Nuclear Energy: an interactive nuclear physics course

Nuclear Energy is an interactive nuclear physics course about where nuclear energy comes from and how we use it. Its 23 short sections cover nuclide notation, the mass defect and E = mc², the binding energy curve, fission and chain reactions, how a reactor works, radioactive decay, alpha, beta and gamma radiation, half-life, nuclear waste and fusion.

It opens with a chain reaction spreading through a field of uranium-235 and control rods holding it steady: the whole idea of a reactor in one picture.

What the course covers

Where the energy comes from

A nucleus weighs slightly less than the protons and neutrons it is made from. That missing mass, the mass defect, is the binding energy holding it together, through E = mc². Iron-56 sits near the top of the binding energy curve, so splitting heavy nuclei (fission) and joining light ones (fusion) both release energy.

Reactors

In fission, uranium-235 absorbs a slow neutron and splits, releasing energy and more neutrons that can split more nuclei. A reactor keeps that chain reaction exactly critical: the moderator slows neutrons so they are captured, control rods absorb spares, and the coolant carries heat away to make steam for turbines.

Radioactive decay and half-life

Unstable nuclei decay by giving out alpha particles, beta particles or gamma rays, each with different penetrating power. Nobody can predict when one nucleus will decay, but in a large sample half of them decay in a fixed time, the half-life.

Here x is time in minutes and y is the percentage of unstable nuclei left. Each half-life halves what remains, so the curve never quite reaches zero.

Try a question from the course

Nuclide notation writes the mass number A (protons plus neutrons) at the top and the atomic number Z (protons) at the bottom. Uranium-235 has A = 235 and Z = 92, so it has 92 protons and 235 − 92 = 143 neutrons.

Now read a new nuclide, then press Mark to check your answer in the course.

Who this course is for

• GCSE physics students revising atomic structure, radioactive decay, half-life, fission and fusion.
• A-level and other advanced physics students working with mass defect, binding energy and nuclear equations.
• Anyone who wants an informed view on nuclear power, waste and the promise of fusion.

What you need to know first

The course page suggests Particles first, for protons, neutrons and antimatter. You need standard form for E = mc² and tiny masses, and halving repeatedly for half-life.

How long it takes

There are 23 sections and most take a few minutes. Learners without a plan can open two sections of a course a day, in order, so the whole course takes 12 days. A plan removes the daily limit and lets you go straight to any topic, such as half-life.

Read next

Physics · Atoms and particlesBinding energy calculator: from the mass defect, in MeVTurn a nucleus's mass defect into its binding energy in MeV or joules, with the working, plus how to find the mass defect and binding energy per nucleon.