What do fuel rods do in nuclear reactors?

Answer 1

Uranium

Answer 2

The fuel rods in a nuclear reactor, whether they are cylindrical or flat plates, are designed with two purposes. The first is to seal in the nuclear fuel. Nuclear fuel, when it is used in the reactor, becomes contaminated with highly radioactive fission fragments. The presence of the leftovers presents an extreme hazard because of the radioactivity, and it is quite long-lived. When the fuel is spent, we can remove the fuel bundle (during refueling) knowing the radioactive material inside will stay sealed, stay contained, welded tight within the fuel rod. The other function of the fuel rods is to set up the geometry of a reactor. Let's look at that.

The thing that actually starts any nuclear chain reaction is a spontaneous fission event that releases neutrons. The neutrons initiate and build the chain (and are better at doing that if they slow down). But only if there is enough fissionable material nearby to set up a critical mass. Critical mass in a nuclear weapon is achieved by slamming sub-critical chunks of fissionable material together. In a nuclear reactor, control rods, which absorb neutrons, are pulled out, and at some point there isn't enough neutron-absorbing material in the core to stop the reaction. It begins. The fuel rods, because of their size and shape, contribute to the engineering solution of laying out the core (which is composed of fuel bundles) so that it will go critical when the rods are extracted a certain amount. The spacing is also set up to allow primary coolant to move throughout the core and remove the heat effectively as it acts to slow down the neutrons which will continue the chain.

(Update: This is "MaxxFordham." I can't take credit for most of this answer; I just corrected some minor errors. But to whomever gave me a recommendation trust point: thanks.)

Answer 3

The fuel pellets inside the rods heat themselves internally from the fission of the fuel in them. The fuel rods are heated by conduction from direct contact with the hot fuel pellets.

Answer 4

Fuel cells in a nuclear reactor hold uranium dioxide, a concentrated form of power for the reactor. There are several hundred fuel cells which are held within the reactor core.