Blog Archive » Three Mile Island Memories

As someone who lived for a few years right near TMI I dont understand how anyone could think the accident was worse then Chernobyl. I mean the plant is still running today, if you drive by it you wouldn't even know there was ever an accident (except for the towers not producing steam).

On the other hand the top of Chernobyl blew off from steam pressure, and as far as I know the area is littered with abandoned homes.

As a former design engineer in the nuclear business I have to make the following comments;

1) The lessons of TMI are far from forgotten. TMI is one of the most studied accidents and the lessons learned are incorporated throughout engineering and technical training.

2) Anyone who claims TMI was worse than Chernobyl is an idiot. One of the major lessons learned from TMI was that the design basis and safety strategies of western reactors work. This despite the serious operator training and control room design flaws that were exposed by the accident.

3) Anyone who mentions Chernobyl and TMI in the same breath does not know what they are talking about. A few facts about Chernobyl; these RMBK reactors were originally designed to generate plutonium for bombs and then scaled up for electric power generation which created all sorts of operational problems. When I was an undergrad my nuke prof said the design was inherently unstable and an accident was inevitable. The western countries had tried for years to get them to shut them down. On the night of the accident the engineers disabled 4 or 5 safety systems in order to run a turbine spin down test. This test was ordered by Moscow and the previous lead engineer was fired for not completing it prior to the last planned shutdown.

4) TMI experienced a partial core melt. I read an engineering report after the accident that it was technically and economically feasible to fix the damaged reactor. The PR nightmare this would create dictated that it would not be fixed. Chernobyl's core was blown sky high by a steam explosion and fuel rods littered the plant site, thus killing the responding firemen with lethal doses of radiation. There is no dispute regarding which core had more damage.

5) The claim that the containment would have cracked due to "pressure spikes" except that TMI was specially reinforced to protect against aircraft impact is engineering nonsense. First, these are different design requirements and operate on different physical principles. Second, if the accident exposed such a serious deficiency in the design of "normal" containment buildings it would have resulted in the shutdown or at least a reduced operating power at all other plants of similar design. No such regulatory action ever occurred.

6) While it is scary to write about "releasing radioactive gases into the atmosphere" the reality is that such releases are pretty harmless. These gases are typically biologically and physically inert and quickly dissipate in the wind to harmless background radiation levels. One of the major lessons learned from TMI was that the more dangerous biologically active materials like radioactive iodine or potassium do not escape and tend to stick to other material even in a core melt. That is if you have a containment building, unlike Chernobyl.

7) It is insulting to say that the operators did not know what was going on with the reactor "so they guessed" as if they started pushing buttons and pulling levers willy-nilly. The operators knew that the information they were receiving was not complete or wrong. The biggest problem was that their training was flawed and incorporated an assumption that was incorrect -- thus leading them to take actions that made the situation worse.

About the only thing that I agree with Cringely on is that we should be building nuclear reactors now.