Graphite-Water Reactor

(also uranium-graphite reactor), a thermal-neutron nuclear reactor in which graphite is used as the moderator and ordinary water is used as the coolant; it belongs to the class of channel reactors. The core of the graphite-water reactors consists of graphite blocks penetrated by metal channels through which the coolant flows. The fuel elements are placed within the channels or on their exterior walls. The core is surrounded by a sealed jacket.

The main distinguishing feature of graphite-water reactors is the absence of a heavy, bulky housing to contain the pressure. By increasing the number of channels it is possible to construct a high-powered reactor (up to 5 gigawatts). In reactors of this type, the fuel cells may be changed by a special remote-control device without shutting down the reactor and without lowering its output (recharging during operation). The high thermal conductivity of water (the coolant), the good nuclear-physical properties of graphite (the moderator), and special design features provide high technical and economic performance levels of atomic power plants with graphite-water reactors. Like all graphite-moderated reactors, the graphite-water reactor has low energy intensity per unit volume of the core.

Graphite-water reactors are most widely used in the USSR. Among these are the reactor in the atomic power plant of the Academy of Sciences of the USSR (the first in the world), the reactors of the first and second units of the Belo-iarsk Atomic Power Plant, and the reactor of the Siberian Atomic Power Plant.