Method for controlling reactivity of boric acid-free reactor

Abstract

The present invention provides a method for controlling the reactivity of a boric acid-free reactor in a secondary system of a pressurized light-water reactor, wherein: a turbine and a main water feeding system of a pressurized light-water reactor comprise a steam generator (S / G), a high-pressure turbine, a low-pressure turbine, a high-pressure feedwater heater, and a low-pressure feedwater heater; the high pressure turbine is provided with extracted steam ① and ② capable of heating feedwater, the low pressure turbine is provided with extracted steam ③ and ④ capable of heating feedwater, the high-pressure feedwater heater is provided with high pressure heaters ① and ② for receiving extracted steam from the turbines to heat feedwater, and a low-pressure feedwater heater is provided with low pressure heaters ③ and ④ for receiving extracted steam from the turbines to heat feedwater; and when operated with constant reactivity and temperature set as default values, the high-pressure heater ① receives extracted steam ② of the high-pressure turbine to heat feedwater, the high-pressure heater ② receives extracted steam ① of the high-pressure turbine to heat feedwater, the low-pressure heater ③ receives extracted steam ④ of the low-pressure turbine to heat feedwater, and the low-pressure heater ④ receives extracted steam from the low-pressure turbine ③ to heat feedwater.

Description

Boron-free reactor reactivity control method

[0001] The present invention relates to controlling the reactivity of a reactor core for boron-free operation by selectively supplying the discharge of high-pressure heaters and low-pressure heaters to a plurality of feedwater heaters in a boron-free pressurized water reactor to control the feedwater temperature of a steam generator.

[0002] A reactor reactivity control device for boric acid-free operation, which stores a neutron absorber on the upper part of a guide tube during normal reactor operation and can inject the neutron absorber into the guide tube through a door system in the event of a reactor accident, is disclosed in Korean Patent Publication No. 10-1928422.

[0003] The reaction control device provided inside the reactor includes a door system provided on the upper part of a guide tube placed inside the outer wall container of the reactor and an actuator installed outside the door system and having an electromagnet.

[0004] The door system comprises a neutron absorber storage section having an internal space communicating with a guide tube, an absorber housing installed inside the neutron absorber storage section for storing the neutron absorber, and an opening / closing device for opening / closing the absorber housing so that the neutron absorber can be introduced into the guide tube.

[0005] The opening mechanism is supported by the magnetic force of the electromagnet, and opens by losing the magnetic force of the electromagnet when the reactor power is lost. A plurality of door systems are provided, and a single actuator can operate the plurality of door systems. The actuator further includes a dummy mass for balancing the plurality of door systems.

[0006] Korean Patent Publication No. 10-2013-0012318 discloses a method for controlling the temperature of a reactor coolant, which compensates for the excess reactivity resulting from the reduced amount of boron by setting the temperature of the coolant somewhat higher instead of reducing the amount of boron injected into the coolant in the initial core state, and then reduces the overall excess reactivity and the amount of boron, a toxic substance, by lowering the temperature of the coolant according to the burnup of the nuclear fuel.

[0007] The method for controlling the temperature of the reactor coolant controls the excess reactivity of the reactor by including a step of gradually lowering the temperature of the coolant circulating inside the reactor from the initial core state as the combustion of nuclear fuel progresses.

[0008] The coolant temperature in the initial core state is the temperature to reduce the excess reactivity according to the amount of boron injected into the coolant in the initial core state.

[0009] The temperature of the coolant is controlled by controlling the temperature of the secondary cooling water cooled in the condenser and the amount of secondary cooling water supplied to the heat exchanger.

[0010] Based on the same burnup of nuclear fuel, the lower the reactor output, the lower the coolant temperature is controlled.

[0011] [Prior Art Literature]

[0012] [Patent Document]

[0013] (Patent Document 1) Korean Patent Publication No. 10-1928422

[0014] (Patent Document 2) Korean Patent Publication No. 10-2013-0012318

[0015] In nuclear power plants, pressurized water reactors use control rods and boric acid to control the reactivity of the core, but in the case of boric acid-free pressurized water reactors, the boric acid reactivity control means cannot be used, so other reactivity control means are required.

[0016] Therefore, the present invention proposes a method for controlling the reactor reactivity by indirectly controlling the core reactivity in a boric acid-free pressurized water reactor through the feedwater temperature control method and the purge distribution method of the high-pressure turbine / low-pressure turbine and the purge amount control method.

[0017] In the method for controlling the reactivity of a boron-free reactor of a secondary system of a pressurized water reactor of the present invention, the turbine and main feedwater system of the pressurized water reactor include a steam generator (S / G), a high pressure turbine, a low pressure turbine, a high pressure feedwater heater, and a low pressure feedwater heater.

[0018] The high-pressure turbine of the present invention is provided with extraction high-pressure turbines ① and ② capable of heating feedwater, and the low-pressure turbine is provided with extraction low-pressure turbines ③ and ④ capable of heating feedwater.

[0019] The high-pressure feedwater heater of the present invention comprises high-pressure heaters ① and ② that receive air from a turbine and heat the feedwater, and the low-pressure feedwater heater comprises low-pressure heaters ③ and ④ that receive air from a turbine and heat the feedwater.

[0020] In the present invention, in cases where a change in the reactivity of the reactor core is not required (determined by a previously set exhaust distribution method going to the steam generator (S / G steam generator), the high-pressure heater ① receives the exhaust air ② of the high-pressure turbine and heats the feedwater, the high-pressure heater ② receives the exhaust air ① of the high-pressure turbine and heats the feedwater, the low-pressure heater ③ receives the exhaust air ④ of the low-pressure turbine and heats the feedwater, and the low-pressure heater ④ receives the exhaust air ③ of the low-pressure turbine and heats the feedwater.

[0021] In the present invention, when an increase in the reactivity of the reactor core is required (the feedwater temperature going to the steam generator (S / G steam generator) is lowered by the following extraction distribution method), the high-pressure heater ① receives the extraction ④ of the low-pressure turbine to heat the feedwater, the high-pressure heater ② receives the extraction ③ of the low-pressure turbine to heat the feedwater, the low-pressure heater ③ receives the extraction ② of the high-pressure turbine to heat the feedwater, and the low-pressure heater ④ receives the extraction ① of the high-pressure turbine to heat the feedwater.

[0022] In the present invention, when a decrease in the reactivity of the reactor core is required (the feedwater temperature going to the steam generator (S / G steam generator) increases by the following extraction distribution method), when the reactivity is suppressed and the feedwater temperature increases, the high-pressure heater ① receives the extraction ① of the high-pressure turbine to heat the feedwater, the high-pressure heater ② receives the extraction ② of the high-pressure turbine to heat the feedwater, the low-pressure heater ③ receives the extraction ③ of the low-pressure turbine to heat the feedwater, and the low-pressure heater ④ receives the extraction ④ of the low-pressure turbine to heat the feedwater.

[0023] In the present invention, when it is necessary to control the feedwater temperature for the microreactivity of the reactor core, the high-pressure heater ① receives the combined extraction from the ① extraction of the high-pressure turbine and the ④ extraction of the low-pressure turbine as one through a three-way valve and heats the feedwater, and the high-pressure heater ② receives the combined extraction from the ③ extraction of the low-pressure turbine and the ② extraction of the high-pressure turbine as one through a control valve and heats the feedwater.

[0024] The present invention has the effect of providing a means for controlling the reactor reactivity by selectively supplying the discharge of high-pressure heaters and low-pressure heaters to a plurality of pole heaters in a boron-free pressurized water reactor, thereby controlling the feedwater temperature of a steam generator and thereby controlling the reactivity of a reactor core.

[0025] Figure 1 is a schematic diagram of the steam generator, turbine, and main feedwater system of a pressurized water reactor.

[0026] The reactivity of a nuclear reactor core can be controlled by changing the reactivity control means, such as direct neutron absorbing materials and indirect thermal-hydraulic conditions, which can affect the number density of neutrons that contribute to nuclear fission.

[0027] In the case of commercial pressurized water reactors, solid B4C (boron carbide) control rods that directly absorb neutrons and liquid boric acid are used as control means, but since liquid boric acid cannot be used in boric acid-free reactors, other reaction control means must be considered.

[0028] In the present invention, the control means of a boric acid-free pressurized water reactor is to control the temperature change of the reactor coolant and moderator.

[0029] The temperature of the coolant and moderator is inversely proportional to the reactivity, so the reactivity can be controlled by adjusting the temperature when necessary.

[0030] In a pressurized water reactor, the coolant circulates in a closed loop and changes its temperature through heat exchange with the steam generator, and the steam generator can be controlled by the flow rate and temperature of the feedwater, which is the condensate returned to the turbine.

[0031] Therefore, the reactivity of the reactor core can be controlled by controlling the flow rate or temperature of the feedwater, which is the steam generator condensate.

[0032] However, changes in the flow rate of the condensate, which is the feedwater, can cause rapid changes in the water level and pressure of the steam generator in a pressurized water reactor, so it is necessary to control the temperature of the condensate, which is the feedwater.

[0033] Figure 1 is a schematic diagram of the steam generator, turbine, and main feedwater system of a pressurized water reactor.

[0034] The turbine and main water supply system of a pressurized water reactor includes a steam generator (S / G) (100), a high pressure turbine (HP TBN) (200), a low pressure turbine (LP TBN) (300), a high pressure feedwater heater (400), and a low pressure feedwater heater (500).

[0035] The high-pressure turbine (200) is equipped with high-pressure turbine ① and ② extractors capable of heating feedwater.

[0036] The low-pressure turbine (300) is equipped with the ③ and ④ exhausts of the low-pressure turbine that can heat the feed water.

[0037] The high-pressure feedwater heater (400) is equipped with high-pressure heaters ① and ② that receive exhaust air from a turbine and heat the feedwater.

[0038] The low-pressure feedwater heater (500) is equipped with low-pressure heaters ③ and ④ that receive exhaust air from the turbine and heat the feedwater.

[0039] Basically, the turbine exhaust is used as a heater heat source for the feedwater heater to heat the feedwater of the steam generator (S / G) (100).

[0040] It includes major components such as a chemical addition system for cooling a steam generator (100), a condenser system, an auxiliary feed pump system, and an air separation system (Daerator).

[0041] The steam generator feedwater is circulated to the steam generator after the condensate that has passed through the turbine is reheated through the feedwater heater.

[0042] At this time, the feedwater heater heats the feedwater by using the high heat of the high-pressure turbine and low-pressure turbine exhaust.

[0043] However, the type and amount of extraction of high-pressure turbines and low-pressure turbines currently used in high-pressure feedwater heaters and low-pressure feedwater heaters are designed to be fixed.

[0044] This causes a certain amount of discharge to be sent to the high-pressure feedwater heater and the low-pressure feedwater heater in a fixed order at a given output.

[0045] The number of high-pressure and low-pressure turbines and the number of high-pressure and low-pressure heaters can be added and used as needed.

[0046] The high pressure turbine (200) is equipped with the ① and ② exhausts of the high pressure turbine capable of heating the feed water, but is not limited thereto, and a configuration in which the high pressure turbine (200) is configured to add the exhausts of the high pressure turbine capable of heating the feed water is possible.

[0047] The low-pressure turbine (300) is equipped with the ③ and ④ exhausts of the low-pressure turbine capable of heating the feedwater, but is not limited thereto, and the low-pressure turbine (300) is configured to have an exhaust of the low-pressure turbine capable of heating the feedwater added thereto.

[0048] Therefore, the present invention proposes a control method for controlling reactor reactivity by controlling feedwater temperature through a method of bleed distribution and a method of bleed amount control of a high-pressure turbine and a low-pressure turbine.

[0049] Feedwater temperature control method through purge distributionMethod of controlling reactivity (feedwater temperature)High pressure heater①High pressure heater②Low pressure heater③Low pressure heater④Default (constant reactivity / temperature) ②purge connection of high pressure turbine①purge connection of high pressure turbine④purge connection of low pressure turbine③purge connection of low pressure turbineIncrease in reactivity (drop in feedwater temperature)④purge connection of low pressure turbine③purge connection of low pressure turbine②purge connection of high pressure turbine①purge connection of high pressure turbineSuppress reactivity (increase in feedwater temperature)①purge connection of high pressure turbine②purge connection of high pressure turbine③purge connection of low pressure turbine④purge connection of low pressure turbineIf fine reactivity (feedwater temperature) control is necessary, add a control valve to ④purge of low pressure turbine and ①purge of high pressure turbineAdd a control valve to ③purge of low pressure turbine and ②purge of high pressure turbine--

[0050] In the method of controlling the feedwater temperature through the discharge distribution, the default value indicates the number of discharges that the feedwater heater receives as a heat source in normal conditions, and at this time, the high-pressure / low-pressure heaters ①② / ③④ receive discharges ②,① / ④,③ from the high-pressure and low-pressure turbines, respectively.

[0051] In cases where suppression of the reaction rate is required, high pressure / low pressure heaters ①② / ③,④ with large extraction energy receive extraction from ①,② / ③,④ of high pressure / low pressure turbines, and in the opposite case, high pressure / low pressure heaters ① / ② / ③ / ④ receive extraction from ④ / ③ / ② / ① of low pressure / high pressure turbines.

[0052] In addition, when fine reactivity and feedwater temperature control are required, the function can be implemented by adding an exhaust valve, a control valve, a 3-way valve, etc. to the ④ / ①, ③ / ② exhaust lines of the low-pressure / high-pressure turbine supplied to the feedwater final stage (high-pressure heaters ① and ②).

[0053] That is, the control method of controlling the reactor inlet temperature by controlling the feedwater temperature using the energy difference of the exhaust in a pressurized water reactor and ultimately controlling the reactor core reactivity is specifically explained as follows.

[0054] (1) When the reaction rate and temperature are set to the default value (default value)

[0055] High-pressure heater ① receives the exhaust air of high-pressure turbine ② and heats the feed water.

[0056] High-pressure heater ② receives the exhaust air from the high-pressure turbine ① and heats the feed water.

[0057] Low-pressure heater ③ receives the exhaust air from the low-pressure turbine ④ and heats the feed water.

[0058] The low-pressure heater④ receives the exhaust air of the low-pressure turbine ③ and heats the feedwater.

[0059] (2) In case of increased reactivity (decrease in water supply temperature)

[0060] The high-pressure heater ① receives the exhaust air from the low-pressure turbine ④ and heats the feedwater.

[0061] The high-pressure heater ② receives the exhaust air from the low-pressure turbine ③ and heats the feedwater.

[0062] The low-pressure heater ③ receives the exhaust air from the high-pressure turbine ② and heats the feedwater.

[0063] The low-pressure heater④ receives the exhaust air from the high-pressure turbine ① and heats the feedwater.

[0064] (3) In case of suppressing the reaction (increasing the water supply temperature)

[0065] High-pressure heater ① receives the exhaust air from the high-pressure turbine ① and heats the feedwater.

[0066] High-pressure heater ② receives the exhaust air of the high-pressure turbine ② and heats the feed water.

[0067] The low-pressure heater ③ receives the exhaust air of the low-pressure turbine ③ and heats the feedwater.

[0068] The low-pressure heater ④ receives the exhaust air from the low-pressure turbine ④ and heats the feedwater.

[0069] (4) When micro-reactivity (water supply temperature) control is required

[0070] High-pressure heater ① receives the 3-way valve bleed from the high-pressure turbine's bleed ① and the low-pressure turbine's bleed ④, and heats the feedwater.

[0071] The high-pressure heater ② receives the exhaust from the low-pressure turbine's ③ exhaust and the high-pressure turbine's ② exhaust through a control valve and heats the feedwater.

[0072] In [Table 1], the default value indicates the number of bleeds that the feedwater heater receives as a heat source in normal conditions, and at this time, the high-pressure / low-pressure heaters ①② / ③④ receive bleeds ②,① / ④,③ from the high-pressure and low-pressure turbines, respectively.

[0073] In cases where suppression of the reaction rate is required, high pressure / low pressure heaters ①② / ③,④ with large extraction energy receive extraction from ①,② / ③,④ of high pressure / low pressure turbines, and in the opposite case, high pressure / low pressure heaters ① / ② / ③ / ④ receive extraction from ④ / ③ / ② / ① of low pressure / high pressure turbines.

[0074] In addition, if fine reactivity and water temperature control are required, the function can be implemented by adding an exhaust valve or a 3-way valve to the lines ④ / ① and ③ / ② supplied to the final stage of water supply (high-pressure heaters ① and ②).

[0075] Therefore, it is possible to control the reactivity of the reactor core for boron-free operation by selectively supplying the high-pressure heater and the low-pressure heater to multiple feedwater heaters in a boron-free pressurized water reactor and controlling the feedwater temperature of the steam generator.

[0076] The present invention has the effect of providing a means for controlling the reactor reactivity by controlling the reactivity of a reactor core in a boric acid-free pressurized water reactor.

[0077] Although the present invention has been described in detail through representative examples above, those skilled in the art will understand that various modifications can be made to the above-described embodiments without departing from the scope of the present invention.

[0078] Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by all changes or modifications derived from the patent claims as well as the equivalent concepts of the patent claims.

[0079] [Explanation of symbols]

[0080] 100: Steam Generator (S / G)

[0081] 200: High Pressure Turbine (HP TBN)

[0082] 300: Low Pressure Turbine (LP TBN)

[0083] 400: High-pressure feedwater heater

[0084] 500: Low-pressure feedwater heater

Claims

1. In a method for controlling the reactivity of a boron-free reactor in the secondary system of a pressurized water reactor, The turbine and main feedwater system of the pressurized water reactor includes a steam generator (S / G) (100), a high pressure turbine (200), a low pressure turbine (300), a high pressure feedwater heater (400), and a low pressure feedwater heater (500). The high pressure turbine (200) is equipped with ① and ② exhaust fans that can heat the feed water. The low pressure turbine (300) is equipped with ③ and ④ exhaust fans that can heat the feed water. The high-pressure feedwater heater (400) is equipped with high-pressure heaters ① and ② that receive air from the turbine and heat the feedwater. The low-pressure feedwater heater (500) is equipped with low-pressure heaters ③ and ④ that receive exhaust air from the turbine and heat the feedwater. If the reaction rate and temperature are set to the default value, The high-pressure heater ① receives the exhaust air of the high-pressure turbine ② and heats the feed water. The high-pressure heater ② receives the exhaust air of the high-pressure turbine ① and heats the feed water. The low-pressure heater ③ receives the exhaust air from the low-pressure turbine ④ and heats the feed water. A method for controlling the reactivity of a boron-free reactor in the secondary system of a pressurized water reactor, characterized in that the low-pressure heater ④ receives the exhaust of the low-pressure turbine ③ and heats the feedwater.

2. In paragraph 1, In addition to the ① and ② blowers that can heat the feed water, it is possible to add a blower to the high pressure turbine (200). A method for controlling the reactivity of a boron-free reactor in a secondary system of a pressurized water reactor, characterized in that a low-pressure turbine (300) can be provided with an additional blower in addition to the blowers ③ and ④ capable of heating feedwater.

3. In paragraph 1, If the reaction rate increases and the water supply temperature decreases, The high-pressure heater ① receives the exhaust air from the low-pressure turbine ④ and heats the feed water. The high-pressure heater ② receives the exhaust air of the low-pressure turbine ③ and heats the feed water. The low-pressure heater ③ receives the exhaust air from the high-pressure turbine ② and heats the feed water. A method for controlling the reactivity of a boron-free reactor in the secondary system of a pressurized water reactor, characterized in that the low-pressure heater ④ receives the exhaust of the high-pressure turbine ① and heats the feedwater.

4. In paragraph 1, If the reaction is suppressed and the water supply temperature rises, The high-pressure heater ① receives the exhaust air from the high-pressure turbine ① and heats the feed water. The high-pressure heater ② receives the exhaust air of the high-pressure turbine ② and heats the feed water. The low-pressure heater ③ receives the exhaust air of the low-pressure turbine ③ and heats the feed water. A method for controlling the reactivity of a boron-free reactor in the secondary system of a pressurized water reactor, characterized in that the low-pressure heater ④ receives the exhaust of the low-pressure turbine ④ and heats the feedwater.

5. In any one of paragraphs 1 to 4, When it is necessary to control the feed water temperature for micro-reactivity, The high-pressure heater ① receives the 3-way valve bleed from the high-pressure turbine's bleed ① and the low-pressure turbine's bleed ④ and heats the feedwater. A method for controlling the reactivity of a boron-free reactor in the secondary system of a pressurized water reactor, characterized in that the high-pressure heater ② receives the exhaust from the low-pressure turbine's ③ exhaust and the high-pressure turbine's ② exhaust through a control valve and heats the feedwater.

Images