Usually boron is alloyed with steel, boron is a very good neutron absorber.
The number of control rods in a reactor will vary with the size and the design.
fuel rods and control rods
The control rods inside a nuclear reactor are made out of Boron.
nuclear reactor control rods
control rods.
By the control rods and by the moderator.
Not really. Control rods are used to start up and shut down a nuclear reactor.
They are used in nuclear reactor to control the rate of fission of uranium and plutonium. Because these elements have different capture cross sections for neutrons of varying energies, the compositions of the control rods must be designed for the neutron spectrum of the reactor it is supposed to control.
Known as fuel rods, these are hollow metal rods that contain the uranium fuel for a nuclear reactor.
number of control rods
We see the use of control rods in a reactor to absorb neutrons. These rods are often made of boron.
In order to slow down the chain reaction in a nuclear reactor, i.e. to reduce KEff, you would insert the control rods.