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Mike Gray on: The Inevitability of an Accident
Mike Gray Q: Was it unusual for something to go wrong in these monster plants?

MG: The one thing that the incident at Three Mile Island proved is that Murphy's Law is as immutable as the laws of Einstein. If anything can go wrong, it will. And in designing these enormous plants without any sort of slow progression of working their way up through smaller versions of this thing, they had created the potential for disaster without realizing it, because there were many things at work inside this plant that it turns out they had little understanding of.

Q: Was Three Mile Island an accident that was expected to happen?

MG: Absolutely not. All of the people at the top of the Nuclear Regulatory Commission were stupefied by this accident. This was exactly what they had thought that they had prevented. They had designed these safety procedures and they had -- the plants had been designed to save themselves. And that's true. And it would have worked. If the operators had not intervened in that accident at Three Mile Island and shut off the pumps, the plant would have saved itself. They had thought of absolutely everything except what would happen if the operators intervened in anyway. That was the one thing they hadn't taken into consideration, that what would happen to a human being sitting at that console at four o'clock in the morning if all of a sudden 90 alarms went off around the room and the gauges were behaving in exactly the opposite direction of everything they'd ever been taught. Are the operators now supposed to sit on their hands and wait and see what's gonna happen? Of course they're not gonna do this. We know this is not human nature. But engineers think in terms of making the machine perfect, and they had perfected the machines' safety mechanisms so that if something like this happened, the machine would take care of itself. But, they had not figured on taking care of the operators and their sanity in such a moment.

Q: It wasn't only human failure. It was the valve.

MG: Yes. Well, that valve was improperly designed. The valve on top of the pressurizer, which was the chief element that failed in this accident, is like a drawer that's too wide. You know how you pull on a drawer and, if it's wider than it is deep, it kind of -- well, that valve had been designed that way. That was a mistake, an engineering error. So that instead of sliding freely, it had a tendency to twist. So it failed, and it failed in the open position and they didn't know it. They didn't realize that it had failed in the open position because the instruments on the control panel told them that it was closed. It turns out that instrument was improperly designed because it didn't tell you whether the valve was closed. All it told you was that the valve switch had been closed. So the valve was supposed to be closed, but there was no way for those operators down there in the control room to know that it wasn't.

Q: That was not the first time that had happened.

MG: No. The accident at Three Mile Island had occurred some months earlier at a plant outside Toledo. Davis Bessie was the plant. And they had a real heart thumper that was an exact precursor of what happened at Three Mile Island. There was an inspector in Chicago who, in going over the records, realized that these operators in Toledo had taken exactly the wrong action in response to what was called a "loss of coolant" accident. In other words, the cooling liquid inside the reactor -- that you lose some of it somehow and they didn't know how they'd lost it. It turns out how they lost it was from this little valve there which had jammed just like it would jam a few months later in Three Mile Island. But, they managed in Toledo -- somebody there happened to notice something on one of the gauges that told him that that valve might be open. And just on a hunch, he closed the block valve, which is in the line below that valve, sealed it off and saved the plant. Now that warning from Toledo, if it had gone out to all the rest of the similar nuclear power plants, the accident at Three Mile Island would not have happened and that plant would have remained an anonymous sand bar in the middle of the Susquehanah. We would never have known about that plant, that would have been it because the operators at Three Mile Island would have benefitted from this experience and they would have closed this block valve and that would have saved the day.

Unfortunately, in the nuclear power industry at that time, there was a tremendous amount of fear that public hostility to nuclear power was gaining the upper hand. There were a lot of protests about nuclear power. People were beginning to question the fundamental concept and so forth. As a consequence, the nuclear power industry evolved, over the years, a siege mentality. So instead of describing this accident at Toledo as an accident, they described it as an "unplanned event," which it certainly was. But, they described it in such obscure language that even the other operators of identical plants, for example, the one at Three Mile Island, were not able to read this report and get anything out of it. So it not only effectively concealed from the public and the press that this very dangerous accident had occurred in Toledo, it concealed this knowledge from the other operators of identical plants around the country. And as a consequence, that night in March of 1979, when the valve stuck on top of the pressurizer again, the operators at Three Mile Island had no knowledge of the situation in Toledo, and they went through exactly the same sequence of mistakes. Unfortunately, there was nobody there to notice the essential instrument that was caught in Toledo. As a consequence, we had the closest brush with nuclear disaster we have ever had in the continental United States.

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