Nuclear power engineering in the Soviet Union

Thermophysical Reactivity Control of RBMK-1000

“…In practice, it is assumed that in all reactor operation regimes maximum graphite temperature must not exceed the threshold temperature of 750 ... 800 ºC [1], in which the oxidation of graphite in the presence of water vapor is more intense. Essential factor that determine the reliability and safety of nuclear power plants with water-graphite reactors, is the reliability of the graphite moderator (stack), especially in transient regimes.…”

“…RBMK units design allows changing the composition of the purge mixture [1]. Graphite stack temperature is primarily depends on thermal reactor output and nitrogen concentration in purge mixture (further CN), because its components have different thermal conductivity coefficients.…”

“…Changes in reactor power associated with thermal cycling stress in graphite and can lead to premature failure of graphite stack [2,3]. Moreover, fluctuations in the average graphite stack (moderator) temperature lead to corresponding changes in the reactor reactivity, because the RBMK units have a significant positive moderator temperature coefficient on reactivity feedback effect [1,4,5].…”