US-12626830-B2 - Method of synthesizing reactor core power distribution for reactor core protection system based on in-core instrument signal using ordinary kriging method

Abstract

A method of synthesizing reactor core power distribution is disclosed. According to the method, the power of all fuel assemblies in a reactor core is calculated from powers of fuel assemblies in which in-core instruments are located using the ordinary kriging methodology. Also, a hot-pin power distribution of each fuel assembly is synthesized from the power of all fuel assemblies calculated, whereby more accurate hot-pin axial power distribution, rather than pseudo hot-pin axial power distribution, may be synthesized.

Inventors

• Young Min Kwon
• Byung Chan Baek
• Dong-Su Kim
• Wook Lee
• Do-young OH

Assignees

• KEPCO NUCLEAR FUEL CO., LTD.

Dates

Publication Date

20260512

Application Date

20211230

Priority Date

20211228

Claims (4)

1. 1 . A method of synthesizing reactor core power distribution for a reactor core protection system based on an in-core instrument signal using an ordinary kriging method, the method comprising steps of: (a) calculating a power of all fuel assemblies in a reactor core from powers of fuel assemblies in which in-core instruments are located using the ordinary kriging method; (b) obtaining axial power distribution of a node for each fuel assembly by artificial neural network synthesis of axial power distribution based on results of step (a); and (c) obtaining hot-pin power distribution of the node for each fuel assembly by multiplying the axial power distribution of the node obtained in step (b) by a 1-pin correlation factor obtained from a reactor core design code and a ratio of the powers of the fuel assemblies to an average power of an entire reactor core, wherein in step (c), the hot-pin power distribution of the node is calculated by multiplying the axial power distribution of the node by the ratio of a power of the fuel assembly to the average power of the entire reactor core and the 1-pin correlation factor corresponding to the node, as in the following equation, PD jl = FZ jl × ∑ k = 1 5 ⁢ P jk P AVG × [ ( 1 - pin ) / RPF ] jl , [ Equation ] wherein PD jl is the hot-pin power of an l th node of a j th fuel assembly, FZ jl is the axial power distribution of the l th node of the j th fuel assembly, P jk is a calculated power of a k th level of the j th fuel assembly, P AVG is the average power of the entire reactor core, and [(1−Pin)/RPF] jl is the 1-pin correlation factor corresponding to the l th node of the j th fuel assembly.
2. 2 . The method of claim 1 , wherein step (a) comprises calculating weighted values for known surrounding power values of a point of the reactor core, and predicting a power of a specific fuel assembly in the reactor core by a weighted linear combination of the power values of the fuel assemblies, which are in the surrounding of the specific fuel assembly and in which the in-core instruments are located, based on the weighted values calculated.
3. 3 . The method of claim 2 , wherein the weighted values are calculated to minimize error variance of the power of the specific fuel assembly in the reactor core.
4. 4 . The method of claim 1 , wherein in the step (a), the power of the fuel assembly in which the in-core instrument is not located is determined by multiplying a value predicted by using weighted values for the powers of fuel assemblies in which the in-core instruments is located by a power correction factor for the fuel assembly obtained from the reactor core design code.

Description

STATEMENT REGARDING SPONSORED RESEARCH This invention was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea under the project Number 20206510100040. TECHNICAL FIELD The present disclosure relates to a method of synthesizing reactor core power distribution using an in-core instrument in a reactor core protection system and, more particularly, to a method of synthesizing based on reactor core power distribution for a reactor core protection system using an ordinary kriging method. BACKGROUND ART In order to keep a nuclear reactor safe, it is very important to monitor and check a state of the reactor in real time, so it is required for the reactor to meet strict requirements from a design stage. In particular, in order to monitor axial power distribution of a reactor core in real time, a plurality of ex-core neutron flux detectors disposed along the perimeter of the reactor is provided at three levels (an upper part, a middle part, and a lower part) along an axial direction of the reactor core, whereby the axial power distribution of a reactor core is synthesized on the basis of ex-core neutron flux detector signals of three levels, which are measured through the ex-core neutron flux detectors. As such, as shown in Korean Patent No 10-0009517, conventional core protection system axial power distribution synthesis calculates power of outer region of core of three levels using the ex-core neutron flux signal measured by an ex-core neutron flux measurement system in an outer region inside the reactor, and on the basis of the calculated power of outer region of core, average power of outer section of core of three levels is calculated by reflecting a control rod shadow coefficient, and on the basis of this, axial power distribution of a core average of the number of 20 is synthesized using a Cubic Spline function. FIG. 1 is a view showing a conceptual diagram of a core protection and monitoring system. As shown in FIG. 1, the axial power distribution in a core average calculated is the average across the core, so a pseudo hot-pin power distribution is calculated by multiplying by a radial peak coefficient Fxy. The radial peak coefficient is installed in the core protection system database in a form of a look-up table, thereby being used after being loaded from the database according to a control rod insertion state. According to Korean Patent No. 10-1614772, an artificial neural network-based method of synthesizing power distribution for a core protection system is composed of an input layer, an output layer, and at least one hidden layer, wherein each layer includes at least one node. Here, each node uses a neural network circuit to determine an optimal connection strength between each of the nodes constituting the neural network circuit through learning based on various core design data applied to the reactor core design of a nuclear power plant, thereby being constituted to synthesize the axial power distribution of the reactor core based on the ex-core neutron flux detector signal measured through the ex-core neutron flux detector during the operation of the reactor, wherein the neural network circuit is configured to have therein nodes each of which is connected to a node of another layer, but the connection between the nodes is made such that strength of each connection varies according to the learning result. The method of obtaining the pseudo hot-pin power distribution by synthesizing the axial power distributions of the core average of the number of 20 using ex-core neutron flux signals and multiplying by the radial peak coefficient gives a margin calculated less than an actual one due to the excessively conservative reflection of the radial peak coefficient. Accordingly, the operation of the nuclear reactor may be restricted even though the actual operation margin is sufficient. Documents of Related Art (Patent Document) Patent Document 1. Korean Patent No. 10-0009517 (Mar. 23, 1981)Patent Document 2. Korean Patent No. 10-1614772 (Apr. 18, 2016) DISCLOSURE Technical Problem Accordingly, the present disclosure has been made keeping in mind the above problems occurring in the related art, and an objective of the present disclosure is to provide such that calculating a power of all fuel assemblies using an ordinary kriging method from powers of fuel assemblies where in-core instruments are located and synthesizing a hot-pin power distribution of each fuel assembly from the power of all fuel assemblies calculated. Technical Solution In order to accomplish the above objective, there may be provided a method of synthesizing reactor core power distribution for a reactor core protection system based on an in-core instrument signal using an ordinary kriging method according to one aspect of the present disclosure, the method including steps of: (a) calculating a power of all fuel assemblies in a react