Tuesday, August 26, 2008

Fears raised over pebble beds

Source: http://www.thetimes.co.za/

A new foreign report casts a further shadow over SA’s troubled nuclear project, but a local research company says there’s no need for alarm. Bobby Jordan reports.

The research centre that invented pebble bed nuclear reactors has rung alarm bells over the safety of the technology — which features prominently in SA’s R350-billion nuclear energy programme.

The safety concerns are contained in a report released this week by the world-renowned state-owned German Jülich Nuclear Research Centre.

Ironically, a team of Jülich researchers is helping SA develop a commercial-size pebble bed reactor based on the prototype that Jülich operated for more than 20 years. If successful, the project could provide much-needed electricity to the local market — and the reactors could be exported worldwide.

Now the latest report, authored by a senior Jülich nuclear safety researcher, casts a further shadow across SA’s beleaguered nuclear project. The report signposts higher-than- anticipated temperatures generated by fuel pebbles used in the prototype reactor (AVR), which was closed in 1988 — but is still the subject of much research.

The chief scientist in charge of exporting Pebble Bed Modular Reactor (PBMR) technology at the Jülich Centre this week denied any crisis of confidence among the nuclear fraternity, and said that although the report was important, it would not undermine confidence in SA’s nuclear energy ambitions. The report has been slated as alarmist by SA’s PBMR company, which is spearheading local research.

PBMR spokesman Tom Ferreira said that although useful, the latest report was “no basis for concern”.

Some of the fears raised in the Jülich report include:

ý The graphite pebbles in the original reactor experiment in Germany generated much more heat than expected, sending temperatures soaring to more than 1450 C — at least 300 degrees hotter than the maximum temperature allowed for in the design of SA’s PBMR;

ý The movement of the pebbles brushing up against one another inside the reactor created a dangerous level of highly radioactive graphite dust — something that was partly unexplained;

ý The risk of graphite fires, like the one at Chernobyl in 1986, cannot be ruled out; and

ý The prototype reactor in Germany is extremely contaminated by metallic fission products, which escaped from fuel elements during operation. The contamination, possibly due to unexpectedly high temperatures, is higher by a factor of more than 10000 than acceptable for modern reactors. This also creates huge decommissioning costs.

The report suggests the SA government may have jumped the gun in pushing for a demonstration PBMR plant at Koeberg, when there is still a need for a prototype pebble bed reactor to understand reasons for high temperatures.

The German report also raises questions about whether senior SA officials have been downplaying safety concerns about pebble bed technology.

Jülich scientists this week confirmed that draft copies of the latest report have been in the possession of SA authorities since December.

So far the pebble bed programme has cost the SA taxpayer about R4-billion, is years behind schedule and is over budget. SA plans to build as many as 30 pebble bed reactors, which collectively would represent about 20% of Eskom’s potential R350-billion nuclear building programme of about 20000 MW. The country’s current mainly coalfired power supply is 39000 MW.

Ferreira said the report was not a consensus position for the Jülich centre. He said many of the points raised in the report were disputed by other scientists.

Tony Stott, Eskom senior manager of Nuclear Stakeholder Management, said: “Eskom is aware of the report and its findings. Eskom has requested independent nuclear consultants, who are assisting Eskom with the safety evaluation of the PBMR Demonstration Power Plant technology, to investigate and establish the basis of the report and determine whether any aspects warrant introduction into the safety evaluation of the technology.”

He said the safety analysis process was still under way.

Source: http://www.thetimes.co.za/


Paaristha said...


Could you please date this article.

Paaristha Oomadath

Emmett Walker said...

Nuclear power is strong and dangerous too.We should be careful to use this power.

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