Radioactive waste from nuclear power stations is a man-made source of background radiation - AQA - GCSE Physics - Question 5 - 2020 - Paper 1

One nuclear fuel is uranium.

In a nuclear reactor, a neutron is absorbed by a uranium nucleus, which causes the nucleus to become unstable. This instability leads to the nucleus splitting into two smaller nuclei, referred to as fission fragments, along with the release of 2 or 3 additional neutrons. These neutrons can then initiate further fission reactions in other uranium nuclei, creating a chain reaction. Additionally, gamma rays are emitted, which carry away energy from the reaction.

In nuclear fusion, lighter nuclei, such as isotopes of hydrogen, join together to form a heavier nucleus, releasing a substantial amount of energy. This process converts some of the mass of the nuclei into energy, as described by Einstein's equation, $E=mc^2$, where E is the energy, m is the mass lost, and c is the speed of light.

The advantage of radioactive waste having a shorter half-life is that it decreases in activity more quickly, posing less long-term risk to the environment and human health. This means there is less time required for monitoring and waste management, reducing the potential impacts of radiation exposure.