METHOD FOR ORGANIZING THE NATURAL CIRCULATION OF LIQUID METAL COOLANT OF A FAST NEUTRON NUCLEAR CHAIN REACTOR

Abstract

The invention relates to the field of nuclear engineering and can be used to organize the natural circulation of liquid metal coolant in the heat sink of a fast neutron nuclear reactor.

In order to create a driving pressure of circulation without using pumping equipment and to provide the required direction of natural circulation of the liquid metal coolant in the heat sink circuit of the fast neutron nuclear reactor in the absence of heat transfer from the reactor before filling the pipelines and equipment of the lifting and downing sections of the circuit, they are pre-heated by electric heating to temperatures T.sub.1 and T.sub.2, respectively, which are selected from the condition of inequality: .sub.1(T.sub.1).Math.g.Math.H.sub.1>.sub.2(T.sub.2).Math.g.Math.H.sub.2+P, where: .sub.1(T.sub.1) is the density of the liquid metal coolant at temperature Ti of pipelines and equipment in the lifting section;

.sub.2(T.sub.2) is the density of the liquid metal coolant at temperature T.sub.2 of pipelines and equipment at the downing section;
H.sub.1 is the height difference between the inlet and outlet of the lifting section;
H.sub.2 is the height difference between the inlet and outlet of the downing section;
.sub.P is the hydraulic resistance of the circuit; g is the acceleration of gravity. The circulation of the coolant in the circuit and the transition to natural circulation mode are carried out simultaneously until the nuclear reactor reaches its rated operating parameters by creating a moving pressure of the circulation due to the difference in densities .sub.1(T.sub.1) and .sub.2(T.sub.2) of the liquid metal coolant on the lifting and downing sections of the circuit, respectively.

Claims

1. A method of organizing the natural circulation of liquid metal coolant in the heat sink circuit of a fast neutron nuclear reactor, including pre-heating of the pipelines and equipment of the lifting and downing sections of the heat sink circuit with their subsequent filling with heated coolant, starting the coolant circulation in the circuit and switching to the natural circulation mode, characterized in that pipelines and equipment of the lifting and downing sections of the coolant circuit are pre-heated by electric heating respectively, to temperatures T.sub.1 and T.sub.2, which are selected from the conditions of inequality:
.sub.1(T.sub.1).Math.g.Math.H.sub.1>.sub.2(T.sub.2).Math.g.Math.H.sub.2+P, where: .sub.1(T.sub.1) is the density of the liquid metal coolant at temperature T.sub.1 of pipelines and equipment in the lifting section; .sub.2(T.sub.2) is the density of the liquid metal coolant at temperature T.sub.2 of pipelines and equipment at the downing section; H.sub.1 is the height difference between the inlet and outlet of the lifting section; H.sub.2 is the height difference between the inlet and outlet of the downing section; .sub.P is the hydraulic resistance of the circuit g is the acceleration of gravity, and the circulation of the coolant in the circuit is launched simultaneously with the transition to the natural circulation mode and until the nuclear reactor reaches its nominal operating parameters due to the difference in densities .sub.1(T.sub.1) and .sub.2(T.sub.2) of the liquid metal coolant, respectively, in the lifting and downing sections of the circuit.

Description

[0011] The essence of this invention is illustrated by drawings, where a diagram of a heat sink circuit of the fast neutron nuclear reactor is presented in the FIG. 1, and FIG. 2 shows a graph of the development of natural circulation without using a pump.

[0012] The heat sink circuit contains heat source 1, which can be used as a heat exchanger that is connected to the first reactor circuit (not shown in the drawing) or a nuclear reactor (not shown in the drawing). The output of heat source 1 is connected by means of a lifting pipe 2 with the input of the device for removing heat 3, which is used as an air heat exchanger. Sectional electric heaters 4 are installed on the lifting pipe 2 along the entire length. The outlet of heat removal device 3 is connected by downing pipe 5 to heat source 1 through a tank to compensate thermal expansion of coolant 6. Sectional electric heaters 7, similar to electric heaters 4, are installed on downing pipe 5 along the entire length. The heat sink circuit is connected to the tank of filling and drainage system 8 by means of drainage pipe 9 with valve 10. Heat 100 source 1, heat removal device 3 and tank for compensating thermal expansion of the coolant 6 are equipped with sectioned electric heaters (not shown in the drawing). To minimize heat loss, the heat sink circuit (pipelines 2, 5, 9, heat source 1, heat removal device 3 and tank for compensating thermal expansion of the coolant 6) is provided with thermal insulation (not shown in the 105 drawing).

[0013] The method is as follows.

[0014] To organize the natural circulation of the liquid metal coolant, which is used as sodium, the following sequence of actions is performed in the heat sink circuit of the research fast neutron nuclear reactor. Sectionalized electric 110 heaters 4 and 7 are switched on for heating pipelines and equipment for the lifting and downing sections of the heat sink circuit to the calculated temperatures T.sub.1=230 C. and T.sub.2=210 C., respectively. At the same time, the settings of the current regulators provide heating and maintaining the temperature for heat source 1230 C., for the lifting pipe 2230 C., for the 115 heat removal device 3210 C., for downing pipe 5 and the tank for compensating thermal expansion of coolant 6210 C. Then, evacuation and argon filling of the heat sink circuit are successively performed, and after reaching the required composition of the heat sink circuit gaseous medium, sodium is supplied to the heat sink circuit through the drainage pipe 9 with a 120 flow rate of 2 m.sup.3/h and temperature of 225 C. from the tank of the filling and drainage system 8, by opening the valve 10. In start-up mode, the heat source 1 does not work as a heat exchanger, but is used only for the passage of the coolant through it. When sodium reaches the required level in the tank for compensating thermal expansion 6, valve 10 is closed. The pressure in the gas 125 cavity of tank for compensating thermal expansion 6 rises to 0.14 MPa. In the process of filling the heat sink circuit, the sodium coolant receives the temperature of the pipelines walls and the equipment of the circuit, as a result of which a driving pressure of natural circulation is created in the desired direction. As shown in FIG. 2 under the influence of the natural circulation 130 pressure created by the initial temperature difference T.sub.1 and T.sub.2 of the walls of lifting pipeline 2 and lowering pipeline 5, the sodium flow rate increases from zero to a stabilized value of 3.76 kg/s for 150 s and then remains constant. In the steady state of natural circulation, heat removal device 3 provides the necessary reduction in the temperature of the coolant at the entrance of the 135 downing section. The temperature of sodium at the inlet and outlet of the circuit elements is 210 C. at the input of the heat source 1, 225 C. at the output of heat source 1, 230 C. at the input of heat removal device 3, 210 C. at the output of heat removal device 3. To calculate the temperatures T.sub.1 and T.sub.2, the following values were used: the height of heat source output 16.2 m, 140 the height of heat removal device input 311.1 m, the height of heat removal device output 3-8.4 m, the height of heat source input 16.9 m, coolant density on the lifting section .sub.1(T.sub.1)896 kg/m3, the density of the coolant in the downing section .sub.2(T.sub.2)901 kg/m3, the height difference between the inlet and outlet of the lifting section H.sub.1-4.9 m, the height 145 difference between the inlet and outlet of the downing section H.sub.21.5 m, the hydraulic resistance of the circuit1,600 Pa.