Corrosion Concerns at U.S. Nuclear Reactors

In 2002, the plant, Davis-Besse, in Oak Harbor, Ohio, developed leaks in parts on the vessel head, allowing cooling water from inside the vessel, at 2,200 pounds per square inch of pressure, to leak out.

The cooling water contains boric acid, which is used to control the speed of the nuclear reaction, and the acid ate away a chunk of the steel the size of a football, leaving nothing but a thin stainless-steel liner to maintain the reactor’s integrity.

The company assumed it had solved the problem. But recently the new vessel head showed the same leakage pattern. Once again, the parts prone to leaking are nozzles through which the control rods for the reactor pass.

From the New York Times' Green blog.