mining and in 1967 this function was taken over by Nuclear Fuels Corporation of South Africa (Nufcor), which in 1998 became a subsidiary of AngloGold Ltd. It produces over 1000 tonnes U₃O₈ per year from uranium slurries trucked in from various gold mines and Palabora copper mine.

In 2006 SXR Uranium One obtained its mining right for the Dominion project, with construction then 80% complete. Dominion started production early in 2007 and will increase to 1730 t/yr by 2011. Production cost is expected to be US$ 14.50/lb U₃O₈. The first sales contract for 680 tonnes was announced in November 2006. The new order mining right incorporates black empowerment targets for employment.

Dominion has indicated resources of 29,500 tonnes U₃O₈ at 0.081% and inferred resources of 83,000 tonnes U₃O₈ at 0.038%.

In February 2007 UraMin increased its stake in the Ryst Kuil uranium project in the central Karoo Basin to 74%. Some 22,000 tonnes U₃O₈ resources are estimated.

Fuel cycle, R&D

Originally fuel for Koeberg was imported, but at the height of sanctions the Atomic Energy Corporation (AEC) was asked to set up and operate conversion, enrichment and fuel manufacturing services for Koeberg. These have now been closed down. Enrichment was undertaken at Valindaba, 60 km north of Johannesburg, by a unique aerodynamic Helikon vortex tube process developed in South Africa. Since this was not economic both centrifuge and molecular laser isotope processes were being explored when operations ceased. The semi commercial plant was of 300,000 SWU/yr capacity.

The AEC became the Nuclear Energy Corporation of South Africa (Necsa), which was established as a public company under the Nuclear Energy Act, 1999 and is wholly-owned by the State. Its main functions are to undertake and promote research and development in the field of nuclear energy and radiation sciences and technology, and to process source material, special nuclear material and restricted material. Apart from its main operations at Pelindaba, Necsa is also responsible for radioactive wastes.

Eskom now procures conversion, enrichment and fuel fabrication services on world markets.

Since 1965 the AEC/Necsa has operated a 20 MW tank-type research reactor - Safari-1 - at the Pelindaba nuclear research centre. Since 1981 it used 45% enriched fuel elements manufactured locally from locally-enriched uranium, though the pilot enrichment plant producing this closed in 1990.

Radioactive Waste Management

Necsa operates the national repository for low and intermediate-level wastes at Vaalputs in the Northern Cape Province. This was commissioned in 1986 for wastes from Koeberg and is financed by fees paid by Eskom.

Some low and intermediate-level waste from hospitals, industry and Necsa itself is disposed of at Necsa's Pelindaba site.

Spent fuel is stored at Koeberg.

Decommissioning of two uranium enrichment plants was undertaken by Necsa and financed from state grants.

ZDROJ:http://www.uic.com.au