My physics book mentions that its kinetic energy being released from the splitting of atoms, but it makes more sense for it to be heat energy as the construction of a power plant as shown below is using the energy to heat water to produce steam. Is it really Kinetic energy released from fission or Heat energy, as if it was kinetic then couldn't we directly transfer the kinetic energy to the turbine, without the need of steam.
The fission fragments, a couple of smaller nuclei, a few neutrons, some photons, and some neutrinos, all have kinetic energy as a result of the fission.
In their travels thorough the nuclear reactor the fission fragment often hit atoms and transfer some of their kinetic energy to those atoms which consequently move faster and have more kinetic energy. Moving faster in a random manner and having more kinetic we equate to a rise in temperature, so the reactor core becomes "hotter".
Heat energy is really a specific case of kinetic energy ie it is the kinetic energy of molecules (at least in the thermodynamic sense of heat)
Because nuclear fission generates energy in the form of a combination of energetic particles and electromagnetic radiation in random directions there is no convenient way to directly harness this as kinetic energy and it makes much more sense to absorb the energy of these particles in some other medium and use that to heat water to generate steam.
Effectively using the various types of radiation to heat water turns the random kinetic energy into thermodynamic heat which can then be extracted to do useful work.
There is also the consideration that steam is a good working fluid for power generation as water is abundant and it's boiling point allows for an efficient Rankine cycle plant in the temperature range of practical engineering materials. Or to put it another way steam turbines are a practical and efficient way to convert heat energy into electrical power on a large scale, providing a good balance between capital costs, running costs and overall thermal efficiency.
The products of the nuclear interaction or fission are usually radon or barium with alpha particles and neutrons. The radon or barium have charge and these then interact with charged particles and then net result is charged particles are accelerated. The nuclear energy is converted to kinetic energy, and then by electromagnetic interaction and the acceleration of charge Brehmsstralung radiation in produced. In this way nuclear energy, which is very strong but local or short ranged is converted to electromagnetic energy and photons. These photons are gamma ray photons. These photons then interact with matter and diffuse their energy to produce heat at a much lower energy density.
Temperature is a measure of kinetic energy within matter; even a steel plate that's sitting still on a table has alot of movement happening within it, although it could be said that its atoms are staying in the same configuration. Heat has been described as atoms 'shaking'/'oscillating' at a higher frequency. They cause nearby atoms to do the same, at the expense of their own 'shaking' energy. But heat is just a specific type of movement, if you look at it from the perspective of atoms. Don't take the analogy too seriously though; these things aren't actually spheres shaking back and forth inexplicably