8.21. As part of our study of reactor control, we learned how feedback could affect the behavior of a system, particularly its stability (§5.132).

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Should the output of our system serve as the input to a second system or subsystem and then have one of the second system outputs return as input to the original system, we have a feedback effect. In the case of reactor control, the second system could either reinforce or inhibit an original disturbance signal, leading to an unstable or a stable condition, respectively.

8.22. In the reactor design logical flow diagram shown in Fig. 8.1, the required fuel loading, flux pattern, and power distribution evolve from the nuclear design, and some feedback is provided to both the nuclear data and thermal-hydraulic design activities. Thus, we have a typical procedure initiated by a trial design which is then refined by feedback. Although not shown in the figure, the process involves an evaluative stage in which results are compared with goals. This procedure lends itself to automation using standard computer programming practice.