Chapter 17 · Radioactivity and Nuclear Chemistry
17.8Nuclear Power: Using Fission to Generate Electricity
9 min · two checks
Predict
What does a reactor do with the heat from fission?
The idea
- Describe a reactor as controlled fission plus a heat engine.
- Name the role of control rods and waste.
A power reactor holds the neutron multiplication at one. Control rods, made of neutron absorbers such as cadmium or boron, slide in to slow the reaction and out to let it rise. A moderator, often water, slows neutrons so uranium-235 can catch them more effectively. The energy appears as heat, which boils water, turns a turbine, and turns a generator. The electricity is ordinary. The heat source is nuclear.
The fragments of fission are radioactive and remain so, some of them for many thousands of years. Spent fuel has to be cooled and isolated. Accidents happen when cooling fails and the chain reaction, even after shutdown of the neutron flux, leaves decay heat that can damage the core. Judging nuclear power means holding both facts: a dense, low-carbon energy source, and a waste and safety problem that chemistry and engineering have to design for rather than talk away.
Keep these
- Control rods absorb neutrons and set the rate.
- The plant is a heat engine driven by fission.
- Fission products are radioactive waste and a cooling responsibility.