In a nuclear reaction 235-U is being constantly divided under high neutron flux. After the division we get 2-3 neutrons with high energy and fission products with its own energy. My question is from what source did we get the temperature that is constantly heating the uranium tablet? From photons (gamma radiation) or from high energy neutrons which loses energy while beieng slowed down in water or from phonons(the quasiparticles) which is generated during division of 235-U and then transported trough crystallic structure of 235-U tablet to its surface?

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    $\begingroup$ Not clear enough, can you try and re-phrase it please? $\endgroup$ – Gareth Meredith Jun 11 at 6:46
  • $\begingroup$ In a nuclear reactor the heat from uranium tablet is constantly heating the water wich spins the turbine. My question is from wich process that heat in tablet is generated (wich particle or quasiparticle is responsible for that)? $\endgroup$ – Nikita. L Jun 11 at 6:51
  • $\begingroup$ Ok, so a nuclear reactor does indeed heat - it has to be submerged in a cold substance, like water. The question you ask is which heat is generated? It comes from the nuclear reactions in the generator. Basically what we have is nuclear reactions happening inside the nuclear core, not so dissimilar to the splitting of the atoms with the correct frequencies for the energy to be released. $\endgroup$ – Gareth Meredith Jun 11 at 6:55
  • $\begingroup$ So is that a photons with high energy that are created during split of uranium atom? $\endgroup$ – Nikita. L Jun 11 at 6:57
  • $\begingroup$ But it seems strange to me, because there are no generated photons during reaction $\endgroup$ – Nikita. L Jun 11 at 6:59

When a U-235 nucleus fissions the energy released is as follows:

$$\begin{matrix} \mathrm{\text{KE of fission products}} && 168 \mathrm{MeV} \\ \mathrm{\text{KE of neutrons}} && 5 \mathrm{MeV} \\ \mathrm{\text{gamma photons}} && 7 \mathrm{MeV} \end{matrix}$$


So the vast majority of the heat comes from the KE of the daughter nuclei. The nuclei emerge from the fission with a high kinetic energy and convert this to heat by scattering off other nuclei in the core.

  • $\begingroup$ So, the phonons of the crystaline of uranium tablet? $\endgroup$ – Nikita. L Jun 11 at 7:16
  • $\begingroup$ @Nikita.L phonons are created when the daughter nuclei collide with nuclei on the crystal lattice and the kinetic energy of the daughter nuclei is converted to vibrational energy of the lattice. $\endgroup$ – John Rennie Jun 11 at 7:23

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