Nuclear Plant help

[robertbiferi]

I just wanted to understand something about Nuclear Plants and I thought maybe someone here can just tell me.

The Nuclear Rods get lowered into the water and it Heats the water up to make steam I get this.

Now if the water gets to hot the lower Control Rods in Between the Nuclear Rods to slow down the Nuclear reaction.

And I get all of this but one thing.

When the Nuclear Rods are out of the Water what is going on then why is the Nuclear reaction happening in the air and build up??

 

[duke37]

A nuclear reaction in one fuel element will produce neutrons which are slowed down by the water as moderator so that when they enter the next fuel element they are at an optimum speed to set off the next nuclear reaction.
The nuclear reactions without the modulator will be less than optimum and will die away. This described as sub-critical.

The nuclear reaction produces lots of radioactive elements which gradually decay, taking from microseconds to millions of years. This decay produces heat so that when the prime nuclear reaction is stopped there is still heat produced which must be removed.

 

[jackorocko]

When the Nuclear Rods are out of the Water what is going on then why is the Nuclear reaction happening in the air and build up??

needless to say, if they are not properly contained your local landfill would be more like chernobyl.

 

[KJ6EAD]

http://en.m.wikipedia.org/wiki/Nuclear_reactor#_

 

[robertbiferi]

When you say the Water they are in slows down the reaction I do not understand?

This is what I thought is going on.

All the Rods are in a Bed and are reacting with the Rod next to it and this makes Heat.
Then they lower the Rods in the Water to Heat the water and make steam.

Just tell me if I have this right?

 

[KJ6EAD]

Just tell me if I have this right?

Not really. Nuclear fuel rods in a light water reactor are not just fancy immersion heaters. Read or at least skim the Wikipedia article. Here's a little sample:

"Heat generation

The reactor core generates heat in a number of ways:

* The kinetic energy of fission products is converted to thermal energy when these nuclei collide with nearby atoms.

* Some of the gamma rays produced during fission are absorbed by the reactor, their energy being converted to heat.

* Heat is produced by the radioactive decay of fission products and materials that have been activated by neutron absorption. This decay heat source will remain for some time even after the reactor is shut down."

 

[duke37]

I did not say that the moderator slowed down the reaction. I said that the moderator slowed down the neutrons to nearer an optimum speed so speeding up the reaction and if it is got right will be self sustaining (critical).

 

[(*steve*)]

You will find that there are a large number of reactor designs, and not all of them match this "dipping things in water" model.

I think I should move this to the off-topic section.

I did not say that the moderator slowed down the reaction.

Only a Super Moderator could do that. Hey! I resemble that remark.

 

[robertbiferi]

Thanks but

Ok everything I have been looking at says this.

They take Rods made of Uranium and these go into the Water and the Neutrons from one Rod have a reaction with another Rod and so on and this Heats the water.

And if they want to slow down the reaction the lower Control Rods made of Boron in between the Uranium Rods.

The Control Rods made of Boron absorb the Neutrons from the Uranium Rods to slow down the eaction.

And if they want to shot down the reactor all the way the lower the Control Rods down all the way.

Do I have this right just this?

 

[(*steve*)]

For a particular type of reactor (a la Fukashima?) you have it basically correct.

Remember that the fuel rods are tubes which have pellets of fuel inside them (you can't expose the fuel to water), and I believe the same is true for the control rods.

This may help.

 

[KJ6EAD]

By the way, I'm not just some guy looking stuff up on Wikipedia. I used to make the moderator tubing that surrounds the fuel pellets in fuel rods.

 

[duke37]

And I helped develop the magnox fuel element cans for the natural uranium fuelled, high pressure carbon dioxide cooled, graphite moderated reactors. That was a long, long, long time ago.

 

[robertbiferi]

One thing hat ios a la Fukashima Reactor?

And what do you meen the Uranium Rods have Fuel in them that can not touch the watter? They have Uranium Pellets in them.

 

[davenn]

And what do you meen the Uranium Rods have Fuel in them that can not touch the water? They have Uranium Pellets in them.

did you read the link that steve gave a couple of posts back ?
it explained how the fuel rods are made and answers your above question

Dave

 

[(*steve*)]

One thing hat ios a la Fukashima Reactor?

a la

 

[robertbiferi]

Sorry I can only go back 2. posts but what did you meen that I had it down right how Fukashima Reactor works?

What is a Fukashima Reactor?

 

[(*steve*)]

Sorry I can only go back 2. posts but what did you meen that I had it down right how Fukashima Reactor works?

Scroll up the page, or go to the previous page.

What is a Fukashima Reactor?

a) A spelling mistake (Fukushima)
b) A boiling water reactor
c) Have you been under a rock since 11-Mar-2011?

 

[robertbiferi]

Thanks but

Sorry I know what that Reactor is I read it wrong.

But just 2. things?

Everything I read and watch says they take Rods filled with Uranium and put them in a type of rack with Rods made of Boron inbetween them.

This whole thing is put in a Tank of watter and then they lift the Boron Rods out a little bit to turn the reactor on.

When the Boron Rods are lifted a little out it start to let the Uranium Rods react with the other Uranium Rods and the Neutrons coming off them will Heat the watter.

I get this part but am I right that the Uranium and the Boron is what you are calling Fual in the Rods?

 

[davenn]

.......
I get this part but am I right that the Uranium and the Boron is what you are calling Fuel in the Rods?

No, The Uranium pellets are in the fuel rods. The rods of Boron are separate and they go into "gaps" in the framework between the rods that have the Uranium pellets in them


Dave

 

[robertbiferi]

Thanks but

Ok I did some reading and I see there is 2. types of Reactors B.W.R and this is the Boiling Water Reactor and then P.W.R and this is the Pressure Water Reactor.

Now the B.W.R works like this.

The Reactor Core has Watter in it and the Uranium Rods are in the middel of the Watter. Now the Boron Rods are inbetween the Uranium Rods.

Now they Lift the Boron Rods out and the Uranium Rods give off Neutrons and the Watter keep them from Decaying. So the can enter ather Uranium Rods and have a reaction.

Then the Watter Heats up and the Steam gets pumpt out and into the Turbine. Now after the Steam turns the Turbine it drops down to the Condancer that turns it back to Watter and it gets pumpt back to the Reactor Core..

Do I have this right for the B.W.R??