Why can't nuclear power plants power themselves in the event of a power outage?

this is a very intellectually posed question, with a simple explanation. first, we have to establish how a nuclear plant works (in simple form): a core of uranium/plutonium/other nuclear isotopes is suspended in a metal casing. cooling water is then pumped through this casing, in order to keep the core at a reasonable temperature (to prevent the core from "meltingdown"). the heat generated by this core can be used in a number of ways, typically to create steam energy and power a turbine thus generating electricity. now, nuclear plants ARE typically self-sustained, meaning that the power they generate is both transmitted to electric companies, as well as being used to keep the plant operational. if this flow of energy is interrupted, the EDG's (emergency diesel generators) are activated, in an attempt to keep the water cooled and to prevent a meltdown. when the EDG's were expended, they resorted to the back-up emergency batteries which are supposed to give 8 hours of emergency power. once these were expended, there was no way to keep the cores cooled. in other words, the cores were no longer generating functional energy. the "current" was broken so to speak, so the energy of the core was not being transmitted - it just remained dynamic as heat energy. ^really sorry if any of this is confusing or incorrect, i only have a basic understanding myself..

Genuinely, that's an interesting question. I am doing higher physics at school, and although it is rather advanced I must admit my knowledge is also limited. Uranium will not cool down by itself; it's a chain reaction that goes through more and more and more atoms, constantly increasing the heat. Now until all the atoms are split [which will take a hell of a long time] the uranium will continue to increase in temperature. Therefore, if you just leave it to heat the water to turn the turbines to produce the electricity to cool the uranium, you're gonna get less energy in the form of electricity to cool the uranium than what the uranium gave out in the worm of heat [because nothing it 100% efficient]. Basically, you'll still have more heat being produced than electricity to cool the heat, therefore, you'll just be delaying the process rather than stopping it.

Usually they do. The problem with Japans were pisspoor design to begin with.

Here is an informative site that explains the situation: http://bravenewclimate.com/2011/03/13/fukushima-simple-explanation/ - I know that the backup generators used to cool the reactors were wiped out, but are they even needed? 1. The nuclear reaction was shut off automatically when the earthquake hit, so what's being dealt with is just the residual reaction. It takes one to three years to cool the fuel properly. 2. Because the reaction was stopped, there is no electricity being produced. 3. The water has to be circulated or it will just boil away. It won't move of it's own accord, so electric pumps are used. 4. Normally the water pumps are powered by the grid, but if the grid is off-line the backup generators provide electricity (which they did for an hour before the tsunami hit). There is also an eight hour battery backup, which actually did work for the designed eight hours. 5. The problem occurred because replacement generators couldn't be hooked up in the eight hour time span and the fuel boiled some of the cooling water away partially exposing the fuel. Note that the situation at the Fukushima plant has been improving every day. http://www.iaea.org/newscenter/news/tsunamiupdate01.html

A very well put question. The simple answer is a well cannot produce water once it has run dry. In that same sense a power plant cannot produce power if the mechanisms that actually do produce the power have failed. In the case of a Nuclear Reactor, Fission or a few other types, the same occurs, once the mechanisms of stuff that makes them hot goes or gets out of control, is like Three Mile Island or Chernobyl. There are many reactors that have gone off-line for many reasons or accidents, some where contained and shut down, others will be 'hot' for many many years. The simple fact that I am responding to this question on an Electronic Computing Device almost justifies the need for Man Made Electricity, that fact that we are here and have inhabited the planet for tens of thousands of years without Human Made Electricity proves that it is a luxury and not a necessity. It is a big ole goofy world, I appreciate your wanting to learn, I appreciate your concern, be happy and share the happiness.