Physical start-up of the IBR-2 modernized reactor

Here we present the main results of the investigation of the IBR-2 reactor after the completion of its modernization, which was carried out within the framework of the program of the physical start-up of the reactor in 2010-2011 operated at a low power of up to 30 kW. The IBR-2 reactor was shut down in 2006 since it reached its design service life limits. A considerable part of the reactor main equipment was replaced except for a biological shield, reactivity modulator and technological systems. According to the results of the physical start-up of the modernized IBR-2 reactor the critical loading of the core was 64 fuel assemblies. The remaining uncharged five cells will ensure the reactor service life for no less than 20 years. The efficiency of the control roads of the reactor safety system and the operating speed of the emergency protection system units meet the nuclear safety requirements. The imitation of the accidents connected with the failures of various technological systems that maintain normal functioning of the reactor has demonstrated that in all cases the reactivity insertion rate is less than the acceptable value and the emergency protection system units in any situation will decrease the reactor power to a safe level during the period between pulses. The fast neutron pulse shape is close to Gaussian with a halfwidth at maximum of (220±3) μs. Mean square values of the pulse energy fluctuations do not exceed 5%. The technological systems of the reactor during the physical start-up operated trouble free