The following is a description of a pressurized water reactor plant:

The reactor core consisted of control rods (to add negative reactivity, or reduce the likelihood of fission), and fuel (Uranium-235, which has a high macroscopic cross-section for absorption/fission (It's likely to absorb a neutron and fission).

As the control rods are withdrawn, the fission process starts, as there is a small amount of material that generates "intrinsic source neutrons" (neutrons released by natural isotope decay and at low energy).

As the rods are withdrawn, fission is allowed to occur (the control rods absorb and neutralize any available neutrons). Fission occurs when a low-energy (slow) neutron is absorbed by a U-235 isotope. That isotope becomes very unstable, and will fission (split), releasing energy (in the form of heat) and more neutrons (to continue the fission reaction).

That heat is transferred to the reactor coolant through the fuel module walls (the water itself does not touch the fuel), and the heated coolant is used as a heat source to generate steam to turn turbines and therefore generate electricity. After dumping its heat in the steam generator, the coolant (now cooled) returns to the reactor core.
Source(s):
Ten years of experience in the Naval Nuclear Power field as a Nuclear Elecrtician.


Permalink | Report