The efficiency of a nuclear power plant in comparison to a conventional thermal power plant is

The efficiency of a nuclear power plant is generally less than that of a conventional thermal power plant because of the inherent limitations in its operating temperature and thermodynamic cycle.

In a nuclear power plant, the heat energy is produced by nuclear fission within the reactor core. However, the maximum temperature inside the reactor is limited due to the constraints imposed by fuel element materials, coolant properties, and reactor safety considerations.

Typically, the steam temperature and pressure in a nuclear plant are much lower than those achievable in a conventional coal-fired thermal plant. As a result, the thermal efficiency of a nuclear power plant usually ranges between 30% and 35%.

On the other hand, a conventional thermal power plant using coal or oil can operate at much higher steam temperatures and pressures, achieving an efficiency of about 35% to 42% or even higher with modern supercritical technologies.

Hence, due to the lower operating temperature and pressure of the working fluid in a nuclear plant, its efficiency is comparatively lower than that of a conventional thermal plant.

Therefore, the correct answer is Option C: Less.