What are Endothermic Nuclear Reactions?

A nuclear reaction can be described as a process where two atoms, or two nuclei or nucleus and subatomic particles such as a proton, neutron interact together, and a large amount of energy is produced and new elements are also produced.

A + B $\to$ C + D + Energy

Some reactions naturally occur like in the sun, stars, etc. among which only a few are artificially induced to harness their energy. The reactions once started are like chain reactions, they keep on going and carry on energy interaction for a very long duration and keep on decaying. The reactions which release energy during the reaction are known as an exothermic reaction while the one which absorbs energy are known as endothermic reaction. 

What happens during an endothermic nuclear reaction?

Nuclear reactions, including chemical reactions, involve energy modifications. The energy fluctuations in nuclear reactions, on the other hand, are immense as opposed to even the most energetic chemical reactions. In reality, the energy changes in a normal nuclear reaction are significant enough to cause an observable difference in mass. Throughout this segment, we will discuss the relationship between mass and energy in nuclear reactions and demonstrate how seemingly minor variations in mass that occur during nuclear reactions result in the release of immense quantities of energy.

In an endothermic reaction, energy is absorbed from its surrounding in form of heat. To understand this, let us take an example of an ice cube kept in open. Ice is the solid state of H₂O, the bond between molecules is stronger compared to another state to break these bonds we need external energy, now the process of supplying external energy is known as an endothermic process. During this process, old bonds break and new bonds are formed. The electrostatic forces merging them would leave the bond with a decent amount of energy or strength at a point where it meets up to merge and form up new synthetic bonds. If the energy or force is not disseminated, the new bond will split and detach again. Instead, the new bond will expel the extra energy by exchanging various motions of an electron. Rather, the new structure will expel the extra energy by exchanging various motions of an atom or various particles, and then transforms into a stronger new bond.

Energy Released during Nuclear Reaction:

Let’s take the example of a nuclear reaction. An accelerator is used these days to accelerate the particles example, e, p, n, α, etc.'

If we look at more general reaction,

A + B $\to$ C + D,

As per law of energy mass conservation, E = mc²

We can write for above equation as well,

M_Ac² + K_A + M_Bc² + K_B = M_Cc² + K_C + M_Dc² + K_D

The released during a nuclear reaction is given by Q-value,

Q = K_final – K_Initial = (K_C + K_D) – (K_A + K_B)

Q = (M_Ac² + M_Bc²) - (M_Cc² + M_Dc²)

When the value of Q is greater than zero, mass or binding energy is changed into kinetic energy of the resulting product, and this process is known as an exothermic reaction.

When the value of Q is less than zero, kinetic energy is changed into a mass or binding energy of the resulting product, which is known as an exothermic reaction.

Mass Defect equation is used for those reactions where the number of protons and neutrons both are conserved.

Mass defect = m_x – A.u, where the nucleus X has mass number A.

Threshold Energy: It is the minimum energy that is needed to conserve energy and momentum. Let’s understand this with example.

Let the mass be M_A, M_B, M_C, M_D and kinetic energy of elements be K_A, K_C, K_D and kinetic energy of B be zero.  The momentum of molecules is P_A , P_C , P_{D ,} and the momentum of B be zero. To find the threshold we transform to the centre of the mass frame.

The velocity with respect to the center of mass is given as,

The threshold energy is defined in the center of mass system for the given equation by the condition that C and D are produced with zero kinetic energy.

The threshold kinetic energy K^th in the lab system is given by:

if we eliminate u we obtain: $K^{th}=-\left(1+\frac{M_A}{M_B}\right)Q$

Nuclear Fission

 Nuclear fission generates energy by splitting heavy atoms. In a power plant, the energy s generated by a regulated fission chain reaction to produce heat which produces steam, which is then used in a turbine to create electricity. In a nuclear blast, the reaction occurs very rapidly, and the energy emitted manifests itself as an explosion.

Nuclear Fusion

Nuclear fusion is the result of combining two or more atoms to create one or more atomic nuclei and subatomic particles (neutron or proton). The weight difference between the reactants and the components is interpreted as energy release or absorption. This difference in mass occurs attributed to the variations in atomic binding energy between both the nuclei before and after the reaction. Fusion is the mechanism by which active or main sequence stars and other high-magnitude stars generate vast quantities of energy.

Application:

Power: It is used in power generation. It can be used for large-scale power production. It helps as the plasma is stable. The fusion process produces less nuclear waste.

Some disadvantages could be when weaponized. It could destroy lots of life and cause great loss to humanity.

Context and applications:

This topic is significant in the professional exams for both undergraduate and graduate courses, especially for      

• Bachelors in Science (Physics)
• Masters in Science (Physics)