JPH06194490A - Inspection of degree of burn-up of spent fuel assembly - Google Patents

Abstract

PURPOSE:To prevent misconception of the degree of burn-up of a fuel assembly without requiring any burnup meter. CONSTITUTION:When a fuel assembly is loaded to a spent fuel transportation vessel from a spent fuel storage facility, fuel assembly numbers being fetched from a designated address at the time of handling the fuel assembly according to a correspondence table between the loading schedule fuel assembly number and the address of fuel assembly in a storage facility and read out and inputted by an operator are compared through a relationship between the loading schedule fuel assembly number and the storage address thus preventing erroneous operation of the fuel assembly. With regard to the degree of burn-up of fuel assembly, the degree of burn-up of fuel assembly being managed by an operator or an administrative based on a reactor core management data is compared and collated with that being determined by a nuclear designer for the reactor core of each cycle. It is further compared with a predetermined degree of burn-up required by such facility as spent fuel transportation vessel employing a critical safety design and when decision criteria are not satisfied, an alarm is delivered otherwise the loading is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for verifying burnup of a spent fuel assembly, which is used for preventing misidentification of burnup of burned spent fuel by generating thermal energy by nuclear fission.

[0002]

2. Description of the Related Art Conservative evaluation of criticality safety design for facilities and equipment that handle spent fuel is aimed at new fuel that has not burned at all, without taking into consideration the decrease in reactivity due to burning of spent fuel. This is possible.

However, in this case, the above-mentioned facility / equipment specifications have a critical safety design for the spent fuel having a low reactivity, which is an object of actual handling. Will require the use of. For this reason, criticality safety design that takes into account the decrease in reactivity due to combustion of spent fuel is a rational method, but in this case, measurement and confirmation of burnup are important factors.
In other words, when considering the decrease in reactivity due to combustion of spent fuel in the criticality safety design of spent fuel transportation containers, etc., when the spent fuel is loaded into the transportation containers, the spent fuel to be loaded is It is necessary to confirm that the minimum burnup set in the criticality safety design of containers is achieved.

The following methods are known as typical methods for measuring burnup. In a nuclear power plant, there is a method in which the output of each fuel assembly is periodically measured by nuclear instrumentation in a reactor during operation of the reactor to obtain the burnup of each fuel assembly. This method is called the core management method. Accumulation of fission products and transuranic elements in the fuel assembly depends on burnup, but it is possible to determine burnup by gamma ray measurement or neutron measurement of the fuel assembly. The method of obtaining the burnup based on these is called a burnup meter method.

In this case, in the core management method, the burnup of the fuel assembly is confirmed by the core management data based on the fuel assembly number to be loaded into the spent fuel transportation container, and the transportation container, etc. It is determined whether or not the item can be loaded.

By the way, human factors are greatly involved in the confirmation of the core management data, and there is a concern that human error may be involved, such as misrecognition of burnup. For this reason, when loading containers such as transportation containers, it was necessary to use the burnup meter method in combination with the core management method, and double check to prevent misidentification.

[0007]

However, in nuclear power plants, burnup data by core management is always tracked, but burnup meters are not generally installed.
For this reason, when a double check is performed to prevent misidentification of burnup for a spent fuel transportation container, etc. that incorporates a criticality safety design that takes into account the decrease in reactivity due to combustion, the core management data already implemented In addition to the confirmation by the operator, there was a problem that it was necessary to install a new burnup meter.

According to the present invention, in the burnup data tracking by the core management as described above, the burnup of the spent fuel assembly which can prevent the misunderstanding of the burnup of the fuel assembly can be realized even if the burnup meter is not installed. It is intended to provide a verification method of.

[0009]

A method for verifying burnup of a spent fuel assembly according to the present invention is prepared in advance when a fuel assembly is loaded from a spent fuel storage facility to a spent fuel transportation container or the like. Loading plan Fuel assembly number and correspondence table of addresses in the storage facility of the assembly and fuel that is taken out from the designated address when handling the fuel assembly and read and input by the operator who has not been notified of the loading plan fuel assembly number The fuel assembly number is compared with the fuel assembly number through the relationship between the fuel assembly number and the storage address to determine the fuel assembly number, and the fuel assembly is prevented from erroneous operation. Fuel assembly burnup managed by the operators and managers of nuclear power plants based on core management data at the power plant and the fuel required by the nuclear designer for the core of each cycle. Comparison with aggregate burnup, collates, and equipment such as spent fuel transportation containers employing the criticality safety design considering reactivity reduction by combustion of the fuel assembly,
By comparing with a predetermined burnup required by the facility, if the criterion is not satisfied, an alarm is issued, and if it is satisfied, the loading is executed.

[0010]

The method for verifying the burnup of a spent fuel assembly according to the present invention is as follows, without newly installing a burnup meter.
Combustion of fuel assemblies is prevented by preventing unplanned misloading of spent fuel assemblies and comparing and verifying the burnup by core management and the burnup required by the nuclear designer via the fuel assembly number. In addition to enabling verification of fuel consumption, it is possible to load only spent fuel assemblies that satisfy the minimum burnup required for criticality safety design of transportation containers etc. into spent fuel transportation containers etc.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below. In order to prevent the misinterpretation of the burnup, it is effective to verify the two independent burnup evaluation results, the core management method and the burnup meter method. However, it is also possible to prevent the misinterpretation of burnup by combining burnup evaluation results by core management and sub-methods that can confirm that no human error is involved in this evaluation and data handling process. .

In the present invention, the method by core management is used as the main burnup measuring means, and the sub-means is the combustion of each fuel assembly in the nuclear design information carried out for each cycle of each core. It uses degrees. This information is typically provided in replacement core safety and design documents created for each cycle core. In the safety and design documents of the replacement core (referred to here as the core characteristics manual), the burnup of each fuel assembly at the end of the life of the cycle is described as a design value based on the operation plan. , As the value of the burnup of each fuel assembly at the end of the life of the previous cycle, based on the operating results,
be written.

The burnup described in the safety of the replacement core is a sufficiently confirmed value, and the burnup described in the description of the core characteristics is the method of core management required by the operator / manager of the nuclear power plant. The nuclear design characteristic value of the cycle designed based on the burnup of each fuel assembly evaluated in this way is the fuel assembly in the reactor physics test conducted at the beginning of the cycle. A value that has been verified to be valid by comparing the actual measurement value of unit power distribution measurement, etc. with the design value, and as a result, the burnup of each fuel assembly that is the basis of the nuclear design has also been verified to be valid. Is.

From the above, the burnup or core characteristics described in the safety of the replacement core are replaced by the fuel assembly burnup processed and managed by the operator of the nuclear powerplant based on the core management data at the nuclear powerplant. By comparing and collating with the burnup described in the instruction manual, it will be possible to find out if there is a processing error in the burnup of the fuel assembly.

In the present invention, both the burnup described in the safety of the replacement core and the burnup described in the core characteristics description may be used, or either one may be used. In Section 1, the burnup described in the core characteristics description is taken up as a representative and described.

In a spent fuel transportation container or the like which adopts a criticality safety design that takes into consideration the decrease in reactivity due to combustion of spent fuel, the minimum burnup that enables loading of fuel assemblies is set, This minimum burnup is compared with the burnup data of the core management data and the core characteristics manual. If the minimum burnup is satisfied, loading is permitted, and if it is not satisfied, loading is not permitted. Loading is secured.

From the above, the burnup described in the core characteristics manual is used as the sub-means, and the comparison with the main means and the comparison / judgment with the minimum burnup for loading into the transportation container etc. are performed through the device of the present invention. By implementing the above, human error is prevented, and only the fuel assembly satisfying the minimum burnup set as the criticality safety design condition is loaded into the transportation container or the like.

The method of loading the fuel assembly into the spent fuel transportation container will be described below. At a nuclear power plant, based on the core management data for all fuel assemblies loaded into the reactor, the fuel assembly average burnup, initial enrichment, removal timing from the reactor, etc. are set for the fuel assembly number. It is recorded.

Further, regarding the fuel assemblies stored in the spent fuel assembly storage facility of the nuclear power plant, the stored fuel assembly numbers and the like are arranged corresponding to the addresses of the storage facilities. There is.

On the basis of the above data, a loading plan for a spent fuel transportation container, etc., which is based on the design reduction of reactivity due to combustion as a criticality safety design, is prepared. In case of 20000MWd / t, select fuel assemblies with burnup of more than this value from the above data, and load data such as fuel assembly number, storage facility internal address, fuel assembly average burnup etc. as a loading plan. Organize all planned fuel assemblies and enter them in memory.

In the operation of loading a spent fuel transportation container or the like, the operator is provided with only the information on the internal address of the storage facility to be taken out, and the fuel assembly number of the stored fuel assembly number corresponding to the internal address of the storage facility is given. The information is hidden from the operator. The operator has an address specified along with the extraction order (for example, a)
The fuel assembly is taken out from the tank, the fuel assembly number is read by an underwater television or the like (for example, B-24 is read), and the fuel assembly number B-24 and the fuel assembly number B-24 are input through the terminal device installed on the operation console.

In the present apparatus, first, for the input address i, in the loading plan table previously input in the memory,
It is determined whether or not address a is present in the storage facility address information. If it does not exist, an alert will be issued immediately,
Since the operator may have taken out the fuel assembly from the unscheduled address in the storage facility, restore the fuel assembly to its original state and investigate the cause.

If it is confirmed by this device that the address a is also present in the loading plan, then the fuel assembly number B-24 entered by the operator is previously loaded in the memory. It is judged whether or not it exists in the fuel assembly number information of the plan table. If it does not exist, an alarm is immediately issued, at which time the fuel assembly is returned to its original state and the cause is investigated.

On the other hand, regarding the extracted fuel assemblies described in the core characteristics manual, data such as fuel assembly number, initial enrichment, average burnup of fuel assembly, etc. are separately provided from the first cycle core to the latest core. , Input to the memory of this device. Let this memory be M.

In the present apparatus, if it is confirmed that the fuel assembly number B-24 entered by the operator also exists in the loading plan table, then the fuel assembly number B-24 is next.
This device determines whether or not exists in the memory M,
If it does not exist, an alarm is immediately issued and the cause is investigated.

Fuel assembly number B-24, if present
Fuel assembly average burnup in the loading plan corresponding to
34560MWd / t) and the burnup average burnup in the memory M (for example, 34575MWd / t) (absolute value) (15MWd / t)
It is determined whether or not t) is within the criterion T (for example, 100 MWd / t).

This criterion T is set in consideration of the difference that can normally occur between the core management data and the data described in the core characteristics manual. If the judgment criteria are exceeded, an alarm will be immediately issued by this device, but there is a possibility that there is an error in the burnup data, and the cause will be investigated. If it is confirmed that the judgment criteria are satisfied (| 34560MWd / t-34575MWd / t | <100MWd / t), then these burnups are required from the criticality safety design of the spent fuel transportation container etc. Minimum burnup (20
000MWd / t is set) is input to this device and it is judged whether this value is satisfied. If it is not satisfied, an alarm will be sent immediately by this device, but there may be an error in the loading plan, and the cause should be investigated.

When all of the above judgments are satisfied, a permission signal is transmitted by this device and the spent fuel transportation container or the like is loaded. As described above, this device can verify the burnup of the fuel assembly and prevent inappropriate loading of the fuel assembly.

That is, the procedure for verifying the burnup of the spent fuel assembly is as shown in the flowchart of FIG. Explaining this, first, based on the core management data in the nuclear power plant, the fuel assembly average burnup (BU (A)) and the like are recorded for all the combustion assembly numbers (ID).
(Step ST1). On the other hand, with respect to the fuel assembly stored in the storage facility in the nuclear power plant, the ID and the like are recorded for the address (XY) of the storage facility (step ST2). Next, using these data, a list of fuel assemblies (XY,
ID, BU (A)) is created and input (step ST3).

Then, a procedure for taking out the fuel assembly from the storage facility is prepared in accordance with the procedure for loading the spent fuel transportation container or the like (step ST4). In this table, only XY is shown according to the take-out order, and ID is not shown. Therefore,
The operator takes out the fuel assembly from the XY shown in the above procedure table, reads the ID on the underwater television, etc.
Input (O) and ID (O) (step ST
5).

Next, XY given in step ST3
Then, it is determined whether or not there is a match in XY (O) given in step ST5 (step ST6). If there is no match, an alarm is issued from this device. There is an error in the table. There may be an error in the fuel assembly ejection operation, and the cause is investigated.

In step ST6, XY and XY
If (O) matches, then it is determined whether the ID corresponding to XY of the memory shown in step ST3 and the ID (O) read by the operator shown in step ST5 match (step ST8). . If they do not match, the cause is investigated in step ST7 as described above.

On the other hand, the IDs for all the extracted fuel assemblies described in the core characteristics manual and the BU data (ID
(B) and BU (B)) are separately input (step S
T9), it is determined whether or not there is matching data of ID and ID (B) (step ST10). If there is no matching data, an alarm is issued, but in this case, it is indicated at step ST9. There is a possibility that there is an error in the data described in the description of the core characteristics, and the cause is investigated (step ST11).

Next, an allowable maximum burnup difference T is set for the burnup difference of the core management data for the same fuel assembly and the burnup difference described in the core characteristics manual (step ST1).
2) Compare the difference between BU (A) and BU (B) corresponding to the ID with T given in step ST12 (step S
T13), if the determination condition is not satisfied, an alarm is issued, but in this case, there is a possibility that there is an error in any data regarding the burnup of the fuel assembly, and the cause is investigated (step ST14). .

Subsequently, the minimum burnup BU (C) required by the criticality safety design of the spent fuel transportation container etc. is set (step ST15), and BU (A) and BU (B) are BU.
(C) It is determined whether or not it is above (step ST16), and if the determination condition is not satisfied, an alarm is issued and loading of the spent fuel transportation container or the like becomes impossible, but in this case, there is an error in the loading plan. There is a possibility, and the cause is investigated (step ST17).

On the other hand, when the determination condition is satisfied in step ST16, the permission signal is transmitted and the spent fuel transportation container can be operated without any problem.

[0037]

As described above, according to the present invention, when the fuel assembly is transferred or loaded from the spent fuel storage facility of the nuclear power plant to the spent fuel transportation container or the like, the fuel assembly is prevented from being misidentified. Correspondence table of loading plan fuel assembly numbers and addresses in the storage facility of the assembly prepared in advance and taken out from the designated address when handling the fuel assembly, and read by an operator who is not informed of the loading plan fuel assembly number The input fuel assembly number is compared and judged based on the relationship between the loading plan fuel assembly number and the storage address to prevent misoperation of the fuel assembly and to determine the burnup of the fuel assembly. Is required by the nuclear designer for the fuel assembly burnup managed by the operator / manager and the core of each cycle based on the core management data at the nuclear power plant. Predetermined burnup required by equipment and facilities such as spent fuel transportation containers that compare and collate with the burnup of the fuel assembly and adopt a criticality safety design that considers the decrease in reactivity due to combustion of the fuel assembly And compare
If the judgment criteria are not satisfied, an alarm is issued, and if they are satisfied, the loading is executed.Therefore, a spent fuel transportation container that adopts a criticality safety design that considers the decrease in reactivity due to combustion of the fuel assembly It is possible to safely and swiftly move and load the fuel assembly to the equipment / facility such as, and it is possible to obtain an effect that it is not necessary to newly install a burnup meter for the same purpose.

[Brief description of drawings]

FIG. 1 is a flowchart showing an execution procedure of a method for verifying burnup of a spent fuel assembly according to an embodiment of the present invention.

Claims (1)

[Claims] 1. A loading plan fuel assembly number prepared in advance as a measure for preventing misidentification of a fuel assembly when transferring or loading a fuel assembly from a spent fuel storage facility of a nuclear power plant to a spent fuel transportation container or the like. And the correspondence table of the addresses in the storage facility of the assembly and the fuel assembly number extracted from the specified address when handling the fuel assembly and read and input by the operator who has not been notified of the fuel assembly number. The fuel assembly number is compared and judged through the relationship between the planned fuel assembly number and the storage address to prevent erroneous operation of the fuel assembly, and the burnup of the fuel assembly is determined based on the core management data. The fuel assembly burnup managed by the operator of the power plant is compared with the fuel assembly burnup required by the nuclear designer for the core of each cycle. In addition, if the judgment criteria are not satisfied by comparing with the prescribed burnup required by facilities and facilities such as spent fuel transportation containers, which adopts a criticality safety design that takes into account the reactivity decrease due to combustion of the fuel assembly. Is a method for verifying burnup of spent fuel assemblies that issues an alarm and executes loading when satisfied.