How Do Nuclear Reactions Affect Water Heating in Reactors?

[Crazymechanic]

Hi, in nuclear reactors the water is heated while traveling through the core , now this heat comes from the nuclear reaction taking place in the core fuel assemblies, the part that I wnat to know is which of the elementary particles that come out of that reaction heat the water more and which less,
like i suppose neutrons do the major part and what else?
I guess there are some particles that leak out taking the some of the total energy with them and so on.

 

[mfb]

The neutrons and fission fragments carry most of the energy. In addition, many short-living nuclei are produced. When they decay, they release additional energy as alpha radiation (-> kinetic energy of alpha particle is converted to heat), beta radiation (kinetic energy of electron is converted to heat, kinetic energy of neutrino is lost) and/or gamma radiation (energy of photon is converted to heat).

 

[Naty1]

Not much of the energy comes from emitted neutrons; Over 80%of the energy is carried by the fission nuclei:

When a uranium nucleus fissions into two daughter nuclei fragments, about 0.1 percent of the mass of the uranium nucleus[5] appears as the fission energy of ~200 MeV. For uranium-235 (total mean fission energy 202.5 MeV), typically ~169 MeV appears as the kinetic energy of the daughter nuclei, which fly apart at about 3% of the speed of light, due to Coulomb repulsion. Also, an average of 2.5 neutrons are emitted, with a mean kinetic energy per neutron of ~2 MeV (total of 4.8 MeV).[6] The fission reaction also releases ~7 MeV in prompt gamma ray photons.

http://en.wikipedia.org/wiki/Nuclear_fission#Output

 

[Crazymechanic]

So basically what your saying is that most of the heat comes from the u235 daughters?
So like there are nuclei with smaller atomic numbers as whole hitting the water atoms and causing heat and then besides tat there are some neutrons that fly alone and some high energy photons (gammas) that again fly alone just as elementary particles?
And that altogether causes water to heat up? Ok
But then what happens in nuclear fusion as most of the energy there atleast with the D-T reaction is carried by neutrons is that true? And they call them fast neutrons when they leave the fused nucleus and after they hit like the cooling water of the (proposed) reactor they slow down and become thermal neutrons because they left a lot of their kinetic energy to the water while traveling through it right?

 

[mfb]

But then what happens in nuclear fusion as most of the energy there atleast with the D-T reaction is carried by neutrons is that true?

Right.

And they call them fast neutrons when they leave the fused nucleus and after they hit like the cooling water of the (proposed) reactor they slow down and become thermal neutrons because they left a lot of their kinetic energy to the water while traveling through it right?

A significant part of their energy will heat the blanket, and that will heat the water, but the general concept is correct.