JP2005134288A - Operation method for nuclear power plant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an operation method for a nuclear power plant restraining a dielectric constant of reactor water from rising up, when measuring and inspecting a temperature coefficient of a moderator in start-up of the nuclear power plant. <P>SOLUTION: In this operation method for the nuclear power plant for measuring and inspecting the temperature coefficient of the moderator in the nuclear power plant, a degasing operation for a nuclear reactor is executed before measuring and inspecting the temperature coefficient of the moderator, or a control rod is operated to control neutrons in response to total organic carbon concentration and the dielectric constant of the reactor water after the nuclear reactor is brought into a critical state, so as to remove an total organic carbon. The dielectric constant of the reactor water is thereby restrained from being elevated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for operating a nuclear power plant in which a moderator temperature coefficient measurement inspection is performed when the nuclear power plant is started.

  At the start of the first plant after the completion of the construction of the nuclear power plant, the temperature coefficient of the moderator was measured and inspected when the reactor water temperature was around 50 ° C, and the reactor water temperature was raised to 80 ° C. Later, reactor deaeration operation was performed.

  FIG. 3 is an explanatory diagram of a conventional nuclear power plant operating method. When the reactor water temperature is 30 ° C., the vacuum of the condenser starts to rise, and when the condenser is almost in a vacuum state, the reactor is started to bring the reactor into a critical state. Then, nuclear heating is started when the reactor water temperature is about 50 ° C., and a moderator temperature coefficient measurement inspection (temperature coefficient test) is performed. Furthermore, after the reactor water temperature rises to 80 ° C., the main steam isolation valve (MSIV) and the main steam drain valve (MS drain valve) are opened to make the reactor negative pressure and to supply the reactor water. The reactor is degassed by boiling under reduced pressure. Thereby, oxygen and carbon dioxide dissolved in the reactor water are removed. The same operation is performed when moderator temperature coefficient measurement inspection is performed after large-scale construction related to the nuclear reactor.

In nuclear power plants, stainless steel and nickel-base alloys are used as the main constituent materials, and water is used as the reactor coolant. Oxidizing substances such as these may be generated, and the generated oxidizing substances may be dissolved in the reactor water and cause stress corrosion cracking of stainless steel and nickel-based alloys as constituent materials. Therefore, by injecting hydrogen into the reactor water, the generation of oxidizing substances in the reactor water was suppressed, and the electrochemical potential (corrosion potential) of the material was reduced to reduce the occurrence of stress corrosion cracking. There are some (see, for example, Patent Document 1).
JP 2001-349983 A (FIG. 1)

  However, in the nuclear heating state at the time of the moderator temperature coefficient measurement and inspection, the reactor degassing operation is not performed, and the total organic carbon (TOC) contained in the reactor water is radiolyzed. Since carbonate ions and the like are generated, the amount of increase in the reactor water conductivity may increase. When the reactor water conductivity is increased, the nuclear heating and moderator temperature coefficient measurement and inspection are interrupted until the reactor water conductivity returns to a normal value, which may increase the plant start-up time.

  An object of the present invention is to provide a nuclear power plant operating method capable of suppressing an increase in reactor water conductivity when a moderator temperature coefficient measurement inspection is performed at the time of starting the nuclear power plant.

  The nuclear power plant operating method according to the invention of claim 1 is characterized in that the reactor is deaerated before the moderator temperature coefficient measurement and inspection.

  According to a second aspect of the present invention, the nuclear power plant operating method sets the reactor to a critical state before conducting the moderator temperature coefficient measurement inspection, operates the control rod in accordance with the total organic carbon concentration and the reactor water conductivity, and It is characterized by controlling and removing all organic carbon by radiolysis.

  According to a third aspect of the present invention, the nuclear power plant operating method is such that the reactor is degassed before the moderator temperature coefficient measurement and inspection, the reactor is brought into a critical state, and the total organic carbon concentration and reactor water conductivity are measured. The neutron is controlled by operating the control rod according to the above, and the total organic carbon is removed by radiolysis.

  According to a fourth aspect of the present invention, there is provided a nuclear power plant operating method according to any one of the first to third aspects, wherein two reactor coolant purification system pumps are arranged in parallel when the reactor is deaerated. One unit is stopped from operation, and one unit is operated.

  The nuclear power plant operating method according to the invention of claim 5 is characterized in that, in the invention of any one of claims 1 to 3, the main steam isolation valve is opened after a predetermined time from the start of the reactor degassing operation. To do.

  According to the present invention, since the deaeration operation of the reactor is performed before the moderator temperature coefficient measurement inspection, an increase in the conductivity of the reactor water can be suppressed. When performing degassing operation of the reactor, two reactor coolant purification system pumps are stopped from parallel operation and one unit is operated, so that an effective suction head of the reactor coolant purification system pump can be secured. . Therefore, generation of cavitation in the reactor coolant purification system pump can be suppressed, and damage to the reactor coolant purification system pump can be avoided. Further, since the main steam isolation valve is opened after a predetermined time from the start of the reactor degassing operation, the fluctuation of the reactor water level at the start of the reactor degassing operation can be suppressed.

  FIG. 1 is an explanatory diagram of a nuclear power plant operating method according to an embodiment of the present invention, and FIG. 2 is a system diagram of the nuclear power plant. In the embodiment of the present invention, the reactor degassing operation and the total organic carbon (TOC) decomposition operation are performed on the conventional example shown in FIG. 3 before the moderator temperature coefficient measurement inspection (temperature coefficient test). It is what I did.

  In FIG. 2, the main steam generated in the nuclear reactor 11 is guided to a turbine system (not shown) through a main steam inner isolation valve 12 and a main steam outer isolation valve 13, and the steam that has finished work in the turbine system is condensed water. The water is returned to water by the vessel 19 and supplied to the reactor 11 by a water supply system (not shown). A main steam drain inner isolation valve 14 and a main steam drain outer isolation valve 15 are provided so that drain water is discharged to the condenser 19 via the main steam drain valve 17 or the main steam drain valve bypass valve 18. It has become. In addition, 16 is a warm-up valve and 21 is a control rod.

  In FIG. 1, when the reactor water temperature of the reactor 11 is 30 ° C., the condenser vacuum starts to rise, and when the condenser 19 is almost in a vacuum state, two reactor coolant purification system pumps (CUW) One of the pumps 20 is stopped and one unit is operated. The reason why one reactor coolant purification system pump 20 is operated is to secure the pump suction pressure and suppress the occurrence of cavitation of the reactor coolant purification system pump 20.

  In the embodiment of the present invention, the reactor degassing operation is performed before the moderator temperature coefficient measurement inspection (temperature coefficient test), that is, at a reactor water temperature of about 50 ° C. There is a possibility that the effective suction head NPSH of the purification system pump 20 becomes smaller and lower than the design effective suction head NPSH. Therefore, by operating one reactor coolant purification system pump 20, piping pressure loss is reduced and an effective suction head NPSH is secured, cavitation is suppressed, and damage to the reactor coolant purification system pump is avoided. .

  Then, the main steam drain valve (MS drain valve) is opened at a reactor water temperature of 50 ° C. That is, by opening the main steam drain inner isolation valve 14, the main steam drain outer isolation valve 15, the warm-up valve 16, the main steam drain valve 17, and the main steam drain bypass valve 18, the reactor 11 and the condenser 19 Are connected, and before the moderator temperature coefficient measurement inspection (temperature coefficient test), the reactor 11 is set to a negative pressure and the reactor deaeration operation is started.

  The main steam isolation valve (MSIV) is opened after a predetermined time (6 hours) after the start of the reactor degassing operation. That is, by opening the main steam inner isolation valve 12 and the main steam outer isolation valve 13, the temperature inside the nuclear reactor 11 and the main steam pipe is made uniform, and the main steam inner isolation valve 12 and the main steam outer isolation valve 13. Suppresses reactor water level fluctuations during the opening operation.

  In normal operation, the main steam isolation valve (MSIV) is opened immediately after the start of the reactor degassing operation. Therefore, the reactor water level fluctuates due to pressure fluctuation due to steam condensation. Therefore, by opening the main steam isolation valve (MSIV) after the start of the reactor degassing operation, the temperature in the reactor 11 and the main steam pipe can be made uniform, and the reactor water level fluctuation can be suppressed. can do.

  Then, the nuclear reactor is started to bring the nuclear reactor into a critical state, and a TOC decomposition operation at a low neutron level is performed. The TOC decomposition operation is an operation in which the reactor 11 is made critical and the control rod 21 is operated to maintain the low neutron level and the TOC is decomposed and removed. In this embodiment, the moderator temperature coefficient measurement inspection (temperature Before conducting the coefficient test, the reactor is placed in a critical state and the control rod is operated according to the total organic carbon (TOC) concentration and the reactor water conductivity to control the neutrons at a low level and radiolyze the total organic carbon. Remove. That is, when the reactor water conductivity shows a tendency to increase due to carbonate ions generated by radiolysis of TOC, the control rod 21 is inserted to reduce neutrons.

  In this way, by reducing the amount of radiolysis of TOC and suppressing the increase in the reactor water conductivity, the TOC contained in the reactor water is measured with the moderator temperature coefficient measurement inspection (temperature coefficient) while suppressing the increase in the reactor water conductivity. Remove before test). After that, nuclear heating is started and a moderator temperature coefficient measurement inspection (temperature coefficient test) is performed.

  According to the embodiment of the present invention, the degassing operation of the nuclear reactor and the total organic carbon are removed by radiolysis before the moderator temperature coefficient measurement inspection is performed, so that an increase in conductivity during the temperature coefficient measurement inspection is suppressed. be able to. Further, during the reactor degassing operation, two reactor coolant purification system pumps are stopped from parallel operation and one unit is operated, so that cavitation generation and pumping of the reactor coolant purification system pump 20 occur. Damage can be prevented. Further, since the main steam isolation valve is opened after the time when the steam pipe is sufficiently warmed up from the start of the reactor degassing operation, there is no condensation of steam, and the fluctuation of the reactor water level can be suppressed.

Explanatory drawing of the nuclear power plant operating method concerning embodiment of this invention. System diagram of nuclear power plant. Explanatory drawing of the conventional nuclear power plant operation method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Reactor, 12 ... Main steam inner isolation valve, 13 ... Main steam outer isolation valve, 14 ... Main steam drain inner isolation valve, 15 ... Main steam drain outer isolation valve, 16 ... Warm-up valve, 17 ... Main steam drain Valve, 18 ... Main steam drain bypass valve, 19 ... Condenser, 20 ... Reactor coolant purification system pump, 21 ... Control rod

Claims (5)

  A nuclear power plant operating method for carrying out a moderator temperature coefficient measurement inspection in a nuclear power plant, wherein the reactor is deaerated before the moderator temperature coefficient measurement inspection is performed. .   In a nuclear power plant operating method in which a moderator temperature coefficient measurement inspection is carried out at a nuclear power plant, the reactor is brought into a critical state before the moderator temperature coefficient measurement inspection is conducted, and the nuclear power plant is in accordance with the total organic carbon concentration and the reactor water conductivity. A method for operating a nuclear power plant, wherein a control rod is operated to control neutrons, and radiolytically removes all organic carbon.   In a nuclear power plant operating method in which a moderator temperature coefficient measurement inspection is performed at a nuclear power plant, a degassing operation of the reactor is performed before the moderator temperature coefficient measurement inspection is performed, the reactor is brought into a critical state, and all organic A method for operating a nuclear power plant characterized in that a control rod is operated according to a carbon concentration and reactor water conductivity to control neutrons, and radiolytically removes all organic carbon.   4. When performing deaeration operation of the nuclear reactor, one of the two reactor coolant purification system pumps is stopped from the parallel operation, and the single operation is performed. The nuclear power plant operating method as described.   The nuclear power plant operating method according to any one of claims 1 to 3, wherein the main steam isolation valve is opened after a predetermined time from the start of the reactor degassing operation.

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