New Reactor Is Rust-Prone

http://green.blogs.nytimes.com/2010/06/28/is-a-new-reactor-rust-prone/

June 28, 2010, 1:55 pm
Is a New Reactor Rust-Prone?
By MATTHEW L. WALD
An expert warns that an air pathway in a new reactor design could open the way for the release of radioactive materials.



<snip>

Also under attack is a thick metal shell inside that shield building that critics say might not withstand an accident.

The theory behind separating the shell from the surrounding wall is to avoid a problem in existing reactors, which use a strong concrete building with a metal liner. In case of a serious accident, some argue, that combination of concrete and steel could become a thermos bottle, allowing heat to build up. In the AP 1000 design, the metal is not a liner but an entire separate shell, with a concrete building surrounding it and an air gap in between.

In the event of an accident, the thinking goes, heat flows through the shell and out into the environment rather than getting bottled up and letting the building’s interior get dangerously hot.

But a nuclear engineer, Arnie Gundersen, told a commission committee last week that keeping the metal and the concrete together presents an advantage: essentially, it would be harder for a flaw to appear in both and create a leak. If they are separated, he argued, rust could attack the metal shell in a place that is hard to inspect. What is more, creating a pathway between the metal and concrete that works like a chimney could allow for the release of radioactive materials.

<snip>

The Nuclear Regulatory Commission’s Advisory Committee on Reactor Safeguards, a panel of about a dozen senior experts drawn mostly from academia, gave Mr. Gundersen an hour and fifteen minutes on Friday to make his case, a long period. He outlined rust problems and other containment problems at existing reactors, including Beaver Valley near Shippingport, Pa., Salem in southern New Jersey, and DC Cook in Michigan, on Lake Michigan’s eastern shore.

<snip>

Are there any failures in thicker metal, the committee wanted to know? On Monday morning, Mr. Gundersen dredged one up, at the FitzPatrick reactor in upstate New York. While the geometry of the FitzPatrick plant is very different from the design of the AP 1000, a thick metal part rusted through. The Union of Concerned Scientists explained the problem in 2005.

<snip>