JP5703250B2 - Fissile material storage tank and fissile material storage method - Google Patents

Description

  The present invention relates to a fissile material storage tank and a fissile material storage method for preventing the criticality of a solution storage portion of a fissile material.

  Regarding the handling and management of materials containing nuclear fuel materials, from the viewpoint of critical safety that prevents them from becoming critical without being controlled, it is not possible to design and handle equipment that prevents the conditions that lead to critical conditions from being met. The criticality is guaranteed.

  As an index indicating how close a subcritical system containing nuclear fuel material is to criticality, subcriticality or effective multiplication factor can be cited. Here, the subcriticality indicates that the critical state is reached when the subcriticality is zero, and that the subcriticality is reached when the subcriticality increases. That is, the greater the subcriticality, the farther from the criticality, the safer. These indices may be measured by installing one or more radiation detectors near the system.

  Typical subcriticality measurement methods include exponential experiment method, negative period method, control rod drop method, compensation method, neutron source multiplication method, pulsed neutron source method, inverse dynamics method and reactor noise analysis method. Proposed.

  The negative period method and the control rod drop method require that the system be made critical once in its application, and the application is limited to sub-criticality measurement in a nuclear reactor. It cannot be applied to measurements at facilities. In addition, the inverse dynamic characteristic method and the compensation method require an operation for changing the subcriticality during the measurement.

  Although the pulsed neutron source method can be expected to have high accuracy, it is necessary to shoot external neutrons into the measurement system using a neutron generator, which causes problems of equipment complexity and cost increase.

  On the other hand, for example, the furnace noise measurement method disclosed in Patent Document 4 is subcritical by recording and analyzing the incident signal of the detector for a relatively long time without requiring complicated measurement equipment. It is a technique that can measure the degree.

  In addition, in the exponential experiment method disclosed in Patent Documents 1 to 3, a detector and a neutron source are installed near the system, neutrons are supplied from the neutron source, and the neutron space in the system varies depending on the subcriticality. It is a technique that can measure the subcriticality from the difference in distribution.

  Examples of equipment design and handling that prevent the establishment of conditions that reach critical conditions include handling at a sufficiently thin concentration that cannot become critical, elimination of moderator, management of mass, management of shape, and the like.

  Of these, in shape management, the system shape that can be taken by one system containing nuclear fuel material is a thin flat plate or thin rod that does not have the risk of criticality. And arrangement conditions are also taken into consideration.

When the modified group theory is used, the effective multiplication factor k _eff of one system is expressed by the following equation (1).

k _eff = k _∞ / (1 + M ² B ² ) (1)
Here, k _∞ is an infinite multiplication factor of a medium of one system, B ² is a buckling determined by the shape dimension of one system, and M ² is a moving area of neutrons in the medium.

Using this equation (1), assuming that the estimated critical lower limit multiplication factor for a similar system is k _L ,
B ² > (k _∞ / k _L −1) / M ² (2)
If B ² is set such that holds, criticality management based on the system shape is possible.

The estimated critical lower limit multiplication factor is set from the benchmark data of a similar system, but is generally 0.95 to 0.98. (See Non-Patent Document 1)
B ² is, for example, in the case of shape management of an infinite flat plate having a thickness T,
B ² = (π / (T + 2d)) ²
Similarly, in the case of an infinite cylinder of radius R,
B ² = (2.405 / (R + d)) ²
These can be used for evaluation.

  Shape management is based on the fact that a single container does not become critical when filled with nuclear fuel material. Even when a single container is not critical, it may become critical due to the neutron mutual interference effect between the containers when a plurality of containers of the same size and shape exist in close proximity.

  In order to prevent this, it is necessary to suppress the neutron correlation between the containers. That is, it is necessary to take measures such as increasing the distance between the containers and installing a neutron absorber or a shield between the containers.

In general, if the effective multiplication factor of a single container is k _i , the effective multiplication factor k _p of a plurality of containers is
_{k p <Max (k i /} (1-ω i)) ··· (3)
Is established. Here, ω _i is a solid angle fraction between containers.

Japanese Patent Publication No. 2-51158 Japanese Patent Publication No. 3-17115 Japanese Patent Publication No. 4-58915 JP 2010-210613 A

Criticality Safety Handbook 2nd edition, JAERI1340, Japan Atomic Energy Research Institute, 1999

  In a solution system in which nuclear fuel material is melted or contained, such as purification and cooling of convective water containing nuclear fuel material, uranium solution in a reprocessing facility, and electrolytic extraction from uranium solution, criticality management such as shape management and mass management is performed. Has been done.

  However, there may be a case where a filter, an electrolytic electrode, or the like installed in the pipe is provided as a structure that aggregates all or part of the unspecified nuclear fuel material. Regardless of the intention or intention, the nuclear fuel material aggregates around the equipment having the function of aggregating the nuclear fuel material.

  For example, in a structure in which nuclear fuel material is sucked up from a storage tank by a pump, a strainer, a filter, or the like is usually installed in a suction pipe at the pump inlet in order to prevent foreign matter from entering the pump.

  In such a system, the nuclear fuel material once aggregates around the filter. For example, if the aggregated nuclear fuel material peels and falls due to its own weight when the pump is stopped, it deposits at the bottom of the flow path near the filter. Depending on the amount of nuclear fuel material deposited, the possibility of a criticality accident cannot be denied.

  In addition to the filter, there is a possibility that the non-dissolved fissile material aggregates in the electrode for electrolysis and the stagnation part of the flow path. In addition to general criticality control, special attention is required in the vicinity of the location where the non-dissolved fissile material may agglomerate (hereinafter referred to as “potential aggregation location”). It is.

  Therefore, the present invention provides a criticality for the potential aggregation of fissile material without significantly changing the configuration and processing capacity of the system in which non-dissolved fissile material can potentially aggregate in a solution system containing nuclear fuel material. The purpose is to ensure safety.

In order to achieve the above-mentioned object, the present invention provides a fissile material storage tank for preventing criticality due to agglomerates of a solution of a fissile material, a solution storage container for storing the solution of the fissile material, and the solution An agglomerated part disposed in the solution of the storage container and where the fissile material aggregates; and a flat space or a cylindrical space disposed at the bottom of the solution storage container and extending in the vertical direction. And agglomerate receiving portions that receive the agglomerates that have fallen off from the space by being spatially dispersed so as to be maintained subcritically.

  Further, the present invention provides an aggregate that has fallen off from the agglomerated portion disposed in the solution of the solution containing container that contains the solution of the fissile material in order to prevent criticality of the fissile material containing portion. A fissile material containing method in a fissile material containing tank having an agglomerate receiving portion, a neutron measurement step for measuring neutrons emitted from the agglomerate receiving portion, and a measurement result measured in the neutron measurement step An analysis step for estimating the subcriticality based on the above, and an aggregate discharge step for discharging the aggregate from the aggregate receiver when the subcriticality estimated by the analysis step reaches a specified value. It is characterized by.

  According to the present invention, a solution system containing nuclear fuel material can be used for the potential agglomeration of fissionable material without significantly changing the configuration and processing capacity of the system in which undissolved fissile material can potentially aggregate. Critical safety can be ensured.

It is an elevation sectional view showing a 1st embodiment of a fissile material storage tank concerning the present invention. It is an II-II arrow directional view showing a 1st embodiment of a fissile material storage tank concerning the present invention. It is an elevation sectional view showing a 2nd embodiment of a fissile material storage tank concerning the present invention. It is an elevation sectional view showing a 3rd embodiment of a fissile material storage tank concerning the present invention. It is a side view which shows 3rd Embodiment of the fissile material storage tank which concerns on this invention. It is an elevation sectional view showing a 4th embodiment of a fissile material storage tank concerning the present invention. It is an elevation sectional view showing a 5th embodiment of a fissile material storage tank concerning the present invention. It is a flowchart which shows the fissile material accommodation method by 5th Embodiment of the fissile material accommodation tank which concerns on this invention. It is an elevation sectional view showing a 6th embodiment of a fissile material storage tank concerning the present invention. It is a flowchart which shows the fissile material accommodation method by 6th Embodiment of the fissile material accommodation tank which concerns on this invention. It is an elevation sectional view showing a 7th embodiment of a fissile material storage tank concerning the present invention. It is an elevation sectional view showing an 8th embodiment of a fissile material storage tank concerning the present invention.

  Hereinafter, embodiments of a device having a criticality prevention function according to the present invention will be described with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

[First Embodiment]
FIG. 1 is a vertical sectional view showing a first embodiment of a fissile material storage tank according to the present invention. Moreover, FIG. 2 is a II-II arrow directional view which shows this embodiment.

  A solution containing container 1 (hereinafter “container 1”) contains a solution containing a fissile material. In addition, although the case of the container 1 is shown in the figure, the following content is the same also in piping which accommodates the solution containing a fissile material, for example.

  In order to pump the solution from the container 1, a pipe 2 and a pump 3 are provided. In addition, although illustration is abbreviate | omitted, the supply piping to the container 1 is provided.

  A filter 4 is attached to the suction port in the container 1 of the pipe 2 for protection of the pump 3 and the like. Since the filter 4 is attached for the purpose of separating precipitates, impurities, sol-like or gel-like aggregates, etc., the filter 4 is an agglomeration part that aggregates aggregates of substances including fissile substances.

  The aggregate receiving part 10 is connected to the bottom of the container 1 below the filter 4, and the upper part of the aggregate receiving part 10 is opened in the container 1. The aggregate receiving part 10 extends vertically and horizontally, has a small shape, and can maintain a subcritical state even if aggregates containing a high concentration of fissile material are accommodated in the entire interior thereof. ing.

  Hereinafter, the operation of the present embodiment configured as described above will be described.

  When the operation of the system including the container 1 is continued, the aggregate is gradually accumulated around the filter 4, and the amount of the aggregate present around the filter 4 increases. If the amount of the aggregate increases, it is conceivable that the aggregate separates from the filter 4 and falls due to a fluid force due to the weight of the aggregate or fluctuation of the flow. After the fall, the amount of aggregates accumulated around the filter 4 gradually increases again, and the fall is repeated again.

  The dropped agglomerates fall into the agglomerate receiving part 10 via the bottom of the container 1 each time.

  In the aggregate receiving part 10, the dropped aggregate is spatially dispersed. For this reason, even if an agglomerate containing a high concentration of fissile material is accepted, it remains subcritical.

  As described above, according to the present embodiment, in the solution system containing the nuclear fuel substance, the structure and the processing capacity of the system in which the non-dissolved or precipitated fissionable substance may potentially aggregate are not significantly changed. , Critical safety against potential aggregation of fissile material can be ensured.

[Second Embodiment]
FIG. 3 is an elevational sectional view showing a second embodiment of the fissile material storage tank according to the present invention.

  An electrolytic cell 5 containing a solution containing a fissile material is provided. An anode 5 a and a cathode 5 b connected to an electrolytic power supply 5 c provided outside the electrolytic cell 5 are immersed in the electrolytic cell 5. An agglomerate receiving part 10 is connected to the bottom of the electrolytic cell 5 below the cathode 5 b, and the upper part of the agglomerate receiving part 10 is opened in the electrolytic cell 5.

  The structure of the agglomerate receiving part 10 is the same as that of the first embodiment (FIGS. 1 and 2), expands vertically and horizontally, has a small thickness, and contains agglomerates containing a high concentration of fissile material. Even if it is accommodated in the entire interior, it has a shape that can maintain a subcritical state.

  If the solution containing the fissile material contained in the electrolytic cell 5 is electrolyzed, the material containing the fissile material is deposited on the cathode b. If the electrolysis is continued, the amount of deposits deposited on the cathode 5b gradually increases and may fall due to its own weight.

  The fallen precipitate is accommodated in the agglomerate receiving part 10 via the bottom of the electrolytic cell 5, and the agglomerate receiving part 10 spatially disperses the fallen agglomerate. For this reason, even if an agglomerate containing a high concentration of fissile material is accepted, it remains subcritical.

  In addition, when depositing on the anode 5a, the same effect is given by providing the aggregate receiving part 10 under the anode 5a.

  As described above, according to the present embodiment, in the solution system containing the nuclear fuel substance, the structure and the processing capacity of the system in which the non-dissolved or precipitated fissionable substance may potentially aggregate are not significantly changed. , Critical safety against potential aggregation of fissile material can be ensured.

[Third Embodiment]
FIG. 4 is an elevational sectional view showing a third embodiment of the fissile material storage tank according to the present invention. FIG. 5 is a side view showing the present embodiment.

  This embodiment is a modification of the first embodiment and has a transfer system 20. The transfer system 20 includes a discharge valve 21a, a transfer receiving portion 22, a transfer valve 21b, and a transfer pipe 23.

  The discharge valve 21 a is provided in a nozzle connected to the bottom of the aggregate receiver 10. The receiving part 22 for transfer is a container that temporarily receives the aggregate discharged from the discharge valve 21a. The transfer valve 21 b is opened when the aggregate temporarily received in the transfer receiving portion 22 is transferred to the transfer pipe 23 on the downstream side.

  The receiving capacity of the fissile material in the receiving part 22 for transfer is limited to a capacity that is less than the critical mass.

  Now, when discharging the aggregate from the aggregate receiver 10, the discharge valve 21a is opened, a predetermined amount is stored in the transfer receiver 22, and then the discharge valve 21a is closed. Then, the transfer valve 21b is opened, and only one batch of aggregate stored in the transfer receiver 22 is transferred downstream.

  By doing in this way, even if this one-time aggregate is accommodated in the container of what shape downstream, it will not reach a critical state. That is, the mass management is performed.

  As described above, according to the present embodiment, in the solution system containing the nuclear fuel substance, the structure and the processing capacity of the system in which the non-dissolved or precipitated fissionable substance may potentially aggregate are not significantly changed. , Critical safety against potential aggregation of fissile material can be ensured.

[Fourth Embodiment]
FIG. 6 is an elevational sectional view showing a fourth embodiment of the fissile material storage tank according to the present invention.

  This embodiment is a modification of the third embodiment, and includes a dilution system 30 for reducing the concentration of the aggregated fissile material accommodated in the aggregate receiver 10.

  The dilution system 30 includes a diluent storage tank 31, a diluent supply pipe 32, and a diluent valve 33. The diluent storage tank 31 stores the diluent. The diluent supply pipe 32 connects the diluent storage tank 31 and the transfer receiver 22, and transfers the diluent from the diluent reservoir 31 to the transfer receiver 22. The dilution liquid valve 33 is provided for transferring and stopping the dilution liquid.

  When it is desired to reduce the concentration of the fissile material in the aggregate in the aggregate receiver 10 and transfer the aggregate, it can be performed by opening the dilution liquid valve 33, and the subcriticality can be secured.

  Although this embodiment has been described as a modification of the third embodiment, a dilution system may be further provided in the first embodiment as a modification of the first embodiment in which a transfer system is not provided. In this case, the diluent storage tank 31 and the aggregate receiver 10 are connected.

  As described above, according to the present embodiment, in the solution system containing the nuclear fuel substance, the structure and the processing capacity of the system in which the non-dissolved or precipitated fissionable substance may potentially aggregate are not significantly changed. , Critical safety against potential aggregation of fissile material can be ensured.

[Fifth Embodiment]
FIG. 7 is an elevational sectional view showing a fifth embodiment of the fissile material container according to the present invention.

  This embodiment is a modification of the third embodiment, and further includes a subcriticality confirmation device 40 and a control device 50.

  The subcriticality confirmation device 40 includes a neutron measurement device 41, an analysis device 42, and a display device 43. The neutron measurement device 41 is a device that measures neutrons from the aggregate receiver 10, and includes a neutron detector 41a, an amplifier 41b, and a counting device 41c. The neutron detector 41 a is provided outside the aggregate receiver 10. The installation location of the neutron detector 41 a is not limited to the outside of the aggregate receiver 10, and may be provided inside the aggregate receiver 10.

  The analysis device 42 performs an analysis for estimating the subcriticality of the aggregate receiver 10 based on the result measured by the neutron measurement device 41. This result is displayed on the display device 43. The display device 43 can issue an alarm if necessary.

  The control device 50 receives the subcriticality output of the aggregate receiver 10 estimated from the analysis result in the analysis device 42 as an input, and outputs an open / close signal for the discharge valve 21a and the transfer valve 21b. The control calculation in the control device 50 outputs a fully open signal of the discharge valve 21a when the subcriticality falls below a specified value. The opening degree of the opening command signal may be determined according to the subcriticality. An opening signal is output to the transfer valve 21b after a predetermined time when the opening signal and closing signal of the discharge valve 21a are output.

  FIG. 8 is a flowchart showing the fissile material accommodation method according to the present embodiment. The processing flow of the fissile material accommodation method will be described with reference to FIG.

  Now, the operation related to the fissile material storage tank is being performed (S01).

  First, the neutron from the aggregate receiving part 10 is measured by the neutron measuring device 41 (S02).

  Next, the subcriticality is estimated by the analysis device 42 that analyzes the measurement result measured by the neutron measurement device 41 and estimates the subcriticality (S03).

  It is determined whether or not the subcriticality estimated in step S03 is less than a specified value (S04).

  When it is determined that the subcriticality is less than the specified value, the discharge valve 21a is opened, and the aggregate is discharged from the aggregate receiver 10 to the transfer receiver 22 (S05).

  When it is determined that the subcriticality exceeds the specified value, the process returns to step S02, and step S02 and subsequent steps are repeated.

  After step S05, the neutron from the aggregate receiving part 10 is measured by the neutron measuring device 41 (S06).

  Next, the subcriticality is estimated by the analysis device 42 that analyzes the measurement result measured by the neutron measurement device 41 and estimates the subcriticality (S07).

  It is determined whether or not the subcriticality estimated in step S07 is less than a specified value (S08).

  After step S08, when the subcriticality estimated by the analysis device 42 exceeds the specified value, the discharge to the transfer receiving portion 22 is terminated (S09).

  If it is determined that the subcriticality does not exceed the specified value, the process returns to step S05 and repeats step S05 and subsequent steps.

  In the present embodiment configured as described above, the subcritical state of the agglomerate receiving unit 10 is confirmed, and the accuracy of maintaining a safe state is increased because it is automatically transferred in a state with a margin with respect to the criticality. To do.

  As described above, according to the present embodiment, in the solution system containing the nuclear fuel substance, the structure and the processing capacity of the system in which the non-dissolved or precipitated fissionable substance may potentially aggregate are not significantly changed. , Critical safety against potential aggregation of fissile material can be ensured.

[Sixth Embodiment]
FIG. 9 is an elevational sectional view showing a sixth embodiment of the fissile material storage tank according to the present invention.

  This embodiment is a modification of the fifth embodiment, and a control signal is also output from the control device 50 to the diluent valve 33. In this way, dilution with the diluent from the dilution system 30 is also automatically performed according to the estimation result of the subcriticality.

  In the present embodiment configured as described above, the subcritical state of the transfer receiving portion 22 is confirmed, and a safe state is maintained because the dilution and transfer are automatically performed in a state having a margin with respect to the criticality. Accuracy increases.

  In the present embodiment, the case where the transfer system and the dilution system are provided has been described, but the present invention can also be applied to the case where there is no transfer system and only the dilution system is installed.

  FIG. 10 is a flowchart showing the fissile material accommodation method according to the present embodiment. This method is a modification of the method in the fifth embodiment. That is, a step relating to a dilution system is added to the method in the fifth embodiment. The processing flow of the fissile material accommodation method will be described with reference to FIG.

  After step S04, when the subcriticality estimated by the analyzer 42 becomes less than the specified value, the diluent valve 33 is opened, and the diluent is transferred from the diluent storage tank 31 to the transfer receiver 22 (S15). ).

  After step S15, the neutron measurement in step S06, the subcriticality estimation in step S07, and the determination in step S08 are performed.

  When the estimated subcriticality exceeds the specified value as a result of the determination in step S08, the transfer valve 33 is closed and the transfer of the diluent to the transfer receiver 22 is ended (S19).

  Although this method has been described for the case where there is only a dilution system, even in the case where there is a transfer system in addition to the dilution system, both steps are performed in parallel or in series to receive aggregates. The concentration of the fissile material contained in the aggregate contained in the portion 10 can be reduced.

  As described above, according to the present embodiment, in the solution system containing the nuclear fuel substance, the structure and the processing capacity of the system in which the non-dissolved or precipitated fissionable substance may potentially aggregate are not significantly changed. , Critical safety against potential aggregation of fissile material can be ensured.

[Seventh Embodiment]
FIG. 11 is an elevational sectional view showing a seventh embodiment of the fissile material storage tank according to the present invention.

  When a plurality of aggregate receiving parts 10 are provided, the neutron absorber 61 is provided between the aggregate receiving parts 10. The neutron absorber 61 captures and absorbs neutrons that leak from the aggregate receiver 10 and move to the adjacent aggregate receiver 10 to prevent mutual influence between the aggregate receivers 10. Can do.

  The present embodiment configured as described above can maintain the subcritical state more reliably by preventing the influence of the agglomerate receiver 10.

  As described above, according to the present embodiment, in the solution system containing the nuclear fuel substance, the structure and the processing capacity of the system in which the non-dissolved or precipitated fissionable substance may potentially aggregate are not significantly changed. , Critical safety against potential aggregation of fissile material can be ensured.

[Eighth Embodiment]
FIG. 12 is an elevational sectional view showing an eighth embodiment of the fissile material container according to the present invention.

  When a plurality of aggregate receiving portions 10 are provided, a neutron shield 62 is provided between the aggregate receiving portions 10.

  The neutron shielding body 62 shields the neutrons that leak from the aggregate receiving part 10 and move to the adjacent aggregate receiving part 10 so as not to move to the adjacent aggregate receiving part 10, thereby preventing the aggregate receiving part 10. Mutual influences between each other can be prevented.

  The present embodiment configured as described above can maintain the subcritical state more reliably by preventing the influence of the agglomerate receiver 10.

  As described above, according to the present embodiment, in the solution system containing the nuclear fuel substance, the structure and the processing capacity of the system in which the non-dissolved or precipitated fissionable substance may potentially aggregate are not significantly changed. , Critical safety against potential aggregation of fissile material can be ensured.

[Other Embodiments]
As mentioned above, although several embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. For example, the shape of the aggregate receiving part 10 may be a cylindrical shape extending in the vertical direction in addition to a flat plate.

  Moreover, you may combine the characteristic of each embodiment. For example, a subcriticality confirmation device may be installed for the receiving portion for transfer. Further, the method of discharging from the aggregate receiver 10 by the control device 50 in the fifth embodiment and the method of supplying the diluent to the aggregate receiver 10 by the controller 50 in the sixth embodiment are combined. May be.

  Furthermore, these embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. For example, in the fifth embodiment and the sixth embodiment, each valve is opened and closed by a command from the control device 50, but the operator performs the opening and closing operation of each valve by looking at the output of the display device 43. May be.

  These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

1 ... Container (solution storage container)
2 ... Piping 3 ... Pump 4 ... Filter (aggregation part)
5 ... electrolytic cell 5a ... anode 5b ... cathode (aggregation part)
5c: Electrolytic power supply 10: Aggregate receiving part 20 ... Transfer system 21a ... Discharge valve 21b ... Transfer valve 22 ... Transfer receiving part 23 ... Transfer piping 30 ... Dilution system 31 ... Diluent storage tank 32 ... Diluent supply pipe 33 ... Diluent valve 40 ... Subcriticality confirmation device 41 ... Neutron measurement device 41a ... Neutron detector 41b ... Amplifier 41c ... Counting device 42 ... Analyzing device 43 ... Display device 50 ... Control device 61 ... Neutron absorber 62 ... Neutron shield

Claims (8)

A fissile material storage tank for preventing criticality caused by agglomerates of a solution of fissile material,
A solution storage container for storing a solution of the fissile material;
An agglomerated part that is disposed in the solution in the solution storage container and aggregates the fissile material;
It has a flat space or cylindrical space that is arranged at the bottom of the solution container and extends at least in the vertical direction, and is maintained subcritically by spatially dispersing aggregates that have fallen off the aggregated parts. An agglomerate receiving part to receive,
A fissile material storage tank characterized by comprising: The fissile material storage tank further includes a transfer system for transferring the aggregate from the aggregate receiver.
The transfer system is
A discharge valve provided at an outlet of the aggregate receiver,
A receiving part for transferring once to receive the aggregate discharged from the aggregate receiving part;
A transfer valve provided at an outlet of the transfer receiver;
Have
The capacity of receiving the fissile material in the transfer receptacle is less than the critical mass,
The fissile material storage tank according to claim 1, wherein: The fissile material storage tank further comprises a dilution system connected to the aggregate receiving part,
The dilution system is
A diluent storage tank for storing the diluent,
A diluent supply pipe connecting the diluent storage tank and the receiving portion for transfer;
A diluent valve provided in the diluent supply pipe;
To have a,
The fissile material storage tank according to claim 1 or 2, wherein 4. The plurality of aggregate receiving portions, and further comprising at least one of a neutron absorber and a neutron shielding body provided between the plurality of aggregate receiving portions. The fissile material storage tank according to any one of the above. The fissile material storage tank further includes a subcriticality confirmation device,
The subcriticality confirmation device is:
A neutron measurement device for measuring neutrons emitted from the aggregate receiver,
An analysis device that estimates subcriticality by analyzing the measurement results measured by the neutron measurement device;
Having
The fissile material storage tank according to any one of claims 1 to 4, wherein   In order to prevent criticality of the fissile material container, an agglomerate receiving part for receiving the agglomerate that has fallen off the agglomerated part disposed in the solution of the solution container for containing the fissionable material solution. A fissile material containing method in a fissile material containing tank,
  A neutron measurement step for measuring neutrons emitted from the aggregate receiver,
  An analysis step for estimating the subcriticality based on the measurement result measured in the neutron measurement step;
  Agglomerate discharging step of discharging the agglomerates from the agglomerate receiving part when the subcriticality estimated by the analyzing step becomes a specified value;
  A fissile material containing method characterized by comprising: After the aggregate discharge step,
A temporary storage step for temporarily receiving the agglomerate in the receiving portion for transfer;
A transfer step for transferring from the transfer receiver to the downstream side;
A transfer end step for ending the transfer after the transfer step;
The method for containing fissile material according to claim 6, comprising : A diluent transfer step of transferring the diluent from the diluent storage tank to the aggregate receiver when the subcriticality estimated by the analysis step is less than a specified value;
A dilution liquid transfer ending step for ending the transfer of the dilution liquid from the dilution liquid storage tank to the aggregate receiving part when the subcriticality estimated by the analysis step exceeds a specified value;
The fissile material containing method according to claim 6 or 7, characterized by comprising:

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