One of the possible trends in further improvement of the reactor of the proposed design is to use a micromodule with boiling water in the primary circuit. Fig.5 illustrates the experimental results of an experiment in which the micromodule is filled with water to a certain level (V= 90, 80 and 65% of the total free micromodule volume) and cut off the pressurizer. Thus, the pressure balance under heating-up conditions is due to the gas (steam-gas) volume being in the upper part of the micromodule. It is evident from the figure that a micromodule power of 1070 kW can be reached with V0= 80% at a pressure of 5.3 MPa. With filling V0 = 65 %, such a power is reached at a pressure of З. ЗМРа; the coolant flow rate of the primary circuit with boiling water in both cases being higher than under the non-boilin conditions. It is necessary, however, to note that flow rat fluctuations were observed in a restricted range of powers (e. g. with a amplitude of 1.5 % at V 80 % within the range of power from 250 to 350 kW and 15 % with V = 65 % at a power up to 150 kW.