reply to post by Mr Tranny
My first job out of high school was in a nuclear power plant. You don't just go grab a new diesel generator. The ones we had were about 100 feet
long, weighed many many tons, and had pistons that literally took huge cranes to install. They are installed in place in sections.
The exhaust where I worked was a 36" steel pipe fed through two mufflers ("exhaust silencers") which were themselves water-cooled and were housed
in two massive rooms. I was one of the engineering aides working on the cooling lines for them at one time. They are the size of a mobile home.
A nuclear power plant works backwards to what most people think. The thing is always "on" and takes energy to turn it "off". The control rods have
to be inserted into the reactor core to slow the nuclear reactions, and this has to be accomplished via an electric crane. No human can survive inside
the reactor chamber to do it manually.
It works like this: fuel inside the reactor is always hot, always trying to split atoms which produce more neutrons to split more atoms. The control
rods contain material that intercepts the neutrons and slows the reactions. Inserting the rods slows the reaction speed; removing them speeds the
reaction up. The only way fuel can be used in this way is for it to be shipped in smaller separate containers so the mass of each container is much
less than the critical mass at which the reaction is self-supporting. This all occurs in the inner section of the reactor buildings and is cooled by a
self-contained water system so the system doesn't "melt down", i.e. the machinery doesn't freeze up and become inoperative from too much heat.
Since it is self-contained, there is no way under normal conditions for any radioactive emissions to exit the reactor chamber (which incidentally is
an 8-foot-thick wall of reinforced high-density concrete). This cooling loop runs into a heat exchanger that transfers the heat into a secondary
self-contained loop which runs to the generators. Finally, the secondary cooling water runs through another heat exchanger that uses an outside water
source to cool it back down. The amount of radiation that can seep through both heat exchangers is minuscule, so there is no appreciable contamination
to the surrounding environment.
The amount of energy transferred through this system is incredible, as are the temperatures produced. Both self-contained cooling loops are
pressurized so they do not steam, and we are talking about 60" schedule 120 pipe throughout.
If the generators fail (we had two back-up generators, one for each reactor, each capable of powering either reactor in case of emergency), the only
way to insert the control rods and continue to cool the reactor is using batteries. If they are flying in replacement batteries, this is a very bad
indicator that they are indeed having trouble completing the emergency shutdown protocol and could experience a meltdown.
For those who have asked what a melt down is, it is when the reactor itself becomes so hot that it literally melts the surrounding chamber and
supporting soil, contaminating groundwater and releasing radiation. It is physically impossible for a nuclear reactor ro explode like an atomic bomb;
it's just not made that way. But it is possible for it to run so hot that the building around it and the ground it sits on literally melts. And
remember, without anything to slow it down, the fuel will continue to produce heat and radiation until it is exhausted.
Here's hoping they get these things cooled down.