Why Pressurized Water?
Question:
Why do we use HIGH-PRESURE WATER as coolant to carry away energy
from the fuel rods? Won't the pressurization of water make it
process lots of energy already? How come it can stilll be used to
carry away other energy from the fuel rods?
Answer:
In the pressurized water reactor we do not want the coolant to
boil so we must raise its pressure above the saturation pressure
for the operating temperature of the reactor coolant. Due to the
relative incompressibility of the water the energy requirements
to raise its pressure is a tiny fraction of the thermal energy
transferred from the fuel rods. Also there is a partition of
energy so that the elevated pressure does not reduce the heat
capacity of the coolant.