Photo of Davis-Besse damage

2,000 words about Davis-Besse

Dave Lochbaum
March 25, 2002

If a picture is worth a thousand words, here are 2,000 words about the near-miss at Davis-Besse.

Photo 1, above, looks straight down at the damage to the reactor vessel head. In the center of the picture is the 4-inch diameter penetration for a control rod drive mechanism. Below that penetration is the large area of damage caused by corrosion/erosion. The reactor vessel head is 6-inches thick. The damage removed all six inches of the carbon steel reactor vessel and left only a 3/16-inch thick stainless steel liner.

Photo 2, below, is a side view sketch of the damage. The NRC is very concerned about the part labeled 'nose' in the sketch. It suggests that the damage may have initiated as undercutting (i.e., from within the metal) rather than boring (i.e., from the outer surface inward). If so, than the visual inspections of the reactor vessel surface may not be sufficient to detect the damage until it has progressed too, too far.

Cross section of reactor head

Dave Lochbaum, Nuclear safety engineer
Union of Concerned Scientists
1707 H Street NW Suite 600
Washington, DC 20006-3962
(202) 223-6133 x113
(202) 223-6162 FAX

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