IBR-2 is a pulsed fast reactor of periodic operation. Its main difference from other reactors consists in mechanical reactivity modulation by a movable reflector. The movable reflector is a complex mechanical system providing reliable operation of two parts, which determine the reactivity modulation: the main movable reflector and the auxiliary movable reflector. The rotors of the main and auxiliary movable reflectors rotate in opposite directions with different velocities. When both reflectors coincide near the reactor core, a power pulse is generated.


Table 1. Parameters of IBR-2

Average power, MW 2
Fuel PuO2
Number of fuel assemblies 69
Maximum burnup, % 9
Pulse repetition rate, Hz 5; 10
Pulse half-width, µs:
fast neutrons
thermal neutrons

Rotation rate, rev/min:
main reflector
auxiliary reflector

MMR and АМR material nickel + steel
MR service life, hours 55000
Background, % 7.5
Thermal neutron flux density from moderator surface:
- time average
- burst maximum

~ 1013 n/cm2·s
~ 1016 n/cm2·s

 * at reactor power  2MW [1]



1 - Water moderators
2 - Safety system
3 - Stationary reflector
4 - Fuel assemblies
5 - Cold moderators
6 - Control rods
7 - Main movable reflector
8 - Auxiliary movable reflector


Fuel elements are composed of plutonium dioxide pellets and have a central hole, which allows an increase in the feasible burnup depth by a factor of 1.5.