Reactivity control method of light-water cooled, lightwater moderated nuclear reactor core and apparatus therefor

摘要

This invention relates to a method of controlling the reactivity of light-water-cooled, light-water-moderated reactor core and equipment used in this method.;The reactor core is separated into a water region through which light water passes and a substitution region occupied by a water displacer material with lower neutron moderation effect than that of light water (for example, a rare gas or heavy water). In the case of controlling the reactivity of the core, a fluid in the substituion region is substituted between light water and the water displacer material.;Such a method of controlling the reactivity of the core can be utilized for reactivity compensation in response to neutron energy spectral shift operation, load-follow operation, and a change between low-temperature conditions and high-temperature conditions of reactors.;In order to separate the core into the water region and the substitution region, water displacer tubes (17) consisting of tubes with sealed top ends are provided for a fuel assembly (2). The water desplacer tubes are directly incorporated into the fuel assembly and are directly fixed, or a cluster having the water desplacer tubes are inserted into the fuel assembly.