I have studied about nuclear reactors and also know their functionality.But some how i couldn't get

Slade Higgins

Slade Higgins

Answered question

2022-04-30

I have studied about nuclear reactors and also know their functionality.But some how i couldn't get answers for some my questions.
1) During fission reaction enormous amount of heat is produced and this heat is in the form of flames?
2)If so does the whole reactor core is burnt?and how come water can be in contact with the burning core?
3)Once a fission process is finished will reactor be ready for next usage or it will left for years for less radioactive?
4) Whether the chain reaction is started by introducing neutrons or done automatically by spontaneous emission of fuel rods?
5)If it is due to neutron introduction then how these neutrons attack the pellets containing uranium correctly and how many tries are required?
I have searched for many sources online but couldn't get a clear image.Hope get now.

Answer & Explanation

Leanna Boone

Leanna Boone

Beginner2022-05-01Added 11 answers

1) There are no flames inside a reactor, because the reactor contains a cooling system which removes the heat (and uses it to boil water and spin a turbine), thereby maintaining the reactor core safely below the temperature at which it would burn. Failure of the cooling system will allow the core to catch fire and burn (as it did in the Chernobyl accident).
2) Water is not in contact with anything that is burning. It is inside pipes that run through the core, and the core is not "on fire".
3) As the reactor operates, it uses up the fissionable fuel loaded into its core and its power output falls gradually. At some point, the spent fuel is extracted from the core and fresh fuel is put into it so the reactor can keep operating. The reactor itself is made radioactive by the fission occurring inside it and after its other components (pumps, valves, pipes, etc.) are worn out, the entire device has to be carefully disassembled (so the radioactive parts can be safely stored) or covered up.
4) The chain reaction starts by itself by spontaneous fission once there is enough fuel placed in its core to make it go critical. No external neutron source is needed.
5) This process is complex, and depends on the details of the design of the core and its cooling system. It is dealt with in detail in the field of nuclear engineering.
Jonas Dickerson

Jonas Dickerson

Beginner2022-05-02Added 22 answers

"1) During fission reaction enormous amount of heat is produced and this heat is in the form of flames?"
No, it's mostly in the form of rapidly moving particles; neutrons, fission fragments, lots of stuff. No flames, or to be technical, combustion. This is a nuclear reaction, not a chemical one (flames are chemistry in action).
You might not think of "rapidly moving particles" as "heat", but the definition of heat is literally the amount of energy being transferred between systems. In this case those systems are the nuclear fuel and a surrounding pool of water (typically).
"3)Once a fission process is finished will reactor be ready for next usage or it will left for years for less radioactive?"
When the fuel stops working, which happens over a period of months, it's removed and replaced. In that respect it's similar to a coal plant that's being fed fresh fuel all the time. The only difference is they generally feed the fuel into a nuclear plant in batches, although that's not true for designs like CANDU.
"4) Whether the chain reaction is started by introducing neutrons or done automatically by spontaneous emission of fuel rods?"
Automatically, generally with the removal of some sort of neutron absorber you put into the fuel mass while you're loading it.

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