The NRC established minimum design criteria, called the General Design Criteria (GDC), which every nuclear plant must incorporate. Those are located in Appendix A of 10CFR50. Those design criteria help formulate a plant’s design basis, which show up in the final engineering drawings (single-line diagrams, schematics, wiring diagrams, etc). That design basis must be documented in the licensing basis documents (LBDs) that are submitted to the NRC.