On controllability of neutron flux distribution

As a prerequisite to the optimal control of the neutron flux distribution of large reactors, the controllability of the flux distribution is investigated. The distributed parameter system is reduced to a lumped parameter system by means of truncated modal expansion. In a one dimensional reactor, any number of modes are controllable by a single control rod. To maintain the amplitude of each mode at a prescribed level however, it is necessary to have as many control rods as the number of the modes. Discussions are also presented on the decomposition of the optimal control of flux distribution into those of the individual modes, on the controllability of reactors with feedback, and on the controllability when there is constraint on the control rod speed. (author)