Digital Control of Power Transients in a Nuclear Reactor

An integrated, closed-loop, control system for online operations in nuclear power plants has been developed and demonstrated with an LSI-ll/23 micro-processor on the 5 MWt fission reactor (NITR-II) that is operated by the Massachusetts Institute of Technology. This control system has inherent capabilities to perform online fault diagnosis, information display, sensor calibration, and measurement estimation. Recently, its scope has been extended to include the direct digital control of power changes ranging from 20-80% of the reactor's licensed limit. This controller differs from most of those discussed in theoretical and simulation studies by recognizing the non-linearity of reactor dynamics, calculating reactivity on-line, and controlling the rate of change of power by restricting both period and reactivity. The controller functions accurately using rods of non-linear worth in the presence of nonlinear feedback effects.