Chapter 11: Problem 21

How can a nucleus of uranium- 235 be induced to fission? Describe what happens to the nucleus.

Short Answer

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Answer: To induce fission in a uranium-235 nucleus, you need to hit it with a slow-moving neutron. When the nucleus absorbs the neutron, it becomes unstable and splits into two smaller nuclei, known as fission products. A large amount of energy is released in the form of kinetic energy and gamma radiation. Around 2-3 neutrons are also emitted, which can induce fission in other uranium-235 nuclei, leading to a chain reaction. In nuclear power plants, the energy from this reaction is used to generate electricity, and control rods are used to regulate the process and avoid meltdowns.

Step by step solution

Understanding Fission in Uranium-235

Uranium-235 (U-235) is an unstable isotope of uranium that undergoes fission, which is a process where the nucleus splits into two smaller nuclei. Fission can happen spontaneously, but in most cases, it is induced by the absorption of a neutron by the nucleus of the atom.

Inducing Fission in Uranium-235

To induce fission in a U-235 nucleus, you need to hit the nucleus with a slow-moving neutron. When the U-235 nucleus absorbs this neutron, it becomes uranium-236 (U-236). This new isotope, U-236, has an unstable nucleus and as a result, will break apart into two smaller nuclei.

Understanding The Fission Products

When U-236 undergoes fission, it splits into two smaller nuclei, called fission products. These fission products are typically radioactive isotopes of other elements, such as strontium-90 or cesium-137. The fission process also releases energy in the form of kinetic energy and gamma radiation.

Energy Release and Neutron Emission

During the fission process, a large amount of energy is released. This energy is primarily in the form of kinetic energy of the fission products and the emitted neutrons. The fission of a single U-235 nucleus can release several MeV of energy. Additionally, on average, around 2-3 neutrons are emitted in the fission process. These neutrons can then go on to induce fission in other U-235 nuclei, creating a chain reaction.

Chain Reaction and Controlled Fission

The neutrons emitted during the fission process can be absorbed by other U-235 nuclei, inducing more fission events and creating a chain reaction. This chain reaction is the basis of nuclear power plants, where the energy released during fission is used to generate electricity. In order to control the chain reaction, control rods made of neutron-absorbing materials are used to regulate the number of available neutrons and prevent an uncontrolled chain reaction, which can lead to a nuclear meltdown.

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How can a nucleus of uranium- 235 be induced to fission? Describe what happens to the nucleus.

Short Answer

Step by step solution

Understanding Fission in Uranium-235

Inducing Fission in Uranium-235

Understanding The Fission Products

Energy Release and Neutron Emission

Chain Reaction and Controlled Fission

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