Figure 4.5 is a flow diagram that summarizes the various stages in establishing an optimized nuclear core design that have been described above. This is an involved and rigorous process that typically takes several weeks of man effort and iteration. The overall timescales are heavily dependent on the experience of the designers, the tools at their disposal (including consideration of set-up time, run time, ease of iteration perhaps using graphical interfaces), the experience-base of previous core analysis of the same reactor design, and the nuances of the reactor design itself.

NuScale/SMR-160 Westinghouse SMR

37 fuel assemblies 89 fuel assemblies

Figure 4.4 Comparison of core size for a range of iPWRs and a modern large PWR.

It should be noted that this is not the end of the design and analysis phase for this reactor. From here, interfaces with other elements of the design team begin (e. g., transient analysis, thermal hydraulics, mechanical design and fuel performance), and additional iterations may be required prior to initiating the go-ahead to start manufacturing the fuel (usually approximately 12 to 18 months prior to refueling).