[en] We present the main results of the investigation of the modernized IBR-2 reactor carried out within the framework of the program of the power start-up of the reactor in 2011 operated at a power of up to rated 2 MW. According to the results of the power start-up the reactor and its technological systems operated without fail. The new safety control system meets all design objectives and makes it possible to decrease the reactor power to a safe level during the period between pulses. All fast feedbacks (power, flow and isothermal effect) are negative at all levels of power and sodium coolant flow rate through the core. Pulse energy fluctuations are small (5.9% mean square) and considerably less than those of IBR-2 before its shutdown for modernization. The full width at half maximum is (200±4) μs, which is less than for IBR-2 in 2004 ((245±4) μs). The peak pulse power is 1830 MW, background between pulses 8.6% of mean power. The above-mentioned parameters allow the reactor to maintain its safe and efficient operation at a power of 2 MW at a pulse repetition rate of 5 s^-1