Nuclear Fission

Fission is a nuclear reaction where a heavy, unstable nucleus (like uranium-235 or plutonium-239) splits into two lighter nuclei, releasing a large amount of energy along with neutrons.

• Usually triggered by absorbing a neutron.
• Releases additional neutrons which can trigger further fissions – a chain reaction.
• Used in nuclear power plants and atomic bombs.

\(^{235}_{92}\text{U} + ^{1}_{0}\text{n} \rightarrow ^{141}_{56}\text{Ba} + ^{92}_{36}\text{Kr} + 3\,^{1}_{0}\text{n}\)

Nuclear Fusion

Fusion is the process where two light nuclei (typically isotopes of hydrogen like deuterium and tritium) combine to form a heavier nucleus, releasing even more energy than fission.

• Occurs naturally in stars, including the Sun.
• Requires extremely high temperatures and pressures to overcome repulsive forces between nuclei.
• Fusion is cleaner and safer than fission but currently hard to control on Earth.

\(^{2}_{1}\text{H} + ^{3}_{1}\text{H} \rightarrow ^{4}_{2}\text{He} + ^{1}_{0}\text{n} + \text{energy}\)

Comparison

Aspect	Fission	Fusion
Nuclei involved	Heavy nuclei split	Light nuclei combine
Energy output	High	Very High
By-products	Radioactive waste	Helium (non-radioactive)
Real-world use	Nuclear reactors	Stars & research reactors

Written by Thenura Dilruk