When the reactor vessel for the first unit at the Grand Gulf nuclear plant in Mississippi arrived at the site, it had wooden plugs in the main steam nozzles for protection during shipping. There are four holes each more than two feet in diameter through the reactor vessel’s walls that allow steam produce to flow to the turbine. Once installed at the plant, pipes are welded to the main steam lines. The wooden plugs protected the nozzles to keep their metal surfaces in shape for optimum welded connections.
Workers at Grand Gulf used a heavy metal object, commonly called a headache ball, swung by a tall crane to dislodge the wooden plugs. Or at least they tried it. The headache ball missed the plug and dented the side of the reactor vessel.
General Electric, the reactor’s vendor, dispatched an expert from San Jose, California to Mississippi to examine the problem. After evaluating the size and depth of the dent, the expert determined the damage to the reactor vessel did not have to be repaired.
The following year, the Unit 2 reactor vessel at Grand Gulf was dented. Once again, an errant headache ball was the culprit.
The smartest thing to do after dodging a bullet is not to ask that another be fired because you’re on a hot streak and feeling lucky.
The reports on the damaged reactor vessels did not specify whether the same crane operator was used both years or whether an effort was taken to find an operator with sharper aim. In any case, the method that produced bad results the first time was re-used with the same outcome. Perhaps the first failure could be deemed unexpected, but not the second failure.
There are easier, safer ways to remove wooden plugs from reactor vessel nozzles. All they had to do was hang DO NOT REMOVE signs on the plugs. The plugs would have been gone the next morning.
“Fission Stories” is a weekly feature by Dave Lochbaum. For more information on nuclear power safety, see the nuclear safety section of UCS’s website and our interactive map, the Nuclear Power Information Tracker.