Recent reports show hidden risks of catastrophic failure at dozens of nuclear power-plants, world wide. Those include the Millstone plant in Waterford, CT. They arise from previously unreported manufacturing defects and potential defects in large mechanical components produced at Creusot Forge in France. That manufacturer–soon to be controlled by Électricité de France (EDF), the French power utility–has been in operation since the eighteenth century.
A foundry at Le Creusot, in the highlands of central France, opened in 1782 to make cannons for the kings of France. It has produced steel forgings since 1876. As of 2010, it had the third-largest forging equipment in Europe, featuring a 17 million pound-force press, built in 1956, and a 25 million pound-force press, built in 2008. Its heaviest press can produce thick-wall metal cylinders up to 19 ft in diameter.
Areva–the French nuclear conglomerate once known as Framatome and soon to join with EDF–bought the Creusot factory in 2006 from the Schneider enterprises, its operators since 1835. Areva and predecessors have employed the factory since the 1950s to design and produce large mechanical components of nuclear power-plants: reactor vessels, steam generator shells and pressurizer shells.
Creusot Forge has supplied hundreds of large components for many industrial plants now operating in Europe, Asia, the United States, South America and Africa. Faulty components went to three European Pressurized Reactor (EPR) nuclear units that are under construction in Flamanville, France, and in Taishan, China. Others were produced for two EPR units proposed at Hinkley Point in the UK. Faulty components have already been installed in France and China.
Nature of defects: Yves Marignac of World Information Service on Energy in Paris has supplied a detailed description of the EPR defects. They affect the heads and bottom caps of reactor vessels. Such a vessel is made from large forged parts: a “head,” a cylinder segment with ports for cooling water, two plain cylinder segments and a bottom cap. The last four are welded together, and the head is bolted on top.
Heads and bottom caps have been reported to have major defects caused by improper forging performed at the Creusot Forge factory. According to Mr. Marignac, portions of those thick metal parts have too much carbon in the steel, tending to make them less resistant to thermal shock than they need to be. In the event of a rapid cooldown to recover from an equipment problem, they would be prone to rupture, leading to catastrophic failure.
According to Mr. Marignac, the forging problem leading to “carbon segregation” is an issue known in industry that can be controlled by manufacturing techniques. When Creusot Forge made the EPR parts, starting in 2006, one of each type was supposed to be tested for the “carbon segregation” issue. That requires drilling into a part, extracting solid samples and analyzing them–destroying the part. However, the run of EPR parts, six of each type, was completed without such testing.
Eventually the French nuclear regulatory agency required testing, performed in the fall of 2014. Test failures were soon found. However, by that time three EPR reactor vessels had been completed. They had been delivered to one reactor under construction in Flamanville, France and two under construction in Taishan, China. There they had been installed and connected to other equipment. Reactor vessels and possibly other major components at those sites may have to be removed and scrapped, causing long delays and huge added costs. The Flamanville project is already many years behind schedule, and it has suffered at least a factor of three cost overrun.
Hidden defects: After learning about the defects in EPR reactor vessels, the French nuclear regulatory agency required an audit of nuclear-part manufacturing performed at the Creusot Forge factory. That uncovered potential defects in more than 400 large parts, going back to 1965. The agency has suspended the operating license for one French nuclear-power unit (Fessenheim Unit 2), found to have a defective part. At least 18 French nuclear-power units are being investigated for defects.
Based on the audit in France, at least 17 U.S. nuclear-power units are at risk from potentially defective parts made at the Creusot Forge factory. For example, Millstone Unit 2 in Waterford, CT, has a potentially defective replacement pressurizer. Some units have more than one potential defect. Kerri Kavanagh, a division head at the U.S. Nuclear Regulatory Commission, released a statement last June, committing to “appropriate regulatory and enforcement action if we find issues of safety significance.”
– Craig Bolon, Brookline, MA, September 3, 2016
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