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Srsly you people are you for real?
Wie ein haufen aufgescheuchter Hühner, smh.
How about you read actuall Stuff and inform yourself
and from an actual Nuclear Technician on SA:
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Basic Nuclear Plant Safety Primer for Stupid Goons
The Fukushima Daiichi power plant is a Boiling Water Reactor. It is both moderated (what causes fission) and cooled (what stops the nuclear fuel/waste from getting so hot it melts) by water.
The plant was scrammed (immediately stopped) after the earthquake by inserting control rods (boron-infused 'rods' that prevent further fissions from taking place (by eating up all the neutrons necessary to initiate fission). This happened successfully. The plant is "shut down."
However, after the plant is shut down, there are still certain elements called "delayed neutron precursors" that will STILL released neutrons for some time period after the plant is shut down. These are what cause heat to accrue in a reactor that should theoretically be "shut down". This is why cooling needs to be provided in a typical 2nd generation light-water reactor (what most reactors in the world are) for a good while after shutdown.
Without cooling water, the likely "worst case" will be the reactor pressure vessel (RPV) building up heat, which builds up pressure, which could cause a rupture of the vessel. The fuel rods will spill out radioactive contents, fires might break out, and the reactor is basically a lost cause.
And how does that affect the general populace in terms of radioactive dose?
-Not at all.
The RPV is surrounded by a containment facility designed from the ground up to withstand everything short of hydrogen bombs. Given the semi-spherical distance from the RPV an explosion would have to travel to break through the containment vessel, it is fundamentally impossible (given the energy density the RPV is capable of containing) for there to be straight up "radioactive smoke" or such getting outside of containment. The containment building is constructed to prevent EXACTLY this emergency.
So while this is a worrying emergency, and could represent billions of lost dollars a mess to clean up should the WORST come about, it will still not be another Chernobyl. And given the efforts underway to provide cooling and the fact that the fuel rods are still not exposed to air (When the real danger of fuel melting can occur), there is still time to stop this loss of coolent accident (LOCA).
So we SHOULD worry about this reactor problem, but not for the reason most anti-nuclear activists would have you believe....The Tsunami water isn't the problem, it would never get anywhere NEAR the RPV. The containment building prevents water from getting inside after all. If the tsunami knocked down the containment building, THEN you should begin to worry about things for real.
The fear/problem is an earthquake breaking a coolant pipe into the RPV. This is called a Large scale LOCA (loss of coolant accident). If the primary coolant pipe in a Gen II BWR is severed suddenly, the plant will lose coolant/moderator VERY quickly when it is VERY hot. Water leaves, so moderation goes down, so the reactor shuts down. However, as I said before, the reactor is still VERY hot and needs cooling down, because the fission fragments are radioactive (and radioactive decay generates heat), and delayed neutron precursors can generate more heat as well.
Thus, you still need coolant, and it's not that there's a shortage of water, it's that there's no way to get water INTO the RPV if there's a large LOCA due to a severed pipe or whatever.
I don't know what caused the accident in the first place. I'm doubtful of a tsunami's ability to cause that problem more than the shaking in the earthquake.
For reference, in TMI, the problem was that a pipe was basically left "open" that nobody knew about that kept dumping out the coolant. People did really stupid things (tell the emergency systems not to activate, for one), so the fuel got uncovered and melted. In modern plants even in a LOCA there SHOULD be enough cooling capacity in the ECCS (emergency core cooling system) to keep the fuel covered in water until the decay heat and fuel temperatures are low enough to ensure no meltdown is likely (this is on the order of hours to days)....Fuel in modern nuclear plants is not enriched enough to explode, it is not like a bomb. The containment building around plants are constructed insanely strong, nothing can get out. Soviets never had one around Chernobyl; if they had, no westerner would even know what "Chernobyl" is. The worst that can happen is that the plant is damaged to the point where it cannot be used again, but nobody will die, and no noticeable levels of radiation will leak....Venting Radioactive Gas
Boiling Water Reactors generate power by heating steam in the Reactor Pressure Vessel to the point where it boils, and then sending this steam through turbines to power a generator.
The water in this loop isn't released to the environment, since it is slightly irradiated. When turbine parts are replaced, they are handled as low-level waste due to the water running through them.
This water/steam mixture is what is building pressure inside the RPV. Typical BWRs have pressures around 7 to 8 MegaPascales (Pressurized Water Reactors, which doing boil inside the RPV, typically reach 15+ MPa). This gets higher as the temperature rises and the steam has nowhere to escape too. Another problem with this situation is that the super-saturated and pressurized steam prevents cooling water (emergency coolant usually sprays from above) to reach the fuel before it's flashed to steam itself.
This is the "radioactive steam" that must be released. It is not radioactive in the sense that there are fission fragments loaded all up it in, it is radioactive in the sense that it's been irradiated by being run through the core directly. You would absolutely not want to drink it (well, it's de-mineralized, so that's a bad idea anyway), as it likely contains high volumes of tritium and potentially leaked fission fragments that managed to tunnel through the fuel cladding into the coolant channels (very low probabilities though!).
However, it is not like how the Simpsons showed it would be (Homer on Disability episode, where radioactive steam venting immediately killed crops in a circle)....I actually did a statistical analysis using probability/severity for major disasters throughout history, associated probabilities of future disasters, and their probable severity.
Earthquakes came out, far and away, as the most likely to cause large loss of life. Tsunamis were right behind, followed by hurricanes. Nothing else really got close. Meteors had tremendous devastation, but probabilities too low to worry about.
Dams though, were relatively high up. Their likelihood isn't THAT bad (something like 1 every 20 years), and the severity can be incredible (3 Gorges Dam shattering could be THE terrible disaster all others are compared to someday). Even smaller dam breakings have resulted in hundreds to thousands of dead. I'd need to find my report to find the actual statistics, but it's actually pretty scary to read when you think about how many people live downriver of dams. Compare that to the fact that there are hundreds of reactors that have been operating with uptimes between 70-95% for over 30 years.
Nuclear reactor disasters have, cumulatively including Chernobyl, totaled a few hundred immediate deaths. You could argue about cancer, but those stats are incredibly difficult to compile, and probably wouldn't directly contribute to more than another few hundred deaths.
End result?
When there's an EARTHQUAKE and TSUNAMI already in process, nuclear emergencies are a footnote in that day's events, not a headline....Keep that in mind. It's taken one of the larger earthquakes in our generation to cause a "problem" with a nuclear plant, a problem that will probably result in no loss of life or environmental hazards. This should nearly be a non-story if it weren't for a stigma attached to nuclear power due to a relative sense of ignorance about how they work.
I don't mind that people don't know much about how they work, but I do mind about how the media is projecting this in place of more important REAL stories that need explanation. It's irresponsible journalism....A Brief Explanation About Past Nuclear Disasters, and how Japan's Situation Fits
TMI: In the late 70s, a plant suffered a malfunction. One pipe was left opened, cooling water emptied the reactor core, and the engineers were oblivious to this. When the safety systems screamed at the operators to begin emergency cooling, the engineers OVERRODE the safety mechanisms to keep the cooling from occurring. It was only AFTER they realized the instruments weren't lying to them that they took corrective steps, but it was too late.
The coolant was lost, the core was exposed to air, emergency coolant couldn't be added faster than it was draining, so the fuel heated up. It got so hot, it began melting out of the zircalloy cladding, through several feel of steel, and into the concrete, where eventually it stopped. No radiation was leaked however, due to the wonderful containment building surrounding it.
Chernobyl: A series of human errors in 1986 and a horrible management team led to an ill-advised experiment testing the feasibility of starting up a reactor after immediately shutting it down. The Russian-designed plant is FAR DIFFERENT from American designs, and when it's at low power it can gain power at an astronomical rate (very very exponential). As a result, it went from almost 0 power to WAY TOO loving MUCH POWER in a fraction of a second. The human engineers saw this, and dropped in control rods, which almost immediately caught fire. The entire core (surrounded in molten hot graphite) melted through the floor, which then crashed into the tank of cooling water.
Now I dunno if you know what happens if you let molten hot metal meet large bodies of water, so let me introduce to you the idea of a steam explosion strong enough to throw 800 tons of concrete hundreds of feet away. This was the explosion that scattered radioactive particles all around the site. The subsequent fire carried radioactive smoke all across Europe, and it was the nuclear disaster to end all others. They had no containment building, or else nobody would have known much at all about it.
Because of COUNTLESS differences in building design, plant design, safety codes, employee training, etc, it is impossible for non-Russian plants (which to my knowledge are the only ones who use graphite moderators anymore) to replicate this.
Japan's plant fits much close to the TMI model, but given lessons learned from that event, it is unlikely to reach that bad a situation unless EVERYTHING goes wrong.
It COULD BE that something has gone HORRIBLY wrong, and a leak has been discovered jetting actual irradiated water/steam (containing N-16, H-3, among other radioactive particles). That would be bad. Even that wouldn't be as bad as the simpsons portrayed it during Homer goes on Disability (and the steam kills a cornfield.)...Aber ich glaub ein paar hysterische Spiegel Artikel sind einfacher zu akzeptieren als die reichhaltige Schatztruhe an Wissen die das gesamte Internet darstellt.Radiation and You!
I went to the LaSalle Power Generating Station about half a year ago. It's a BWR, generating about 1.2 GWe (gigawatts electric, which is about 1/3 of the actual energy it creates in the core). I stood about 15 feet from the reactor core itself, which is covered by several feet of concrete (can't remember but I think it was.
I was given a dosimeter upon entry, and had to have it on me at all times. It measures the dose of radiation you receive, to put it simply. If it reached some value I can't remember (a few millirem I think) we were to immediately leave the area.
A millirem is a very small amount. We are constantly bombard with cosmic rays from the sun giving us millirems. Radon gas is a huge source of personal contamination (radon gas gets in your lungs and alpha-decays into other radioactive sources, not good), it gives you millirems. Bricks, marble, and granite all give off radiation. Bananas contain Potassium-20, which is a radioactive isotope. You can't avoid it. And yet, at this plant, a couple millirem in a specific time period is an immediate warning sign.
So after several hours inside a containment building, and often within 100' of an operating reactor and an entire swimming pool of radioactive waste, guess my dose! If you said "about .02 millirem" you are CORRECT! You could stand outside the plant all day and not get any measurable difference in radiation dosage from anywhere else on earth.
So 1000x the outside value of radiation? This means basically NOTHING. I don't know what baseline value they judge "typical operating background radiation" to be at the plant, and without that knowledge it's almost impossible to judge how bad the situation is, other than "still probably not bad". If they give out a figure, like "Doses of 2 rem per hour are expected", then you know poo poo IS BAD, and something inconceivable happened. Otherwise, precautionary evacuations are wonderful tools for keeping order, much better than "OH poo poo IT'S BURNING" evacuations. But it's not a sign that poo poo is GOING DOWN or GETTING REAL....
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