JP7638786B2 - Nuclear emergency decision support device, method and program - Google Patents

Description

An embodiment of the present invention relates to a technology for supporting decision-making in a nuclear emergency.

In order to reduce the risk of public exposure to radiation in the event of an abnormality occurring at a nuclear facility, the Nuclear Emergency Response Guidelines enacted by the Nuclear Regulation Authority stipulate that preventive evacuation of the public will be carried out before radioactive materials are released into the environment. Furthermore, a system is being considered in which an alert will be issued based on the emergency action level (EAL) corresponding to the state of the nuclear facility, and preparations for and implementation of a public evacuation will be made.

Emergency action levels (EALs) are standards for determining the level of urgency when an abnormality occurs at a nuclear facility. EALs are broadly classified into three types based on facility information, radiation levels, etc.: "alert state," "facility site emergency," and "full-scale emergency."

In the event of a nuclear disaster, the national government or the operator will issue an EAL warning and instruct local governments on evacuation and other measures according to the circumstances of the nuclear power plant accident, based on the principles of the Nuclear Emergency Response Guidelines. In response, local governments will draw up specific evacuation routes and evacuation destinations based on their local disaster prevention plans and taking into account the actual conditions of the area, and will instruct residents to evacuate.

On the other hand, a nuclear emergency response system is known that identifies an initiating event based on operational information from a nuclear facility, analyzes the progression of events from the identified initiating event, and creates an evacuation plan based on radiation exposure predictions derived from the analysis results. This known technology makes it possible to predict the start time of the release of radioactive materials.

Furthermore, there are known methods for evaluating the timing of EALs based on event progression analysis, and for evaluating the risk of exposure when protective measures are implemented, taking into account the time to core damage and the time to containment vessel failure. Using these known techniques, it is possible to predict the timing of EALs and the time to containment vessel failure.

JP 2003-215246 A

S/NRA/R Research Report "Research on the Use of Risk Information Related to Emergency Action Levels (EALs)" RREP-2020-2003, 2020

In the above-mentioned regional disaster prevention plans, the time to complete public evacuation is used as an index for determining protection optimization. For this reason, regional disaster prevention plans are designed with preparation and implementation procedures in place so that public evacuation can be completed in the shortest time possible after an EAL warning is issued. As a result, regional disaster prevention plans to date have been unable to grasp information such as how much time there is between the issuance of an EAL warning and the start of the release of radioactive materials, or the urgency of evacuation. For this reason, in the event of an abnormality occurring at a nuclear facility, this has hindered the formulation of safe evacuation plans for local governments that prepare and implement public evacuations.

The above-mentioned publicly known technology makes it possible to predict the time when radioactive material will begin to be released in a hypothetical accident scenario. However, in reality, due to the fact that the phenomenon is unknown and the situation is constantly changing, there is a large degree of uncertainty in the predicted time when radioactive material will begin to be released. It has been difficult to support local government decision-making based on information with such uncertainty.

Embodiments of the present invention have been made in consideration of these circumstances, and aim to provide a decision-making support technology for nuclear emergencies that plans safe public evacuation based on uncertain information.

a calculation unit that calculates a frequency of reaching the final state in each of the extracted sequences based on the branch probability of the branch located at the sequence of the action item whose execution result is undetermined; a third registration unit that registers a start time from the occurrence of the initiating event to the release of the radioactive materials into the environment in each of the sequences; and a creation unit that creates a graph showing the start time of the release of the radioactive materials into the environment and the probability thereof, based on the start time and the arrival frequency in each of the extracted sequences.

Embodiments of the present invention provide a nuclear emergency decision support technology for planning safe public evacuation based on information with uncertainty.

1 is a block diagram of a decision support device for a nuclear emergency according to a first embodiment of the present invention. An event tree consisting of multiple sequences. A formula for calculating the frequency of reaching the final state of a sequence based on branching probabilities. (A) An event tree showing the sequence extraction status when the execution result of the first action item is "success", (B) an event tree showing the sequence extraction status when the execution result of the next action item is "failure". A graph showing the start time and probability of a release of radioactive materials into the environment at the current time after the occurrence of an initiating event. FIG. 11 is a block diagram of a decision support device for a nuclear emergency according to a second embodiment. 13A is a table showing an assessment index of the severity of public evacuation for each sequence in the second embodiment; FIG. 13B is a display showing the urgency of public evacuation; FIG. In the second embodiment, (A) a graph showing the start time and the probability of releasing radioactive materials into the environment when the execution result of the first action item after the occurrence of a triggering event is “success”, and (B) a graph showing the start time and the probability of releasing radioactive materials into the environment when the execution result of the next action item after the execution of the first action item is “failure”. FIG. 11 is a block diagram of a decision support device for a nuclear emergency according to a third embodiment. FIG. 13 is a block diagram of a decision support device for a nuclear emergency according to a fourth embodiment. 2 is a flowchart showing the steps of a decision-making support method in a nuclear emergency according to an embodiment and an algorithm of the decision-making support program.

First Embodiment
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a block diagram of a nuclear emergency decision support device 10A (10) (hereinafter simply referred to as "device 10A") according to a first embodiment of the present invention. Fig. 2 shows an event tree 20 composed of a plurality of sequences S ( _S1 , _S2 , ...). Fig. 3 shows a formula for calculating the arrival frequency P ( _P1 , _P2 ...) of a sequence S ( _S1 , _S2 , ...) to a final state, which is obtained based on the branch probability Q ( _Qa , _Qb ...).

In this way, the device 10A is equipped with a first registration unit 11 that registers an event tree 20 composed of a plurality of sequences S (S ₁ , S ₂ , ...) in which branches 14 (14a, 14b, ...) are defined by the success/failure of the execution results of a series of action items 17 (17a, 17b, ...) that prevent the progression of a nuclear disaster causative event 16 (Figure 2), and a judgment unit 22 that identifies the occurring causative event 16 based on operating information 15 and further judges the execution results (success/failure) of the action items 17 (17a, 17b, ...) in the corresponding event tree 20.

The device 10A further includes an extraction unit 25 that extracts sequences S that have the potential to reach an end state and the potential to release radioactive materials into the environment based on the above-mentioned judgment, a second registration unit 12 that registers the branch probability of whether the execution result of each action item 17 (17a, 17b, ...) is success or failure (shown is the branch probability Q ( _Qa , _Qb, ...) of "failure"), and a calculation unit 26 that calculates the frequency P ( _P1 , _P2 , ...) (Figure 3) of reaching the end state for each of the extracted sequences S ( _S1 , _S2 , ...) based on the branch probability Q of the branch 14 located in the action item 17 whose execution result is undetermined.

The device 10A further includes a third registration unit 13 that registers the start time T from the occurrence of the initiating event 16 in each sequence S to the release of radioactive material into the environment, and a creation unit 27 that creates a graph based on the start time T ( _T1 , _T2 , ...) and arrival frequency P ( _P1 , P2, ...) in each of the extracted sequences S ( _S1 , _S2 , _... ).

The initiating event 16 at the left end of the sequence S (S ₁ , S ₂ , ...) shown in Fig. 2 is an event that can be a cause of accident progression leading to a serious accident (such as core damage) that releases radioactive materials into the environment, and several such events have been identified in, for example, a probabilistic risk assessment (PRA). Starting from this initiating event 16, several measures to prevent the release of radioactive materials into the environment are chronologically headed as action items 17 (17a, 17b ...). Each of the sequences S (S ₁ , S ₂ , ...) is expanded to the final state at the right end by branches 14 (14 _a , 14 _b ...) defined by the success/failure of the execution results of each action item 17 (17a, 17b ...).

Here, the final state of each sequence S ( _S1 , _S2 , ...) is associated with whether the release of radioactive materials into the environment was prevented ("OK") or not ("NG"), and in the case where the release of radioactive materials into the environment was not prevented ("NG"), it is further associated with the scale of the release into the environment. A plurality of event trees 20 defined by each of the plurality of types of initiating events 16 are registered in the first registration unit 11.

If the execution result of each of the action items 17 (17a, 17b...) is "successful", it contributes to preventing the initiating event 16 from progressing, and if the execution result is "failed", it accelerates the progression of the initiating event 16. Therefore, each of the action items 17 (17a, 17b...) has a branch probability Q ( _Qa , _Qb ...) of whether the execution result is success or failure, and the initial value is registered in the second registration unit 12. Although a detailed explanation is omitted, these branch probabilities Q ( _Qa , _Qb ...) can be obtained in advance by a fault tree analysis of multiple component devices that execute the action items 17.

As shown in Fig. 3, immediately after the occurrence of the initiating event 16, when the execution results (success/failure) of all the actions 17 (17a, 17b...) are undetermined, the frequency P ( _P1 , _P2 ...) of reaching the final state of each sequence S ( _S1 , _S2 ,...) is expressed by the above formula. Note that the formula shown in Fig. 3 shows a typical part, and in reality, other coefficients and variables may be added or the formula may be modified.

After the occurrence of the initiating event 16, as the execution results (success/failure) of a series of action items 17 (17a, 17b, ...) are determined sequentially, the frequency P ( _P1 , _P2 , ...) of reaching the final state of each sequence S ( _S1 , _S2 , ...) also changes.

Specifically, when the execution result of the first action item 17a is "success", the branch probability of failure _Qa becomes 0, and changes to _P1 = (1- _Qb ) x (1- _Qc ), _P2 = (1- _Qb ) x _Qc , _P3 = Qb _x (1- _Qc ), _P4 = _Qb x _Qc , _P5 = _P6 = _P7 = _P8 = 0. When the execution result of the first action item 17a is "failure", the branch probability of failure _Qa becomes 1, and changes to _P1 = _P2 = _P3 = _P4 = 0, _P5 = (1- _Qb ) x (1- _Qc ), _P6 = (1- _Qb ) x _Qc , _P7 = _Qb x (1- _Qc ), _P8 = _Qb x _Qc .

The operating information 15 is a control value that changes from moment to moment, such as a process signal of a nuclear facility, and is acquired in real time by the acquisition unit 21. In the unlikely event that a disaster occurs at this nuclear facility, specific operating information 15 corresponding to the initiating event 16 is acquired. Furthermore, when a corrective action 17 (17a, 17b, etc.) is executed to prevent the initiating event 16 from progressing, specific operating information 15 corresponding to the success/failure of the action is acquired.

The judgment unit 22 identifies an initiating event 16 that has occurred in the nuclear facility by analyzing the operation information 15 acquired in real time, and calls up the corresponding event tree 20 from the first registration unit 11. The judgment unit 22 then analyzes the operation information 15 acquired in real time to judge the execution result (success/failure) of a series of action items 17 (17a, 17b, ...) in the event tree 20. Then, as soon as this judgment is confirmed, the execution result (success/failure) is output.

Fig. 4(A) is an event tree 20 showing the extraction status of sequence S (S ₁ , ...S _M ) when the execution result of the first action item 17a is "success". Fig. 4(B) is an event tree 20 showing the extraction status of sequence S (S _m+ 1 , ...S _M ) when the execution result of the next action item 17b is "failure". In this way, the event tree 20 highlights the route of sequence S from the position of the initiating event 16 to the position of the branch 14 corresponding to the action item 17 currently being judged by the judgement unit 22.

The extraction unit 25 (FIG. 1) extracts sequences S that have the possibility of reaching the final state based on the output of the determination unit 22. That is, as shown in FIG. 4A, when the execution result of the action item 17a is determined to be "success" (branch probability Q _a =0; FIG. 3), the arrival frequency P of the sequence S having the "failure" branch 14a becomes 0, making it impossible to reach the final state, while the arrival frequency P of the sequence S having the "success" branch 14a becomes a finite value and making it possible to reach the final state. On the other hand, as shown in FIG. 4B, when the execution result of the action item 17b is determined to be "failure" (branch probability Q _a =1; FIG. 3), the arrival frequency P of the sequence S having the "success" branch 14b becomes 0, making it impossible to reach the final state, while the arrival frequency P of the sequence S having the "failure" branch 14b becomes a finite value and making it possible to reach the final state.

Furthermore, the extraction unit 25 extracts sequences S that have a probability of releasing radioactive materials into the environment, based on the fact that the final state of each sequence S ( _S1 , _S2 , ...) is associated with "OK" (whether the release of radioactive materials into the environment was prevented) or "NG" (whether the release of radioactive materials into the environment was not prevented), as described above.

The calculation unit 26 (Fig. 1) calculates the arrival frequency P ( _P1 , _P2 , ...) (Fig. 3) from the current time to the final state shown by the end of the highlighting in Fig. 4 (A) (B) for each of the extracted sequences S ( _S1 , S2, ...). That is, the calculation unit ₂₆ calculates the arrival frequency P (P1, _P2 , ...) (Fig. 3) of the extracted sequence S ( _S1 , _S2 , ...) based on the branch probability Q of the branch 14 located in the action item 17 whose execution result ( _success /failure) is undetermined.

The third registration unit 13 registers a start time T from the occurrence of the initiating event 16 in each sequence S (S ₁ , S ₂ , ...) until the release of radioactive materials into the environment. This start time T is obtained in advance using, for example, the MAAP code developed by the Electric Power Research Institute (EPRI). This MAAP code can analyze a series of accident progression processes from core damage in a light water reactor, reactor pressure vessel (RPV) damage, and containment vessel (PCV) damage to core-concrete reaction, and the generation, migration, and release of radioactive materials.

That is, in each sequence S (S ₁ , S ₂ , ...), a process analysis can be performed to determine whether, after the occurrence of an initiating event 16, the core will be brought to a state where it can be cooled and the accident will be terminated, or whether the PCV will lose function and a serious accident will occur, such as releasing radioactive materials into the environment.

Of the event trees 20 (Figure 2) registered in the first registration unit 11, the final state of a sequence S in which the release of radioactive material into the environment was prevented through such analysis is associated with "OK" as described above. And the final state of a sequence S in which the release of radioactive material into the environment was not prevented is associated with "NG" as described above. Furthermore, the "NG" final state is also associated with information on the scale of the environmental release obtained from this analysis. Furthermore, the start time T registered in the third registration unit 13 is associated with a sequence S having an "NG" final state.

5 is a graph showing the start time T of the release of radioactive materials into the environment and its probability at the current time after the occurrence of the initiating event 16. In this graph, the start time T from the "occurrence time" of the initiating event 16 is set in classes divided at regular intervals on the horizontal axis, and the arrival frequency P ( _P1 , _P2 ...) of the corresponding sequence S ( _S1 , _S2 , ...) is accumulated to form the probability on the vertical axis. This graph is displayed on the display unit 28.

The creation unit 27 (FIG. 1) creates a graph (FIG. 5) based on the start times T ( _T1 , _T2 , ...) and arrival frequencies P ( _P1 , _P2 , ...) of each sequence S ( _S1 , _S2 , ...) extracted by the extraction unit 25 at the "current time". This allows a safe public evacuation to be planned based on information with uncertainty regarding the release of radioactive materials into the environment. As the execution results (success/failure) of the series of action items 17 (17a, 17b, ...) are determined, the uncertainty regarding the release of radioactive materials into the environment decreases, allowing a safer public evacuation to be planned.

Second Embodiment
Next, a second embodiment of the present invention will be described with reference to Figures 6 and 7. Figure 6 is a block diagram of a nuclear emergency decision support device 10B (10) (hereinafter simply referred to as "device 10B") according to the second embodiment. In Figure 6, parts having the same configuration or function as Figure 1 are indicated by the same reference numerals, and duplicated explanations will be omitted.

As shown in Figure 6, the device 10B of the second embodiment (see Figure 2 as appropriate) is similar to the device 10A of the first embodiment and includes a first registration unit 11 of an event tree 20, a judgment unit 22 of action items 17 (17a, 17b, ...), an extraction unit 25 of sequence S ( _S1 , _S2 , ...), a second registration unit 12 of branching probability Q ( _Qa , _Qb, ...), a calculation unit 26 of arrival frequency P ( _P1 , _P2 , ...), a third registration unit 13 of start time T of environmental release, and a creation unit 27 of a graph (Figure 8).

Furthermore, the device 10B of the second embodiment is equipped with a first evaluation unit 31 that evaluates the severity of public evacuation for each of the extracted sequences S ( _S1 , _S2 , ...) based on the scale of the environmental release, and a second evaluation unit 32 that evaluates the urgency of public evacuation based on the point at which the time integrated value of the arrival frequency P ( _P1 , _P2 , ...) in the graph reaches a threshold value 35.

Fig. 7(A) is a table showing the evaluation index of the severity of public evacuation in each of the sequences S ( _S1 , _S2 , ...) in the second embodiment. Fig. 7(B) is a display result showing the urgency of public evacuation. In this way, the first evaluation unit 31 ranks the severity of each of the sequences S ( _S1 , _S2 , ...) as shown in Fig. 7(A) based on information such as the arrival frequency P, the start time T, and the scale of the environmental release. Furthermore, as shown in Fig. 7(B), it is displayed on the display unit 28.

Figure 8 (A) is a graph showing the start time T of the release of radioactive material into the environment and its probability when the execution result of the first action item 17a after the occurrence of the causal event 16 is "success" as shown in Figure 4 (A). Figure 8 (B) is a graph showing the start time T of the release of radioactive material into the environment and its probability when the execution result of the next action item 17b after the execution of the first action item 17a is "failure" as shown in Figure 4 (B).

In this way, in the graph of the second embodiment, the horizontal axis represents the class of start time, and the arrival frequency P ( _P1 , _P2 ...) stacked along the vertical axis as probability is identified for each severity rank of sequence S ( _S1 , _S2 , ...). Furthermore, as shown in Figures 8(A) and 8(B), it is possible to visually confirm how the probability of the severity rank of environmental release is updated in accordance with the execution results of a series of action items 17 (the passage of the "current time").

The second evaluation unit 32 (FIG. 6) sets the time when the arrival frequency P ( _P1 , _P2, ...) accumulated over time reaches a threshold value 35 as the "scheduled issuance time" of a state of emergency declaration or the like to promote public evacuation. This "scheduled issuance time" also changes with the execution results of a series of action items 17 (the passage of the "current time"), as shown in FIG. 8(A) to FIG. 8(B).

This will enable safer public evacuations to be planned based on uncertain information regarding the environmental release of radioactive materials. By allowing local governments to present safer evacuation routes and evacuation timings that take time into consideration, it will be possible to avoid shortages of evacuation support personnel and road congestion, thereby improving the rescue rate. In addition, the simple and clear display method will allow people to understand the situation regardless of whether they have knowledge of nuclear disasters, making it less likely to cause confusion in the transmission of information, etc.

Third Embodiment
Next, a third embodiment of the present invention will be described with reference to Fig. 9. Fig. 9 is a block diagram of a nuclear emergency decision support device 10C (10) (hereinafter, simply referred to as "device 10C") according to the third embodiment. In Fig. 9, parts having the same configuration or function as Fig. 1 or Fig. 6 are indicated by the same reference numerals, and duplicated explanations will be omitted.

As shown in Figure 9, the device 10C of the third embodiment (see Figure 2 as appropriate) is similar to the device 10B of the second embodiment and includes a first registration unit 11 of an event tree 20, a judgment unit 22 of action items 17 (17a, 17b...), an extraction unit 25 of sequence S ( _S1 , _S2 ,...), a second registration unit 12 of branching probability Q ( _Qa , _Qb ...), a calculation unit 26 of arrival frequency P ( _P1 , _P2 ,...), a third registration unit 13 of start time T of environmental release, a graph creation unit 27 (Figure 8), a first evaluation unit 31 of the seriousness of public evacuation, and a second evaluation unit 32 of the urgency of public evacuation.

Furthermore, in the device 10C of the third embodiment, the first evaluation unit 31 and the second evaluation unit 32 evaluate the seriousness or urgency of public evacuation based on environmental information 30 including at least one of meteorological information and environmental radiation information.

Environmental information 30 consists of climate data from AMeDAS (Automated Meteorological Data Acquisition System), such as rainfall, snowfall, wind direction, temperature, etc., released by the Japan Meteorological Agency, as well as radiation distribution data and distribution forecast data from SPEEDI (Speedy Emergency Prediction of Radiation Impact Network System) and emergency monitoring posts, etc.

The transport analysis unit 36 analyzes the transport direction and distance of radioactive materials based on the environmental information 30 from the location and scale of the release of radioactive materials into the environment. This allows for a detailed, region-specific assessment of the severity and urgency of public evacuation according to the direction and distance of the surrounding area. This enables local governments to present safe evacuation routes and evacuation timing for each region. This makes it possible to avoid a shortage of evacuation support personnel and road congestion, improving the rescue rate.

Fourth Embodiment
Next, a fourth embodiment of the present invention will be described with reference to Fig. 10. Fig. 10 is a block diagram of a nuclear emergency decision support device 10D (10) (hereinafter, simply referred to as "device 10D") according to the fourth embodiment. In Fig. 10, parts having the same configuration or function as Figs. 1, 6, and 9 are indicated by the same reference numerals, and duplicated explanations will be omitted.

As shown in Figure 10, the device 10D of the fourth embodiment (see Figure 2 as appropriate) is similar to the device 10A of the first embodiment and includes a first registration unit 11 of an event tree 20, a judgment unit 22 of action items 17 (17a, 17b, ...), an extraction unit 25 of sequence S ( _S1 , _S2 , ...), a second registration unit 12 of branching probability Q ( _Qa , _Qb, ...), a calculation unit 26 of arrival frequency P ( _P1 , _P2 , ...), a third registration unit 13 of start time T of environmental release, and a graph (Figure 8) creation unit 27.

Furthermore, the device 10D of the fourth embodiment includes an update unit 40 that updates at least one of the branch probability Q and the start time T registered in each of the second registration unit 12 and the third registration unit 13 in accordance with the situation of the nuclear disaster based on the acquired operating information 15.

As the initiating event 16 of the nuclear disaster progresses and the state of the nuclear facility changes, the branch probability Q ( _Qa , _Qb, ...) of each of the action items 17 (17a, 17b, ...) may also change from the initial registered value in the second register 12. Alternatively, regardless of the progress of the initiating event 16, a specific device may become unusable due to poor maintenance or an unexpected breakdown, causing the branch probability Q to change from the initial registered value. For the same reason, the start time T ( _T1 , _T2 , ...) until the release of radioactive materials into the environment may also change from the initial registered value in the third register 13.

Therefore, the update unit 40 updates the branch probability Q and the start time T registered in the second registration unit 12 and the third registration unit 13, respectively, based on the operation information 15 that reflects the change in the state of the nuclear facility. This makes it possible to update the branch probability Q ( _Qa , _Qb, ...) and the start time T ( _T1 , _T2 , ...) at any time (for example, every hour). This also makes it possible to update the graphs (FIGS. 5 and 8) at any time in response to the ever-changing state of the nuclear facility.

This makes it possible to present information that more effectively supports decision-making when planning safer public evacuations by local governments. Furthermore, if the branch probability Q or start time T is not updated in the update unit 40, decision-making support information is presented that indicates that the state of the nuclear facility will not change for a certain period of time.

The steps of the method for supporting decision-making in a nuclear emergency according to the embodiment and the algorithm of the decision-making support program will be described with reference to the flowchart in Fig. 11. First, the event tree 20, the branch probability Q ( _Qa , _Qb ...) of success/failure of the action items 17 (17a, 17b...), and the start time T of the release of radioactive materials into the environment, which have been created or calculated in advance, are initially registered (S11, S12, S13). Of these, the branch probability Q ( _Qa , _Qb ...) and the start time T may be updated from the initial registration based on the operation information 15 acquired from the nuclear facility.

While acquiring operation information 15 of the nuclear facility, if an initiating event 16 occurs, this is identified (S14 No Yes), and the corresponding event tree 20 is called up from the registration (S15). Furthermore, operation information 15 continues to be acquired, and the execution result (success/failure) of action items 17 in this event tree 20 is determined (S16 No Yes). Then, based on this determined execution result (success/failure), a sequence S that has the potential to reach an end state and has the potential to release radioactive materials into the environment is extracted (S17).

Among the extracted sequence S ( _S1 , _S2 , ...), the branch probability Q ( _Qa , _Qb ...) of the branch 14 for which the execution result of the action item 17 is undetermined is retrieved from the registration (S18). Then, based on this branch probability Q ( _Qa , _Qb ...), the arrival frequency P ( _P1 , _P2 , ...) of the sequence S ( _S1 , _S2 , ...) up to the final state is calculated (S19).

Next, the start time T of the environmental release associated with the extracted sequence S is retrieved from the registration (S20). Then, a graph (FIGS. 5 and 8) is created and displayed based on the start _time T ( _T1 , _T2 , ...) and arrival frequency P ( _P1 , _P2 , ...) of each of _the extracted sequences S (S1, S2, ...). Then, the processes from (S16) to (S21) are repeated until the execution results of the series of action items 17 in the sequence S are all determined (S22 No Yes END).

According to at least one of the embodiments of the nuclear emergency decision support device described above, a graph can be created based on the start times and arrival frequencies of the sequences that make up the event tree, making it possible to plan a safe public evacuation based on information that has uncertainty.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention. These embodiments and their modifications are within the scope of the invention and its equivalents as set forth in the claims, as well as the scope and spirit of the invention.

The decision support device described above includes a control device with a highly integrated processor such as a dedicated chip, FPGA (Field Programmable Gate Array), GPU (Graphics Processing Unit), or CPU (Central Processing Unit), a storage device such as ROM (Read Only Memory) or RAM (Random Access Memory), an external storage device such as HDD (Hard Disk Drive) or SSD (Solid State Drive), a display device such as a display, an input device such as a mouse or keyboard, and a communication I/F, and can be realized with a hardware configuration using a normal computer. Therefore, the components of the decision support device can also be realized with a computer processor and can be operated by a decision support program.

The decision support program may be provided in a state where it is pre-installed in a ROM or the like. Alternatively, the program may be provided in a state where it is stored in a computer-readable storage medium such as a CD-ROM, CD-R, memory card, DVD, or flexible disk (FD) in the form of an installable or executable file.

The decision support program according to this embodiment may be stored on a computer connected to a network such as the Internet and provided by downloading it via the network. The decision support device may also be configured by combining separate modules that independently perform the functions of the components and are interconnected via a network or dedicated lines.

10 (10A, 10B, 10C, 10D)... decision support device, 11... first registration unit, 12... second registration unit, 13... third registration unit, 14 (14a, 14b...)... branch, 15... operation information, 16... initiating event, 17 (17a, 17b...)... treatment item, 20... event tree,
21... Acquisition unit, 22... Judgment unit, 25... Extraction unit, 26... Calculation unit, 27... Creation unit, 28... Display unit, 30... Environment information, 31... First evaluation unit, 32... Second evaluation unit, 35... Threshold value, 36... Transport analysis unit, 40... Updating unit, P(P ₁ , P ₂ ,...)... Arrival frequency, Q (Q _a , Q _b ...)... Branch probability, S(S ₁ ,S ₂ ,…)…sequence, T(T ₁ ,T ₂ ,…)…start time.

Claims (7)

a first registration unit that registers an event tree composed of a plurality of sequences in which branches are defined by the success/failure of execution results of a series of actions to prevent the progression of an event that causes a nuclear disaster;
a determination unit that identifies the initiating event that has occurred based on operation information, and determines the execution result of the action item in the corresponding event tree;
an extraction unit that extracts the sequence that has a possibility of reaching an end state and a probability of releasing radioactive materials into the environment based on the determination by the determination unit;
a second registration unit that registers a branch probability of whether the execution result of each of the actions is a success or failure;
a calculation unit that calculates an arrival frequency to the end state in each of the extracted sequences based on the branch probability of the branch located in the action item whose execution result is undetermined;
a third registration unit that registers a start time from the occurrence of the initiating event to the release of the radioactive material into the environment in each of the sequences;
and a creation unit that creates a graph showing the start time and probability of the radioactive material being released into the environment, based on the start time and the arrival frequency in each of the extracted sequences. 2. The nuclear emergency decision support device according to claim 1,
A nuclear emergency decision support system comprising a first assessment unit for assessing the severity of a public evacuation for each of the extracted sequences based on a magnitude of the environmental release. The nuclear emergency decision support device according to claim 1 or 2,
A decision support device for use in a nuclear emergency, comprising a second evaluation unit that evaluates the urgency of public evacuation based on the point in time at which the time-integrated value of the frequency of arrival in the graph reaches a threshold value. 4. The nuclear emergency decision support device according to claim 2, further comprising:
A nuclear emergency decision support device in which the severity or urgency of the public evacuation is assessed based on environmental information including at least one of meteorological information and environmental radiation information. The nuclear emergency decision support device according to any one of claims 1 to 4,
An apparatus for supporting decision-making in a nuclear emergency comprising an update unit that updates at least one of the registered branch probability and the start time in accordance with the situation of the nuclear disaster based on the acquired operational information. A method for supporting decision-making in a nuclear emergency, which is executed by an apparatus including a first registration unit, a determination unit, an extraction unit, a second registration unit, a calculation unit, a third registration unit, and a creation unit,
A step in which the first registration unit registers an event tree composed of a plurality of sequences in which branches are defined by the results of success/failure of execution of a series of actions for preventing the progression of an event causing a nuclear disaster;
The determination unit identifies the initiating event that has occurred based on operation information, and determines the execution result of the corresponding action item in the event tree;
extracting the sequence that has a possibility of reaching an end state and a probability of releasing radioactive materials into the environment based on the determination by the extraction unit;
The second registration unit registers a branch probability of whether the execution result of each of the actions is success or failure;
a step of calculating an arrival frequency to the final state in each of the extracted sequences based on the branch probability of the branch located in the action item whose execution result is undetermined,
the third registration unit registering , for each of the sequences, a start time from the occurrence of the initiating event to the release of the radioactive material into the environment;
and a step of generating a graph showing the start time and the probability of the radioactive material being released into the environment, based on the start time and the arrival frequency in each of the extracted sequences, by the generating unit. On the computer,
A step of registering an event tree composed of a plurality of sequences in which branches are defined by the success/failure of execution results of a series of actions for preventing the progression of an event that causes a nuclear disaster;
Identifying the initiating event that has occurred based on operation information, and determining the execution result of the corresponding action item in the event tree;
extracting the sequences that have a possibility of reaching an end state and a probability of releasing radioactive materials into the environment based on the determination;
registering a branch probability of whether the execution result of each of the actions is a success or failure;
calculating an arrival frequency to the final state in each of the extracted sequences based on the branch probability of the branch located in the action item whose execution result is undetermined;
registering a start time from the occurrence of the initiating event to the release of the radioactive material into the environment in each of the sequences;
creating a graph showing the start time and probability of the radioactive material being released into the environment, based on the start time and the arrival frequency for each of the extracted sequences.

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