how does a nuclear reactor generate heat?

Answer 1

Most nuclear power plants use fission to produce heat by exposing the control rods to the core of the reactor. The further in the control rods are, the hotter the reactor gets due to the number of neutrons splitting the uranium atoms in the core.

Nuclear plants use different methods to create and harness the heat - most "commercial" plants use water and various methods to regulate and cool the reactor, and use the water/heat by products to generate the electricity.

Answer 2

A couple of guys have danced around the answer, and some have given information that is just the opposite. SO, how does it generate heat - the heat is the energy release from the splitting of atoms in the radioactive core of the reactor. The heat is usually transferred away from the core by means of a cooling loop. Then, depending on the type of reactor set-up, the loop either transfers to a clean water loop to make steam and drive the generator, or the loop goes to steam and drives the generator.
And the control rods go into the core to absorb the neutrons and reduce the reaction process. And one last thing, the core is usually designed to stay below critical so they don't have to worry about it being a ticking atomic bomb.

Answer 3

Conventional nuclear reactors consist of a bundle of fuel cells containing uranium. Each fuel cell contains a control rod consisting of special materials that absorb neutrons keeping the reactor shut down while inserted or just critical when the rods are pulled to programmed positions. With the rods pulled and the reactor critical, a cloud of neutrons is free to enter the active fuel and cause uranium atoms to split giving up fission heat energy and more neutrons. Heavy uranium atoms containing too many neutrons are unstable and split into a large and small fragment colliding with and heating up nearby metals of the fuel cell which must be cooled by circulating cooling water. The energetic neutrons collide with moderator (water molecules) and give up even more heat while slowing down to the correct speed to reenter more fuel keeping the chain reaction going. Many neutrons are lost in the process and must be captured by biological shielding to prevent injury to personnel. The short answer is that the nuclear reaction produces energetic fission products (particles) and subsequent decay products that transfer energy of motion to pressurized water molecules heating them up in the process.

Answer 4

Lot more complex than this but I'll give you a short one if you like it.

Uranium and plutonium have unstable/radioactive isotopes that decay or break apart naturally. Refining/concentrating these isotopes allows a significant release of particles called neutrons. When enough of this radioactive material ids put close together one Neutron is released it runs into another nuclei/atom relasing more neutrons and it is a chain reaction of neutrons and heat being released. This heat is then used to heat water and make steam which in turn can turn turbines to make electricity.

An atomic bomb is same principle, but essentially an out of control situation.