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Reactor Shutdown Darkens South Florida
grassy_knoll asks, "So how fragile is the electrical grid, and just what technical problems could shut down five reactors?" "Five reactors at a nuclear power plant in Florida had gone down on Tuesday and two were now back online amid a massive power outage in the southern state, CNN reported. The report on the Turkey Point nuclear plant came as four million people had lost electricity in Miami and elsewhere in Florida, with traffic signals out and major delays on roads, authorities and media said."
Here is FPL's page on the Turkey Point reactor: About Turkey Point. Their site also has a News Releases page, which I'll be watching for updates whenever they get their PR department in gear.
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Uh.. Turkey Point has *2* reactors and 3 major fossil fuel generators (As well as several generators under 5 MWs).
The power outage -- ie, some serious switch failures -- triggered the reactor shutdown. Nuclear reactors are great at supplying base load power but if all of a sudden the grid goes offline, they have nowhere to send that power and have to shut themselves down. (Power reactors don't do well with highly dynamic loads.)
It was not, as some posters seem to have misread even the summary, that the reactors went down first and caused the outage. Mind, once the reactors are down it takes longer to bring the whole grid back up, so in that sense it's contributory.
-- Alastair
I agree, using the word nuclear in this article was not necessary. The only 'story' about the nuclear plant is the safety system activated, disconnected them from the grid, and scrammed the reactor (shut it down), which just results in less electricity to go around when the grid reconnected. Nuclear reactors take a while to start up, and some models get poisoned quickly if they are shut down and can't be restarted for several days.
It was due to a distribution line that failed. For those not familiar with how nuclear reactors work, two of the fission products of concern are I-135 and Xe-135. I-135 will decay into Xe-135 and Xe-135 is a very strong neutron poison (absorbs neutrons). During normal operations Xe-135 is produced from fission or I-135 decay and it is removed by neutron absorption of Xe-135 or by beta decay of Xe-135. If you are operating at high power and have a significant amount of Xe-135 in the core and you suddenly drop power the neutron flux that is removing a significant fraction of your Xe-135 from neutron absorption is gone. But the I-135 in the core still remains and more than compensate the reduction of Xe-135 from direct fission. The result is a Xe-135 spike that will overwhelm certain types of reactors forcing a shutdown and a waiting period for the Xe-135 to decay. For those familiar with the Chernobyl disaster, the reason that the control rods in that core were fully withdrawn was because they were trying to compensate for a xenon transient (since they were operating at high power before they dropped to low power for the test). The Turkey Point reactors don't suffer from the flaws that the RBMKs had, but they will still be shutdown due to xenon transients.
More information Here (pg 34) and here
The fundamental thing that is missing is the amount of power being generated.
You have to cool the steam down somehow, normally it looses energy by turning the generators but if that is not the case the energy needs to go somewhere.
The steam is normally re-condensed and then reused in a closed or semi closed loop depending on whether there are cooling towers. There is no way that the
cooling capacity would be able to dissipate the full load and hence the need to rapidly shut-down. This is the same for coal and gas plants as well.
First off, There are not 5 nuclear reactors at turkey point. there are 5 units. units 1 and 2 are oil and natural gas(fossil) units 3 and 4 are nuclear and unit 5 is a gas turbine unit. The shutdown of the reactors DID NOT cause the blackout contrary to what the slashdot summary says. A failed switch and fire at an electrical substation outside Miami(read: not at the power plant) caused the grid to go into an imbalanced state at which time the plant experianced a loop(loss of offsite power) and did what they are supposed to do. There was no place for the power to go, so they shutdown to stop making it. All the power plants did what they were supposed to do. The fossils were presumably shut down. I'll find out more when I get to work. great, now i'm gonna be late.
Oh Crap, I'm an optimist.....
The AC had his facts in order. Even your quote backs him up. "The initiating event was a malfunctioning disconnect switch." The reactor shutdown was an (expected) response to the initiating event.
Fission products in the fuel have everything to do with why the plant was shut down. Operating nuclear plants run at a significant percentage of their capacity for reasons of economy. A sudden loss of load (as in the disconnect opening) results in the rapid rise in primary coolant temperature due to noplace for the energy to be dissipated. This will result in a reactor shutdown shortly after the load is lost (either by overtemperature or by turbine overspeed trip).
Heck, a sudden loss of turbine load can cause the turbine to overspeed, causing a turbine trip which in turn causes an automatic scram. Since every good discussion needs a car analogy, imagine driving up a steep hill and then knocking the transmission into neutral while keeping the accelerator mashed. RPM goes up, eh?
Even inserting control rods doesn't drop power fast enough to prevent heating up. After shutdown the fission products in the core continue to decay, releasing significant amounts of heat which must be dissipated.
That's what I love about slashdot... folks argue with experts without having a background to do so.
I'm an individual! Just like everyone else!