American PWRs 69 Reactors
Westinghouse 48
Two Loop 6
Three Loop 13
Four Loop 29
Combustion Engineering 14
Babcock & Wilcox 7
Westinghouse PWRs all have one SG and one reactor coolant pump per loop. A loop is the pipe path that the reactor coolant follows from the reactor to the SG to the reactor coolant pump and back to the reactor vessel. Westnghouse PWRs have two, three or four loops. The reactor coolant enters and exits the SGs from the bottom and flows through thousands of pencil width tubes upward into the steam generating area and then downward and out of the SG after passing through a 'U' bend at the top of the tubes. This type of SG is called a 'U' tube SG. The steam exits the SG from the top.
Combustion Engineering PWRs, unlike Westinghouse, all have two reactor coolant pumps per loop and only two SGs. Like the Westinghouse design they are 'U' tube SGs. San Onofre's two PWRs are Combustion Engineering designs. Like the Westinghouse PWRs the steam exits the SG from the top.
Babcock & Wilcox SG tubes, unlike 'U' tube SGs, are straight and the SG is called a 'once through SG'. The reactor coolant enters the SG from the top, flowing downward as it transfers its heat, and exits from the bottom. The steam exits from the side of the SG. B&W PWRs, like the Combustion Engineering PWRs, all have two reactor coolant pumps per SG and only two SGs.
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