PBMR (Pty) Ltd. has taken one more step in its careful journey to build a new type of nuclear power plant – one whose heat will be produced in a continuously refreshed bed of high temperature spheres made of heavy metal and graphite.
On August 22, 2008, the company announced that it had signed a contract for engineering, procurement, project and construction management (EPCM) services to build a 165 MWe commercial scale, emission free, demonstration plant near Cape Town, South Africa. The approximate value of the contract is a quarter of a billion US dollars.
The contract, awarded to joint venture between the Canadian firm SNC-Lavalin Group and the South African firm Murray & Roberts, includes not only the power module, but also a commercial scale fuel manufacturing plant that will produce the 6 cm diameter fuel elements the plant needs.
This contract covers Phase II of a project that has seen its share of successes and challenges.
The pre-development stages of this project date back to the late 1980s when some members of Eskom, South Africa’s main electric power utility, recognized that the company’s existing infrastructure of large coal plants located near highly productive fields was not a model that could be expanded. Those visionaries saw a rapidly growing demand for electric power as the majority population gained entry into the type of lifestyle that had been forcefully denied under apartheid.
A small number of people were aware that Germany had decided to abandon a very promising technology for building small, modular nuclear plants that had proven that they could withstand a complete loss of cooling without causing any damage to the plant. The technology had been successfully demonstrated for more than 20 years at Julich with the AVR.
Unfortunately, strong anti-nuclear movements seized on the events at Chernobyl in 1986 to push the government to deny long term operating permission to the Thorium High Temperature Reactor (THTR), a commercial scale follow on to the AVR. Those same pressures caused Siemens / Interatom to abandon plans to build a series of modular units.
From a marketing point of view in the late 1980s, the pebble bed designs had a glaring challenge; they used graphite as a moderator. At the time, the world had been convinced, through massive repetition of a quarter truth, that it was best to avoid using graphite in a nuclear reactor. The half truth was a lesson learned from Chernobyl, but the other 3/4 of the truth was that it is best to avoid using graphite in a water cooled reactor that is put into an unstable operating condition by operators who feel pressured to complete a poorly designed test.
Darn – it is hard to avoid digressing on this topic. The history is long and fascinating. Bottom line is that Eskom took advantage of Germany’s decision to abandon pebble beds to buy information about the technology for a very good price.
Back to today – the PBMR is very different from a conventional light water reactor. Its fuel design is in use in only one prototype reactor operating in China – the 10 MWth HTR-10 at Tsinghua University. The pebble plants use an inert gas to move the reactor heat to machinery that can convert heat into motion and then into electricity.
In the case of the PBMR, the hot gas will turn turbines that look a lot like combustion gas turbines without exhaust stacks while in the HTR-10 the hot gas circulates through a smoke stack free boiler to produce high quality steam. The Chinese operators of the HTR-10 have been pleased enough with its performance to move forward into commercial scale production.
The current idea for the PBMR modules is that they can be built either individually or in packs. Distributed plants can power concentrations of people – 165 MW is enough for a moderately sized city of well over 100,000 people. To gain economies of scale, PBMR (Pty) Ltd. envisions the modules being grouped in packs of 8 or more to produce as much power on a single site – with a single infrastructure investment and a flexible work force – as a large, more conventional light water reactor.
The economics for the system begin to look really attractive once production volumes exceed 24 modules. Moderate volume series production is a concept that is a bit unfamiliar to people in the conventional nuclear industry, but it is well understood by manufacturers of other large, complex equipment like locomotives, ships, and commercial aircraft.
South Africa, despite some focused opposition from a small group of detractors at Earthlife, has continued to invest in the PBMR project because it makes sense. South Africa desperately needs reliable electrical power to keep lifting the living standards of its population and the PBMR offers a flexible, new way to meet that need. When people realize that the only real alternative to coal – which currently produces 95% of the electricity in South Africa – is nuclear power, they begin to realize that the detractors may be wrong.
Photo credit and disclosure – The pebble in the photo is a personal souvenir that I obtained during a visit to General Atomics in 1994. I have been a fan of high temperature reactors since 1991 and founded Adams Atomic Engines, Inc. in 1993 to explore ways to take advantage of the technology.
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