Chapter 17: Problem 89

A breeder nuclear reactor is a reactor in which U-238 (which does not undergo fission) is converted into Pu-239 (which does undergo fission). The process involves bombardment of U-238 by neutrons to form U-239, which undergoes two sequential beta decays. Write nuclear equations to represent this process.

Short Answer

Expert verified

The nuclear equations representing the process are: \( {}^{238}_{92}U + {}^{1}_{0}n \rightarrow {}^{239}_{92}U \), followed by \( {}^{239}_{92}U \rightarrow {}^{239}_{93}Np + {}^{0}_{-1}\beta + \bar{u} \), and finally \( {}^{239}_{93}Np \rightarrow {}^{239}_{94}Pu + {}^{0}_{-1}\beta + \bar{u} \).

Step by step solution

Neutron bombardment of Uranium-238

The first step in the process is the neutron bombardment of Uranium-238. When a U-238 nucleus captures a neutron, it becomes Uranium-239. The nuclear equation for this step is: \[ {}^{238}_{92}U + {}^{1}_{0}n \rightarrow {}^{239}_{92}U \]

First beta decay of Uranium-239

Uranium-239 undergoes beta decay, where a neutron is converted into a proton, and an electron (beta particle) and an antineutrino are emitted. The nuclear equation for this decay is: \[ {}^{239}_{92}U \rightarrow {}^{239}_{93}Np + {}^{0}_{-1}\beta + \bar{u} \]This results in the formation of Neptunium-239.

Second beta decay to form Plutonium-239

Neptunium-239 also undergoes beta decay similar to the previous step. The nuclear equation for this decay is: \[ {}^{239}_{93}Np \rightarrow {}^{239}_{94}Pu + {}^{0}_{-1}\beta + \bar{u} \]After this step, Plutonium-239 is formed, which is capable of undergoing fission.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Nuclear Fission

Nuclear fission is a process where an atomic nucleus splits into two or smaller, lighter nuclei, releasing a substantial amount of energy. This reaction is crucial in nuclear power generation and atomic weapons. In a breeder nuclear reactor, materials like Uranium-238 ( uranium which ordinarily does not undergo fission) are transformed into fissile isotopes such as Plutonium-239 ( plutonium), which can undergo fission, through a series of reactions involving neutron bombardment and beta decay. This process not only helps to generate power but also creates more fissile material than it consumes, hence the term 'breeder' reactor.

Beta Decay

Beta decay is a type of radioactive decay involving the emission of beta particles from a nucleus. A beta particle can be an electron ( beta- decay) or a positron ( beta+ decay), accompanied by neutrinos or antineutrinos, respectively. This decay process occurs when there is an imbalance in the number of protons and neutrons inside a nucleus. In the context of a breeder reactor, Uranium-239 and Neptunium-239 undergo beta minus ( beta- ) decay, where a neutron in the nucleus transforms into a proton, and the nucleus emits a beta particle (the electron) and an antineutrino.

Neutron Bombardment

Neutron bombardment refers to the process of bombarding a nucleus with free neutrons. Neutrons, being neutral, can penetrate the nucleus without being repelled by the positive charge. In a breeder reactor, Uranium-238 is bombarded with neutrons, causing it to absorb a neutron and become Uranium-239. This event is the initial step that allows nuclear reactors to transmute non-fissionable elements into fissionable ones. It is also a critical aspect of sustaining a nuclear chain reaction where each fission event releases more neutrons which then bombard other nuclei, causing further fission events.

Nuclear Equations

Nuclear equations are representations of nuclear reactions where the identities and numbers of all reactants and products are described. They are balanced, meaning the total mass and the total atomic number are conserved before and after the reaction. In the equations for the breeder reactor, after the initial neutron bombardment, the uranium transforms through two stages of beta decay, represented by precise equations which illustrate the conversion of neutrons into protons within the nucleus and the emission of beta particles and antineutrinos.

Uranium-238 to Plutonium-239 Conversion

The conversion of Uranium-238 to Plutonium-239 is a multi-step process that enables breeder reactors to produce more fuel than they consume. This process begins with Uranium-238 absorbing a neutron, becoming Uranium-239. Subsequently, this new isotope goes through two sequential beta decays, where it morphs first into Neptunium-239 and then into Plutonium-239. The ability to convert abundant Uranium-238 into the much more scarce Plutonium-239, which is capable of undergoing fission, is what makes breeder reactors so resource-efficient and appealing for sustainable nuclear energy production.

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Short Answer

Step by step solution

Neutron bombardment of Uranium-238

First beta decay of Uranium-239

Second beta decay to form Plutonium-239

Key Concepts

Nuclear Fission

Beta Decay

Neutron Bombardment

Nuclear Equations

Uranium-238 to Plutonium-239 Conversion

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