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Three Mile Island Memories

Posted by Soulskill on from the if-it-ain't-broke,-send-it-through-congress dept.

theodp writes "Thirty years after the partial nuclear core meltdown at Three Mile Island, Robert Cringely describes the terrible TMI user interface, blaming a confluence of bad design decisions — some made by Congress — for making the accident vastly worse. While computers could be used to monitor the reactor, US law prohibited using computers to directly control nuclear power plants — men would do that. So, when the (one) computer noticed a problem, it would set off audible and visual alarms, and send a problem description to a line printer. Simple, except the computer noticed 700 things wrong in the first few minutes of the TMI accident, causing the one audible alarm to ring continuously until it was shut off as useless. The one visual alarm blinked for days, indicating nothing useful. And the print queue was quickly flooded with 700 error reports followed by thousands of updates and corrections, making it almost instantly hours behind. The operators had to guess at what the problem was."

1 of 309 comments (clear)

  1. Re:Job's got it right.... by amori · · Score: 5, Informative

    TMI wasn't caused by a computer failure but the accident was made vastly worse by an error of computer design. Specifically, TMI-2 had a terrible user interface.

    See, See. UI is important!!!!

    I'm a nuclear engineer and I think the use of the term UI for the control room is somewhat 'simplistic'. I personally think a major issue was over design in a certain area (redundant alarms), and lack of safety systems that would prevent the core from melting even with a LOCA in place. It was two hours after the shutdown when the fuel melting began at TMI-2. This was a scenario where the operators couldn't understand what was happening. Now from an operator's perspective (who sits in the operator room) you're not looking at a "UI" in the traditional CS sense. Here is an image of a control room: http://www.ornl.gov/info/ornlreview/v38_1_05/images/a11_controls_full.jpg The events leading up to the disaster started on the secondary side (non-core) leading to a LOCA (Loss of Coolant Accident). For those unfamiliar with the term "secondary side". The secondary side of a Nuclear Power Plant is similar to that of any power generating plant, meaning the secondary side does not contain the reactor core.