RU2464656C2 - Method of water feed - Google Patents

Abstract

FIELD: process engineering. ^ SUBSTANCE: invention relates to nuclear power production, particularly, to water treatment in makeup water supply to secondary coolant circuit in standby conditions. Water feed from, mainly, separator into evaporator boiler water distribution chamber and forcing it through second circulation loop evaporator tube bank in standby conditions with nuclear reactor maintained hot by proper heat comprises actuating nuclear reactor in intermittent mode during a day at low power with forcing reactor first coolant circuit liquid-metal heat carrier at low rpm of second coolant circuit makeup water pump. After said low-power actuation, water is preliminarily fed from pressure pipe via makeup water pump into evaporator boiler water distribution chamber to design water level in separator. Then, separator and evaporator water levels are leveled by separator pressure reduction After starting makeup water pump at low rpm, second coolant circuit water temperature is controlled by increasing separator pressure on feeding steam of required parameters Note here that second coolant circuit boiler water temperature increase rate is controlled by linear time ratio not exceeding 1-3 degrees centigrade a minute. ^ EFFECT: ruled out cyclic thermal stresses in heat exchangers. ^ 2 dwg

Description

The invention relates to a heat exchange technique and is intended for use in a water treatment system when feeding secondary circuit feed water in a standby mode while maintaining a nuclear power plant (NPP) with its own heat, operating on a liquid metal coolant in a variable load mode.

A device is known for protecting the heat exchanger from corrosion-thermal damage, comprising a sleeve attached to a shielding element, the latter being made in the form of equidistant disks fastened through gaskets by means of bolts, one of the disks being rigidly attached to the sleeve and the other having a fairing facing inward her / Alexandrovsky Yu.V. etc. A device for protecting a heat exchanger from corrosion-thermal damage. SU A.S. No. 1112223, F22B 37/22. Priority - 11.01.83. Publ. Bulletin of inventions No. 33. 09/07/1984 - analogue.

The disadvantage of this technical solution is that the statistics of experience in the design of heat exchangers and thermal calculations of the latter show that, regardless of the pressure, flow, temperature of the liquid, when leaving the heat exchanger body, thermal cyclic voltages do not arise, and therefore installation of this device inside the heat exchanger and for the liquid exit not required. In addition, valves are not installed on the heat exchanger pipe, and the sealing material in the technique can be: thick paper, rubber, paronite, fluoroplastic, nickel, thermally expanded graphite, and other types, but the facts of their use in such structures are not known in the scientific and technical literature.

A protective device is known for heat exchange tubes fixed in a tube plate containing a cylindrical insert, part of which is located in the heat exchange tube, and part protrudes above the tube plate, the insert being installed in the pipe with the formation of an annular gap and provided on the outer surface with annular protrusions in contact with the pipe, the distance between which exceeds the thickness of the tube plate, and around the protruding on the last part of the insert in the plane parallel to the tube plate, the screen is installed / Emelyanov V.I. and others. Protective device of heat exchange pipes. SU A.S. No. 817396, F28F 19/06. Priority - 04/27/79. Publ. Bulletin of inventions No. 12, March 30, 1981 - prototype.

The disadvantage of this technical solution is the extremely narrow, due to the overall dimensions, scope, since the strengthening of the heat exchange tube bundle in the tube plate is carried out with very small interaxal distances - isthmuses commensurate with the wall thickness of the pipes themselves. In addition, the elements of the device create a large amount of unjustified hydraulic resistance, and the place of their maximum concentration is always associated with the corresponding concentration of thermocyclic stresses.

The technical result of the invention is the elimination of thermal cyclic stresses in the welds of the evaporator connecting the pipes to the tube plate of the latter, an increase in the service life of the nuclear power plant as a whole.

The specified technical result is achieved by the fact that the method of supplying water mainly from the separator to the evaporator boiler water distribution chamber with its subsequent pumping through the tube bundle of the evaporator of the second circulation circuit while maintaining the nuclear power plant in hot condition with its own heat, which consists in the fact that periodically, during the day, they put into operation at low power a nuclear reactor with pumping the liquid metal coolant of the primary circuit of the nuclear power plant, followed by starting at low revolutions of the MPC water pump of the first circuit, and after putting into operation at low power a nuclear reactor with pumping the liquid metal coolant of the primary circuit of the nuclear power plant, water is preliminarily supplied from the pressure pipe through the MPC pump to the evaporator boiler water distribution chamber with reference to the nominal water level in the separator, then the separator water temperature is equalized and the evaporator by reducing the pressure in the separator, after starting at low revolutions of the MPC pump, the rate of increase of the water temperature of the second circuit is controlled, increasing the pressure separator steam supply required parameters, while controlling the growth rate of the boiler water temperature of the second circuit MOC produce a linear relationship with time, not exceeding the value (1-3) ° C per minute.

The essence of the invention is illustrated by drawings, where:

figure 1 - presents the pneumohydraulic diagram of the nuclear power plant;

figure 2. - a longitudinal section of the boiler chamber of the evaporator.

The method of supplying water is carried out on a nuclear power plant operating on a liquid metal coolant in the mode of variable loads, including a reactor 0 with an active zone 1, the nuclear fission reaction in which is carried out using the actuators of the control rods 2. Next, a superheater 3, an evaporator 4 follows the path of the liquid metal coolant , a centrifugal pump 5, and again returns to the volume of the reactor 0. The movement of the boiler water of the second circuit is carried out from the separator 6, designed as a storage tank tions appropriate volume of a boiler water and steam perform drying functions. After feeding separator 6 with water and mixing it with the volume of water of separator 6, boiler water of separator 6 is formed, which, due to the forced circulation pump (MPC) 7, enters the distributor chamber 8 of boiler water of evaporator 4, then bypassing the tube of evaporator 4, it enters again separator 6, which, due to separation devices, carries out the drying of the steam-water mixture and sends the dried steam to the superheater 3, followed by supply to the turbine 9, from where it again enters the separator 6 through the condenser 10, fed by Iodically due to leaks in the capacitor 10 with make-up water.

The method of water supply is as follows.

When maintaining the nuclear power plant in hot state with its own heat, it becomes necessary to heat the liquid metal coolant to prevent the latter from freezing in the covers of the control and core protection system 2 in the upper level region, since in this case the nuclear power plant will be uncontrollable. For this, a nuclear reactor is put into operation at low power with pumping the liquid metal coolant of the primary circuit of the nuclear power plant, but to select excess heat and prevent damage to the corresponding equipment, the second circuit of the MPC is connected. As a result of the circulation of the entire volume of the liquid metal coolant of the primary circuit, its temperature is equalized. But when a sufficiently large volume of boiler water with a low temperature arrives from the discharge pipe of the separator 6 into the distributor chamber of the evaporator 8, large values of thermocyclic stresses can occur in the welds of the pipes with the tube plate of the evaporator 8, leading to cracks in the neck of the tube plate and, as a result to inter-circuit softening. To eliminate this damage, the boiler water from the pressure pipe of the separator 6 is passed through small volumes of MPC 7 through the pump until the boiler water level in the separator 6 reaches the nominal mark, then the pressure in the separator 6 is reduced so that the temperature of the boiler water in the separator 6 and in the evaporator 4 caught up. After that, start the pump at low revolutions of the MPTs 7 pump and control the rate of increase in the temperature of the boiler water of the separator 6, increasing the pressure in the separator 6 by supplying the necessary parameters, while controlling the rate of increase of the temperature of the boiler water of the second circuit of the MPTs is linearly time-dependent, not exceeding the value (1-3) ° С per minute, confirmed by calculations and experimental verification on a full-scale nuclear power plant.

The use of a water supply method with the proposed sequence of technological operations eliminates the occurrence of thermal cyclic stresses in the most vulnerable unit of the heat exchange equipment — the evaporator tube plate — and, as a result, will increase the operational reliability resource of the nuclear power plant as a whole.

Claims (1)

The method of supplying water mainly from the separator to the evaporator boiler water distribution chamber with its subsequent pumping through the tube bundle of the evaporator of the second circulation loop while maintaining the nuclear power plant in hot condition with its own heat, which consists in the fact that periodically, during the day, commissioning is carried out at low power nuclear reactor with pumping the liquid metal coolant of the first circuit of the nuclear power plant with subsequent start-up of the second circuit water at low speed of the MPC pump, characterized in that after commissioning at a low power nuclear reactor pumping the liquid metal coolant of the primary circuit of the nuclear power plant, water is preliminarily supplied from the pressure pipe through the MPC pump to the evaporator boiler water distribution chamber with reference to the nominal water level in the separator, then the water temperature of the separator and evaporator is equalized by reducing the pressure in the separator, after starting at low revolutions of the pump, the MPC controls the rate of increase in the water temperature of the second circuit, increasing the pressure in the separator by supplying the necessary steam parameters, while controlling the growth rate of the temperature of the boiler water of the second circuit of the MPC is linearly dependent on time, not exceeding 1-3 ° C per minute.

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