Measurement of reactivity of RB reactor safety rods by means of digital optical incremental encoder

For accidental analyses of HERBE fast-thermal core, an accurate reactivity time function p(t) for the RB reactor safety rods is necessary. In this paper, it is determined in two steps. First, safety rods reactivity-position p(z) function is measured using inverse method, and second, rod position-time z(t) function is measured by PC computer with digital optical incremental encoder. In previously proposed method, z(t) is determined by measurement of rod drop times and assuming constant acceleration during any particular interval of a rod motion (author)