KR102587750B1 - Method for categorization of function in consideration of function significance - Google Patents

Abstract

The present invention relates to a functional category classification method considering functional importance, comprising the steps of identifying safety functions of a nuclear power plant from nuclear power plant design data; Establishing evaluation factors for evaluating the safety importance of the safety function; It includes the step of evaluating the safety function according to the evaluation factors and assigning a functional category to the safety function, where the evaluation factors include (1) the severity of the result when the safety function fails, and (2) the necessity of the safety function. It includes the frequency of occurrence and (3) whether the relevant safety function contributes to reaching a controllable state or a safe state.

Description

Function category classification method considering function importance {Method for categorization of function in consideration of function significance}

The present invention relates to a functional category classification method considering functional importance.

The safety level of system structural equipment (SSC), which is a basic element of nuclear power plant design, has been classified according to the “deterministic function” performed by the SSC according to the US ANSI/ANS-51.1.

However, recently, the IAEA is requesting that the safety level classification of SSC be determined according to “importance considering risk.” In Korea, nuclear power plants are still designed based on deterministic functional classification. Therefore, in order to meet overseas requirements related to the export of nuclear power plants, it is necessary to develop a functional category classification method based on "assessment of importance that affects safety" rather than a deterministic standard for the relevant function in nuclear power plant design.

Korean Patent Publication No. 2014-0055294 (published on May 9, 2014)

Therefore, the purpose of the present invention is to provide a functional category classification method considering functional importance.

The object of the present invention is to provide a functional category classification method considering functional importance, including the steps of identifying safety functions of a nuclear power plant from nuclear power plant design data; Establishing evaluation factors for evaluating the safety importance of the safety function; It includes the step of evaluating the safety function according to the evaluation factors and assigning a functional category to the safety function, where the evaluation factors include (1) the severity of the result when the safety function fails, and (2) the necessity of the safety function. This is achieved by including the frequency of occurrence and (3) whether the relevant safety function contributes to reaching a controlled state or a safe state.

The safety functions include (1) reactivity control function, (2) heat removal function of nuclear reactor and fuel storage, (3) radiation shielding and radiation emission limitation function, and (4) other safety functions of (1) to (3) above. Other safety features that are not included in the function may be included.

The severity of the consequences when the relevant safety function fails is determined by comparing the analysis result when the relevant safety function fails with a limit value, and the limit value may include a limit value in the physical field and a limit value in the field of radiation emission.

The physical sector limits include nuclear fuel damage, coolant system pressure, and containment building pressure, and the radioactivity emission sector limits may include on-site dose standards and off-site dose standards for each accident.

The assignment of the functional category is carried out according to the functional category selection criteria, and the functional category selection criteria can be prepared by considering the status of the power plant that requires the relevant safety function, the point in time when the relevant safety function is needed, and the degree of impact when the relevant safety function fails. there is.

Regarding the severity of the consequences when the safety function fails, the severity can be determined based on the variable value that has the most serious impact when the safety function fails.

According to the present invention, a functional category classification method considering functional importance is provided.

1 is a flowchart of a functional category classification method according to an embodiment of the present invention;
Figure 2 is an example of detailed classification of safety functions in one embodiment of the present invention,
Figure 3 is an example of power plant status and occurrence frequency used for assigning functional categories in one embodiment of the present invention,
Figure 4 is an example of detailed classification of functional categories in one embodiment of the present invention.

The present invention is a power plant functional category classification methodology that classifies and evaluates the functions necessary for the design and operation of a nuclear power plant according to their importance and reasonably determines the category of the function.

“Function importance assessment” refers to evaluating how much a function in a nuclear power plant affects the safety goals, and the corresponding function category is classified according to that degree.

In the present invention, instead of classifying the functional categories of nuclear power plants according to existing deterministic functions, the procedure and method are to identify "how important a function affects the safety of a nuclear power plant" and classify the categories of the corresponding functions according to their importance. is to provide.

The present invention will be described in detail below with reference to the drawings.

Hereinafter, 'function' is limited to 'safety function' related to safety, but 'function' in the present invention is not limited to 'safety function'.

1 is a flowchart showing the classification method according to the present invention. The present invention below can be carried out by computers and communication (Internet, etc.) devices.

First, the safety functions of the nuclear power plant are identified from the nuclear power plant design data (S100).

The safety function is,

(1) Reactivity control function,

(2) heat removal function of the reactor and fuel reservoir;

(3) radiation shielding and radiation emission limiting functions;

(4) Other safety functions that are not included in the above safety functions (disaster protection and prevention, radioactive material monitoring and worker protection, power plant operation, etc.) may be included.

Safety functions can be classified in detail as shown in Figure 2.

In this step, all safety functions, including core safety functions required for nuclear power plant design, are identified. Derive and confirm the relevant safety functions required in all driving conditions, including normal driving. Safety functions that are not credited in the safety analysis are also checked in a complementary manner. When identifying safety functions, the structural method is to identify them through a three-step process in the order of core functions, upper functions, and lower functions, and then create a function identification list.

Here, the function credited in the safety analysis refers to a function that is assumed to be operated in the safety analysis (failure probability = 0, usually refers to an important operator action performed through manual operation). Therefore, safety functions that are not credited in safety analysis can be explained as safety functions that are likely to fail.

Next, evaluation factors for evaluating the safety importance of safety functions are established (S200).

The evaluation factors are (1) the severity of the consequences when the relevant safety function fails, (2) the frequency of occurrence in which the relevant safety function is required, and (3) the probability that the relevant safety function reaches the controlled state or safe state. Including whether or not it contributes.

(1) The severity of the result is judged by calculating the limits in the physical field and the limits in the radiation emission field, respectively. , RADSTAR, STARS, RUNT-G, etc.).

The severity of the consequences when the safety function fails is determined by comparing the analysis results when the safety function fails with the limits, and the limits include limits in the physical field and limits in the field of radioactive emissions. Here, the limits in the physical field include nuclear fuel damage, coolant system pressure, and containment building pressure, and the limits in the field of radioactivity may include on-site dose standards and off-site dose standards for each accident.

Regarding the severity of the consequences when the relevant safety function fails, the severity is judged based on the value of the variable that has the most serious impact when the relevant safety function fails.

The frequency of occurrence that requires the relevant safety function in (2) is first determined by the frequency of initial accident occurrence. If the initial accident occurrence frequency is not available, the frequency defined in the plant state classification can be applied. Power plant states to be considered during design are divided into normal state and accident state. The frequency of occurrence according to the power plant status applies the relevant information defined at the time of design.

To determine the controllable state for each safety function in (3) and whether it contributes to reaching a safe state, refer to abnormal procedures, emergency procedures, etc. to determine the relevant accident (AOO and DBA/DEC and serious accident) and operation method (automatic start/manual start). ) and the time of operation (within/after 30 minutes after the accident).

A safety function to reach a controllable state refers to a safety function that requires automatic or short-term operation to reduce potential hazards. For example, this could be a reactor shutdown, heat removal, or safety injection function. A safety function to reach a safe state is a function required to reach a "safe state" after reaching a "controllable state" and is a safety function that requires manual operation or long-term operation. For example, it can be a core residual heat removal function necessary for long-term cooling of the core heat after depressurization of the "reactor cooling system (RCS)."

Afterwards, the safety function is evaluated according to the evaluation factors and a functional category is assigned to the safety function (S300).

Assignment of functional categories is performed according to the functional category selection criteria. The criteria for selecting a functional category are prepared by considering the condition of the power plant that requires the relevant safety function, the point in time when the relevant safety function is needed, and the degree of impact when the relevant safety function fails.

An example of the power plant status and frequency of occurrence used to assign functional categories is shown in Figure 3, and the detailed classification of functional categories is shown in Figure 4.

Additionally, engineering judgment and probabilistic safety evaluation results can be considered based on the selection criteria, and the category of the safety function can be finally determined through a meeting of experts.

In classifying safety function categories, it is possible to apply quantitative standards for functions important to safety, and optimal category assignment according to their importance is achieved. Through this, it is possible to improve the reliability and quality of nuclear power plant design and further contribute to safe device design, production, construction, and operation. In addition, the functional classification method and procedure of the present invention can be used as a technical basis for functional category classification when designing a nuclear power plant. Furthermore, by securing the technical basis for safety function classification in designing nuclear power plants, it is expected that competitiveness will be improved when exporting nuclear power plants.

The above-described embodiments are examples for explaining the present invention, and the present invention is not limited thereto. Anyone skilled in the art to which the present invention pertains will be able to implement the present invention by making various modifications thereto, so the scope of technical protection of the present invention should be determined by the appended claims.

Claims (6)

In the functional category classification method considering functional importance,
Identifying safety functions of a nuclear power plant from nuclear power plant design data;
Establishing evaluation factors for evaluating the safety importance of the safety function;
It includes the step of evaluating the safety function according to the evaluation factors and assigning a functional category to the safety function,
The above evaluation factors are (1) the severity of the consequences when the relevant safety function fails, (2) the frequency of occurrence in which the relevant safety function is required, and (3) the relevant safety function reaches a controllable state or safe state. Including whether it contributes to
The safety function is,
(1) Reactivity control function,
(2) heat removal function of the reactor and fuel reservoir;
(3) Radiation shielding and radiation emission limiting functions and
(4) Other safety functions that are not included in the safety functions of (1) to (3) above are included,
The severity of the consequences if the above safety function fails is:
The decision is made by comparing the analysis results in case of failure of the relevant safety function with the limit values,
The limits include physical field limits and radioactive emission field limits,
The physical field limits include nuclear fuel damage, coolant system pressure, and containment pressure,
The above radiation emission field limits include on-site dose standards and off-site dose standards for each accident,
The assignment of the above functional categories is carried out according to the functional category selection criteria,
The criteria for selecting the above functional category are prepared by considering the condition of the power plant that requires the relevant safety function, the point in time when the relevant safety function is needed, and the degree of impact when the relevant safety function fails.
Regarding the severity of the consequences if the above safety function fails,
A method of determining severity based on the value of the variable that has the most serious impact when the safety function fails. delete delete delete delete delete

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