A Digital Start-Up Control Uniit for Nuclecar Reactors

The use of digital circuits for control of a nuclear reactor in the start-up range was proposed in a paper given by S. N. Lehr and V. P. Mathes at the Nuclear Engineering and Science Conference in 1959. A control of this type eliminates the many periodic adjustments that are required with linear circuits and results in a more accurate, reliable, and maintenance free unit. This paper describes the design and development of such a unit which computes and displays digitally the reactor level and period over nine decades of power. The level of the reactor is obtained from a discriminator and binary counter which resolve 2.5 m. v. pulses spaced as little as one microsecond apart. A time modulation technique incorporating binary counters for comparison and read-out is used to compute the period with a short term memory employed to provide statistical smoothing.