JP3054039B2 - Plant maintenance support equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for supporting planning work of a plant and the like, and more particularly to an apparatus for supporting planning of a maintenance work of a plant.

[0002]

2. Description of the Related Art Maintenance of facilities and equipment in a large-scale plant such as a nuclear power plant represented by a nuclear power plant and a chemical plant needs to be performed rationally in consideration of the importance of each facility and equipment. is there. In other words, if the equipment / equipment breaks down, the equipment / equipment that is more likely to lead to plant shutdown etc. is considered to be more important and the inspection frequency is increased. It is necessary to achieve so-called multiplexing. Conventionally, the selection or determination of these maintenance methods has been based on FMEA (Fa
It is qualitatively performed by a method such as iler Mode Effect Analysis). In addition, some quantitative evaluation methods have been proposed in Introduction to Reliability Engineering (by Maruzen Bookstore Hiroshi Shiomi).

[0003]

However, according to the conventional evaluation method, when a plurality of maintenance methods exist for one facility / equipment, it does not become an index of which one of these maintenance methods should be selected. There was a problem. Also, simply calculating the importance of individual facilities and equipment based on the value criteria that lead to plant shutdown is not normally used, for example, in an emergency core cooling system of a nuclear power plant. Has a problem that it is not possible to accurately evaluate equipment and devices that do not affect the system. That is, there is a problem that it is not possible to evaluate safety-related facilities and equipment that operate only when a failure or abnormality occurs, such as the emergency core cooling system.

[0004] The present invention has been made to solve the above-mentioned problems, and is an evaluation of the operation rate of equipment with a view to plant shutdown and a stochastic safety evaluation with a view to plant safety. And a maintenance support apparatus for a plant that can select an optimal maintenance method based on the same standard.

[0005]

In order to achieve the above-mentioned object, a plant maintenance support apparatus according to the present invention comprises a means for storing probability data of an event leading to a major accident; Means for calculating an expected value of loss based on the probability data, means for storing probability data of an event leading to a plant shutdown, means for calculating an expected value of loss based on the probability data for an event leading to a plant shutdown, Means for adding two types of expected loss values, means for selecting at least one maintenance method, calculating cost required when each of the selected maintenance methods is performed, and an added value of the expected loss value. Compare the cost of selected maintenance,
Means for selecting a minimum maintenance method whose maintenance cost is equal to or less than the expected loss value and selecting the minimum maintenance method as an optimal maintenance method.

In the above-mentioned maintenance support apparatus for a plant, the means for calculating the cost required for the maintenance method includes a first calculating means for calculating the minimum cost by changing the frequency of the maintenance work, and at least one of the first calculating means for calculating the minimum cost. A second calculating means for calculating the cost by the maintenance method and calculating the lowest cost thereof, and a third calculating means for calculating the cost when at least one facility is changed and calculating the lowest cost thereof. It may have a calculating means.

[0007]

The present invention has the above-described configuration, and evaluates safety-related facilities and equipment by performing safety-related evaluations in addition to the plant operation rates of individual facilities and equipment. It is possible to make an appropriate judgment on the maintenance method of these devices.

[0008] In addition, by evaluating each of the evaluation regarding the plant operation rate and the evaluation regarding the safety in terms of the cost for maintenance, the evaluation can be performed according to a common standard. In addition, by converting the maintenance method into cost and comparing the cost with the cost of loss in the event of a failure of the corresponding equipment / equipment, it is possible to rationally determine whether to adopt this maintenance method.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a plant maintenance support apparatus according to the present invention will be described below with reference to the drawings. FIG.
1 is a block diagram illustrating a configuration of a maintenance support device for a nuclear power plant. The safety evaluation data storage means 10 stores a fault tree in which core damage of a nuclear reactor is a top event. The fault tree has, for example, the configuration shown in FIG. 2, and includes a primary event P _i which is a direct cause event leading to core damage which is a top event, and a direct event leading to this primary event P _i. The lower-order events are sequentially referred to as elementary events p _i, such as secondary lower-order events P _ij which are events due to
Up to a tree diagram.

[0010] From this fault tree, a logical expression (Boolean expression) that gives the probability of a plurality of elementary events p leading to core damage
f (p) is derived. Then, the logical expression f (p)
Substituting the occurrence probability λ for each elementary event p in, and multiplying this by the damage amount D, the economic power loss in the case of core damage in a nuclear power plant having a plurality of elementary events p The expected value E _R can be calculated. If this is expressed by the formula,

E _R = D * f (p) (1)

Therefore, the occurrence probability λ of a certain elementary event p _{i
When i} changes to λ _ix , the expected loss value E _R also changes to E _Rx . This variation ΔE _R is

ΔE _R = E _R −E _Rx = D * {f (p; p _i = λ _i ) −f (p; p _i = λ _ix )} (2)

The expected loss value calculation means 12 determines how much the economic loss leading to core damage changes with a change in the maintenance method for a certain elementary event p _i , ie, the change ΔE in the expected loss value. _R is calculated based on equation (2).

The operating rate evaluation data storage means 14 stores a fault tree in which the stoppage of the nuclear power plant is a top event. This fault tree is shown in FIG.
The primary lower event Q _i , which is the top event that directly leads to the shutdown of the plant, is the top event, and the direct cause that leads to this primary event Q _i is the event Lower-order events such as a certain second-order lower-order event Q _ij are sequentially analyzed up to elementary events q _i , which are represented as a tree diagram.

As in the case of the core damage described above, a logical expression (Boolean expression) g (q) that derives the probability of a plant shutdown from a plurality of elementary events q is derived. And this logical expression g
By substituting the occurrence probability κ for each elementary event q in (q) and multiplying this by the amount of damage C, the economical cost of a nuclear power plant having a plurality of elementary events q when the plant is shut down The expected value E _{S of the} loss can be calculated. If this is expressed by the formula,

E _S = C * g (q) (3)

Therefore, the probability κ of occurrence of a certain elementary event q _{i
When i} changes to κ _ix , the expected loss value E _S also changes to E _Sx . This variation ΔE _S is

ΔE _S = E _S −E _Sx = D * {g (q; q _i = κ _i ) −g (q; q _i = κ _ix )} (4)

The expected loss value calculating means 16 determines how much the economic loss leading to plant shutdown changes with a change in the maintenance method for a certain elementary event q _i , that is, the change ΔE _{S in} the expected loss value. Is calculated based on equation (2).

As described above, evaluation from two viewpoints,
That is, the expected value of the economic loss from both the evaluation on the safety and the evaluation on the operation rate can be evaluated in the same unit of cost. Stated another way, the economic loss of a certain event can be evaluated both when it is evaluated from the viewpoint of safety and when it is evaluated from the viewpoint of availability.

Therefore, by summing the expected value E _R of the economic loss related to safety with respect to a certain event and the expected value E _S of the economic loss related to the operation rate, the economic loss caused by the occurrence of the event is evaluated. it can.

Therefore, one event (p _i = q _i )
It can be seen that the amount of change in the expected value of the loss can be added. That is, the change amount V of the total expected value of the loss when the probability that a certain event (p _i = q _i ) occurs changes from λ _i (= κ _i ) to λ _ix (= κ _ix ) can be expressed by the following equation (2). ) And (4), and

V = ΔE _R + ΔE _S (5) The addition means 18 performs this calculation.

V expressed by the equation (5) can be considered as an expected value of economic profit that can be enjoyed when the probability of occurrence of a certain event is reduced by the maintenance. Hereinafter, this V is referred to as an expected value of profit.

Next, the cost M for changing the maintenance method
Is calculated by the cost calculating means 20 of the maintenance method. The cost calculation means 20 of the maintenance method calculates, for at least one maintenance method, the smallest increase in cost ΔM in the method. However, the case where ΔM exceeds V is not considered. The cost calculation of this maintenance method will be described later in detail.

When the costs of a plurality of maintenance methods have been calculated, the maintenance method selection means 20 selects the maintenance method with the lowest cost increase among the calculated cost increases ΔM of the respective maintenance methods. Is done. In other words, the one with the largest V-ΔM has a large economic benefit and a small increase in maintenance cost, which indicates that the maintenance method is efficient.

Finally, the result display means 24 displays the selected maintenance method.

Hereinafter, the calculation of the cost of the maintenance method whose description has been suspended will be described in detail. Maintenance methods are roughly classified into the following three groups according to their properties. The first group is a group for changing the frequency of maintenance and inspection / maintenance. In other words, the group can change the length of the inspection cycle and the replacement cycle of the spare parts to change the maintenance cost. The feature of this group is that the maintenance method (frequency) and cost continuously change.

The second group is a group for changing the maintenance method itself. For example, the case where the inspection method is changed from the appearance inspection to the disassembly inspection, the case where the inspection of a certain device is changed from the patrol to the monitoring device, and the like belong to this group. A feature of this group is that, unlike the first group, the maintenance methods and costs do not change continuously.

The third group is a group for improving the equipment itself. For example, this group includes a case where a spare device is added to be on standby and a case where a plurality of devices are installed and multiplexed. The feature of this group is that the Boolean expression itself is changed.

For those belonging to the first group,
Optimum values of the inspection cycle and the replacement cycle can be obtained. In general, given that the probability of occurrence of core damage R = f (p) and the probability of occurrence of plant shutdown S = g (q), core damage and plant shutdown are caused by specific elementary events p _i and q _i . Assuming that the occurrence probability of specific elementary events p _i , q _i is λ, the probability of reaching

R = aλ + b (6) S = cλ + d (7) Here, the specific elementary events p _i and q _i have different notations depending on whether the same event is viewed from the viewpoint of safety and from the viewpoint of the operating rate. Are essentially equal. A, b, c, and d in the equations are constants obtained from the Boolean equations f (p) and g (q).

[0028] The prime event p _i, for q _i, to change the service method (such as frequency), the elementary event p _i, if the probability that q _i is generated becomes λ'from lambda, the expected value of the loss From the equations (6) and (7), the change amounts ΔE _R and ΔE _S of

ΔE _R = D * a * (λ−λ ′) (8) ΔE _S = C * c * (λ−λ ′) (9) Further, if the maintenance is complete, that is, if the occurrence probabilities of the elementary events p _i and q _i become 0, the change amounts ΔE _RE and ΔE _SE of the expected values of the losses are expressed by the following equations (8) and (9). λ
By substituting = 0, the equations (2) and (4)

Equation 8] _{ΔE RE = D * a * λ} = D * {f (p; p i = λ) -f (p; p i = 0)} ... (10) ΔE SE = C * c * λ = C _{* {g (q; q i} = λ) -g (q; q i = 0)} relation (11) is obtained.

On the other hand, it is assumed that the relationship between the occurrence probability λ and the annual maintenance cost M is given.

Λ ′ = λ * h (M) (12) where the function h (M) is a model for reducing the probability of occurrence of elementary events p _i and q _i , and h (0) = 1, h (∞) = 0, which is a monotonically decreasing function. Therefore, the expected value V of the profit is given by the equations (5) and (8) to (12).

V = ΔE _R + ΔE _S = (ΔE _RE + ΔE _SE ) {1-h (M)} = V _E * {1-h (M)} (13) Where V _E = ΔE _RE + ΔE _SE is a Boolean expression f
It is a numerical value that can be easily obtained from (p) and q (p). In order to maximize the effect of maintenance, it is sufficient that VM is maximized. Therefore, an optimum maintenance cost M _op can be obtained by differentiating VM with M to obtain an extreme value. That is, by transforming equation (13),

-H '(M _op ) = 1 / V _E (14) is obtained, and as an example of the function, h (M) = exp (-
μ _i M), equation (14) can be solved,

The following equation is obtained: M _op = ln (μ _i * V _E ) / μ _i (15) Here, μ _i is a constant representing the maintenance effect of certain elementary events p _i , q _i .

As described above, in the maintenance methods belonging to the first group, the optimum maintenance method (maintenance frequency) and the optimum maintenance method (maintenance frequency) can be determined by determining the function h (M) representing the change in the probability of occurrence of an event accompanying the maintenance. The change amount ΔM of the maintenance cost at that time can be obtained.

Note that h (M) = exp (-
In the model represented by μ _i * M), μ _i * V _E <1
In the case of (1), the loss increases as the maintenance is performed without an extreme value, and the failure rate cannot be effectively reduced.

Next, as for the maintenance methods belonging to the second group, various maintenance methods affecting the occurrence probability λ of the specific elementary events p _i and q _i are selected, and in each maintenance method, the equation (5) ), The expected value V of the profit is calculated, and the maintenance cost M and the change ΔM at that time can be calculated. Then, a maintenance method that gives the maximum V-ΔM can be selected. It can be seen that the maintenance method in which V-ΔM is negative is a maintenance method that results in loss from an economic viewpoint.

Finally, regarding the security methods belonging to the third group, the Boolean expressions f (p) and g (q) themselves are changed to f '(p) and g' (q) as described above. Therefore, the expected values of loss ΔE _R and ΔE _S are

ΔE _R = E _R −E ′ _R = D * {f (p) −f ′ (p)} (16) ΔE _S = E _S −E ′ _S = C * ｛g (q) − g ′ (q)｝ (17), and the expected value V of the profit is obtained from Expression (5). In the case of the method belonging to the third group, the change amount ΔM of the maintenance cost corresponds to a value obtained by dividing the cost Y associated with the change of the maintenance method by the number n of operating years in the future. Therefore,
What is necessary is just to select an improvement method that maximizes VY / n. Then, the cost M required for the improvement and the variation ΔM thereof can be calculated.

As described above, the optimum maintenance method is selected for each of the three groups.
The maintenance method with the largest ΔM is calculated as the optimal maintenance method.

[0035]

As described above, according to the present invention, safety-related facilities and equipment are evaluated by performing safety-related evaluations in addition to the plant operation rates of individual facilities and equipment. It is possible to make an appropriate judgment on the maintenance method of these devices.

Further, by evaluating the evaluation regarding the plant operation rate and the evaluation regarding the safety by converting them into the cost for maintenance, the evaluation can be performed according to a common standard. In addition, by converting the maintenance method into cost and comparing the cost with the cost of loss in the event of a failure of the corresponding equipment / equipment, it is possible to rationally determine whether to adopt this maintenance method.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a preferred embodiment according to the present invention.

FIG. 2 is an explanatory diagram of a fall tree in which core damage is a top event.

FIG. 3 is an explanatory diagram of a fall tree in which a plant stop is a top event.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Safety evaluation data storage means 12, 16 Expected loss value calculation means 14 Operating rate evaluation data storage means 18 Addition means 20 Cost calculation means of maintenance method 22 Maintenance method selection means 24 Result display means

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G06F 17/50 G06F 17/60

Claims (2)

(57) [Claims] 1. Means for storing probability data of an event leading to a major accident, means for calculating an expected loss value based on the probability data for an event leading to a major accident, and storing probability data of an event leading to a plant shutdown Means for calculating an expected loss value based on the probability data for an event leading to plant shutdown; means for adding the two expected loss values; and at least one maintenance method selected and selected. Means for calculating the cost required when performing each maintenance method, and comparing the added value of the expected loss value with the selected maintenance cost, the maintenance cost is equal to or less than the added value of the expected loss value, Means for selecting a minimum maintenance method and selecting the optimum maintenance method as an optimal maintenance method. 2. The maintenance support apparatus for a plant according to claim 1, wherein the calculation means for calculating the cost required for the maintenance method includes: a first calculation means for calculating a minimum cost by changing a frequency of the maintenance work. A second calculating means for calculating the cost of at least one maintenance method and calculating the lowest cost thereof, and calculating the cost of changing at least one facility and calculating the lowest cost thereof Third calculating means for performing
A maintenance support device for a plant, comprising: