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

7786 Views

See similar Physics A Level tutors

Related Physics A Level answers

All answers ▸

Derive an expression to show that for satellites in a circular orbit T^2 ∝ r^3 where T is the period of orbit and r is the radius of the orbit.


Determine an approximate value for the acceleration of free fall using a tennis ball, metre ruler and a stopwatch.


What's the moment of a force and why would I need to understand it?


An electron moving at 1000 m/s annihilates with a stationary positron. What is the frequency of the single photon produced?


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