Question

Write the nuclear reaction that produces \({ }^{233} \mathrm{U}\) from \({ }^{23}\) Th following the absorption of a neutron.

Short answer

The reaction is ^{233}_{90}Th + ^{1}_{0}n ightarrow ^{233}_{92}U via decay of ^{233}_{91}Pa.

Step-by-step solution

Understand the Initial and Final Isotopes

We start with the isotope thorium-233 ( ^{233}_{90}Th ight) and it absorbs a neutron to become uranium-233 ( ^{233}_{92}U ight). This transformation is what we will describe using a nuclear reaction equation.

Write the Reaction Equation

In the initial reaction, thorium-233 absorbs a neutron ( ^{1}_{0}n ight). Subsequently, it undergoes beta decay. The nuclear reaction can be written as: ^{233}_{90}Th + ^{1}_{0}n ightarrow ^{233}_{91}Pa + eta^{-} ^{233}_{92}U ight). The intermediate product is protactinium-233 ( ^{233}_{91}Pa ight), which undergoes beta decay to form uranium-233 ( ^{233}_{92}U ight).

Break Down Each Part of the Reaction

Initially, the neutron is absorbed by thorium, increasing its atomic mass number by 1 but not affecting the atomic number: ^{233}_{90}Th + ^{1}_{0}n = ^{234}_{90}Th. Then, this unstable thorium goes through beta decay, resulting in the formation of ^{233}_{91}Pa and emitting a beta particle (eta^{-}), ultimately yielding ^{233}_{92}U.

Key concepts

Neutron Absorption

Neutron absorption is a vital part of many nuclear reactions, including those involved in producing isotopes like uranium-233. Imagine a neutron, which is neutrally charged, colliding with an atomic nucleus. This neutron can be absorbed by the nucleus, increasing its mass number by one unit. This process does not alter the atomic number, as neutrons do not carry any charge.

For thorium-233, absorbing a neutron turns it into a heavy form of thorium, now labeled as \(^{234}_{90}Th\). Because the mass number increases to 234 while keeping the atomic number the same, the element remains thorium but now has more mass and is usually unstable.

• This instability often leads to other reactions, such as beta decay, which helps the unstable isotope achieve a more balanced state.

Beta Decay

Beta decay is a type of radioactive decay where a neutron in an unstable nucleus is transformed into a proton. This process also releases a beta particle, which is a high-energy, high-speed electron, or positron. Since protons define the atomic number of an element, beta decay increases the atomic number by one, transforming one element into another.

In the reaction involving thorium-234, after neutron absorption, the unstable isotope undergoes beta decay. The emitted beta particle means that a neutron has been converted into a proton, turning the thorium-234 into protactinium-233, \(^{233}_{91}Pa\). This step in the reaction is crucial for eventually forming uranium-233, as it shifts the element up one spot on the periodic table.

Thorium-233

Thorium-233 is a naturally occurring radioactive isotope of thorium with 90 protons and 143 neutrons. It is represented as \(^{233}_{90}Th\). This isotope is less stable and plays a key role in nuclear reactions, especially when aiming to produce nuclear fuel like uranium-233.

When thorium-233 absorbs a neutron, it temporarily becomes thorium-234 before undergoing further radioactive decay. Since thorium-233 is used to breed uranium-233, understanding its behavior during neutron absorption and subsequent transformations is essential for nuclear fuel cycles. This makes thorium-233 important not only in scientific research but also in practical applications such as energy production.

Uranium-233

Uranium-233 is an isotope of uranium with 92 protons and 141 neutrons, represented as \(^{233}_{92}U\). It is a fissile material, meaning it can sustain a nuclear chain reaction, which is important for some nuclear reactors.

The creation of uranium-233 from thorium-233 involves multiple steps, starting with neutron absorption and proceeding through beta decay. This process is central to the thorium fuel cycle, which is an alternative to the more common uranium and plutonium cycles. The end result is a valuable isotope for nuclear power generation due to its ability to release large amounts of energy upon fission.

Protactinium-233

Protactinium-233 is a radioactive isotope with 91 protons and 142 neutrons, represented as \(^{233}_{91}Pa\). It plays a transient yet critical role in the production of uranium-233. After thorium-233 absorbs a neutron and becomes thorium-234, it undergoes beta decay to form protactinium-233.

Protactinium-233 itself will undergo another beta decay, losing another electron to become uranium-233. Although it is merely an intermediate in the process, understanding protactinium-233’s role helps clarify the transformation sequence from thorium to uranium, showcasing its temporary yet crucial step in the nuclear reaction chain.