Just a reminder: The "famous" pebble bed modular reactor was ABANDONED this year [View All]

[jpak]

Pebble Bed Modular Reactor Project Canceled

http://news.softpedia.com/news/Pebble-Bed-Modular-Reactor-Project-Canceled-135840.shtml

For a long time, physicists have said that conventional nuclear power is a lot less safe than a prospective new technology, called pebble-bed nuclear reactor. A proof-of-concept for the new approach should have been constructed in South Africa, but the nation's government announced last week that it would effectively stop funding for this project. The company in charge of building the facilities, Pretoria-based Pebble Bed Modular Reactor (PBMR), is now about to fire about 75 percent of its 800-strong staff, most of which are scientists, physicists and engineers, Nature News reports.

“The resources available to the company will not sustain the current cost structure,” officials at the company announced. The same statement also showed that the new measure was very likely to trigger an exodus of sorts, which would see a large number of nuclear experts leaving the country for more welcoming positions in other countries. However, critics to the new technology say that South African authorities have already funded the project for too long, even if signs showed clearly that no clear outcome would be produced from this effort.

Experts in the African nations began working on this technology in the mid-1990s, when they licensed it from the German Julich Research Center. Authorities hoped that by developing this approach they could transform the country's nuclear energy sector into a lucrative business model that could then be exported in other nations as well. “It caught the mood in South Africa, and the feeling among South Africans was that their technology was as good as anybody's. This was their chance to show the world what they could do,” says University of Greenwich in London energy-policy researcher Steve Thomas.

The PBMR was set up in 1999 by the Johannesburg-based Eskom, which is the country's main electricity producer. The end goal of the research was the development of an economically viable reactor that would use enriched uranium fuel. The thing about the new approach is that the radioactive material would be embedded in graphite sphere called “pebbles,” which are no larger than a tennis ball. The fuel could therefore run at temperatures between 750 and 1,600 degrees Celsius, and also not melt down even if the helium liquid regularly used for cooling was lost. This safety feature persuaded many.

<more>

It's probably a good thing becasue these so-called "meltdown proof" reactors had serious safety issuses (according to US nuclear scientists anyway....)

The Pebble-Bed Modular Reactor (PBMR): Safety Issues

http://www.aps.org/units/fps/newsletters/2001/october/a6oct01.html

<snip>

Conclusion

The greatest amount of experience worldwide with nuclear reactor technology has been with the LWR. Even so, many outstanding technical and safety issues with LWR technology remain unresolved, and new surprises in well-established areas, like metallurgy, continue to arise. The development needed to take a new and unproven technology like the PBMR to a point where one can have confidence in the workability of the design will be substantial. Fundamental issues associated with the relationship between fuel quality control and fuel behavior under normal and accident conditions will have to be resolved, probably through extensive testing. While it is hard to estimate the amount of time and effort that would be required to do a satisfactory job, it is clear that the schedule that has been proposed by Exelon is inadequate for the task.

To get over the high hurdle of public acceptance, new nuclear plants should be clearly safer than existing ones. This is not the case with the PBMR. This problem is compounded by Exelon's desire to reduce safety margins required for current plants. In the aftermath of Chernobyl, the U.S. nuclear industry tried to reassure the public that such an accident could not happen here because U.S. reactors were equipped with robust containments, unlike Chernobyl. This argument will make it more difficult for Exelon to justify its choice of PBMR containment to th

<snip>

....and there was that thingy about another "meltdown proof" pebble bed reactor that had an "oopsie" in Germany in the '80's...

The demise of the pebble bed modular reactor

http://www.thebulletin.org/web-edition/features/the-demise-of-the-pebble-bed-modular-reactor

<snip>

Critical faults in the PBMR design

For some, helium-cooled, graphite-moderated reactors such as the PBMR have always been the ultimate evolution of fission reactor design. The use of helium and graphite allows the reactor to burn the fuel efficiently and to operate at much higher temperatures than conventional light water reactors. It is hoped the temperatures would be high enough to allow for the reactor's heat to be used directly for industrial processes such as hydrogen production and tar sands processing. High temperature reactors can also be designed to use thorium-based fuel as well as uranium and can be developed as fast neutron reactors that don't need moderators.

In Germany, a 15-megawatt-electric prototype PBMR was designed, built, and operated from 1967 to 1988, followed by a 300-megawatt-electric demonstration Thorium High Temperature Reactor, which only operated from 1985 to 1988. A report explaining the delays and problems in the German pebble bed design became public in 2008 when the Jülich Center released a review of its previous pebble bed reactor work.1 It was Jülich's design, specifically the prototype pebble bed reactor, which South Africa had taken as the basis for its PBMR.

The prototype, known as the AVR (Arbeitsgemeinschaft VersuchsReaktor or Research Group Experimental Reactor) had been portrayed to the South African public as an unqualified success. The new Jülich report, however, presented a starkly different picture. In particular, it found that the AVR's fuel had reached dangerously high temperatures during operation. Although the exact temperature reached inside the reactor is unknown, melt strips placed within dummy fuel pebbles, which are designed to withstand heat of up to 1,400 degrees Celsius, melted, meaning the reactor was being operated beyond the design limits for the fuel. The report disagreed with a 1990 Association of German Engineers report on the AVR that stated that high temperatures within the reactor were solely the result of poor-quality fuel. Other factors, as yet unknown, were probably involved, the Jülich report concluded.

According to the South African PBMR joint venture, the maximum fuel operating temperature within the reactor should not exceed 1,130 degrees Celsius.2 If the large temperature variations observed in the AVR are a guide, however, this assumption is far too optimistic, and the PBMR's fuel would fail. The Jülich report found that such fuel failure would contaminate reactor components on an order of magnitude higher than similar contamination in traditional light water reactors, and would thus increase decommissioning costs. The report concludes that irradiated graphite dust created by the rubbing of fuel pebbles within the AVR as they worked themselves through the reactor could become a major safety issue in the case of an accident.

<more>

and pronuclear idiots wanted to build these things without robust containment structures....

idiots

yup!

Bye Bye Famous Pebble Bed Modular Reactor - we hardly knew ya!

:rofl: