JPH01312491A - Method for preparing fuel exchange procedure - Google Patents

Abstract

PURPOSE:To implement the method for preparing fuel exchange procedure enabling the preparation of fuel exchange programs using computers by making it possible to minimize the number of fuel taking-out bodies and to secure regions for fuel exchange working with a formalized approach. CONSTITUTION:An initial fuel arrangement 1 for a core, an objective fuel arrangement 2 and a core-related working 3 are inputted. At first, a fuel 4 which is taken out in cycle is selected. Said fuel 4 is incorporated in the initial fuel arrangement 1 and is not incorporated in the objective arrangement 2. A fuel taking-out pattern 5 is determined for every one core-related working in association with the core-related working 3. Said fuel taking-out pattern 5 is applied to the initial fuel arrangement 1 so that the overlapping of the fuel taking-out patterns 5 and the overlapping of the fuels 4 which are taken out in cycle are maximized. Thus, a first intermediate fuel taking-out objective 6 is determined. Then a second intermediate fuel taking-out objective 7 is determined so that a part of the fuels 4 which are taken out in cycle in a range, wherein supporting of a control rod is not lost, based on the objective 6. Then, the front half of a fuel exchange procedure 8 is determined in the reverse direction of the executing order with the initial fuel arrangement 1 as the objective based on the second objective 7. The rear half of the procedure 8 is determined in the executing order from the objective 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for creating a fuel exchange plan for planning procedures for fuel removal, loading, and rearrangement during periodic inspection of a nuclear reactor.

(Prior Art) Generally, fuel exchange during periodic nuclear reactor inspections is carried out for the following basic purposes.

■Remove fuel with advanced burnup and low reactivity that will not be used in the next cycle's core (it may be reloaded after the next cycle).

■In order to maintain the required reactivity in the core, load new fuel or fuel that has been removed in the previous cycle and still has some reactivity (reloaded fuel).

■Fuel is rearranged (shuffling) so that the reactor shutdown margin and reactor core performance meet the limit values using the remaining fuel from the previous cycle and the newly loaded fuel.

Here, the target fuel loading pattern is evaluated and created using a design code before planning the fuel exchange work.

In the refueling plan, in addition to achieving the final goal of the core state, it is also necessary to achieve the core state necessary to perform core-related work during refueling.

For boiling water reactors, the following core-related operations are involved in the fuel exchange procedure:

■Control rod drive system (CHD) inspection.

■Replacement of in-core neutron detectors (local output monitor, intermediate area monitor, neutron source area monitor).

■Replacement of control rod (CR).

■Fuel removal based on exposure reduction measures for in-service inspection (+81).

For these operations or monitoring, it is necessary to extract fuel and withdraw control rods.

Furthermore, among the fuels that will be subsequently loaded into the core as fuel for the next cycle, safety regulations require that two fuels of each fuel type, starting with the fuel with the highest burnup, be visually inspected for soundness. Therefore, these selected fuels must be temporarily removed from the furnace during refueling operations.

The main purpose of the refueling work plan is to reduce the amount of work necessary for refueling as much as possible, taking into account the work steps required during these periodic inspection processes, and to change the intermediate steps necessary for core-related work from the previous cycle's fuel placement. The goal is to create the target fuel arrangement and then complete the fuel arrangement for the next cycle.

The following are the main constraints for creating fuel exchange work procedures.

■Securing margin for reactor shutdown.

■Secure support for control rods.

■Prohibition of withdrawal of control rods adjacent to fuel and movement of fuel to the control rod withdrawal position.

■Avoiding fuel removal that would cause a neutron source range monitor (SRM) lower limit.

According to safety regulations, the reactor shutdown margin is to ensure that even if one control rod is not inserted, the reactor becomes subcritical by inserting other control rods. The reactor core characteristic value (neutron multiplication coefficient) is required to be 0.99 or less when all control rods with high power are withdrawn from the fully inserted state.

Regarding control rods, boiling water reactors use cross-shaped control rods, which are inserted and withdrawn between four fuel bodies.

Only the lower part of the control rod is connected to the drive mechanism, and the control rod is supported by surrounding fuel to prevent it from falling over. Therefore, fuel can be extracted from up to two bodies diagonally, and fuel extraction from two adjacent bodies around the control rod is prohibited.

In order to further extract fuel, a dummy bundle with a shape that replaces the fuel, or a DBG (Double Bladder) with a shape of two dummy bundles connected diagonally.
e-Guide) is required.

Some core-related work requires the removal of control rods as a prerequisite, such as inspecting the control rod drive system or replacing the control rods themselves, but safety regulations prohibit the removal of control rods adjacent to fuel. ing. Originally, it would be desirable to have all the control rods inserted into the reactor core, but since this is not possible due to core-related work, the control rods are pulled out after all the fuel around the control rods is removed using the aforementioned DBG or the like. Fuel is not allowed to be loaded at the position where the control rod has been pulled out, and the pulled out control rod cannot be inserted unless the DBG etc. are set to ensure control rod support.

Even when replacing an in-core neutron detector installed at a different location from the control rods, one of the diagonally located control rods and the entire fuel around it may be removed as a work area for the replacement.

Constraints related to control rods or fuel exchange operations must be taken into account when creating the fuel exchange procedure, and the created fuel exchange procedure is carefully designed using pieces and boards that simulate the fuel arrangement. has been confirmed.

If a large amount of fuel is removed around the SRM used for subcriticality monitoring, the lower limit of detection may be reached. In situations where more fuel is extracted locally around the SRM than in the entire reactor core, the SRM count will be low, and even if the subcriticality of the reactor is small, it will be difficult to judge from the detector information. <
＜, undesirable in terms of criticality control.

Efficiently creating a fuel exchange procedure under such constraints requires a large workload, and since it is important for safety, it also imposes a large mental burden.

Furthermore, factors that make the work environment more difficult include the need to shorten the work process, and time constraints such as the target fuel arrangement not being finalized until just before the start of work. Furthermore, since it is impossible for many people to plan the fuel exchange work in parallel, the workload of the person in charge of planning becomes extremely heavy.

In the conventional method of creating a fuel exchange procedure, in order to secure the necessary work area for core-related work, the work procedure is sequentially set appropriately from the initial fuel arrangement, and the fuel removal is determined by trial and error. The amount of fuel required to secure the necessary area is determined by being added during the process of creating the work procedure. The fuel exchange procedure created in this way is highly dependent on the skill of the individual in charge, contains some wasteful parts of the work, and is not able to fully meet the demands for shortening the work process. Ta.

(Problems to be Solved by the Invention) As described above, in the conventional method of creating a fuel exchange procedure, improvements are made to an appropriately determined fuel exchange procedure as a method for reducing the number of procedures. A trial-and-error approach was taken to ensure constraint conditions, and there was no clear evaluation procedure for minimizing the number of refueling procedures.

Therefore, it has been difficult to support the creation of fuel exchange plans using computers because it is not possible to specify an approach that should be standardized as a method for creating procedures.

The present invention has been made in response to such conventional circumstances,
Provides a method for creating a fuel exchange procedure that allows a computer to create a fuel exchange plan by minimizing the number of fuel removal units and securing a refueling work area using a standardized approach. It's about doing.

[Structure of the Invention] (Means for Solving the Problems) That is, the present invention takes as input an initial fuel arrangement of a reactor core, a target fuel arrangement, and a core-related work, and provides a system that includes the initial fuel arrangement and the target fuel arrangement. select the cycle removal fuel that is not included in the core-related work, and set a first intermediate fuel removal target from the initial fuel arrangement so as to maximize the overlap between the fuel removal patterns determined for each core-related work and the cycle removal fuel. a step of determining a second intermediate fuel removal target from which a portion of the cycle fuel removal within a range that does not lose control rod support is determined from the first intermediate fuel removal target; and from the second intermediate fuel removal target. The reactor periodic schedule is determined by the steps of determining the first half of the fuel exchange procedure in the reverse order of execution with the initial fuel placement as the target, and determining the second half of the fuel exchange procedure in the order of execution starting from the second intermediate fuel removal target. Fuel removal during inspection,
It is characterized by creating loading and rearrangement procedures.

(Function) In the present invention, as shown in FIG. 1, the initial fuel arrangement 1, target fuel arrangement 2, and core-related work 3 of the reactor core are performed manually. Select the cycle extraction fuel 4 that is not included, and maximize the overlap between the fuel extraction patterns 5 and the cycle extraction fuel 4 by selecting the fuel extraction pattern 5 determined for each core-related operation in relation to the core-related work 3. By applying it to the initial fuel arrangement 1 such that the first intermediate fuel withdrawal target 6
Establish. Next, a second intermediate fuel removal target 7 is determined, in which a portion of the cycle fuel 4 is removed from the first intermediate fuel removal target 6 without losing support of the control rods. Then, from this second intermediate fuel extraction target 7 to the initial fuel arrangement 1
With this goal in mind, the first half of the fuel exchange procedure 8 is determined in the reverse order of execution, and the second half of the fuel exchange procedure 8 is determined in the order of execution starting from the second intermediate fuel removal target 7.

In other words, if there is no need to perform core-related work, the number of cycle fuels 4 N out and the total number of fuel bodies loaded in the core N
From R, the minimum value N oain of the fuel exchange step when an ideal fuel exchange is performed is determined.

N m1n-2・N out+ (N R-N out
) Such an ideal procedure would result in an ideal fuel transfer sequence: move the repositioning fuel into the empty space from which the fuel was removed, with a movement target there, and transfer it back to the newly created space. There is a series of paths in which the fuel to be loaded is placed in the space created at the end after the relocation fuel has been moved without waste, and the combination of these paths. This can be realized when all fuel movements can be described in . At this time, all of the fuel movement operations, including fuel removal, rearrangement, and loading, are completed in one go. However, in actual refueling operations, it is impossible to minimize such steps due to core-related work and ensuring margin for reactor shutdown.

As described above, in the refueling plan, in addition to realizing the final goal of the target fuel arrangement 2, it is necessary to realize the core state necessary for performing core-related work during the refueling.

This intermediate target core state is not determined arbitrarily, but changes based on the judgment of the refueling plan creator. Consider the shortest step in the procedure in an actual refueling operation. First, in order to secure a work area for core-related work, of the fuel taken out from the reactor to the fuel pool, fuel that is not included in cycle removal fuel 4, that is, fuel targeted for relocation, is classified as temporary storage fuel. Become.

Regarding this temporary storage of fuel, compared to the previous ideal fuel transfer sequence, there is an increase of at least 1 step per temporary storage fuel. At this time, if no DBG or dummy bundle is used and no control rod operation is required, the minimum number of steps N m1nl for the temporary fuel number N terap is N m1nl - N m1n +
It becomes N temp. However, for core-related work,
Some require control rod withdrawal, and control rod withdrawal and insertion each require one step. Even in core-related work that does not require direct control rod removal, if fuel is removed to secure a work area and support for adjacent control rods is lost, control rods must be temporarily removed. In order to withdraw the control rod, the four fuels around it must be taken out according to safety regulations, so if there is any fuel in the vicinity that is not included in the fuel 4 to be taken out from the cycle, it becomes temporary fuel. Furthermore, a DBG is normally used to ensure support for the control rods during this fuel removal. One step each is required for the initial setting of the DBG and return to the fuel pool, and if the goal is to minimize the number of steps, it is sufficient to sequentially allocate one DBG to the control rod withdrawal points and use it. The number of control rods to be pulled out + 1 is the number of steps required to move the DBG. In fact, fuel transfer and D
Because there is a difference in the handling at the fuel exchange machine when moving BG,
In order to make the work process more efficient, as many DBGs as there are available are often used together. In this case, the number of control rods that need to be pulled out is NCR, and the number of DBGs used is N
If it is DBG, the minimum number of steps Noain2 is
N m1n2- N m1n+N temp+2 *
N CR+ N DND-INT (NCR/NDBG
+2)・N DBG. Regarding the use of dummy bundles, they may be needed in special cases such as moving fuel around control rods to adjacent positions, or they may be used to assist in supporting control rods, but their frequency of use is quite limited compared to DBGs. . Regarding the use of dummy bundles, the number of uses + 1 step is required for each dummy bundle. From the above study, it is clear that in order to minimize the number of steps in the refueling procedure, it is important to reduce the number of temporarily stored fuel bodies and the number of control rods that need to be withdrawn. Therefore, if the fuel arrangement allows for the same core-related work, it is necessary to minimize the number of temporarily stored fuel by choosing the one with fewer withdrawn control rods. It can be seen that if such a core state is selected as an intermediate target, an efficient fuel procedure can be realized by making the procedures before and after it as close as possible to the idealized movement sequence described above. In the actual fuel exchange work process,
In addition to the goal of shortening the fuel procedure, there is also a desire to proceed with core-related work as much as possible if there is time to do so before implementing it. Even in this case, it is necessary to secure a work area for core-related work, so the additional work will be fuel removal. Moreover, since it is not desired to increase the total number of steps in the work procedure, the fuel to be extracted is limited to cycle-derived fuel and fuel that will not cause new control rod support to be lost.

The above concept is reflected in the configuration of the present invention.

In FIG. 1, initial fuel arrangement 1 and target fuel arrangement 2 are as follows:
It defines the fuel identifier and the fuel's initial and final locations. If the fuel is contained in the core of initial fuel arrangement 1 and not contained in the core of target fuel arrangement 2, the fuel is removed and is contained in the core of initial fuel arrangement 1 and transferred to the core of target fuel arrangement 2. If it is included in the target fuel arrangement 2, the fuel is relocated, and if it is not included in the initial fuel arrangement 1 but is included in the target fuel arrangement 2, the fuel is loaded.One step of fuel movement is associated as a basic operation. The cycle removal fuel 4 transfer is at the beginning of the idealized fuel transfer sequence described above.

Once the core-related work 3 is defined, the fuel to be removed in relation to it is determined. A fuel removal pattern 5 is determined for each core-related work, but since the direction is arbitrary, the fuel to be removed is not uniquely determined. Therefore, the following should be considered as a guideline for determining the fuel to be extracted.

■Minimize the loss of support in control rods that are not directly related to core-related work.

■Minimize the number of fuels taken out other than cycle fuel 4.

(2) Select the direction of the fuel removal pattern 5 with respect to the core-related work object so that the cycle removal fuel 4 is included in the fuel removal pattern 5.

■Choose the direction of the fuel removal pattern 5 relative to the core-related work object so that the fuel removal patterns 5 overlap each other as much as possible.

Guidelines (1) and (2) directly express the conditions for minimizing the number of steps described above, but are not very suitable as a guideline for searching for an extraction target.

Therefore, guidelines (2) and (2) are mainly used as a guideline for searching for the extraction target. That is, the direction of the fuel removal pattern 5 with respect to the core-related work object is determined in consideration of maximizing the overlap between the fuel removal pattern 5 and the cycle removal fuel 4 and maximizing the overlap between the fuel removal patterns 5. By determining and applying this to the initial fuel arrangement 1, the first intermediate fuel removal target 6 is determined. In the first intermediate fuel removal target 6, a work area is secured to perform all core-related work, and for each piece of fuel removed, information to explain the reason for removal can be obtained. The first intermediate fuel removal target 6 is a state in which fuel is further removed from the initial fuel arrangement 1 in which the reactor shutdown margin is secured in design, and the reactor shutdown margin is clearly secured.

If it is possible to take out part of the cycle removal fuel 4 from the first intermediate fuel removal target 6 without losing control rod instructions, the newly created fuel arrangement will be the same as the first intermediate fuel removal target 6. A work area for all core-related work has been secured, and there is also sufficient margin for reactor shutdown.

Also, this fuel removal should not be a direct cause of increasing the number of steps. In order to respond to the request to proceed with the core-related work as much as possible if there is time to spare before carrying out the core-related work, the cycle removal fuel 7
The fuel arrangement from which a portion of the fuel is removed is defined as the second intermediate removal target 7. The second intermediate fuel removal target 7 does not need to be a state in which the maximum number of cycle removal fuels 7 that can be removed without losing control rod support is removed. In the actual refueling work process, the work is interrupted at any step between the first intermediate fuel removal target 6 and the second intermediate fuel removal target 7, and core-related work is started. The fuel exchange procedure from the first intermediate fuel removal target to the second intermediate fuel removal target 7 does not require the use of the DBG and is only fuel removal, and there are no particular restrictions on the work order. The procedure is determined in the reverse order of execution from the second fuel removal target 7 to the first intermediate fuel removal target 6, and the fuel is exchanged in the reverse order of execution from the first intermediate fuel removal target 6 to the initial fuel arrangement 1. Determine the first half of step 8. At this time, 1. The final arrangement of the DBG will be determined so as not to interfere with core-related work, and the procedure for allocating the movement of the DBG to the control rod extraction location will also be created in the reverse order of execution. After that, the second half of the fuel exchange procedure 8 is determined in the order of execution, with the second intermediate fuel removal target 7 to the target fuel arrangement 2 as the target, while taking into consideration the reactor shutdown margin.

In this way, a refueling procedure that minimizes the number of fuel extraction units and secures a refueling work area can be realized using a standardized approach.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 2, in the refueling procedure creation method of this embodiment, an initial fuel arrangement 1, a target fuel arrangement 2, and a core-related work 3 are input.

First, the final movement target 103 is determined based on the initial fuel arrangement 1, the target fuel arrangement 2, the identification names 101 of all fuels that can be taken out for core-related work, and the absolute coordinates 102 on the initial core. This final movement target 103 indicates the absolute coordinates of the reactor core or fuel pool in the target fuel arrangement 2, and from this, the fuel belonging to the cycle extraction fuel 4 is determined.

On the other hand, core-related work 3 is defined regarding control rods, in-core neutron detectors, and fuel, and the positional relationship between these core-related work objects 104 and the fuel is determined based on the absolute coordinates 102 in initial fuel arrangement 1. . When the core-related work 3 is defined, the fuel to be removed in relation to this is determined, and the core-related work 3 that caused the removal is recorded as information on the fuel. Note that in the initial state, it is assumed that there is no core-related work 3 for all fuels.

A fuel removal pattern 5, that is, a fuel removal state necessary for the work, is determined for each core-related work 3, but since the direction is arbitrary, the fuel to be removed is not uniquely determined. The fuel removal pattern 5 is shown as a relative positional relationship centering on the core-related work object 104, that is, a set of relative coordinates, and the fuel that must be removed even if the direction is changed in this pattern is defined as a fixed removal pattern 105. , a variable extraction pattern 106 is used for fuel that may not be extracted due to other pattern directions. In core-related work that targets the fuel itself, such as fuel removal for 131 hour exposure reduction and fuel removal for visual inspection, a fixed removal pattern 105 is created for the target fuel alone. In such a case, there is no other pattern to choose from, so the fuel is selected as the first fuel to be extracted. There is no problem even if there is only the fixed take-out pattern 105 and no variable take-out pattern 106 because all the fuel corresponding to the take-out pattern is to be taken out, but if there is a variable take-out pattern 106, there is room for selection in the fuel to be taken out. It's coming. For example, as shown in FIG. 3, the fuel removal pattern during CHD inspection is a fixed removal pattern in which four bodies around the control rod are removed. For control rod replacement and local power monitor (LPRM) replacement, a fixed retrieval pattern is used for the four rods around the core-related work target, while a variable retrieval pattern is used for the other six or three rods.

Therefore, first, the fuel corresponding to the fixed extraction pattern 105 is determined as the fuel extraction target, and then the fuel corresponding to the fixed extraction pattern 105 is determined as the fuel extraction target.
By maximizing the overlap between the combination of directions with the previously determined fuel removal pattern and the overlap between the variable removal patterns, the number of fuel bodies to be removed can be minimized and the removal area necessary for core-related work can be achieved. Determine the target for fuel removal to ensure the following. This evaluation is performed as the sum of the number of overlaps with the already determined fuel take-out pattern and the number of overlaps between the variable take-out patterns, or the sum of the sum of both numbers multiplied by an appropriate weighting coefficient in the direction of the variable take-out pattern 106. ,
Can be treated quantitatively.

If the fuel around the SRM is unnecessarily removed, the lower limit of the SRM count may occur, as described above, and the fuel exchange operation may not be carried out smoothly. Therefore, in addition to the evaluation of maximizing the overlapping fuel in the fuel extraction pattern, if the selected direction of this fuel extraction pattern is selected in a manner that includes fuel around the SRM that has not yet been targeted for extraction, , the above evaluation avoids unnecessary fuel removal around the SRM by reducing the number of overlapping fuel patterns. In this case, the weighting coefficient for the number of fuels around the SRM can be appropriately selected, but except for the fuel Jν output for SRM replacement, Sl? In a case where four fuels around M are extracted, it is preferable to increase the weighting coefficient and avoid selecting such fuel extraction as much as possible.

As an evaluation function to minimize the number of fuel extraction bodies,
Although this is directly indicated by the number of overlapping fuel removals described above, depending on the combination of fuel removal patterns, there is a possibility that control rods may newly lose support.

In addition to evaluating the maximization of overlapping fuel in a fuel removal pattern, if this combination of fuel removal patterns loses support for control rods that have not yet been targeted for extraction, the number of overlapping fuels in the pattern should be reduced. This avoids unnecessary control rod withdrawal and associated fuel removal. In this case, the withdrawal and insertion of control rods and the accompanying use of DBG,
Then, a weighting coefficient corresponding to the number of steps required for temporary storage and return of fuel is multiplied.

An example of an evaluation function for the number of overlaps in fuel extraction taking into consideration the above evaluation is as follows.

Nov, 1 -α °N1flNout +79 ・ΣNi1
lNj-7. NN1nN5Rj − 1 δ ・NR(Ni) nNRout ・(Ntea+p(NR)+4) where, Nov, I: Number of overlaps of fuel extraction in direction i, N
1nNout: Number of overlaps between the extraction pattern Ni in direction i and the extraction fuel, ΣN1nNj: extraction butter j of other work object j
>Nj, N i 11 NSRM' : Number of overlaps between the fuel around the SRM and the direction 1 (7) extraction pattern, NR (N i ) 11 NRout Out of the control rod extraction caused by the extraction pattern in two directions i. , the number of control rods not included in the control rod extraction target N tea+p (N R): the number of temporary fuels accompanying the extraction control rod NR, α, β, γ, δ: weighting coefficients for each evaluation element.

Variable extraction pattern 1 for all core-related work objects
Among the combinations of 06 directions, the combination with the maximum value of the sum of the number of overlapping fuel removal bodies was selected, thereby minimizing the number of temporary fuel storage locations and securing the work area necessary for core-related work. Based on the above, a first intermediate fuel removal target 6 that can reduce the number of work steps as much as possible is determined.

Here, the first intermediate fuel removal target 6 does not include the placement of the DBG, so in order to realize the intermediate target at this stage, the DBG must be used to secure the work area necessary for core-related work. It is necessary to take it out of the furnace once. However, once the core-related work is completed, the DBG will be used to reinsert the control rods.
will be returned to the furnace. In this case, the number of extra work steps increases by the number of DBGs used. In many cases, if it does not interfere with core-related work, DBG
may be left in the furnace. Therefore, if there are two DBGs taken out diagonally across the control rods, place them in an empty area outside the area required for core-related work.

However, such a free area is not necessarily secured on the first intermediate extraction target 6 determined as described above. Therefore, of the fuel of the first intermediate withdrawal target 6,
The fuel contained in the cycle extraction fuel 4 and which can be extracted without losing the support of the control rod is further selected as extraction candidates, and among them, the fuel that can be extracted in the maximum number as possible, that is, the fuel that can be extracted in two pieces diagonally across the control rod is selected. Select them in order to secure a place to place the DBG during core-related work. In the current core configuration, four high-burnup fuel bodies are placed around a specific control rod, and there is a place where all four bodies around the control rod become the cycle fuel 4, so such a location must be secured. It doesn't really matter. If there is still cycle removal fuel 4 that can be removed without losing support for the control rods, then the fuel removal target should be selected as appropriate to meet the request to proceed with the work as much as possible if there is time before starting core-related work. Additionally, a second intermediate fuel withdrawal target 7 is determined.

From the second intermediate fuel removal target 7, the execution order of fuel removal at locations other than the DBG placement position, movement of the DBG, and fuel removal at the DBG placement position is determined in the reverse order so that the first intermediate fuel removal target 6 is achieved. For example, the fuel exchange procedure 8 from the first intermediate fuel removal target 6 to the second intermediate fuel removal target 7 can be performed. Since the DBG movement source is the position where the four fuel bodies around the control rod were taken out and the control rod was pulled out, the DBG movement can be easily determined. Similarly, if fuel removal and DBG movement are determined in the reverse order of execution and the initial fuel arrangement 1 is achieved, the fuel movement procedure from the initial fuel arrangement 1 to the first intermediate fuel removal target 6, i.e. The first half of fuel exchange procedure 8 is completed. By reversing the DBG movement during core-related work, movement selection can be made easily and without waste. In the first half of fuel exchange procedure 8, except for moving the DOG and withdrawing the control rods, any fuel removal other than temporary storage will always occur at the beginning of each fuel transfer bus in the ideal fuel transfer sequence described above. Therefore, if the number of temporarily stored fuels is minimized, the number of steps in the first half of the procedure will be minimized.

Regarding the second half of fuel exchange procedure 8, since there is no need to secure a special work area on the way to target fuel placement 2, it is necessary to follow the idealized fuel transfer sequence as much as possible while observing the reactor shutdown margin limit. Select fuel exchange work procedures according to the order of execution.

These fuel transfer sequences include target fuel placement 2 and
From the comparison with the intermediate fuel removal target 6, a plurality of derived fuel transfer buses may be selected and executed as necessary.

First, at the position where the control rod is pulled out, out of the fuel that should be loaded around it, prioritize the fuel that can be loaded in two diagonal directions in the first movement of one of the fuel transfer buses. Move the DBG, insert the control rod, and load this fuel. As for this fuel, in addition to relocated fuel, temporarily stored fuel can also be considered. Temporarily stored fuel is ideally a part of a fuel transfer bus separated to ensure core-related work, but loading temporary fuel according to Target Fuel Arrangement 2 minimizes the number of steps. become. Second
The first step of the ideal fuel transfer sequence for the fuel transfer bus would be to transfer the fuel in the target fuel placement 2 corresponding to the empty fuel position in the intermediate fuel removal target 6 from somewhere. After determining the DBG movement and fuel loading/movement so that all the fuel extraction points at the control rod extraction position are loaded with two diagonal fuels in this way, the DBG
Take it out of the furnace. After that, while adhering to the reactor shutdown margin limit, sequentially move any fuel at the head of the fuel transfer bus in the ideal fuel transfer sequence, and complete the second half of fuel exchange procedure 8 up to target fuel placement 2. create.

Note that once the insertion of the control rods is completed and the loading of two diagonal fuel bodies at that position is completed, all control rods will be supported by at least two diagonal fuel bodies. Depending on how the fuel transfer bus is selected, there is a possibility that the control rods will lose support again.

In this case, it is necessary to select another path that does not lose support for the control rods, but if an alternative procedure is not possible due to constraints, a DBG or a dummy bundle will be used as an auxiliary method. In this case, the number of steps inevitably increases, but by minimizing the use of DBGs and dummy bundles, the number of steps can be minimized.

As described above, according to this embodiment, by minimizing the number of fuel extraction units, the number of work steps can be minimized.
A refueling procedure that secures a work area for core-related work can be realized using a standardized approach, and a computer can efficiently create a refueling work plan.

FIG. 4 shows a configuration example when the present invention is applied to a computer system. Information on the initial fuel arrangement 1 and the target fuel arrangement 2 is recorded in the fuel database 107. Information related to this and specific to the target atomic couplant is recorded in the work environment database 108. After the person in charge of refueling work planning inputs and instructs core-related work, the fuel removal patterns recorded in the refueling work knowledge base 109 are applied to evaluate combinations of fuel removal patterns.

As a result, a first intermediate fuel removal target 6 is generated, and a second intermediate fuel removal target 7 is generated by evaluating the fuel that can be extracted without losing support of the control rods. The procedure from the second intermediate fuel removal target 7 to the EOC core arrangement and the BOC core arrangement is searched, and the determined refueling work procedure 8 is displayed on the output display device 110.

In addition, since the work procedure allows for sections from the first intermediate fuel removal target to the second intermediate fuel removal target that can be selected depending on the margin of the periodic inspection process, a fuel exchange work plan that can be adapted to the actual situation of the periodic inspection process can be secured. can be created.

In addition, in the above embodiment, when determining the direction of the variable extraction pattern, instead of considering the combination of extraction patterns of all core-related work, the mutual distance is determined based on the positional relationship of each core-related work object. It is also possible to set the evaluation order so that the number of fuel bodies to be extracted is small, and to take into account the overlap of the variable extraction patterns of the two core-related work targets in order to perform a limited minimization of the number of fuel bodies to be extracted. In this case, if the refueling target can be divided into several groups whose variable extraction patterns do not overlap with each other, the combination of extraction patterns may be determined independently for each group. It is also possible to execute a plurality of cases in which the evaluation order of the combinations is changed, and select the one with the minimum number of fuel extraction bodies among these cases. Furthermore, it is easy to select the one with the smallest number of fuel take-off bodies among a plurality of cases in which the weighting coefficient regarding the number of fuel take-off bodies for evaluation is changed. In addition, in the above embodiment, the dummy bundle and DBG were not used in combination to minimize the number of control rods to be withdrawn, but the use of these should be assumed when selecting a combination of withdrawal patterns. is of course possible.

[Effects of the Invention] As explained above, according to the present invention, a fuel exchange procedure that minimizes the number of fuel extraction units and secures a core-related work area during periodic inspections is realized using a standardized Ablower broach. It is possible to create a fuel exchange plan using a computer.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the basic configuration of the present invention, Fig. 2 is a diagram showing the configuration of an embodiment of the present invention, Fig. 3 is a diagram showing an example of a fuel extraction pattern, and Fig. 4 is a diagram showing the basic configuration of the present invention. It is a diagram showing an example of the configuration when used in a system. 1... Initial fuel placement 2... Target fuel placement 3... Core related work 4... Cycle Removal fuel 5...
...Fuel removal pattern 6...1st
Intermediate fuel removal target 7... Second intermediate fuel removal target 8... Fuel exchange procedure Applicant Japan Atomic Energy Corporation Applicant
Toshiba Corporation Representative Patent Attorney Sasa Suyama - Figure 1

Claims (1)

[Claims] (1) Input the initial fuel arrangement of the reactor core, target fuel arrangement, and core-related work, select the cycle extraction fuel that is included in the initial fuel arrangement but not included in the target fuel arrangement, and perform each core-related work for each of the core-related work. determining a first intermediate fuel extraction target from an initial fuel arrangement so as to maximize the overlap between the determined fuel extraction patterns and the cycle extraction fuel; and determining control rod support from the first intermediate fuel extraction target. determining a second intermediate fuel removal target from which a portion of the cycle-taken fuel is removed within a range that will not be lost; and a fuel replacement procedure performed in the reverse order of execution, aiming at the initial fuel arrangement from the second intermediate fuel removal target. and a step of determining the second half of the fuel replacement procedure in the order of execution from the second intermediate fuel removal target to create a procedure for fuel removal, loading, and rearrangement during a periodic inspection of a nuclear reactor. Features: How to create a fuel exchange procedure.