The Instrumentation and Control Circuits of Nuclear Reactors

The chain reaction which takes place in a nuclear reactor is a regenerative process and can therefore be unstable, so the fission rate must be closely controlled in order that the nuclear reaction may proceed at a rate which is both useful and safe. Electronic circuits play a vital part in this, and their reliability must be exceedingly high, as many reactors are required to run for months without interruption and for years without an unscheduled shutdown. This paper considers in a very elementary way the dynamic behavior of a reactor and the circuit requirements associated with maintaining the power level constant. The additional problems associated with starting-up and the automatic shutting-down of a reactor are briefly surveyed and the use of automatic data-handling is considered. It is concluded that not all instrumentation and control problems presented by existing types of reactor have been satisfactorily solved and that more advanced reactors will present still more difficult problems.