Three Mile Island Shuts Down After Pump Failure

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Three Mile Island Shuts Down After Pump Failure

Posted by samzenpus on Thursday September 20, 2012 @04:33PM 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."

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And, cue shitstorm.. by Anonymous Coward · 2012-09-20 16:34 · 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 · 2012-09-20 16:40 · Score: 5, Insightful
  
  Yes.
  
  Not that that's going to stop the shitstorm
2. Re:And, cue shitstorm.. by Black+Parrot · 2012-09-20 16:58 · Score: 4, Funny
  
  Yes.
  Not that that's going to stop the shitstorm
  Clearly, we need more backup pumps for shitstorms.
  
  --
  Sheesh, evil *and* a jerk. -- Jade
3. Re:And, cue shitstorm.. by Anonymous Coward · 2012-09-20 17:14 · Score: 3, Interesting
  
  Yep. Basically, everything worked as it was meant to. Problem will be fixed soon and life will continue as usual.
  Also, if one wishes to scare greenies half to death: http://www.nrc.gov/reading-rm/doc-collections/event-status/event/2012/
4. Re:And, cue shitstorm.. by Anonymous Coward · 2012-09-20 17:32 · 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.
5. Re:And, cue shitstorm.. by ozmanjusri · 2012-09-20 17:45 · Score: 3, Insightful
  
  Maybe.
  I'll reserve judgement on what's actually happened, because this industry has a history of salamitaktic, lying, cover-ups and manipulation of public opinion.
  It's possible this innocuous announcement is the start of a series of press-releases, each admitting to progressively worse problems. If that's the case, all the Pollyannas on Slashdot will have vanished by the time the real scope of the event is clear.
  
  --
  "I've got more toys than Teruhisa Kitahara."
6. Re:And, cue shitstorm.. by Anonymous Coward · 2012-09-20 18:03 · 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).
7. Re:And, cue shitstorm.. by Anonymous Coward · 2012-09-20 18:11 · Score: 3, Informative
  
  Um, no. This is how these things are supposed to fail.
8. Re:And, cue shitstorm.. by TheLink · 2012-09-20 19:16 · Score: 4, Funny
  
  Nah potassium iodide, 130mg.
  --
  
  Too many replies beneath your current threshold
9. Re:And, cue shitstorm.. by thegarbz · 2012-09-20 19:55 · Score: 4, Informative
  
  Of course it's not graceful but a shutdown as a result of equipment failure never is. Steam venting isn't graceful, but then neither is a SCRAM.
  I work in the process industry and the only time a shutdown is ever graceful is through carefully planned and usually long duration operator actions. Even then some processes they just get it down to a stage where there will be minimal damage and then hit the trip button and hope nothing breaks.
  The key thing here is what shutdown the process was a safety system which prevented a hazardous event from occurring, rather than hazardous event occurring and causing the shutdown. Compared to that this event really can be considered quite graceful.
10. Re:And, cue shitstorm.. by Anonymous Coward · 2012-09-20 20:00 · Score: 4, Informative
  
  "Three Mile Island is still shutdown Thursday night. Around 220 Thursday afternoon, people who live near the nuclear power plant heard a loud noise, saw steam and then the plant automatically shut down.
  This is the second time that this has happened in the past month."
  http://www.whptv.com/news/local/story/UPDATE-3-Thursdays-TMI-shutdown-is-the-second-in/_Z1vYirDt0ybASp0FZhmUw.cspx
  
  "The Nuclear Regulatory Commission said Thursday that it was satisfied with Exelon’s repairs following a reactor shut-down at Three Mile Island on Aug. 22.
  The NRC said a small leak in the reactor coolant system was caused by “micro-cracks” in a diaphragm in a pressurized heater bundle within the containment barrier. The cracked diaphragm was made of alloy 600; it was replaced with one made of stainless steel, and the unit was powered back up."
  No doubt the saga will continue.
11. Re:And, cue shitstorm.. by dbIII · 2012-09-20 20:03 · Score: 4, Interesting
  
  It doesn't sound like a graceful shutdown
  A "graceful" emergency shutdown of a large thermal power station unit is actually bloody noisy as the steam goes into the blow down vessel/s.
  Also any water that touches the turbines doesn't actually go into the reactor, it goes through heat exchangers where the working fluid of the reactor is on the other side.
  Disclaimer: I'm familiar with the turbine side (fairly universal amoong all thermal power stations of the same size) but in my case the boilers were all coal fired. There are many similarities to the point where one of my co-workers was a Russian turbine engineer with a lot of nuke experience (and some scary stories).
12. Re:And, cue shitstorm.. by Chrisq · 2012-09-20 20:19 · Score: 2
  
  Um, no. This is how these things are supposed to fail.
  I don't know why this is modded down - its absolutely correct. Nuclear reactors are designed to be "fail safe". If a pump breaks, the system shuts down. There are probably backup pumps in case the shutdown fails too, etc.
13. Re:And, cue shitstorm.. by Anonymous Coward · 2012-09-20 20:23 · 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.
14. Re:And, cue shitstorm.. by bcmm · 2012-09-20 20:45 · Score: 4, Insightful
  
  To be fair to the shitstorm, there are historical reasons to be a bit worried when Exelon describe something as a planned release of steam with minimal release of radioactive material. Lets hold out for the NRC report.
  
  --
  # cat /dev/mem | strings | grep -i llama
  Damn, my RAM is full of llamas.
15. Re:And, cue shitstorm.. by waferbuster · 2012-09-20 21:46 · Score: 2
  
  Man, and just yesterday I had mod points. Too funny.
  
  --
  I'm an individual! Just like everyone else!
16. Re:And, cue shitstorm.. by zmooc · 2012-09-20 21:51 · Score: 3, Insightful
  
  As far as I'm aware (and that's not that far, but far enough to reply to this) this kind of pressurized water reactor cannot really shutdown very gracefully. Once such a reactor gets going at normal power levels for some time, it can not shutdown very quickly. The best it can do, is to stop most of the fission reaction (in this case probably a so called Emergency SCRAM). Afterward the SCRAM, the fuel rods will still be Pretty Hot and initially they will still produce about 7% of their normal power due to fission product decay. After a day that's down to about 0.4%, which in this case would still be something like 4 megawatts or so. More than enough to keep things in a closed, well-isolated reactor Really Hot for months to come.
  So, in fact, the shutdown-sequence is not graceful at all; it is an extended process that requires active cooling (and therefore working power) and supervision and will result in disaster if it is interrupted for some amount of time.
  
  --
  0x or or snor perron?!
17. Re:And, cue shitstorm.. by osmifra · 2012-09-20 21:56 · Score: 2
  
  IF something actually goes bad in Nuclear energy its very hard to cover up something that anyone can measure with a freaking tool!!!! Stop spreading FUD, there's no high levels of radiation and that can easily be measured by anyone. Wanna see cover ups in energy? Go look for carbon mines and fuel refineries and then tell me something. With far more accidents deaths and nature crimes per year each than all nuclear accidents combined.
18. Re:And, cue shitstorm.. by PopeRatzo · 2012-09-21 00:14 · Score: 2
  
  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 we've got every reason to trust Exelon.
  "Clean, safe, and too cheap to meter".
  
  --
  You are welcome on my lawn.
19. Re:And, cue shitstorm.. by nojayuk · 2012-09-21 00:54 · Score: 4, Informative
  
  "Basically, when you add the costs of decomissioning and waste storage, they become pretty expensive. For the tax payer, of course."
  Actually no. US and most other Western power reactor operators pay into funds for decommissioning their reactors and also for waste disposal on a kWhr basis. The US rate for waste disposal is 0.25 cents/kWhr which goes to the US government as it is in charge of all high-level nuclear waste since it is seen as a security risk. The current fund total is about 36 billion dollars IIRC. It's the taxpayer that has to deal with coal-slurry lagoons, mercury and other nasties in the exhaust stack, the buildup of CO2 in the atmosphere etc. Legislative attempts to cut down such releases under the EPA and such are a "war on coal" according to, surprise suprise, the coal-mining and coal-burning industry.
  As for nuclear power costs in the US, fuel costs are about 0.5 cents/kWhr and operations (running the plant, refurbishing the generators, landscaping the area etc.) are about a cent/kWhr. The killer cost is construction which is all up-front and expensive. It means that once a nuclear power station is up and running it starts paying off the 30 or 40 year financial instrument it took to build it and the owners really want to keep it running 24/7/365 to pay the capital and interest accruing.
20. Re:And, cue shitstorm.. by AmiMoJo · 2012-09-21 01:16 · Score: 3, Insightful
  
  That's not what fail safe means. In this case when the pump failed a number of things had to happen for the failure to be safe. The reactor probably SCRAMed and emergency cooling kicked in. Without those systems and careful management by staff the reactor could fail like Fukushima did.
  If it were fail safe the failure of the pump itself would have made the whole thing completely shut down into a safe and inactive state. I used to work in fire suppression for buildings and when we had a fire door that was "fail safe" that meant it was held locked shut by an electro magnet, so if the power failed for some reason it would automatically unlock and allow people to escape. In fact even if the control system stopped communicating it would open. No action by anyone or anything else required.
  
  --
  const int one = 65536; (Silvermoon, Texture.cs)
  SJW, n: "Someone I don't like, and by the way I'm a fuckwit" - AC
21. Re:And, cue shitstorm.. by iamgnat · 2012-09-21 01:18 · Score: 4, Interesting
  
  ozmanjursi didn't post any fact and yes I dispute their claims. The nuclear industry in the US has proven to be safe, they promptly report even minor incidents, and to the best of my knowledge have never lied about conditions at their plants or the scope of an event. What happened in other countries has no bearing on what happens in the US until there is evidence to the contrary.
  As osmifra points out, the fossil fuel power supply industry (mining up through the power plants themselves) do have a long history of raping the natural resources, not providing safe working conditions for their workers (miners), being horrible polluters, and having massive lobbying arms to make sure that any regulations that do get passed to curb these things have no teeth to actually stop them. Nuclear power, on the other hand, is very tightly regulated (see lobbying power of the fossil power as a big part of that) and does none of those things.
22. Re:And, cue shitstorm.. by Medievalist · 2012-09-21 01:41 · Score: 2
  
  Nuclear power, on the other hand, is very tightly regulated
  By the nuclear power industry. It's called "regulatory capture".
23. Re:And, cue shitstorm.. by Anonymous Coward · 2012-09-21 02:13 · Score: 2, Interesting
  
  This would be news if we read that... A coolant pumps failed and the reactor safey system did not respond as it should have.
  Let's put this in perspective.
  As a reactor operator, I have personally caused an automatic rapid reactor shutdown (called a reactor SCRAM in US Navy nucelar power terms) myself from an invalid coolant pump combination [note 1].
  I'm not sure what TMI uses for setpoints but in general...
  A reactor safety system compares running coolant pumps to measured power output. For a given pump combination, you can run at a certain power level. When the Power:Flow ratio exceeds a setpoint, the protection system will immediately take action. If a pump fails and you are above your power limit for the new lower setpoint... bam, protection system kicks in. No harm, no foul. That's what it does and it did it.
  Getting off topic but my story anyway..
  Note 1
  In my case, the pump did not fail, I failed. I am not the only one that has done this and it happens a lot. We were running some test drills that put the plant into an abnormal but perfectly acceptable coolant pump combination (one pump in each loop running in fast). This was after we had lost a turbine generator. Everything was fine until we started losing the other turbine generator which was not planned. In the protection system we had, when you change a coolant pumps speed, you go through a condition for a fraction of a second where the pump is considered "off" by the protection system and it actually is because it's wired to prevent both fast and slow speed windings from being powered at the same time. It compared power:flow and it scrammed. I shifted pumps too fast based on the conditions I had seen and what I expected to happen next. In my mind I assumed we were about to have a complete loss of flow if I did nothing as that other electrical turbine went away. Frequency was starting to flucuate and I took action. At the same time, they were restoring vaccuum to that turbine and it never actually went away. Maybe my unloading gave it enouhg time to reocver, maybe not. The whole situation from doing good and stable to the shit hitting the fan and a total reactor shutdown was about 10 seconds. Given the overall situation of events, nothing happened to me even though I technically caused the protective action because I may have potentially saved a worse condition of no flow which would have taken a much longer time to recover from if I did nothing.
24. Re:And, cue shitstorm.. by HornWumpus · 2012-09-21 03:32 · Score: 4, Informative
  
  It's called spinning reserve. Mostly turbines running at idle and hydro units that are river flow limited on generation anyhow. The hydro units in particular are not wasting any energy waiting to be called on. That said they are limited on ramp rate as putting a 'wall of water' down most rivers is not allowed (for good reasons; dangerous, erosive. Also strands fish when it stops). The exception there is when one reservoir cascades directly into another, those can more or less ramp as fast as the equipment will allow (which is pretty fast).
  Also note: the system just lets the voltage drop (browns out) while the 'ready reserve' units spin up. 120 VAC is purely nominal. Talk to someone that designs 120VAC power supplies. They should function down to about 95V IIRC. This is by design.
  Also also note: most transmission areas are both importing and exporting at any given time. They can always just cut their exports and shift a part of the issue to their neighbors. Increasing imports isn't likely to happen in the middle of the day. The lines were likely running at max capacity to begin with.
  
  --
  John McAfee 'It was like that time I hired that Bangkok prostitute; to do my taxes, while I fucked my accountant'
25. Re:And, cue shitstorm.. by Anonymous Coward · 2012-09-21 03:39 · Score: 2, Interesting
  
  The NRC Event Report:
  
  Power Reactor Event Number: 48325
  Facility: THREE MILE ISLAND
  Region: 1 State: PA
  Unit: [1] [ ] [ ]
  RX Type: [1] B&W-L-LP,[2] B&W-L-LP
  NRC Notified By: DAVID LEWIS
  HQ OPS Officer: JOHN KNOKE Notification Date: 09/20/2012
  Notification Time: 16:15 [ET]
  Event Date: 09/20/2012
  Event Time: 14:16 [EDT]
  Last Update Date: 09/20/2012
  Emergency Class: NON EMERGENCY
  10 CFR Section:
  50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL
  50.72(b)(2)(xi) - OFFSITE NOTIFICATION
  Person (Organization):
  CHRISTOPHER CAHILL (R1DO)
  Unit SCRAM Code RX CRIT Initial PWR Initial RX Mode Current PWR Current RX Mode
  1 A/R Y 100 Power Operation 0 Hot Shutdown
  Event Text
  AUTOMATIC REACTOR TRIP DUE TO REACTOR PROTECTION SYSTEM ACTUATION
  "On September 20th at 1416 EDT, Three Mile Island automatically tripped due to a flux to flow imbalance as a result of a trip of the 'C' reactor coolant pump. The cause of the trip of the 'C' reactor coolant pump is still under investigation.
  "The electrical grid is stable and unit 1 is being supplied by offsite power. All control rods have fully inserted. Decay heat is being removed by main feedwater flow to both steam generators that are exhausting via the normal main condenser cooling loop under manual control. Preliminary evaluation indicates that all plant systems functioned normally following the reactor trip, except for automatic operation of turbine bypass valve control due to failure of the automatic control function to control precisely at setpoint. Three Mile Island remains stable in hot shutdown mode while conducting the post trip review. No radioactive releases were experienced as a result of this event.
  "This event is reportable under 10 CFR 50.72(b)(2)(iv)(B), Reactor Protection System (RPS) actuation, and under 10 CFR 50.72 (b)(2)(xi) due to an information release to local officials. Both are four hour reports.
  "The licensee notified the NRC Resident Inspector."
  The licensee has notified the state and local governments, and will be making a media release.
  As far as your note on condenser steam dumps, it is true they aren't rated at full load. For a reactor trip that isn't a problem since only decay heat (6% at the time of trip and decreasing afterwards) is need to be removed. In a trip the condenser steam dumps would reduce the reactor coolant system temperature to the shutdown band. This report really doesn't explain the loud noise. Why there would be a venting of steam for a turbine bypass valve failure is unknown. If they wanted to isolate it they could have shut the main steam stops. But they claim they are cooling via condenser steam dumps. As far as NRC event reports, this one is unimpressive and doesn't explain what it needed to do. I expect there will be a followup report clarifying to the NRC what operator actions were taken and how they vented steam.
  
  Plus, dumping to atmosphere has the added benefit is that the whole plant staff knows immediately that they are staying late.
  Been there.
26. Re:And, cue shitstorm.. by tibit · 2012-09-21 04:53 · Score: 2
  
  Voltage dropping was helpful when a lot of the load was resistive (incandescent lightbulbs, linear regulators in most low-voltage equipment, etc.). As the voltage dropped, the power demand dropped as well. These days, the switching power supplies are negative resistances and as the voltage drops the power demand doesn't drop. In fact, due to typically lower efficiencies with lower input voltage, the power demand goes up as the input voltage drops! From what I imagine, one fine day the U.S. grid won't be able to cope gracefully with such loads in presence of lowered generating capacity. That day isn't very far away. Every data center and every plant where servo drives or induction motors are used is already such a negative resistance load. Due to switch to fluorescent lightbulbs and brushless drives in appliances, never mind all the IT/entertainment tech in homes, homes are becoming such a load as well. I have checked the effective differential impedance of my home with AC working and a bunch of other things turned on, and it is negative -- I don't recall the exact complex value. There were about 3 extra Watts wasted due to inefficiencies per every Volt of voltage drop over a constant-power ideal, going from 135V to 105V (I used a buck/boost transformer to vary the voltage going to the panel). That was an average over 1 minute with A/C going full blast, the computers on, cellphones charging, TV on, freezer and fridge compressors going, and both washer and dryer operating. The dryer has a tight digital temperature controller and will present a roughly fixed load in spite of lower input voltage. Of course mechanical thermostats acted the same way, but with an order of magnitude slower response.
  
  --
  A successful API design takes a mixture of software design and pedagogy.
27. Re:And, cue shitstorm.. by tibit · 2012-09-21 05:04 · Score: 2
  
  This thinking shows that you have absolutely no clue about how real functional process safety engineering is done. Fail safe means that when you have a certain number of failures (for a nuke plant probably two), things are still safe. So you can have, say, a concurrent turbine trip and a pump failure in a primary circuit, and things should end up in a safe state. Fail safe doesn't imply passive safety, it's only your fantasy and a view that's not shared by those who actually deal with functional safety. Passive safety may be a means of achieving functional safety of a process system, but it's by no means the ultimate cure-it-all in spite of what clueless fools spout left right and center. Passive safety isn't a fix for bad functional safety engineering. Fukushima was was an example of the latter. You can't tell a-priori that some passive safety in the system would not have prevented other problems. For all I know passively safe reactor might have prompted "savings" in other aspects of the design, say putting it lower and closer to the ocean, for example.
  
  --
  A successful API design takes a mixture of software design and pedagogy.
28. Re:And, cue shitstorm.. by bobbied · 2012-09-21 05:40 · Score: 2
  
  I don't think tidal would be useful at all times, but that aside... We've pretty much maxed out the hydroelectric capacity we have here in the US (unless you count the dams they are taking down) and geothermal capacity is *extremely* limited. Other "renewable" sources are not reliable enough to depend on for peak capacity needs.
  Nuclear power is not a good source of peak capacity because they are hard (and/or expensive) to throttle up and down due to fuel cycle considerations. Fossil fueled plants will be with us for a *long* time, because they are easy to throttle up and down. Not to say we could not use a LOT more Nuclear plants but we will need to somehow shift loads from peak times to off peak times to make the best use of their fuel.
  One scheme I've seen that looked promising was to pump water up a hill when electric rates where cheap (i.e. at night) then selling the hydroelectric power you could generate from the water and sell it at peak rates during the day. Maybe we could get the background electric rate cheap enough for that to work by building a few Nukes...
  
  --
  "File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
Some one in 7G messed up by Joe_Dragon · 2012-09-20 16:55 · Score: 4, Funny

Some one in 7G messed up
Add it all up by medcalf · 2012-09-20 16:56 · 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
1. Re:Add it all up by tehcyder · 2012-09-20 21:12 · Score: 4, Funny
  
  At least the music was better back then. Now get off my lawn.
  
  --
  To have a right to do a thing is not at all the same as to be right in doing it
2. Re:Add it all up by arth1 · 2012-09-21 00:04 · Score: 2
  
  Lots of good things happened in '79.
  - Smallpox was eradicated
  - The Sony Walkman was introduced (am I the only one missing those?)
  - Sony and Philips presented (prototype) CDs
  - Voyager I took pictures of Jupiter
  - Pioneer 11 took pictures of Saturn
  - Ariane was launched
  - Usenet started
  But I don't want a repeat, because in 1979, we almost ended life on this planet too, when NORAD erroneously detected a large amount of missiles from USSR heading towards the US. An operator had loaded a test tape into the live system without changing the system status to test.
  And almost equally horrible, the top song of the year was "My Sharona" by Knack.
  If I could get a re-run of a year, it would have to be 1776. Nothing of importance happened then...
Re:Three Mile Island is STILL open?!?!?! by quenda · 2012-09-20 17:23 · Score: 4, Interesting

Why not? You might be surprised to hear that the Chernobyl power station operated until 2000, 16 years after the well known incident.
Fukishima may not do so well. Losing a single reactor, as the US and USSR did, may be seen as bad luck. Losing three of them is an embarassment.
Re:No redundancy by sjames · 2012-09-20 17:38 · 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.
Re:No redundancy by treymd · 2012-09-20 17:42 · Score: 2

The fact that it is a nuclear reactor means that it SHOULD have backups, and backups for those backups, and if that should fail, there is a backup for that. Perhaps NASA should run our nuclear power plants.
Re:No redundancy by quenda · 2012-09-20 17:45 · Score: 2

They do have redundancy. The power station is connected by a grid to other power stations.
Normally they also have multiple reactors at one site, but for some reason TMI #2 has had an extended outage.
Re:No redundancy by treymd · 2012-09-20 17:46 · Score: 2

That is actually sort of alarming to me since they probably install 4 identical pumps at the same time each with a rated lifetime that is about the same. So when the first fails, the others are surely soon to follow, And that takes us full circle to why if one fails, the system is designed to shut down.
Re:No redundancy by treymd · 2012-09-20 17:48 · Score: 2

I believe it was stated that #2 is so polluted that it is on permanent shutdown.
They posted a shot of the incident by Grayhand · 2012-09-20 18:07 · Score: 2

http://3.bp.blogspot.com/_drqO7qJ_y4o/SrW1QkqR9wI/AAAAAAAAET4/4uV5HzzK9Ko/s1600-h/3mileisland.jpg
Re:Three Mile Island is STILL open?!?!?! by dbIII · 2012-09-20 20:11 · Score: 2, Interesting

It was a huge deal. A plant with a control system that wouldn't even pass regulations at a fertilizer works showed that you couldn't play fast and loose with nukes just because there were no regs to prevent you doing so, so that meant improvement of some other plants, shutting down some absolute deathtraps of the 50s and 60s, and a move towards better designs.
'If radiation was released'? by Anonymous Coward · 2012-09-20 20:13 · Score: 2, Funny

What is this? Come on America -are you turning into a load of cheese-eating surrender monkeys? The US should take pride in releasing the best and biggest cloud of radiation money can buy.
Re:Three Mile Island is STILL open?!?!?! by tehcyder · 2012-09-20 21:11 · Score: 4, Insightful

Implying Three Mile Island was even a big deal.
If this was a fucking software discussion I'd be calling you a paid shill for the nuclear power industry now and getting modded up for it.

But as the slashdot groupthink is that anyone who is not 100% a cheerleader for nuclear power is some tree-hugging commie, we all know what will happen.

--
To have a right to do a thing is not at all the same as to be right in doing it
Pansies by smooth+wombat · 2012-09-21 00:24 · Score: 4, Insightful

I live within the 10 mile "danger" zone (cue Kenny Loggins) and lived through the initial incident in 79. In fact, I was out delivering papers every day during the entire incident.
This is nothing to be mentioned on a tech site. It has no relevance whatsoever other than the fact that the system did what it was supposed to.
Stop the panicking and hyperbole about how bad nuclear energy is. Compared to the amount of health related issues coal has produced, nuclear energy ranks about as dangerous as rabbit attacks

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We will bankrupt ourselves in the vain search for absolute security. -- Dwight D. Eisenhower
1. Re:Pansies by cmdr_klarg · 2012-09-21 01:53 · Score: 2
  
  about as dangerous as rabbit attacks
  That is not an ordinary rabbit ... 'tis the most foul, cruel and bad-tempered thing you ever set eyes on. He's got huge, sharp-- he can leap about-- look at the bones!
  
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  THE SOFTWARE, IT NO WORKY!!!
Re:Germany by dywolf · 2012-09-21 00:55 · Score: 3

Nothing is future proof. Everything, particularly mechanical things, breaks down and needs repair replacement eventually. That what constant inspections and preventative maintenance are for. Nuclear plants are no different.

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The guy who said the election was rigged won the presidency with the second-most votes.
Why is this a story? by J'raxis · 2012-09-21 03:46 · Score: 3, Insightful

Why is this a story?
Because a simple mechanical device failed? Wow, that's news. Because the safety measured at the plant functioned exactly as designed? Yup, that's certainly news. Because the residents in the area heard a loud noise? Stop the presses!
Or because when anything happens at a nuclear power plant---including it functioning exactly as designed---the anti-nuclear luddites and other assorted fearmongers leap on the (non-)story in order to push their agenda?

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Liberty in your lifetime