Uranium-235

Definition

Uranium-235 is a naturally occurring isotope of the element uranium that is fissile, meaning it can sustain a nuclear chain reaction. It is the primary isotope used in nuclear reactors and nuclear weapons due to its unique nuclear properties.

5 Must Know Facts For Your Next Test

1. Uranium-235 makes up only about 0.7% of natural uranium, the rest being the non-fissile isotope uranium-238.
2. The fission of uranium-235 releases a large amount of energy, which can be harnessed in nuclear power plants or used in nuclear weapons.
3. The fission of uranium-235 produces two or three neutrons, which can then go on to split other uranium-235 nuclei, sustaining the chain reaction.
4. Uranium-235 has a half-life of approximately 704 million years, meaning it takes that long for half of the atoms in a sample to decay.
5. Enrichment of uranium-235 is a crucial step in the nuclear fuel cycle, as it increases the concentration of the fissile isotope for use in nuclear reactors or weapons.

Review Questions

• Explain the significance of the fissile nature of uranium-235 and how it relates to its use in nuclear reactors and weapons.
  • The fissile nature of uranium-235 means that its nucleus can be split by the absorption of a neutron, releasing a large amount of energy and additional neutrons that can then split other uranium-235 nuclei, sustaining a nuclear chain reaction. This property makes uranium-235 the primary isotope used in nuclear reactors, where the controlled fission of uranium-235 is used to generate electricity, as well as in nuclear weapons, where the uncontrolled fission of uranium-235 is used to create a devastating explosion.
• Describe the process of uranium enrichment and explain why it is a crucial step in the nuclear fuel cycle for uranium-235.
  • Uranium enrichment is the process of increasing the concentration of the fissile uranium-235 isotope relative to the non-fissile uranium-238 isotope. This is necessary because natural uranium contains only about 0.7% uranium-235, which is not enough to sustain a nuclear chain reaction in most nuclear reactors. By increasing the uranium-235 concentration through enrichment, the fuel can be used more efficiently in nuclear reactors, producing more energy per unit of fuel. Enrichment is a crucial step in the nuclear fuel cycle, as it enables the use of uranium-235 in both nuclear power generation and nuclear weapons production.
• Analyze the significance of the half-life of uranium-235 and how it relates to the long-term storage and disposal of nuclear waste.
  • The half-life of uranium-235, which is approximately 704 million years, is a crucial factor in the long-term storage and disposal of nuclear waste. This extremely long half-life means that uranium-235 and its decay products remain radioactive for an incredibly long time, posing challenges for the safe and responsible management of nuclear waste. The long-lived radioactivity of uranium-235 and other actinides in spent nuclear fuel requires the development of robust, long-term storage and disposal solutions, such as deep geological repositories, to ensure the protection of the environment and human health for thousands of generations. The half-life of uranium-235 is a key consideration in the design and implementation of nuclear waste management strategies.

Related terms

Radioactive Decay:

The process by which an unstable atomic nucleus spontaneously loses energy by emitting radiation in the form of particles or electromagnetic waves.

Nuclear Fission:

The splitting of a heavy atomic nucleus, such as uranium or plutonium, into smaller nuclei, which releases a large amount of energy.

Nuclear Chain Reaction:

A self-sustaining sequence of nuclear fission reactions, where the neutrons released by one fission event trigger additional fission events.