Yesterday, regional anti-nuclear organizations asked federal nuclear energy regulators to launch an investigation into what it claims are “newly identified flaws” in Westinghouse’s advanced reactor design, the AP1000. During a teleconference releasing a report on the subject, participants urged the Nuclear Regulatory Commission to suspend license reviews of proposed AP1000 reactors.
In its news release, even the groups making these allegations provide conflicting information on its findings. In one instance, the groups cite “dozens of corrosion holes” at reactor vessels and in another says that eight holes have been documented. In all cases, there is another containment mechanism that would provide a barrier to radiation release.
Below, we examine why these claims are unwarranted and why the AP1000 design certification process should continue as designated by the NRC.
In the AP1000 reactor design, the
Compared to the example cited in the report, the AP1000 containment vessel is more accessible for inspection and makes use of thicker, corrosion-resistant steel. NRC requirements for inspection and maintenance, as well as operational testing, would preclude an undetected corrosion of steel used in the reactor containment structure.
The report alleges that the
Furthermore, the AP1000 containment vessel is made of high-quality, 1.75” thick steel. Water corrosion as specified in the critics’ report would require rates that simply are not credible. Operational testing and inspection would reveal any flaw, especially those significant enough that could lead to a hole of the hypothetical size stated.
Finally, the containment vessel itself is built to American Society of Mechanical Engineers codes that have more than 100 years of proven safety margin protection to the public.
For a copy of Arnold Gundersen's statement and visuals used in the report, see http://fairewinds.com/reports
For more on the AP1000’s safety features, click here.
NEI Rapid Response
Picture of the AP1000’s containment vessel bottom head at China’s Sanmen nuclear station. Courtesy of the
After taking a closer look at the critics' report and materials, there are quite a few bits of data and claims that don't all jibe with each other. The NRC study Gunderson's report cites (pdf) says that there "have been at least 66 separate occurrences of degradation in operating containments." NIRS' press release claims 77 and Gunderson's press conference statement says more than 80 (p. 1). Talk about a counting mess. So what's the real number? Here's the NRC doc from above:
"Since 1986 [to 2000], there have been over 32 reported occurrences of corrosion of steel containments or liners of reinforced concrete containments" (p. 5).
The other 34 containment degradation occurrences were "related to the reinforced concrete or post-tensioning systems," (p. 6) which had nothing to do with corrosion. Thus, less than half of the examples the critics cite aren't directly related to the AP1000 issue they think they've discovered.
As well, while the anti's claim that there are 77 instances of degradation, according to the NRC pdf from above, just "one-fourth of all containments have experienced corrosion" (p. 5).
The critics claim that this is an AP1000 issue but corrosion is an issue that all designs have to address. One of the ways the AP1000 design addresses corrosion penetration is its 1.75 inch thick steel plate containment liner (as mentioned above). The existing nuclear plants have steel plates that are less than half of the thickness of the AP1000 and only a handful of those had corrosion problems that penetrated containment (all were promptly addressed once discovered, page 5 from NRC). As well, the Beaver Valley containment which Gunderson constantly references corroded 3/8" of a hole. Yet, his analysis gives little credit to the difference in steel thicknesses between designs. Well, we've noted above that the critics' numbers are all mixed up, guess it makes sense that this difference is mis-understood too.