Each subsystem is assigned a two or three letter code. All of the components in a subsystem are then named with that code an additional letter indicating what it is, and number. EG. the primary coolant loop is called the Primary System, its code is PS, the primary coolant pumps are PS-P1 through PS-P4, the valve from PS-P3 and PS-P4 back to the reactor vessel (starboard loop) is PS-6V. Pipes are named by their subsystem, an index, and and diameter, so the line from the starboard pumps (PS-P3 and PS-P4) is PS-12-12 9/16".

You will see the subsystem codes on drawing numbers as well, but not as consistently. I have a bunch of drawings starting with "SC-48" however I haven't seen mention of an SC subsystem.

My text copyright 2020 Tommy Johnson, all rights reserved. I believe the Savannah documentation is property of MARAD or the US government.