View from B-Deck, one deck up.
Savannah has a pressurized light-water reactor (PWR). First the reactor core generates heat, second high pressure water in the primary coolant loop carries the heat to the steam generator, third inside the steam generator heat from the primary coolant loop vaporizes the water in a secondary (low pressure) loop producing steam, forth the steam line directs the steam to the main turbine in the engine room causing it to turn the turbines which turn the shafts and propellor. Another turbine drives a generator which produces electricity. Finally, The unused steam goes to the condenser where it is condensed into water. The resulting water is pumped out of the condenser, reheated, and pumped back to the steam generator.
The reactor core contains fuel assemblies which are cooled by high pressure water (1750 PSIA), which is circulated by electrically powered pumps (the primary cooling system). The amount of heat generated is controlled by the position of the control rods (boron steel rods that can be raised or lowered between the fuel rods) and the temperature of the primary cooling loop water (higher temperature yields lower power).
Inside Reactor Containment Vessel Forward of Reactor can be seen the large reactor pressure vessel (painted in orange). Inside the reactor are the fuel and control rods that are used to generate heat and control the nuclear chain reaction. Around the rods circulates the high pressure, high temperature (around 500 degree) water of the primary cooling loop.
On the port side is one of the two steam generators on top connected to its heat exchanger at the bottom by downcomers and risers (all painted in purple). The primary loop water circulates through small tubes in the heat exchanger. Around it is the water that is heated to create steam that powers the turbines in the engine room.
Forward of reactor and steam generators is the base of the pressurizer (in grey.) It is a large tank to allow room for the expansion and contraction of the water in the primary loop. Forward on port is an effluent condensing tank (in white.)
In the illustration above the primary (high pressure, radioactive) water cooling loop is in red. The secondary (low pressure, non-radioactive) water and steam loop is in blue.