PLEASE.PLEASE help?

Question

1. What is the "bullet" used to start a nuclear fission reaction?

2.Why is the fission reaction that takes place in a nuclear reactor called a chain reaction?

3. What fuel is used in a nuclear fission reaction? in a nuclear fusion reaction?

4. what are the main parts of a nuclear fission reactor? How is the rate of the fission reaction in a nuclear reactor controlled?

I need these answers for a test tomorrow and i forgot my book! it's 8th grade science.

Answer 1

help me too! D:

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Answer 2

1) A neutron.

2) Because neutrons cascade from one atom of uranium or plutonium (the fuel) after one atom has been struck.  The released neutrons then strike other atoms, which release more neutrons, etc.

3) Uranium 238 or Plutonium 239

4) Reacor Vessel, Reactor Core, Coolant, Heat Exchanger, Moderator (AKA Control Rods).  The reaction is controlled by raising or lowering the moderators.  The further out they are, the less neutrons are adsorbed by the moderators, and the faster the reaction.