JP2009216581A - Method and installation for evaluating earthquake-proof safety of storage container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a safety evaluation method for evaluating safety in an appropriate condition in the analysis of behaviors of a storage container when external force acts on it in an unfixed state. <P>SOLUTION: In the method for evaluating earthquake-proof safety of the storage container which accommodates radioactive material and is fixed on a pedestal in an unfixed state, a model of the storage container for analysis including the pedestal is made, and the amount of lift is calculated when the external force like an earthquake load acts on the storage container. Then, safety is evaluated on the basis of the calculated amount of lift. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a seismic safety evaluation method for storage containers and a seismic safety evaluation facility for storage containers.

  The fuel that has been used for a certain period in the core of the nuclear power plant facility is taken out of the core and temporarily stored in a spent fuel pool or the like. The fuel for which the predetermined cooling period has ended is finally carried out to a reprocessing plant, where it is reprocessed, and uranium and plutonium are taken out as resources for reuse.

  Currently, spent fuel generated at nuclear power plants is increasing along with power generation demand, so that spent fuel generated in Japan will exceed the processing capacity of the reprocessing plant even if the reprocessing plant is in operation. It needs to be managed and stored properly during the period until it is reprocessed.

  As a method of managing and storing inside or outside the site of a nuclear power plant, there are dry storage methods such as dry cask storage, vault storage, silo storage, concrete cask storage, and water pool wet storage methods. In view of cost and long-term stable storage, dry storage is attracting attention. Among dry storage systems, the cask storage system currently in practical use is a method of storing spent fuel in a dry cask that is a radioactive substance storage container.

  The cask includes a metal cask and a concrete cask, and the metal cask can be used for both conveyance and storage. On the other hand, a concrete cask is a cask used for storage, and during transportation, spent fuel is stored in a container called a canister, and the canister is stored in a transport cask and transported. In the storage facility, the metal cask is stored for a predetermined period as it is without transferring spent fuel.

  On the other hand, the canister is pulled out from the transport cask, loaded into a concrete cask prepared in advance, and stored for a predetermined period.

  Here, in the storage facility, when the cask is unloaded from the trailer by the overhead crane and transported to the storage position, the floor height of the storage building is increased to secure the space for the traveling and lifting of the overhead crane. The storage building is larger than the capacity. Moreover, metal casks and concrete casks are usually very heavy (for example, about 100 to 200 tons), and a large overhead crane is required.

  In order to solve this problem, conventionally, an air pallet type transfer device capable of reducing the floor height of a storage building has been proposed. The air pallet conveying device is configured to include a self-propelled cart having an air pallet that is installed and fixed on a gantry and is mounted on the lower side of the gantry. At the time of transport, the air pallet is attached to the lower side of the gantry and air is supplied from the cart side to the air pallet so that the storage container is floated and transported.

  However, in a storage facility using an air pallet transport device, it may be assumed that the storage container becomes unfixed when the supply of air is interrupted. And the method of evaluating the seismic safety of the storage container in this case is required.

  Patent Document 1 describes a seismic design method for a structure that evaluates an influence of a seismic load applied to a storage container in a non-fixed state as a nonlinear phenomenon. However, this method is an evaluation method based on nonlinear time history analysis, and is not an evaluation focusing on an increase in internal energy given by seismic force.

  Even during the transportation of spent fuel, even if an inclination occurs due to an earthquake or the like, it is required that the basic safety functions such as the containment function, the shielding function, the heat removal function, and the criticality prevention of the storage container are not affected.

  However, it is not practical to evaluate the safety against earthquakes by conducting tests with actual machines, etc., because it takes a lot of time and cost. It is desirable to evaluate

  However, when analyzing the behavior of an unfixed storage container during an earthquake by simulation or the like, it is necessary to construct a storage system to evaluate the safety under appropriate safety conditions.

JP 2002-146718 A

  An object of the present invention is to realize a safety evaluation method for evaluating safety under appropriate conditions in analyzing the behavior of a storage container when an external force is applied to the storage container without being fixed.

  The method for evaluating seismic safety of a storage container according to the present invention is a method for evaluating seismic safety of a storage container that contains a radioactive substance and is fixed to an unfixed gantry, and is a model for analyzing the storage container including the gantry. And the amount of lift when an external force such as an earthquake load is applied to the storage container is calculated, and the seismic safety is evaluated based on the calculated amount of lift.

  According to the present invention, the energy from the external force applied to the storage container when analyzing the behavior of the storage container when the storage container containing the radioactive substance is in an unfixed state and an external force such as an earthquake load is applied. The safety can be evaluated without excessively setting the above condition on the safe side.

  The present invention relates to a seismic safety evaluation method and evaluation equipment for a storage container, and relates to a seismic safety evaluation method for an unfixed storage container. For example, the present invention relates to a technique for evaluating safety by analyzing the behavior when an external force such as an earthquake is applied in a non-fixed state of a gantry in which a storage container containing a radioactive substance is fixed.

  The best mode of the present invention is a storage container in which a storage container containing a radioactive substance is fixed to an unfixed gantry, that is, a safety evaluation method for an unfixed storage container via the gantry. A model for analysis is created, behavior when an external force is applied to a storage container in a non-fixed state is calculated from evaluation of energy application, and safety is evaluated based on the calculated result. By this method, it is possible to evaluate the safety of the storage container in the non-fixed state by matching by analysis without performing a test with an actual machine or the like.

  When the safety evaluation of the storage container in the non-fixed state is performed by this analysis, an analysis model capable of expressing the behavior when an external force acts on the storage container in the non-fixed state is set.

  Each part constituting the non-fixed storage container is modeled by applying simple elements such as concentrated mass W, beam element B, and spring element S. Thereby, the behavior of the storage container can be easily evaluated from the energy from the external force applied to the storage container.

  FIG. 1 is a schematic configuration diagram showing a storage container in a non-fixed state, which is an object of safety evaluation of the present invention.

  Reference numeral 1 denotes a storage container containing spent fuel, and reference numeral 2 denotes a frame on which the storage container 1 is mounted. The storage container 1 is fixed to the gantry 2 via a fixing bracket (described later). The width | variety of the mount frame 2 is made larger than the diameter of the storage container 1, and it is hard to fall down. Here, the non-fixed state refers to a state in which the storage container 1 is fixed to the gantry 2 that is not fixed.

  Reference numeral 3 denotes a floor surface on which the gantry 2 is placed, and 4 denotes the center of gravity of the storage container 1 including the gantry 2. Furthermore, a broken line 201 is a line segment that connects the fulcrum 5 of vibration of the center of gravity 4 and the center of gravity 4. Here, the length of the line segment 201 is a.

  Since it is in an unfixed state, it is necessary to confirm that the behavior of the storage container 1 and the gantry 2 does not affect the basic safety when an external force such as an earthquake load is applied to the storage container 1. Therefore, at the design stage, it is necessary to evaluate the movement of the non-fixed storage container 1 when an external force is applied to the storage container 1 and to design a sufficient safety.

  FIG. 2A shows the behavior of the storage container 1 when an alternating load such as an earthquake load is applied to the storage container 1. When an external force such as an alternating load is applied to the storage container 1, the other side rises with one side of the gantry 2 as a fulcrum. At this time, the energy applied to the gantry 2 is an increase in the internal energy of the storage container 1. Therefore, this internal energy is converted into kinetic energy or potential energy, and the storage container 1 and the gantry 2 start rocking vibration.

  Since the storage container 1 and the gantry 2 are fixed and integrated by a fixing metal fitting, the whole can be handled as a rigid body. Hereinafter, unless specifically described, the storage container 1 is interpreted as including the entire storage container 1 and the gantry 2, that is, the gantry 2. Good.

  Further, when contacting the floor surface 3, that is, when colliding, a part of the kinetic energy of the vibrating storage container 1 and the gantry 2 is dissipated. This is the same phenomenon as that when a hard sphere collides with the yield surface, the speed after the collision does not coincide with the speed before the collision. Since the floor surface 3 on which the storage container 1 is placed is not a complete non-yield surface, the coefficient of restitution is not 1, and energy dissipation is observed when the gantry 2 is in contact with the floor surface. .

  In this figure, (a), (b), (c) and (d) show the states of the rocking vibrations of the storage container 1 and the gantry 2 at different times.

  FIG. 2B shows temporal changes in potential energy, kinetic energy, and internal energy at this time. Here, the times corresponding to the states (a), (b), (c) and (d) in FIG. 2A are shown in (a), (b), (c) and (d) in FIG. 2B. .

In (a) and (c), the potential energy is minimized and the kinetic energy is maximized. At this time, since the gantry 2 is in contact with (collises with) the floor surface 3, internal energy dissipation due to the collision occurs. Here, the times corresponding to (a) and (c) are denoted by T _i−1 and T _i . In (b) and (d), the potential energy is maximized and the kinetic energy is minimized.

  It is known that the energy imparted to the storage container 1 and the gantry 2 due to an earthquake or the like gradually increases while repeating vibrations, but dissipates kinetic energy each time it comes into contact with the floor surface 3.

2B, the internal energy by dissipation of energy at time _{T i-1} is the internal energy _{p i-1,} and the time _{T i} reaches p _'i. That is, the internal energy increases by p ′ _i −p _i−1 between time T _i−1 and time T _i . At time T _i , the internal energy becomes p _i due to energy dissipation. That is, the internal energy at the moment of collision is reduced by p _'i -p _i.

  FIG. 3 shows a flowchart of an embodiment relating to the seismic safety evaluation method for a storage container in an unfixed state according to the present invention. The safety evaluation method according to the present embodiment includes a process (S101) of taking design information including the structure of a storage facility, a cask (storage container) and a gantry, specifications (shape, weight, etc.) of the cask (storage container) and the gantry, A step of setting an input condition for analyzing a condition of seismic motion, that is, a vibration characteristic of a storage container (S102), a step of evaluating a vibration characteristic including calculation of a spectral range and vibration energy (S103), and a storage container are provided. A step of evaluating energy (S104), and a step of calculating safety (an amount of lift) from the applied energy and evaluating safety (S105).

  In the step of determining the safety evaluation amount (S105), it is determined whether the storage container has fallen from the floating amount.

  FIG. 4 is a side view showing a floating state of the unfixed storage container in the present invention.

  In this figure, the storage container 1 and the gantry 2 are inclined by an angle θ with the fulcrum 5 as an axis, and the end of the gantry 2 opposite to the fulcrum 5 is raised by a height h.

Moreover, FIG. 5 is a side view which shows the fall limit of the storage container of the non-fixed state in this invention. In this figure, when the center of gravity 4 of the storage container 1 and the gantry 2 falls outside the vertical line 6 passing through the fulcrum 5 at one end of the gantry 2, it falls down. Therefore, the fall limit condition of the lift amount h at the other end of the gantry 2 in the state of FIG. 4 is set as H ^* , and if the calculated lift amount h is less than H ^* , the safety is evaluated as not falling. . At this time, the angle θ in FIG. 4 is expressed as θ ^* .

  FIG. 6 is a schematic configuration diagram showing an embodiment relating to the seismic safety evaluation facility for an unfixed storage container according to the present invention.

  Reference numeral 8 denotes a computer system, which basically inputs information on the shape and position of the center of gravity of the storage container (storage container information) and information on the shape and position of the center of gravity (base information) and inputs seismic wave information. The input port 81, the CPU 82, the RAM 83, and the ROM 84 are included. The ROM 84 includes a recording medium that stores a program for controlling the CPU 82. This recording medium is called a storage unit. Further, according to this program, the CPU 82 inputs information on the shape and position of the center of gravity of the storage container, information on the shape of the base and position of the center of gravity, and further inputs seismic wave information, and exchanges data with the RAM 83. While performing arithmetic processing. The earthquake resistance, which is the result of the calculation process, is output to the output processing unit 9, and a determination relating to earthquake resistance is performed.

  FIG. 7 shows an example of a program flow for predicting a fall in the evaluation flow shown in FIG.

  FIG. 7 shows a flowchart of an embodiment relating to the seismic safety evaluation method for an unfixed storage container according to the present invention. The safety evaluation method of the present embodiment includes a step (S103) for evaluating vibration characteristics, a step (S104) for evaluating energy to which the storage container is applied, and a safety evaluation amount from the applied energy. And calculating a certain “lift amount” to evaluate safety (S105).

  First, design information such as the structure of the storage facility, the storage container 1 and the gantry 2 is taken in (S101). Next, an input condition 102 for analyzing the vibration characteristics of the storage container is set (S102). Input conditions include design earthquake motion, storage container specifications (dimensions, weight, etc.), gantry specifications (dimensions, weight, etc.).

  Next, vibration analysis is performed (S103). This vibration analysis (S103) is performed in two steps, that is, a step of setting a spectral range for evaluating the vibration characteristics of the storage container to be evaluated (S103a), and a time history analysis based on this model. A step of calculating vibration energy (S103b) is included.

  Further, the step of evaluating the energy to be applied to the storage container from the vibration energy (S104) has five steps, that is, the step of calculating the time change of the vibration energy (S104a), and the maximum value of the applied energy per unit time. A step of calculating (S104b), a step of setting an accumulated time width for determining the energy to be applied (S104c), a step of calculating the accumulated energy (S104d), and a step of calculating the maximum accumulated energy (S104e). Here, in the steps from (S104c) to (S104e), the maximum value of the stored energy may be determined by performing iterative calculation.

Further, the step of calculating the safety evaluation amount (S105) includes a step of calculating the lift amount from the stored energy (S105a), and a step of performing a fall evaluation from the lift amount (S105b). Whether the storage container has fallen or not is determined from the floating amount.
<Evaluation of vibration characteristics: S103>
Evaluate the vibration characteristics when an external force is applied to an unfixed storage container. Here, the vibration characteristic (vibration constant) evaluated in (S103a) of FIG. 7 is a reference document (Akiyama et al., Prediction of falling of rigid body using energy spectrum, Architectural Institute of Japan, 488, 49-55. ), It can be generally expressed as equation (1) from the equation of motion of the mass vibration system.

Further, in the above-mentioned reference, the spectrum width considered in the vibration characteristics of the rigid body is T _{0 to} T ₁ , and T ₀ and T ₁ are expressed when the floor ground plane shape of the rocking vibration structure is rectangular. It is described that it can be obtained by (2) and formula (3).

Therefore, in the evaluation of the vibration characteristics, the vibration energy calculated by the expression (1) is also used, and the vibration energy is evaluated from the expressions (2) and (3).
<Evaluation of energy applied: S104>
The time change _EV (t) of the energy velocity that the storage container in the non-fixed state calculated in the vibration characteristic evaluation (S103) is given from the seismic energy can be expressed by Equation (4).

  By differentiating the equation (4), the energy applied per unit time, that is, the energy velocity can be calculated as in the equation (5).

  In order to predict the falling of the storage container from the energy expressed by the energy speed applied to the storage container, it is appropriate to evaluate the applied energy speed accumulated within the time until the storage container falls. For this reason, the energy rate of time accumulation given to the storage container can be calculated as shown in Equation (6) by integrating the energy rate given per unit time with the time width T from an arbitrary time t. . Here, t may take the beginning of the earthquake (time 0), but from the viewpoint of shortening the calculation time, an appropriate time should be determined in advance from the time when the earthquake begins to increase until the peak of the earthquake is reached. May be.

  In order to determine whether or not toppling is possible, the maximum value of the energy speed in consideration of the time width T is obtained and evaluated by Expression (7). In this case, the maximum value of the energy velocity is calculated using t and T as parameters.

<Falling evaluation: S105>
FIG. 4 shows the relationship between the center of gravity position 4 of the storage container 1 and the floating amount h. As shown in this figure, the floating amount h due to the rocking vibration is based on the assumption that the maximum value Δ ( _E V _max ) of the internal energy given from the seismic force is converted into the potential energy increment. The quantity h ₀ is determined by the following equation (8). In addition, g is a gravitational acceleration.

Then, the lift amount h of the gantry end when the lift amount h _{0 at} the center of gravity position 4 occurs is calculated and compared with the lift amount H ^* which is the fall condition shown in FIG. Can be evaluated.

  FIG. 8 is a graph schematically showing temporal changes in internal energy calculated according to the flow of FIG.

  In FIG. 8, the horizontal axis is a time having a scale that is substantially equivalent to the elapsed time of the earthquake, and the vertical axis is an equivalent velocity that equivalently indicates the energy at the time of the earthquake. In the figure, the temporal change in the total energy storage amount is the internal energy storage amount when it is assumed that there is no dissipation of internal energy, and is calculated using equation (4) according to the concept of the reference. This is an increasing function. This is the time history analysis performed in (S103) of FIG. Here, since the calculated amount of accumulated internal energy does not take into account energy dissipation due to a collision or the like, the maximum value of the amount of accumulated energy imparted by seismic waves or the like can be obtained. If safety evaluation of whether or not to fall is performed based on this, it results in excessively demanding a safe specification of the storage container, and the storage equipment including the storage container becomes extremely expensive.

  Actually, energy dissipation occurs, so that the energy storage amount is lower than the above maximum value. That is, if safety evaluation is performed in consideration of energy dissipation, the cost for the safe specification of the storage container should be able to be greatly reduced.

  Therefore, in (S104), the analysis is performed in consideration of the energy dissipation condition including the coefficient of restitution between the gantry and the floor surface.

  The temporal change in the energy time accumulation amount is calculated using the equations (5) and (6), and is a concept newly introduced in the present invention. This is performed in (S104). That is, the time change of the energy time accumulation amount in FIG. 8 is a result of reassessing the total energy accumulation amount obtained by accumulating and evaluating the energy applied from the earthquake over the entire time of the earthquake while dividing the time width.

  Since the analysis performed in this (S104) takes into account energy dissipation such as a collision, the influence of the initial internal energy on the internal energy accumulation amount in the latter period is negligible. For this reason, the above-mentioned time t can be set to any time after the seismic wave starts to increase. This has the effect of shortening the analysis time.

Then, the time width T is changed within an appropriate range, the expressions (6) and (7) are calculated, and the maximum value Δ ( _E V _max ) of internal energy, which is an important value in safety evaluation, is calculated. . The time width T may be set using a time interval determined by the period of the rocking vibration of the storage container when the energy applied from the external force to the storage container is calculated.

  FIG. 9 shows an embodiment of a mass system vibration model executed in the step (S103) of evaluating the vibration characteristics in the evaluation flow of FIG.

  In this vibration model, the storage container 1 fixed to the gantry 2 by the fixing bracket 10 is composed of a spring element Sb that models the mass point determined by the gravity center 41 of the storage container 1 and the centroid 42 of the gantry 2 and the vibration phenomenon of the gantry 2. And the beam Bb connecting the spring elements.

  In the case of the present embodiment, this is a model for individually inputting the specifications of the storage container 1 and the gantry 2 in the step of inputting conditions (S102).

  FIG. 10 shows another embodiment relating to a mass system vibration model.

  The vibration model in this figure is a vibration model of a storage container in which the mass point 43 of the lid 301 of the storage container 1 is provided on the upper part of the storage container.

  In the case of the present embodiment, this is a model for individually inputting the specifications of the storage container 1, the gantry 2 and the lid 301 in the step of inputting conditions (S102).

  The models shown in FIGS. 9 and 10 automate the calculation of the entire center of gravity 4 used for the analysis shown in FIG.

It is a schematic block diagram which shows the storage container of the non-fixed state which is the object of safety evaluation by this invention. It is a schematic diagram which shows the movement at the time of the earthquake of the storage container of the non-fixed state which is the object of the safety evaluation by this invention. It is a graph which shows the change of the energy state at the time of the earthquake of the storage container of FIG. 2A. It is a flowchart which shows one Example regarding the safety evaluation method of the storage container of the non-fixed state by this invention. It is a side view which shows the floating state of the storage container of the non-fixed state in this invention. It is a side view which shows the fall limit of the storage container of the non-fixed state in this invention. It is a schematic block diagram which shows one Example regarding the seismic safety evaluation equipment of the storage container of the non-fixed state by this invention. It is a program flow which shows the safety evaluation method of the storage container of the non-fixed state by this invention. It is a graph which shows the calculation result of the energy time accumulation amount by this invention. It is a schematic diagram which shows one Example of the mass system vibration model in the safety evaluation of the storage container of the non-fixed state by this invention. It is a schematic diagram which shows the other Example of the mass system vibration model in the safety evaluation of the storage container of the non-fixed state by this invention.

Explanation of symbols

  1: storage container, 2: mount, 3: floor surface, 4: center of gravity, 5: fulcrum, 6: vertical line, 8: computer system, 9: output processing unit.

Claims (6)

  A method for evaluating the seismic safety of a storage container containing a radioactive substance and fixed to an unfixed gantry, wherein a model for analysis of the storage container including the gantry is created, and an earthquake load is applied to the storage container A method for evaluating seismic safety of a storage container, characterized by calculating a floating amount when an external force is applied and evaluating the seismic safety based on the calculated floating amount.   A method for evaluating the seismic safety of a storage container containing a radioactive substance and fixed to an unfixed gantry, wherein a model for analysis of the storage container including the gantry is created, and an earthquake load is applied to the storage container Calculating a floating amount when an external force is applied, evaluating earthquake-proof safety based on the calculated floating amount, and calculating the floating amount based on rocking vibration generated in the storage container, Seismic safety evaluation method for storage containers.   A method for evaluating the seismic safety of a storage container containing a radioactive substance and fixed to an unfixed gantry, wherein a model for analysis of the storage container including the gantry is created, and an external force such as an earthquake load is applied to the storage container Calculating the amount of lift when activated, evaluating the seismic safety based on the calculated amount of lift, and calculating the amount of lift from the energy applied to the storage container by the external force Seismic safety evaluation method for storage containers.   A method for evaluating the seismic safety of a storage container containing a radioactive substance and fixed to an unfixed gantry, wherein a model for analysis of the storage container including the gantry is created, and an earthquake load is applied to the storage container The amount of lift when an external force is applied is calculated, the seismic safety is evaluated based on the calculated amount of lift, and the energy applied to the storage container by the external force is calculated for the calculation of the amount of lift. A method for evaluating seismic safety of a storage container, characterized in that the calculated energy is calculated within a range of divided time widths.   A method for evaluating the seismic safety of a storage container containing a radioactive substance and fixed to an unfixed gantry, wherein a model for analysis of the storage container including the gantry is created, and an external force such as an earthquake load is applied to the storage container Is calculated from the energy applied to the storage container by the external force, the safety is evaluated based on the calculated floating amount, and the time width used for calculating the energy is calculated as follows: A method for evaluating seismic safety of a storage container, wherein the method is set using a time interval determined by a period of rocking vibration generated in the storage container.   A facility for evaluating the seismic safety of storage containers that contain radioactive materials and are fixed to an unfixed gantry, and is used to create an analysis model for seismic safety evaluation of the storage containers connected to the gantry An input port for inputting container information, gantry information, and seismic wave information, a storage unit storing a program used to calculate energy given to the storage container by seismic waves, and calculating the energy by executing the program A storage container seismic safety evaluation facility, comprising: a calculation section that performs a determination section that performs an earthquake resistance safety evaluation of the storage container based on the calculated energy.

Images