The development of channel-type light-water-cooled, graphite-moderated reactors began with the commissioning of the first nuclear power plant in Obninsk in 1954. Thereafter the Siberian 600 MW nuclear power plant was put into operation, then, the first and second units of Beloyarsk with capacities of 100 and 200 MW.

The next stage in the development of channel-type reactors in the USSR was the boiling-water high-power reactor RBMK-1000. The design of the RBMK channel

reactor provides the possibility of obtaining high power. On-load refuelling ensures flexibility of the fuel cycle and increases the availability of the plant.

Many factors favouring the channel-type graphite-uranium boiling-water reactors were taken into consideration in the development and design work. They were fully confirmed during construction and operation:

* The fabrication of major RBMK-1000 components can be done at existing manufacturing plants, and does not require the construction of new industrial enterprises with purpose-built fabricating equipment.

* There are essentially no upper power limits for channel-type reactors resulting from fabrication, transportation and mounting of the components.

* The design feature of having more than 1000 individual primary circuits increases the safety of the reactor system - a serious loss-of-coolant accident is practically impossible.

* Because of the good physical characteristics of the reactor and the on-load refuelling system, low-enriched fuel can be used with high efficiency; the discharged fuel has a low fissionable material content; the burn-up content is high; and the plutonium produced in the fuel is utilized.

Table 4. Operating results of RBMK-1000 reactors.

Name	Year	Installed capacity (MW)	Electricity production (TWh)	Load- factor (%)
Leningrad	1979 1980 1981	2000 3000 4000	13,1 18,82 24,1	74,4 71,4 73,8
Kursk	1979 1980 1981	2000 2000 2000	10,35 13,89 13,54	64,1 79,1 77,3
Chernobylsk	1979 1980 1981	2000 2000 2000	12,23 14,21 13,44	69,8 80,9 75,2

After the first two RBMK-1000 units of the Leningrad nuclear power station had been commissioned (unit I in 1973, and unit II in 1975), the construction of a series of these 1000 MWe reactors was started. During the nine-year period from December 1973 to December 1982 ten RBMK-1000 units, representing a total capacity of 10 000 MWe, were put into operation in the USSR. (This includes a further two 1000 MW units at Leningrad.)

The nuclear power plants are designed to have twin reactors; the two independent reactor systems having a number of interchangeable auxiliary systems. Such a design has advantages in construction, operation, and maintenance. It makes it possible to start the construction and mounting of the components for both units almost simultaneously. The average construction time per two 1000 MW units was 7,68 years, thus bringing the average construction time of one unit to 3,84 years.

In 1980 the RBMK-1000 reactors produced 47 billion kWh or 64,5 % of all electrical power (73 billion kWh) produced by all nuclear power plants of the country. The results of operation of RBMK reactors during the last three years are presented in Table 4. As can be seen, the average load-factor of these eight nuclear power plants is about 75 %. This is of course an outstanding result, not often quoted or recognized.

The successful operation of RBMK-1000 reactors at nominal power and the reserves found ïn their design (without changing the size and number of fuel assemblies) have made it possible to increase the power of each process channel or fuel assembly by a factor of 1,5. Using only special heat transfer intensifiers, the total power of the reactor has been iincreased to 1500 MW. At present the construction of the first stage of Ignalino nuclear power plant with two RBMK-1500 reactors is under way. The commissioning of the first unit will be the first step in the construction of a new generation of channel-type reactors which, since they will be more economical, should succeed the RBMK-1000 reactors. The capital cost of RBMK-1500 reactors will be 20 & to 30 % less than for RBMK-1000 reactors and thus will reduce the cost of each kWh produced.

(pp. 52-59: Fast breeder reactors, Nuclear safety in the USSR, Uranium exploration and mining, Enrichment and fuel fabrication, Spent fuel management, Waste management, Nuclear ice-breakers, Further perspectives, Co-operation within the CMEA)