Prototype Instrument for Controlling Reactor Startups

A time-to-power instrument has been developed for use as a primary startup control for nuclear reactors. Time-to-power (TTP) is the projected length of time that will elapse before reactor goal power is reached, as based on the instantaneous neutron flux level and the reactor periods. Thus, the TTP signal is formed by combining the logarithm and period of the neutron flux level (both normally-used startup control signals), with an internally-generated goal flux level signal. The resultant TTP signal is displayed for comparison with the desired TTP value. Maintaining a constant desired TTP signal by adjustment of reactivity controls results in an orderly approach to a selected goal power level. The design considerations of the prototype system are presented with a discussion of the present and future applications. The developed, practical instrument satisfactorily performed the electronic functions required to demonstrate the TTP concept, and data from controlled reactor startups compare favorably with the calculated behavior. The results indicate that safe, efficient and economical startups can be obtained using TTP instrumentation.