(i) A balanced equation showing nuclear fission of Uranium nucleus is

₉₂U²³⁵ + ₀n¹ → ₅₆Ba¹⁴¹ + ₃₆Kr⁹² + 3(₀n¹) +200MeV.

(Uranium)    (Barium Krypton)

(ii)
1. To maintain the steady rate of fission, the neutron absorbing material known as controller is used. The controller rods are made of cadmium.

2. A moderator is a suitable material to slow down neutrons produced in the fission. For this the moderator rods are graphite rods. 

Energy released per fission    = 200 MeV.

                                      = (200 x 10⁶) x 1.6 x 10^-19J
Now 320 MW = 320 x 10⁶ Js
Therefore, 
No. of fission per second = 

Nuclear fusions taking place in the form of carbon-nitrogen cycle or proton-proton cycles is the most probable source of energy in stars.

An atomic reactor is a furnace in which energy is produced by the nuclear fission process.

The essential component of a reactor are as follows :

(i) Fuel: Uranium enriched with U²³⁵ or Pu²³⁹.

(ii) Moderator: The function of the moderator is to slow down the neutrons. Heavy water. Graphite or beryllium oxide is used as moderator.

(iii) Control rods : To control the chain reaction from becoming violent, rods of neutron absorbing materials like boron steel or cadmium can be inserted into the reactor core.

(iv) Coolant: The fusion product carry large kinetic energy with them. This is manifested as rise in temperature. Heat energy so produced is utilised in vapouring water or liquid sodium.

(v) Shielding: The entire reactor is provided with a thick concrete wall so that radiations emitted during the operation of a reactor may not be hazardous to a person in immediate vicinity.