Slashdot Mirror

← Back to Stories (view on slashdot.org)

Three Mile Island Shuts Down After Pump Failure

Posted by samzenpus on from the a-bit-of-a-problem dept.

SchrodingerZ writes "The nuclear power station on Three Mile Island in Pennsylvania shut down abruptly this afternoon. Its shutdown was caused when one of four coolant pumps for a reactor failed to work. 'The Unit 1 reactor shut off automatically about 2:20 p.m., the plant's owner, Exelon Corporation, reported. There is no danger to the public, but the release of steam in the process created "a loud noise heard by nearby residents," the company said.' If radiation was released into the environment, it is so low that it thus far has not been detected. The plant is a 825-megawatt pressurized water reactor, supplying power to around 800,000 homes, thought there has been no loss of electrical service. Three Mile Island was the site of a partial nuclear meltdown in 1979. The Unit 2 reactor has not been reactivated since."

7 of 247 comments (clear)

  1. And, cue shitstorm.. by Anonymous Coward · · Score: 5, Insightful

    But, to be fair, isn't this how these things are suppose to work? Something fails, everything gracefully shuts down?

    1. Re:And, cue shitstorm.. by fredgiblet · · Score: 5, Insightful

      Yes.

      Not that that's going to stop the shitstorm

    2. Re:And, cue shitstorm.. by Anonymous Coward · · Score: 5, Interesting

      It doesn't sound like a graceful shutdown. We'll have to wait for the NRC event report tomorrow. A reactor cooling pump trip would typically initiate a reactor protection trip (scram). The steam generators would cool the primary by sending steam to the condenser steam dumps. Instead there was a loud noise which indicates that steam was being vented to the atmosphere via the atmospheric steam dumps. This implies that the main steam stops (isolation valves to the turbines) shut. Potential causes for that would be excessive cooldown (an interlock), loss of the condenser vacuum, or a secondary equipment fault. None of these is normal.

      I'm guessing that it was probably an electrical fault. A reactor cooling pump trip and secondary pumps could be powered from the same electrical buses since they are not considered safeguards equipment. The other possibility is that the operators didn't control the cooldown properly, or there was an I&C fault that tripped an interlock for the main steam isolation valves.

      Disclaimer: I'm familiar with Westinghouse PWRs, but not the Babcock & Wilcox PWRs. So take what I say with a grain of salt.

    3. Re:And, cue shitstorm.. by Anonymous Coward · · Score: 5, Interesting

      Oh for fucks sake. There are event classifications if shit goes really wrong. Since they didn't even declare an Unusual Event (lowest of four classifications), things are under control. It appears that there may have been complications during the trip, but there is no emergency. And for your information, if there is an emergency the plant has to declare it within 15 minutes and inform state and local authorities within another 15 minutes. The people who make these decisions are licensed by the NRC and can be held personally responsible. They are also legally protected from any type of retaliation for taking action based on safety concerns. They aren't going to cover it up for three reasons: 1) their families live nearby, 2) the legal ramifications are severe, and 3) they could easily get another job at any other plant in the country (~2000 workers of their level of training in an industry that wants 3000 or 4000).

    4. Re:And, cue shitstorm.. by Anonymous Coward · · Score: 5, Informative

      This is a very accurate reply with one exception. Generally, the condenser can't support the steam output of the steam generators (they're normally rated around 10-25% of full load). Most plants in the US will steam dump to atmosphere because it's easier and doesn't put unnecessary strain on the equipment.

      Plus, dumping to atmosphere has the added benefit is that the whole plant staff knows immediately that they are staying late.

      Source: I am an I&C engineer that has worked on many US and European units.

  2. Add it all up by medcalf · · Score: 5, Insightful

    Embassy attacks. Crap economy. Foreign policy humiliation. Three Mile Island. Am I the only one who didn't like 1979 the first time, and don't want a replay?

    --
    -- Two men say they're Jesus. One of them must be wrong. - Dire Straits
  3. Re:No redundancy by sjames · · Score: 5, Informative

    They ARE there for redundancy. For safety reasons, a reactor must not be operated without adequate redundancy. So, one of the redundant pumps failed and the system shut down in an orderly manner. That is necessary since it takes just a wee bit longer to swap in a cold spare pump than it does for a disk in a RAID.

    It would be technically possible to run the reactor on 3 pumps but safety would be compromised.

    The best way to know a pump will run is to have it running. That's why they keep all 4 running under normal conditions.