Channel-Type Reactor

a nuclear reactor consisting of a system of separate channels constructed such that the space between the channels is filled with a neutron moderator. The fuel elements along with the nuclear fuel are located within each channel and are cooled by an individual flow of the coolant. The flow to and from the coolant is realized through a piping system.

In principle the size of the core of a channel-type reactor is not limited because of the design features. In view of the tendency to increase unit reactor outputs, it is the core that favorably distinguishes channel-type reactors from shell-type reactors for which an increase in output and, correspondingly, an increase in the size of the core involve difficulties in the manufacture, transport, and installation of large shells. The separation of the coolant and moderator in channel-type reactors allows good neutron balance and effective heat removal in the core. This is achieved by the proper selection of the materials for the moderator and coolant. Channel-type reactors in which graphite serves as the moderator and industrial water serves as the coolant have been intensively developed, since graphite has satisfactory nuclear characteristics and the industrial water has good thermo-physical properties.

Using special systems, it is possible to refuel channel-type reactors during operation, that is, without stopping and cooling the reactor. This improves the economic features of the power installation and allows a steady output of electricity. A core consisting of separate channels permits individual control of the state of each fuel assembly and in the case of damage, immediate replacement. However, in view of the considerable size of the core of channel-type reactors, the specific load is a number of times less than, for example, in shell-type reactors and usually does not exceed, on the average, 15 kW per 1 / of the core. The branched piping system for the coolant inlet and outlet complicates installation and servicing and increases the probability of leakage.

Various types of channel-type reactors have gained wide distribution in many countries. For example, the SGHWR reactor with a heavy-water moderator and boiling-light-water coolant (Great Britain), the NPR carbon-uranium reactor with a water coolant (USA), the AGR carbon-uranium gas-cooled reactor (Great Britain), the CANDU channel-type reactor with a heavy-water moderator and coolant (Canada), and the KC-150 gas-cooled reactor with heavy-water moderator (Czechoslovakia). The USSR has accumulated experience in the construction and use of channel-type reactors, including research reactors, power reactors, breeder reactors, and their combinations (dual-purpose reactors). Graphite, heavy water, and beryllium are used as neutron moderators in channel-type reactors and industrial water, steam-water mixture, superheated steam, and carbon dioxide are used as coolants.

The good economic features and absence of limitations in increasing the unit output of channel-type reactors favor further development despite the low power intensity of their cores. The construction of a number of atomic power plants with lot-produced carbon-uranium water-boiler RBM-K channel-type reactors in series with a power output of 1,000 MW is planned in the USSR. The first of these two-reactor atomic electric power plants—in Leningrad—is in the assembly stage.