KR20160025088A - Multipoints thermocouple in In-Core Instrument assembly, system and method for post severe accident reactor internal status monitoring using the same - Google Patents

Abstract

The present invention relates to a post severe accident reactor internal status monitoring system. The post severe accident reactor internal status monitoring system includes an in-core instrument assembly which is inserted into a reactor and measures neutrons and temperatures in the reactor; and a diagnosis part which determines the state of the reactor based on the temperature measured by the in-core instrument assembly. The in-core instrument assembly includes at least two thermocouples and quickly supports the importance of an accident progressed by temperature monitoring according to each part of the reactor core, the important accident entry from a progress speed, and important determination for a power plant.

Description

TECHNICAL FIELD [0001] The present invention relates to a nuclear reactor internal state monitoring system and monitoring method using a multi-thermocouple furnace inner nuclear measurement instrument,

The present invention relates to a nuclear reactor internal condition monitoring system using a furnace inner nuclear measuring instrument including a plurality of thermocouples to cope with serious nuclear accident, and a method for monitoring internal state of a reactor vessel.

The In-Core Instrument Assembly used in the nuclear power plant is installed in the reactor to detect the neutrons generated in the reactor fission reaction process, to measure the output distribution and the combustion degree of the nuclear fission within the reactor, to measure the reactor core outlet temperature .

Referring to FIGS. 1 and 2, the conventional nuclear reactor inner nuclear measurement device 100 is a core instrument measuring three-dimensional real-time neutron quantities in a reactor of a nuclear power plant with a total length of about 35 meters. In addition, a total of 61 furnace inner nuclear measurements of APR1400 are inserted inside the reactor to monitor the neutron flux inside the reactor core and the temperature at the top of the reactor core.

Referring to FIG. 2, the conventional furnace inner nuclear measurement instrument 100 includes five neutron detectors 20 (five strands) and a pair of cables having a circular cross section. The thermocouple 10 for measuring the temperature of the reactor outlet (Two strands) 10a and 10b, one background detector 30 for correction of the detector signal (one strand), and eight other filler cables 40 (eight strands) . Here, each of the thermocouple 10, the background detector 30, and the filler cable 40 has substantially the same length and diameter.

Referring to FIG. 1, the furnace inner nuclear measurement device 100 is inserted into the reactor 1 through a guide tube 5.

Referring to FIGS. 1 and 2, a conventional furnace nuclear measurement apparatus 100 uses a K-type thermocouple that is unique to the end of the furnace, It is.

That is, the conventional furnace nuclear measurement device 100 measures only the temperature of the core upper end 2a. If a serious accident that may occur in the event of a serious accident occurs, the core temperature information is completely lost when the core upper end 2a is damaged. Direct temperature distribution measurement to monitor the cooling, overheating, oxidation and damage conditions of the reactor core, lower and upper ends of the reactor vessel lower cavity (1a) and reactor core lower head (1b) This is impossible. Therefore, it is difficult to identify the internal state of the reactor vessel for optimal response to serious accidents, and to establish an accident response strategy such as cooling and hydrogen removal.

Korean Patent Laid-Open Publication No. 10-2014-0010501 (published Jan. 27, 2014)

The present invention provides an internal state monitoring system and monitoring method for a nuclear reactor core reactor which can monitor the cooling and overheating states of the core of each core of the nuclear reactor core in the event of a major accident and monitor the level of the reactor vessel It has its purpose.

The present invention also provides a method for monitoring an oxidation state caused by a hydration reaction between a core and a steam in each part of a nuclear reactor core in the event of a major accident and a bad damage state in which the normal geometry of the core can not be maintained The present invention provides a monitoring system and a method for monitoring the internal state of the reactor.

It is another object of the present invention to provide a monitoring system and method for monitoring the internal state of a nuclear power reactor, which can monitor the amount of generated hydrogen which may explode from the oxidation amount of each part of the core in the event of a serious accident.

In addition, the present invention provides a system and method for monitoring the internal state of a reactor core reactor which is capable of monitoring the state of relocation of core melt in a reactor vessel bottom cavity over time after a serious accident, The purpose is to do.

In accordance with an embodiment of the present invention, the installed internal state monitoring system of the Kokubu reactor includes a reactor internal neutrality measuring instrument for measuring the neutron and temperature inside the reactor, Wherein the furnace inner nuclear measurement instrument includes at least two thermocouples, and at least two of the furnace inner nuclear measurement instruments are inserted into the reactor at regular intervals.

In addition, the at least two thermocouples in the reactor core internal state monitoring system may have different heights along the longitudinal direction.

The diagnosis unit may determine at least one of the damage of the core, the position of the damaged core, the amount of hydrogen generated in the reactor, the relocation state of the core melt, and the reactor penetration point of the core melt based on the temperature measured in the at least two thermocouples Can be determined.

In addition, when at least one of the damage of the core, the position of the damaged core, and the amount of hydrogen generated in the reactor is determined, it can be determined based on the oxidation time of the core material and the time of exposure to the high temperature.

Also, at least one of the repositioning state of the core melt and the reactor penetration point of the core melt may be based on the temperature of the lower cavity or the lower head of the reactor lower part.

A method for monitoring an internal state of a reactor using a furnace inner nuclear measuring instrument according to an embodiment of the present invention includes the steps of: (A) placing at least two thermocouples in a furnace inner nuclear measuring instrument; (B) disposing the at least two thermocouples at different heights along the longitudinal direction; (C) inserting at least two of said furnace inner nuclear measurements into said reactor; And (D) measuring the temperature inside the reactor at different heights through the thermocouple.

The reactor core monitoring method may further include: (E) determining whether the core is damaged, the position of the damaged core, the relocation state of the core melt based on the temperature inside the reactor measured in the step (D) And determining at least one of the penetration points.

In addition, when at least one of the damage of the core, the position of the damaged core, and the amount of hydrogen generated in the reactor is determined, it may be based on the oxidation time of the core material and the time of exposure to the high temperature.

In addition, when determining at least one of the rearrangement state of the core melt and the reactor penetration point of the core melt, the temperature may be based on the temperature of the lower cavity or the lower head of the lower portion of the reactor.

In accordance with one embodiment of the present invention, the internal state monitoring system and monitoring method of the KHNP reactor is provided for monitoring the temperature of each reactor core and monitoring the reactor vessel water level, It has the advantage of being able to make quick decisions quickly.

In addition, the present invention provides an advantage of providing temperature information about inside of the reactor even when the core outlet temperature measuring instrument used in the early stage of the serious accident is lost through monitoring the temperature of each part of the reactor core have.

In addition, the monitoring system and monitoring method of the internal state of the reactor of the present invention can observe the temperature and the speed of cooling or overheating of the respective parts through the monitoring of the temperature of each part of the reactor core, And provides information that can be used to determine whether the safety measures already in effect are effective.

In addition, the present invention provides a system and method for monitoring the internal state of a nuclear reactor, which determines whether or not a nuclear reactor core damages the nuclear reactor core, There is an advantage of providing information that can be.

In addition, the present invention provides a system and method for monitoring the internal state of a nuclear reactor, which utilizes the amount of hydrogen generated from the oxidation of the reactor core in the event of a major accident at the nuclear power plant, There is an advantage to provide.

In addition, the present invention provides a system and method for monitoring the internal state of a nuclear reactor using a nuclear reactor core, The starting point of operation can be determined optimally and the core melt can be confined within the reactor vessel barrier.

Figure 1 illustrates the installation of a conventional furnace nuclear instrument at the reactor core.
2 is a longitudinal cross-sectional view of a conventional furnace core instrument.
FIGS. 3 to 5 illustrate a nuclear reactor core reactor internal state monitoring system according to a first embodiment of the present invention.
FIG. 6 illustrates a nuclear reactor internal nuclear reactor internal state monitoring system according to a second embodiment of the present invention.

 BRIEF DESCRIPTION OF THE DRAWINGS The invention is susceptible to various modifications and can be made into various embodiments, and specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, number, step, operation, element, component, or combination thereof described in the specification, But do not preclude the presence or addition of features, numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, the same reference numerals will be used for the same constituent elements in the drawings, and redundant explanations for the same constituent elements will be omitted.

3 to 6 illustrate a system 1000 for monitoring the internal state of a nuclear reactor core according to an embodiment of the present invention. Referring to FIGS. 3 to 6, the system for monitoring the internal state of a nuclear reactor core reactor according to an embodiment of the present invention may include a furnace inner nuclear measurement device 100 'and a diagnosis unit 200.

The furnace inner nuclear measurement apparatus 100 'according to an embodiment of the present invention is inserted into the reactor 1 to measure the neutron and the temperature inside the reactor 1. Here, the furnace inner nuclear measurement device 100 'includes at least two thermocouples (a first thermocouple, a second thermocouple, and a fifth thermocouple). The at least two thermocouples 11, 12, 13, 14, and 15 may be formed to have different heights along the longitudinal direction to measure the temperature of the center portion and / or the bottom portion of the core 2, .

At least two of the furnace inner nuclear measurement devices 100 'according to an embodiment of the present invention may be inserted into the nuclear reactor 1 and may be disposed at a certain interval in the reactor core 2. Referring to FIGS. 3 to 6, the furnace inner nuclear measurement device 100 'may be inserted into a nuclear reactor through a guide tube 5 installed under the nuclear reactor.

The diagnosis unit 200 according to an embodiment of the present invention may measure the state of the reactor 1 based on the temperatures measured at the thermocouples 11, 12, 13, 14, and 15 included in the furnace inner nuclear measurement device 100 ' It can be judged. 3, a separate transmission cable 300 connected to the end of the furnace inner nuclear measurement device 100 'is installed, and temperature information is transmitted from the furnace inner nuclear measurement device 100' to the diagnosis unit 100 'through the transmission cable 300 200).

Preferably, the diagnosis unit 200 controls the cooling, overheating, oxidation, damage and melting state (position and degree) of the core 2, the relocation state of the reactor vessel lower cavity 1a of the core melt, And the threat of departure of the head 1b.

The present invention may include at least two furnace inner nuclear measurement devices 100 '. The furnace inner nuclear measurement apparatus 100 'according to an embodiment of the present invention may be installed in the core 2. [ In the case of the critical internal state monitoring system 1000 according to an embodiment of the present invention, a total of 61 internal non-nuclear state measuring instruments 100 'may be inserted into the reactor 1.

3 to 6, the furnace inner nuclear measurement apparatus 100 'according to an embodiment of the present invention may include a thermocouple 10 as many as the number of the conventional furnace inner nuclear measurement apparatus 100' (11, 12, 13, 14, 15).

Referring to FIGS. 3 and 5, the furnace core measurement apparatus 100 'according to the first embodiment of the present invention may further include two thermocouples by further arranging thermocouples. 3, in the case of the upper middle thermocouple 11 of the thermocouple included in the furnace inner nuclear measuring instrument 100 ', the temperature of the upper end core 2a of the core is measured in the same manner as the conventional furnace inner nuclear measuring instrument, It is possible to provide a lower reactor cavity lower cavity 1a located below the core to sense the temperature of the lower reactor cavity 1a. 4, in the case of the upper middle thermocouple 11 of the thermocouple included in the furnace inner nuclear measurement device 100 ', the temperature of the uppermost core 2a of the core is measured and the temperature of the lower thermocouple 15 is measured, Can be installed in the reactor vessel lower head 1b located at the lower side of the core to measure the temperature of the reactor vessel lower head 1b. Alternatively, referring to FIG. 5, two thermocouples may be included in each of the neighboring furnace inner nuclear measurement devices 101, 102. In this case, each upper thermocouple 11 measures the temperature of the uppermost core 2a of the core in the same manner as the conventional furnace inner nuclear measuring instrument, and the lower thermocouple 15 included in the first furnace inner nuclear measurement device 101 is located below the core And the lower thermocouple 15 included in the second furnace inner nuclear measurement device 102 is installed in the lower reactor cavity 1a located at the lower side of the reactor core to measure the temperature of the lower reactor cavity 1a, It is possible to measure the temperature of the reactor vessel lower head 1b by installing it on the container lower head 1b.

Referring to FIG. 6, according to a second embodiment of the present invention, at least two (shown as five in FIG. 6) furnace inner nuclear measuring instruments 103 and 104 may be included. In this case, the upper thermocouple 11 included in the adjacent furnace inner nuclear measurement devices 103 and 104 measures the temperature of the uppermost core 2a of the core in the same manner as the conventional furnace inner nuclear measurement device 100, And 15 'are provided at intersections of the reactor vessel lower cavity 1a or the reactor vessel lower head 1b located below the core to measure the temperature of the reactor vessel lower cavity 1a or the reactor vessel lower head 1b . For example, the lower thermocouple 15 installed in the first furnace inner nuclear measurement device 103 measures the temperature of the lower reactor cavity 1a and the lower thermocouple 15 'installed in the second furnace inner nuclear measurement device 104 measures the temperature of the reactor vessel And may be installed at a height that can intersect with each other to measure the temperature of the lower head 1b.

6, the thermocouples 12, 13 and 12 '13' located inside the core of the thermocouple included in the furnace inner nuclear measurement instrument 103 and 104 according to the second embodiment of the present invention can rapidly Can be placed adjacent to the dimple of the guide tube 5 forming the physical contact of the guide tube 5 with the furnace inner nuclear measurement devices 103 and 104 for measurement.

6, each of the thermocouples is provided with the most uniform size of the space represented in the core 2 and the shape of the space closest to the sphere so that the temperature at different heights in the core 2 Can be measured. For example, five thermocouples (11, 12, 13, 14, 15) are included in the first Nuclear instrument 103 in the reactor of the APR1400 having a core height of 162 inches, The first thermocouple 11 included in the first furnace inner nuclear measurement device 103 and the second furnace inner nuclear measurement device 104 are both included in the first furnace And may be installed at the core top 2a. The second thermocouple 12 included in the first furnace inner nuclear measurement device 103 is installed at the position of the dimple at the upper end of the guide tube 5 and the third thermocouple 13 is disposed at the position of the lower dimple of the guide tube 5, (14) may be installed at the lower core (2b) of the core. The second thermocouple 12 'included in the second furnace inner nuclear measurement device 104 is installed at a height between the second thermocouple 12 and the third thermocouple 13 included in the first furnace inner nuclear measurement device 103, The third thermocouple 13 'included in the second furnace inner nuclear measurement device 104 is disposed between the third thermocouple 13 and the fourth thermocouple 14 included in the first furnace inner nuclear measurement device 103, The fourth thermocouple 14 included in the furnace inner nuclear measurement device 104 may be installed at the lower core 2b similarly to the fourth thermocouple included in the first furnace inner nuclear measurement device 103. [ According to the second embodiment of the present invention, the second thermocouple 12, 12 'and the third thermocouple (not shown) included in the neighboring first furnace inner nuclear measurement device 103 and the second furnace inner nuclear measurement device 104, respectively, 13 and 13 'are arranged so as to intersect with each other so that the reliability of the temperature sensing in the core 2 according to the height can be improved without adding another thermocouple.

A thermocouple according to an embodiment of the present invention is a K-type thermocouple and can sense 0 to 1260 at a measuring point. The K-type thermocouple is a thermocouple made by joining the ends of dissimilar dissimilar metals (chromel, alumel). It can measure the temperature by sensing the minute electromotive force depending on the temperature at the opposite end of the heat. Therefore, if at least two K-type thermocouples are arranged at different heights along the length direction (the lengths of the thermocouples are different from each other), the temperature at different heights can be measured, as in the embodiment of the present invention.

The existing Nuclear Nuclear Instruments could only measure the temperature of the core top 2a and could not provide the temperature for the remaining core 2 and the reactor vessel bottom cavity 1a or the reactor vessel bottom head 1b below the reactor vessel properly, It is necessary to estimate the internal state from the outside of the reactor by the experts, and it takes time for the adjustment and estimation work on the estimation in this process, and also the error problem of the estimation result may occur.

The furnace inner nuclear measurement apparatus 100 'of the present invention measures the temperature from the lower portion of the core to the upper portion of the core and provides the cooling, overheating, oxidation, and damage position states to determine the seriousness of the accident, It is possible to minimize the safety threat due to serious accidents by accurately grasping the situation in the reactor and the threat of the safety function and implementing appropriate measures timely. In particular, the temperature and temperature trends for each core area are used to determine 1) the suitability of reactor core cooling, 2) the estimation of reactor water level, 3) the feasibility of applying core cooling through the interior of the reactor, 4) Based on the degree of oxidation of the core, it is possible to estimate the amount of hydrogen which is a risk of explosion. In addition, by observing the temperature distribution of the thermocouple 15 of the lower cavity 1a and the lower head 1b at the lower portion of the reactor vessel, it is possible to grasp the arrangement state of the core core melt in the core melt according to the time of serious accident, It is possible to provide important information for establishing countermeasures to mitigate the serious accident such as ensuring the reactor health through cooling the reactor outside by judging the threat and timing.

The diagnosis unit 200 according to an embodiment of the present invention can determine the damage of the core 2 according to the oxidation time of the core material and the time of exposure to the high temperature. The zircaloy oxidation amount and the accompanying amount of hydrogen in the hydration reaction of a specific thermocouple are calculated from the temperature of the thermocouple after the accident, the time of exposure to the temperature, and the vapor concentration derived from the reactor vessel water level Calculate using the equation. The total hydrogen generation rate in the reactor (1) can be estimated from the thermocouples (11, 12, 13) by the hydration reaction, and the degree of core damage in the representative space can be estimated by using the degree of oxidation of all zircaloys and the core temperature trend. , 14, 15) in the representative space.

According to one embodiment of the present invention, the furnace inner nuclear measurement device 100 'may be inserted into the reactor 1 at 50 to 70 times. In the case of APR1400, which is currently in operation in Korea, 61 non-nuclear nuclear measuring instruments (100 ') can be inserted into the reactor.

Each of the thermocouples 11, 12, 13 and 14 belonging to the core 2 has a predetermined space formed according to the same distance rule as another thermocouple adjacent to the core in the core 2, Is defined as a representative space and the amount of the fuel covering material causing the hydration reaction included in the representative space is defined together.

A method for monitoring a nuclear power reactor according to an embodiment of the present invention includes the steps of disposing at least two thermocouples in a furnace inner nuclear measuring instrument, disposing the at least two thermocouples at different heights along the longitudinal direction, Inserting the inner nuclear instrument into the reactor, and measuring the core temperature through the thermocouple.

The method of monitoring a critical reactor according to an exemplary embodiment of the present invention is based on the temperature inside the reactor measured at the step of measuring the temperature inside the reactor with different heights through the thermocouple, Position of the core melt, a relocation state of the core melt, and the reactor penetration point of the core melt.

At least one of the damage of the core, the location of the damaged core, and the amount of hydrogen generated in the reactor may be based on the oxidation time of the core material and the time of exposure to the high temperature. The explanation related to this is detailed above and is omitted.

Alternatively, at least one of the repositioning state of the core melt and the reactor penetration point of the core melt may be based on the temperature of the lower cavity or lower head of the reactor lower part. The explanation related to this is also described in detail above, so it is omitted.

1000: Kofu nuclear reactor internal condition monitoring system
1: reactor vessel
1a: Reactor vessel bottom joint
1b: Reactor vessel bottom head
2: Core
5: Guide tube
100, 100 ', 101, 102, 103, 104: furnace inner nuclear measuring instrument
10: Thermocouple
11: first thermocouple, 12: second thermocouple,
13: third thermocouple, 14: fourth thermocouple,
15: fifth thermocouple,
20: Neutron detector
30: background detector
40: Filler cable
200:
300: Transmission cable

Claims (9)

A furnace inner nuclear instrument inserted into the reactor to measure the neutron and temperature inside the reactor;
And a diagnosis unit for determining the state of the reactor based on the temperature measured by the furnace inner nuclear measurement device,
Wherein the furnace inner nuclear measurement includes at least two thermocouples,
Wherein the reactor inner nuclear measurement device is arranged so that at least two nuclear reactors are inserted into the reactor at regular intervals. The internal state monitoring system of claim 1, wherein the at least two thermocouples are different in height along the longitudinal direction. 3. The method of claim 2, wherein the diagnosis unit is further configured to determine whether the core is damaged based on the temperature measured in the at least two thermocouples, the position of the damaged core, the amount of hydrogen generated in the reactor, The internal state monitoring system of the Kobu Kobo reactor to determine at least one of the time points. The method of claim 3,
Wherein the determination of at least one of the damage of the core, the position of the damaged core, and the amount of hydrogen generated in the reactor is made based on the oxidation time of the core material and the time of exposure to the high temperature, Reactor internal condition monitoring system. The method of claim 3,
Wherein at least one of the repositioning state of the core melt and the reactor penetration point of the core melt is based on the temperature of the lower cavity or the lower head of the lower portion of the reactor. A method for monitoring internal state of a nuclear reactor using a furnace inner nuclear measurement instrument,
(A) disposing at least two thermocouples in the furnace inner nuclear instrument;
(B) disposing the at least two thermocouples at different heights along the longitudinal direction;
(C) inserting at least two of said furnace inner nuclear measurements into said reactor; And
(D) measuring the temperature inside the reactor at different heights through the thermocouple. 7. The method of claim 6,
(E) determining at least one of the damage of the core, the position of the damaged core, the relocation state of the core melt, and the reactor penetration point of the core melt, based on the temperature inside the reactor measured in the step (D) Further comprising: means for monitoring the reactor core. The method according to claim 7, wherein when determining at least one of the damage of the core, the location of the damaged core, and the amount of hydrogen generated in the reactor, the oxidization of the core material and the exposure to the high temperature, Nuclear reactor monitoring method. The method according to claim 7, wherein the method is based on the temperature of the lower cavity or the lower head of the lower reactor when determining at least one of the rearrangement state of the core melt and the reactor penetration point of the core melt.

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