Nuclear Fission (GCSE Physics)

Nuclear Fission

Splitting Nuclei

• We can split a nucleus. Through the process of nuclear fission, we can split a large, unstable nucleus into 2 smaller particles. For example Uranium-235, which is a naturally occurring isotope of Uranium. This is made possible through the use of a nuclear reaction.
• Nuclei undergo induced fission. Nuclei don’t often split up on their own; instead, they have to undergo induced fission. During this process, they absorb a neutron, which leads to fission.
• Spontaneous fission is rare. Sometimes, a nucleus doesn’t have to absorb a neutron to undergo fission. This is called spontaneous fission, but this is very rare.

Process of Nuclear Fission

• The nucleus absorbs a neutron. In most fission reactions, the unstable nucleus will absorb a neutron as the first step.
• The nucleus splits into 2. Once the neutron has been absorbed, the nucleus will split into 2 smaller ‘daughter‘ nuclei. Energy is released through the fission reaction.
• Neutrons and gamma rays are emitted. The nucleus will also emit 2 or 3 high energy neutron when the fission reaction is happening. As well as 2 or 3 neutrons, gamma rays are also emitted.

Products of Nuclear Fission

• Fission products have KE. The neutrons and 2 smaller nuclei released in a fission reaction are highly radioactive and will have kinetic energy. The KE allows the fission products to move away from the original reaction site.
• Gamma rays carry excess energy. Any energy that is not absorbed by the products of the reaction is given to the gamma rays. This means that the gamma rays will move away from the reaction site as well, often at very high speeds.
• Neutrons can start a chain reaction. The neutrons released from a fission reaction will have kinetic energy. Therefore, the neutrons can move around and become absorbed by another large, unstable nucleus. This will lead to a second fission reaction, resulting in a chain reaction.