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25th Anniversary Of Three Mile Island
fbform writes "March 28, 2004 is the 25th anniversary of the Loss Of Coolant Accident (LOCA) at the nuclear power plant on Three Mile Island, Pennsylvania. It's a good time to reflect on the impact it has had on our nuclear safety policy and interface design in general."
Oblinks to related wikipedia articles:
Three Mile Island
List of nuclear accidents
It's a shame that incidents such as this have contributed to the overall bad image of nuclear power. There is still a lot of potential which will probably never be revealed because the public at large are scared of what could happen if something went wrong.
The truth is that modern techniques could probably make nuclear power an extremely safe alternative.
Free iPods - now in the UK!
Fusion power is the way to go. It's potentially much safer and can generate a ton of electricity without air pollution.
That would make things much worse in the event of a meltdown. The radioactivity has to go somewhere, and instead of being pelted into the air or lingering in and around the reactor it would wind up getting leached into the soil and causing massive contamination of any watercourses within a few kilometres, which would probably be even worse and slow down long-term dispersal of radioactive particles.
"Oh little isle, of 3 Mile. How still you make us die.
Above the town of Middletown, the glowing clouds scud by.
Yet in thy dark streets shineth, the everlasting glow.
We'll all mutate, and radiate. And then we'll die, you know"
Don't blame Durga. I voted for Centauri.
I noticed recently that in Arizona so few people have clotheslines. It is 100 degrees and sunny for most of the year there, but most people still seem to dry their clothes in the electric clothes dryer.
That approach is not as common in Australia, where we take advantage of 100 degrees of sunshine to get our clothes nice and dry.
Are we weird, or what?
...is seeing how the fuck these accidents actually happen. Both Chernobyl and TMI seem to be based on a ridiculous chain of events fuelled by unfortunate coincidence, fallible mensuration equipment and human idiocy.
For instance, at TMI, there was a massive chain of events going like this (I'm taking this from the Wikipedia article). If any of these steps were omitted an accident never would've happened:
1. "The plant's main feedwater pumps in the secondary non-nuclear cooling system failed at about 4:00 a.m. on March 28, 1979"
2. "This failure was due to either a mechanical or electrical failure and prevented the steam generators from removing heat."
3. "First the turbine, then the nuclear reactor automatically shut down. Immediately, the pressure in the primary system (the nuclear portion of the plant) began to increase."
4. "to prevent that pressure from becoming excessive, the pressurizer relief valve (a valve located at the top of the pressurizer) opened."
5. "The valve should have closed when the pressure decreased by a certain amount, but it did not. Signals available to the operator failed to show that the valve was still open. As a result, the stuck-open valve caused the pressure to continue to decrease in the system."
6. "Meanwhile, another problem appeared elsewhere in the plant. The emergency feedwater system (backup to main feedwater) was tested 42 hours prior to the accident. As part of the test, a valve is closed and then reopened at the end of the test. But this time, through either an administrative or human error, the valve was not reopened -- preventing the emergency feedwater system from functioning."
7. "As the system pressure in the primary system continued to decrease, voids (areas where no water is present) began to form in portions of the system other than the pressurizer."
8. "Because of these voids, the water in the system was redistributed and the pressurizer became full of water."
9. "The level indicator, which tells the operator the amount of coolant capable of heat removal, incorrectly indicated the system was full of water."
10. "Thus, the operator stopped adding water. He was unaware that, because of the stuck valve, the indicator could, and in this instance did, provide false readings."
And so on and so forth. This is terrific shit. Seeing how many stages the thing went through just makes me glad this happened somewhere other than the decomposing USSR. With better engineering of measurement tools the whole thing would never have happened.
In all seriousness, if anybody has any questions they'd like me to pass on I'd be more than willing to. I'll post the answers here or in a JE or somewhere.
Triv
Compare the Soviets worst accident- dozens dead in the short term, thousands dead early from long term effects- with the United States worst accident- Three Mile Island. The radioactivity release from TMI was projected to cause less than 1 premature death from the hundreds of thousands of people potentially exposed to anything, and in twenty five years since, no one has been able to prove that they were adversly affected by the accident, healthwise.
Including the people who work there.
Nuclear Power is perfectly safe when done right, and it's done right in the US. The worst that could happen in the US in an accident condition is that parts of the power plant are destroyed. And for even that to happen, so many very closely watched things would have to go wrong that it's basically not going to happen.
So shut off your lights if you don't like nuclear power, and go back to your cave.
Alcohol, Tobacco and Firearms should be the name of a store, not a government agency.
How DARE you suggest that we pollute the pristine magma of the earths core with your unnatural nuclear waste. It would be a crime against nature to bury radioactve material under the earths crust.
People like you make me sick.
All Troll + "offtopic" mods are meta moderated as "Unfair", because you abused the system.
Chernobyl was a completely different animal to TMI. Operators at the plant brought that disaster entirely upon themselves. They were doing an "experiment" to see what the minimal resources were to keep the plant operating, overriding automatic shutoffs and other alarms in the process. Eventually, they overrode one alarm too many.
TMI was much more of a true accident. A valve malfunctioned to start the whole thing, something that didnt require a direct human action to occur.
The One Rule Of Chess You'll Ever Need: Don't play someone who carries a kit in their bookbag.
If they had used analog dials instead of digital readouts, the operators would have seen a bunch of dials all pegged high, instead of seeing what looked like an instrument failure.
Given that data, there's chance that when steam bubbles started forming in the primary system outside of the pressurizer (your "voids"), the operators would not have shut down the primary reactor coolant pumps (the big pumps that circulate water between the core and steam generators). The operators shut down those expensive pumps because the steam bubbles caused them to start cavitating, which would eventually destroy them. If those pumps had been kept running, the core would have received some cooling, and the operators would have known that more was wrong...
Maybe if the operators had known that core temps were going through the roof they would have acted totally differently.
PS - I have no idea how the operators could have missed a stuck-open relief valve - even a steam relief valve from the top of the pressurize. When those things lift, it sounds and feels like a train going by...
From 3F05:
Burns: Homer, your bravery and quick thinking have turned a potential Chernobyl into a mere Three Mile Island. Bravo!
I used to work in the radiation safety field and went on a technical tour of TMI just before the change in owners (current owner is AmerGen).
We were able to visit some aspects of the non-functioning side - the cooling towers (I have photos I took while standing inside one, and here's another), the empty turbine room, and the control room.
Surprisingly standing around the skeletons of the non-functioning cooling towers wasn't nearly as strange as comparing the turbine rooms between the functioning and non-functioning sides of the plant.
Anyone who has seen a turbine room in any kind of large power plant knows how huge they are. The turbine room used for the functioning reactor was hot, noisy, and full of intimidatingly large equipment. The huge emptiness of the unused turbine room was just plain strange in comparison.
IMNSHO, the worst thing about the TMI accident was the lack of communication both inside and outside of the plant. We can only hope that we've learned from our mistakes.
People do not realize that:
1) 80% of electricity in France is nuclear (Paris vacation, anyone?)
2) There is more radiation in the U.S. Congress due to its granite construction than is permitted outside a nuclear plant
3) If you take 4 cross-country airplane trips, you get more radiation than allowed at nuclear plants
4) If you live in mountains (Colorado) you also get more radiation, due to the altitude
5) Best estimates are for 325 long term general population deaths arising out of the Chernobyl radiation escape. Guess how many cancers due to oil/coal burning plants elsewhere?
6) Current nuke plant designs have a bias for automatically stopping the reaction at the slightest or even gravest out of spec situation. Imagine your car's engine designed to stop every time you rev up/speed/your dome light burns out.
Fact is, greenies have scared the public, we are currently poisoning our air with oil/coal power plants, creating thousands of new cancers every year. Thanks, tree-huggers.
The next pasture is always greener
Reminds me of a quote by Terry Pratchett:
I once absend-mindedly ordered Three Mile Island dressing in a restaurant and, with great presence of mind, they brought Thousand Island Dressing and a bottle of chili sauce.
With the posting of the Chernobyl story yesterday, this should make some of us pause and think about what could have been...
Very true. It allows us to realize how fortunate it is that our engineers rejected the open-pile design which caused Chernobyl to be so dangerous. It also makes me thankful that, due to the skillful design, the TMI incident is a disaster only in the terms of public-relations among those who don't understand, or want to understand the science.
I don't think that anyone who isn't rabidly anti-nuclear power would consider these to events to be anywhere near equivalent. It says a lot for the systems that, despite the chain of human and mechanical failures, the incident at TMI was limited to such a small environmental impact. That wasn't by luck, it was by design decisions, choosing a much safer way to use nuclear energy to create power.
Bringing Chernobyl into the context of TMI shows that the person doing so either doesn't understand the science, or is trying to use fear of Chernobyl to convince others who don't understand the differences.
Chernobyl was a graphite-moderated reactor, which means that the fast neutrons were slowed by bouncing off the carbon atoms.
An interesting thing about water is that it has two effects in fission reactors:
1. It acts as a moderator (bouncing neutrons off the hydrogen atoms of water molecules is one of the best ways to slow a neutron down).
2. Water also acts as a poison to the chain reaction. The hydrogen atoms do have an affinity to sucking up neutrons and turning themselves into deuterium and tritium. This effect causes the fission chain reaction to peter out.
Which effect predominates depends on the physical geometry of the core and the layout of fuel, water, control rods, graphite, whatever else is in the core.
At TMI the moderation effect of water predominated, at Chernobyl the poison effect.
This means that at Chernobyl the primary coolant acted as a poison to the chain reaction - so remove the coolant and the nuclear reactions run amok - not an explosion, but all kinds of bad stuff. And that "bad stuff" includes, IIRC, a phase transformation of the graphite at a really high temperature that releases a lot of energy.
Conversely, at TMI when the core lost its coolant fission stopped and only decay heat from the radioactive decay of fission products remained - more than an order of magnitude less than rated reactor peak power depending on power history of the reactor (i.e., if the reactor has been running at 100% power for a few weeks, decay heat production is maxed at about 7% of full power, and decays rapidly)
But the loss of coolant at Chernobyl and resultant runaway nuclear reactions caused a steam explosion of the remaining coolant in the core that severed all emergency coolant connections into the core (and kill everyone in the reactor building itself, IIRC). This steam explosion probably would not have breached any containment vessel, but the later energy release from the graphite and the fires almost certainly would have anyway.
And Chernobyl was all caused by dumbasses shutting down the reactor protective systems designed to prevent them from running the reactor in such a condition. Chernobyl had safety features to prevent operation in the range where the disaster that happened would be possible (which was actually highly dependent on power history since the radioactive fission products also have a huge effect on fission in the core [ iodine-136, IIRC]), but since the engineers had a test they just had to perform even though the reactor hadn't been shutdown for a few days like it was supposed to be, they simply shut down the system that was designed to prevent the reactor from going kaboom.
The parent is correct.. if worded badly.
TMI was a case of automatic safety systems being overrided by undertrained human operators. As the story paragraph mentioned, TMI was a stark lesson in control systems design.
In the control room the operators had no feedback about how much water was in the reactor core, just one gauge showing the level of water in the pressurizer tank near the top of the system. When a valve near the top of the pressurizer stuck open (referred to as the PORV or pressure operated relief value) the steam that normally kept the water near the bottom of the pressuizer tank started leaking out. More water flashes to steam.... and TMI is now losing water. The operators saw the opposite, the water level was rising on the level gauge for the pressurizer and they started reducing and eventually draining water out of the system thinking some malfunction was causing water to be introduced. None of the operators was able to step back from the initial theory that water levels were rising, despite large amounts of contradicting information. (Hours into the incident an off-duty operator arrived and with a fresh set of eyes figured out what was happening)
There are a lot more things that went wrong that night... (the initial shutdown was caused by water accidentially getting into the compressed air supply for the pneumatic control systems in the steam room, a valve closed at the wrong time and burst one of the steam lines to the power turbines)
TMI is a fascinating example of how multiple redundant systems still can fail, given a long string of "coincidences" One can argue that failures of this type are like winning the lotto, their is little chance of it happening on on particular day, but given enough days it is certain to happen to someone. Hence the need for "fail safe" designs.
No, it [nuclear power] is not safe
.
Nothing is completely safe. Thing is, the alternatives - the real, viable alternatives -- to nuclear power are even less safe.
You may recall the recent FDA advisory warning pregnant women and children to limit their intake of several types of fish because of mercury contamination in those fish.
The FDA guidelines call for children and pregnant women -- and women who "may become pregnant" to abstain completely from shark, swordfish, king mackerel, or tilefish, and to limit intake to six onces of albacore tuna a week.
What you might not have heard is that the panel that made the recommendation contained two members who were former lobbyists for the fishing industry -- or that another member, a scientist, not a lobbyist, resigned in protest because he believes that even six onces a week of albacore tuna is dangerous, and that that recommendation was only made because of industry lobbying.
What you also might not have heard is that the primary source of mercury in fish is from "mercury rain" -- and the primary source of mercury rain is from coal fired power plants
As it happens, the EPA is retreating from plans to more closely regulate mercury pollution from power plants, and "just coincidently" some of the language justifying that retreat is word-for-word the same as language in utility company memos.
So on the one hand, the fishing industry influences the FDA to soft-pedal its warnings to children and pregnant women, and on the other hand the power industry gets the EPA to continue to allow pollution.
And this is not to mention the other dangers of coal: despoiling the environment by digging it up, despoiling the air with smog when it's burnt, giving miners black-lung, etc.
I grew up a few miles from Three Mile Island, and I was still there when the accident happened, and I'll take clean nuclear power any day. Even in the worst case, we can contain a nuclear plant accident -- but we can't contain an ocean of mercury contaminated fish.
Opinions on the Twiddler2 hand-held keyboard?
For years now, the folks guarding nuclear plants have been armed to the teeth.
They have no-fly zones around nuclear plants now. Not really because flying inside the line gets you shot down, but so they can aim a SAM at an incoming threat without worrying about hitting the wrong plane (not that they're worried about hitting the wrong plane - it's really that they're worried about missing the right one).
So let's pretend we're mad as hell and not going to take it any more. What's the plan?
9/11 style air attack won't work. You'll either get SAMed or the containment building will likely survive the impact.
Armed assault will be met with armed resistance. The minute the attack starts, someone presses the panic button and the cavalry arrives.
No, the only credible terrorist threat in my mind is an inside job - someone gets a job as a plant worker and sabotages the plant. If the plant were a fail-safe design, however (as a previous posted pointed out, current plants are designed with redundant systems, but are not fail-safe), the worst the criminal could do is shut the plant down and perhaps try and disperse the fuel with explosives (note that due to a failsafe system, he won't get any help dispersing the fuel from the plant itself). His ability to smuggle explosives into the plant without being detected will limit the effectiveness of that plan. Never mind that he'd have to be able to breach the containment building (yes, even a fail-safe reactor will likely have one).
Sabotage is certainly a threat at current nuclear facilities, just as it is a threat at, for example, petrolium refineries (I'd actually put Richmond, CA ahead of, say, San Onofre on a threat list). Better design mitigates that risk, just as it mitigates so many other risks.
After rocky flats, the detroit reactor neer explosion, hanfords non stop spew of radiation and of course after the nation had been glowing with nuke test fallout for 30 years, THEN they decide to wimp out because a reactors failsafes actually began working to the point where there was little radiation leakage ? WTF ?
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The russians on the other hand, their main food production area is not EPA weenie HOT, its will I die of this THIS year hot. And they keep all the reactors of the same type going because if they shut them down they'll FREEZE to death.
In the US most of our energy problems are self inflicted, political scams to run up energy sales prices, the oil companies sticking it to the consumer every time the EPA sticks it to them, calfornia sucking up all the cheap natural gas so they can have "clean" power and then the people in the northern states who relied on that for home heating now have their bills tripple or more. While those using heating oil and some cases even just electricity are now paying less while carbon fouling the air like crazy. And don't think that coal is "non-nuclear" the ash from burning that doesn't go up in the air is contains enough uranium and thorium to be a potential source of reactor fuel. http://www.ornl.gov/info/ornlreview/rev26-34/text
At least in a nuclear plant they keep the waste and fuel contained, not blasted out of a smoke stack or floating around on some barge until they can find a country to unload it in.
The energy has to come from some place. And it HAS to come from YOUR BACK YARD because the grid wasn't made to have power generated in a designated dirty state like kentucy, or tennessee and transmitted all the way to the east coast. The question is, do you want CO2 and thorium ash spewing plant in every city, or a reactor powering 12 cities and giving some neurotic mommies a panic attack 6 times a day.
As for alternate energy, solar cells take a lot of power to make, windmills take energy to machine and transport to the location, micro-turbines/water wheels require a certain type of landscape and water supply. All these are great if you live in the middle of nowhere. Solar heating/cooling is great if you can afford to have it worked into your house.
But the bulk of your power needs still come from coal and nuclear power. And nuclear power can't continue if you have to bury every ton of concrete ever touched by 12 extra neutrons in some dump. And coal burning can't go on for another hundred years or we'll run out of air. This means we have to come up with some sort of reasonable nuclear regulation, acceptable loses, etc.
It has long since been recorded as a fact that any system relying on human reliability is unreliable.
Both Chernobyl and TMI happened because the humans didn't fulfill their role in the reliability chain.
In both cases, humans misreading or misinterpreting information worked against the automatic protection systems correct safing actions.
To technocrats like us, the obvious solution is fully automatic, unmanned atomic powerplants.
Considering that we cannot even drive a car 20km by computer, I don't think we are anywhere close to ready for that sort of challenge yet.
So while nuclear energy may be ready, we're not.
(And there's also that pesky detail about the spent fuel.)
Poul-Henning Kamp -- FreeBSD since before it was called that...
No, that's simply not true.
Union Carbide in Bhopal: 3000 to 8000 dead; over 100000 injured.
Chisso Corporation at Minimata: mercury poisoning kills hundreds, with at least 3000 people afflicted.
The Grandcamp in Texas: Fertilizer explosion kills nearly 600; over 3500 injured.
Chernobyl: fewer than 100 deaths to date; fewer than 1500 known attributable radiation-related illnesses. Potential premature deaths due to excess radiation exposure estimated to be 3000, but we'll have to wait and see.
Nuclear power is dangerous, but there's a lot worse out there. Look up deaths attributable to coal-fired power plants sometime.
Well,
..... for politicians and regulation that is.
The trush is that nuclear power is already the safest and cleanest power source in the USA - even when you include taking care of radioactive waste.
The truth is, as has been pointed out here several times, that coal powered plants in the USA (trace radiation) are more radioactive then nuclear plants.
The truth is, that 3 mile island was the ultimate example of why nuclear power in the US is so safe. Even in worse case scenarios, and with 20 simeltanious managment and design failures - nothing harmfull happened to anybody.
The truth is, the movement against nuclear power has far more to do with OPEC financing than concern for safety, liabilities, or the environment.
The truth is that 3 mile island wasn't a nuclear disaster by any measure, it was a political disaster.
The truth is that dealing with nuclear waste isn't a problem either, it's also a political problem.
The sad truth is that we could all have had clean, cheap, safe, and environmentally friendly power a long time ago. But big huge nuclear powerplants are just simply too tempting of a target
Unfortunately, the popular mob is all to often like a herd buffalos, the stampeed that saves one from a lion kills thousands as they head toward the cliff.