Doubt

Nuclear criticality: if in this process the neutron population remains relatively constant then we state that the reactor has achieved criticality. There are many variables that can change the state of the reactor, but a good design will try to keep the reactor inherently stable. In a nuclear reactor, the reactor operator ues control rods to effectively or actually (depending on construction) absorb neutrons. By changing the position of these rods in the core he can change the status of criticality.