How do control rods work in a nuclear fission reactor?

In Nuclear Fission, neutrons collide with radioactive atoms (eg Uranium-235) in order to split the atom into two smaller atoms and releasing energy. The more neutrons there are the faster the reaction so to slow it down you need to remove the neutrons.

This is done using control rods which absorb excess neutrons (reactions require 1 neutron and release 3 so there quickly becomes too many neutrons). They are composed of a material which has many stable isotopes (like Boron) so when the atoms absorb a neutron, they still don't become radioactive. If the reaction is going too fast, the control rods are lowered into the reactor, this increases their surace area to absorb neutrons. If the reaction is going too fast they are rasied up so less neutrons are absorbed.

Answered by Jordan H. Physics tutor

7772 Views

See similar Physics A Level tutors

Related Physics A Level answers

All answers ▸

How would we calculate the distance covered by a train that starts at rest, then accelerates to 5km/hr in 30 mins then stays at this constant speed for 12 minutes?


Find an expression for the escape velocity of a test object.


Two current carrying wires are placed next to each other and anti-parallel currents are allowed to flow. Is the magnetic force between the wires attractive or repulsive?


An alpha particle is accelerated with 5MeV of kinetic energy towards the nucleus of a gold atom with atomic number 79. What is the distance of closest approach that is reached by the alpha particle?


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences