JP2020148769A - Detection method and detection device of loss of seal in canister, canister, and concrete storage container - Google Patents

Abstract

To properly detect in-leak of inert gas in a concrete cask/concrete silo canister, without the release of radioactive material.SOLUTION: In the detection method of loss of a sealed structure of a canister 4 stored vertically in a concrete cask 2, the canister 4 is sealed with spent fuel and an inert gas with a higher thermal conductivity than the outside air, and, the internal pressure is controlled to negative. When at least one of the bottom temperature TB, lid temperature TT, and sidewall temperature TS of the canister 4 changes beyond a predetermined threshold, it is determined that the sealed structure of the canister 4 has been damaged.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method and a detection device for detecting a loss of sealing of a canister, and a canister and a concrete storage container. More specifically, the present invention relates, in particular, to a technique for detecting loss of sealability in a metal canister of a concrete cask / concrete silo used for long-term storage management of spent fuel.

A concrete cask / concrete silo type storage facility as a means for storing highly radioactive substances represented by spent fuel of a nuclear reactor includes a canister for storing the spent fuel and a cask body for storing the canister. Since the decay of fission products in the spent fuel continues even after the fuel is removed from the reactor, the canister generates heat during storage. Therefore, in the concrete cask, for example, as shown in FIG. 27, an air flow path 103 is provided between the canister 101 for accommodating the fission products and the cask body 102, and the cooling air 104 is allowed to flow through the canister 101. I try to remove the heat. Specifically, an air introduction port 105 is provided in the lower part of the cask body 102 and an air outlet 106 is provided in the upper part, and the cooled air 104 heated by cooling the canister 101 rises in the air flow path 103. The air is discharged from the air outlet 106, and new air is taken in as the cooling air 104 from the air introduction port 105 (Patent Document 1).

Inside the canister of the concrete cask, along with the spent fuel, a gas with good thermal conductivity and inertness (specifically, helium gas) is usually positive pressure to improve the heat removal performance by the convection effect. It is filled with.

Japanese Unexamined Patent Publication No. 2003-194729

The canister for storing spent fuel in a concrete cask / concrete silo is made of metal (specifically, for example, stainless steel) and the lid is welded. For this reason, leakage from the canister is not assumed in the design of concrete cask / concrete silo. However, in order to ensure the safety of spent fuel in long-term storage management, stress corrosion cracking (also called "SCC") occurs in the canister during storage due to the salt contained in the outside air, and the sealing performance is lost. Countermeasures against leakage of canisters to prevent this have become an issue.

Therefore, an object of the present invention is to provide a method and a detection device for detecting a loss of seal in a canister of a concrete cask / concrete silo without releasing an internal gas to the environment when the seal is lost.

In order to achieve such an object, in the method of detecting the loss of the sealed structure of the canister vertically stored in the concrete cask, the canister is an inert gas having a higher thermal conductivity than the outside air together with the used fuel. Is sealed and the internal pressure is negative, and the canister's sealing structure is impaired when at least one of the canister bottom temperature, lid temperature and side wall temperature changes beyond a predetermined threshold. I try to judge it.

Further, in the method for detecting the loss of sealing of the canister of the present invention, when the bottom temperature and the lid temperature of the canister rise above a predetermined threshold value and the side wall temperature falls below a predetermined threshold value, the sealing structure of the canister is set. You may decide that it has been damaged.

Further, the method for detecting the loss of sealing of the canister of the present invention is when the temperature difference between any two temperatures of the bottom temperature, the lid temperature and the side wall temperature of the canister exceeds a predetermined threshold value. , It may be determined that the sealing structure of the canister is impaired.

Further, the method for detecting the loss of sealing of the canister of the present invention seals the canister when the temperature difference between the bottom temperature of the canister and the temperature of the outside air taken into the concrete cask changes beyond a predetermined threshold value. It may be determined that the structure has been damaged.

Further, the method for detecting the loss of sealing of the canister of the present invention seals the canister when the temperature difference between the lid temperature of the canister and the internal temperature of the concrete lid of the concrete cask changes beyond a predetermined threshold value. It may be determined that the structure has been damaged.

Further, in the method for detecting the loss of sealing of the canister of the present invention, the heat flux calculated from the bottom temperature of the canister and the temperature of the outside air taken into the concrete cask or the estimated index temperature in the canister changes beyond a predetermined threshold value. At that time, it may be determined that the sealing structure of the canister is damaged.

The device for detecting the loss of the seal of the canister of the present invention is a device for detecting the loss of the seal structure of the canister vertically stored in the concrete cask, in which an inert gas having a higher thermal conductivity than the outside air is used together with the used fuel. A canister that is sealed and has a negative internal pressure, a temperature sensor that measures at least one of the canister bottom temperature, lid temperature, and side wall temperature, and measurement value data from the temperature sensor are input. It has a seal loss determining unit that determines that the sealing structure of the canister is damaged when the input measured temperature value changes beyond a predetermined threshold.

Further, in the canister seal loss detection device of the present invention, all measured values of the canister bottom temperature, lid temperature and side wall temperature are input from the temperature sensor to the seal loss determination unit, and the canister lid temperature and side wall temperature are input. May be determined that the sealing structure of the canister is impaired when the temperature rises above a predetermined threshold and the side wall temperature falls below a predetermined threshold.

Further, in the canister seal loss detection device of the present invention, measured value data of at least two temperatures of the canister bottom temperature, lid temperature and side wall temperature are input from the temperature sensor to the seal loss determination unit. It may be determined that the sealing structure of the canister is impaired when the temperature difference between the two temperatures changes beyond a predetermined threshold.

Further, the canister loss of seal detection device of the present invention further includes a temperature sensor for measuring the temperature of the outside air taken into the concrete cask, and the seal loss determination unit includes the bottom temperature of the canister and the outside air taken into the concrete cask. When the measured value data with the temperature is input and the difference between the bottom temperature of the canister and the temperature of the outside air changes beyond a predetermined threshold, it may be determined that the sealing structure of the canister is damaged. ..

Further, the canister seal loss detection device of the present invention further includes a temperature sensor for measuring the internal temperature of the concrete lid of the concrete cask, and the seal loss determination unit includes the canister lid temperature and the internal temperature of the concrete lid. When the measured value data is input and the difference between the lid temperature of the canister and the internal temperature of the concrete lid changes beyond a predetermined threshold, it may be determined that the sealing structure of the canister has been damaged.

Further, the canister loss of seal detection device of the present invention further includes a temperature sensor for measuring the temperature of the outside air taken into the concrete cask, and the seal loss determination unit includes the bottom temperature of the canister and the outside air taken into the concrete cask. When the measured value data with the temperature is input and the heat flux calculated from the bottom temperature of the canister and the temperature of the outside air taken into the concrete cask or the estimated index temperature in the canister changes beyond a predetermined threshold. It may be determined that the sealing structure of the canister is impaired.

Further, the present invention is a method for detecting the loss of the sealing structure of a canister that is horizontally stored in a concrete silo, in which the canister is sealed with an inert gas having a thermal conductivity higher than that of the outside air together with the used fuel. The internal pressure is regarded as a negative pressure, and the temperature of at least one of the bottom temperature of the canister, the lid temperature, the lower side wall temperature in the horizontal position, and the upper side wall temperature in the horizontal position changes beyond a predetermined threshold. When it does occur, it is determined that the canister's sealing structure has been damaged.

Further, the method for detecting the loss of sealing of the canister of the present invention is when the bottom temperature and the lower side wall temperature of the canister rise above a predetermined threshold value and the lid temperature and the upper side wall temperature fall above a predetermined threshold value. It may be determined that the sealing structure of the canister is impaired.

Further, the method for detecting the loss of sealing of the canister of the present invention changes the temperature difference between any two temperatures of the bottom temperature, the lid temperature, the side wall lower temperature and the side wall upper temperature of the canister beyond a predetermined threshold value. When this occurs, it may be determined that the sealing structure of the canister has been damaged.

Further, the present invention is a device for detecting the loss of the sealing structure of a canister that is horizontally stored in a concrete silo, in which an inert gas having a higher thermal conductivity than the outside air is sealed together with the used fuel and the internal pressure is increased. A temperature sensor and a temperature sensor that measure the temperature of at least one of the canister bottom temperature, the lid temperature, the side wall lower temperature in the horizontal position, and the side wall upper temperature in the horizontal position. When at least one temperature measurement value data from is input and the input measurement temperature value changes beyond a predetermined threshold, the sealing loss determination unit that determines that the sealing structure of the canister is damaged I try to have it.

Further, in the canister loss detection device of the present invention, measured value data of the canister bottom temperature, lid temperature, side wall lower temperature and side wall upper temperature are input from the temperature sensor to the seal loss determination unit, and the bottom of the canister. When the temperature and the lower side wall temperature rise above a predetermined threshold and the lid temperature and the upper side wall temperature fall above a predetermined threshold, it may be determined that the sealing structure of the canister is impaired.

Further, in the canister seal loss detection device of the present invention, the seal loss determination unit is subjected to measurement value data of at least two temperatures of the canister bottom temperature, lid temperature, side wall lower temperature and side wall upper temperature from the temperature sensor. Is input, and when the difference between the two temperatures changes beyond a predetermined threshold, it may be determined that the canister's sealing structure has been impaired.

Further, the canister according to the present invention is characterized by comprising the detection device for the loss of sealing of the canister according to any one of claims 7 to 12 and claims 16 to 18.

Further, the concrete storage facility according to the present invention is characterized by including the canister according to claim 19.

According to the method for detecting the loss of sealing of the canister and the detecting device of the present invention, it is possible to accurately detect that the sealing structure of the canister configured so that the initial internal pressure is a negative pressure is impaired. It is possible to improve the usefulness and reliability of a canister in a standing posture / a horizontal posture as a detection method and a detection means for loss of sealing property.

According to the canister sealing loss detection method and detection device of the present invention, even if the canister sealing structure is damaged, in-leak occurs until the internal pressure of the canister becomes equal to the atmospheric pressure (1 atm) from the negative pressure. By detecting the above, it becomes possible to prevent the release of internal gas containing radioactive substances to the outside environment.

Furthermore, according to the detection method and detection device of the loss of seal of these canisters, even if the seal structure of the canister is damaged, the internal gas containing radioactive substances is not immediately released to the outside environment. Since the phenomenon that the temperature of the spent fuel rises occurs, it is possible to detect the occurrence of in-leakage in the canister while preventing the release of the internal gas containing radioactive substances to the outside environment. Moreover, if the occurrence of in-leakage is detected before the internal pressure becomes equal to the atmospheric pressure, environmental pollution will not be caused, so that it is not necessary to consider the allowable leakage amount.

It is a schematic structural drawing which shows an example of the storage facility to which the first embodiment of the canister seal loss detection method and the canister seal loss detection device which concerns on this invention can apply (the concrete cask is a vertical sectional view, and is a vertical sectional view. The canister is a side view). It is a figure which shows the position of the temperature of each part with respect to the canister in 1st Embodiment. FIG. 2A is a front view of the canister in the vertical position. FIG. 2B is a plan view of the canister in the vertical position. FIG. 2C is a bottom view of the canister in the vertical position. It is a functional block diagram which shows an example of the 1st Embodiment of the detection device of the seal loss of a canister which concerns on this invention. It is a schematic structural drawing which shows an example of the storage equipment to which the 2nd Embodiment of the canister seal loss detection method and the canister seal loss detection apparatus which concerns on this invention can apply (the concrete silo is a vertical sectional view, and is a vertical sectional view. The canister is a side view). It is a figure which shows the position of the temperature of each part with respect to the canister in the 2nd Embodiment. FIG. 5A is a side view of the canister in the horizontal posture. FIG. 5B is a front view of the canister in the horizontal posture. FIG. 5C is a rear view of the canister in the horizontal posture. It is a functional block diagram which shows an example of the 2nd Embodiment of the detection device of the seal loss of a canister which concerns on this invention. It is a vertical cross-sectional view which shows the temperature measurement position together with the schematic structure of the model of the storage facility used in the verification example. It is a figure which shows the temperature measurement position together with the schematic structure of the model of the storage facility used in the verification example. FIG. 8A is a plan view of the canister in the vertical posture. FIG. 8B is a bottom view of the canister in the vertical position. Pressure changes and the canister lid temperature T _T of the case where the initial pressure in the verification example of 0.8 atm, canister bottom temperature T _B, and is a diagram showing the relationship between the change in the canister side wall temperature T _S. Pressure changes and the canister lid temperature T _T of the case where the initial pressure in the verification example of 0.5 atm, canister bottom temperature T _B, and is a diagram showing the relationship between the change in the canister side wall temperature T _S. Pressure changes and the canister lid temperature T _T of the case where the initial pressure in the verification example of 0.1 atm, canister bottom temperature T _B, and is a diagram showing the relationship between the change in the canister side wall temperature T _S. It is a figure which shows the change amount of the temperature of each part by the negative pressure degree of the initial internal pressure of each part of the canister model in the verification example. Pressure changes and the bottom of the case where the initial pressure in the verification example of 0.8 atm - cover the temperature difference [Delta] T _BT (i.e., the temperature difference between the canister bottom temperature T _B and the canister lid temperature T _T) relationship between the amount of change It is a figure which shows. Pressure changes and the bottom of the case where the initial pressure in the verification example of 0.5 atm - cover the temperature difference [Delta] T _BT (i.e., the temperature difference between the canister bottom temperature T _B and the canister lid temperature T _T) relationship between the amount of change It is a figure which shows. Pressure changes and the bottom of the case where the initial pressure in the verification example of 0.1 atm - cover the temperature difference [Delta] T _BT (i.e., the temperature difference between the canister bottom temperature T _B and the canister lid temperature T _T) relationship between the amount of change It is a figure which shows. Pressure changes and the bottom of the case where the initial pressure in the verification example of 0.8 atm - side wall temperature difference [Delta] T _BS (i.e., the temperature difference between the canister bottom temperature T _B and the canister side wall temperature T _S) relationship between the amount of change It is a figure which shows. Pressure changes and the bottom of the case where the initial pressure in the verification example of 0.5 atm - side wall temperature difference [Delta] T _BS (i.e., the temperature difference between the canister bottom temperature T _B and the canister side wall temperature T _S) relationship between the amount of change It is a figure which shows. Pressure changes and the bottom of the case where the initial pressure in the verification example of 0.1 atm - side wall temperature difference [Delta] T _BS (i.e., the temperature difference between the canister bottom temperature T _B and the canister side wall temperature T _S) relationship between the amount of change It is a figure which shows. Negative圧度another bottom of the initial internal pressure in the verification example - the amount of change in the side wall temperature difference [Delta] T _BS, the amount of change in the canister bottom temperature T _B, and is a diagram showing a variation of the canister lid temperature T _T. It is a figure which shows the temperature of the heating element before an in-leak according to the negative pressure degree of the initial internal pressure in the verification example. It is a figure which shows the temperature rise degree of the heating element before and after the in-leak according to the negative pressure degree of the initial internal pressure in the verification example. It is a graph which shows the relationship between the gas type inside a canister and the change of a fuel temperature. It is explanatory drawing which shows the boundary condition of the bottom of a canister. It is a graph which shows the relationship between the heat flux passing through the bottom surface and the internal pressure (initial 0.1 atm He). It is explanatory drawing which shows the internal-external boundary condition at the bottom of a canister. _{(T H} '-T _B') and the internal pressure is a graph showing the relationship between the (initial 0.1 atm He). It is a perspective view which shows by cutting out a part of the conventional concrete cask.

Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings.

<< First Embodiment: Vertical Canister >>
1 to 3 show a method for detecting a canister seal loss and a first embodiment of a canister seal loss detection device according to the present invention.

In the present embodiment, the case of the storage facility 1 in which the canister 4 is stored in the concrete cask 2 in a vertical position, which is also called a concrete cask type, will be described.

The storage facility 1 takes in the internal cooling outside air 5 for cooling the canister 4 housed in the concrete container 3 of the concrete cask 2 from the air supply port 6 and from the exhaust port 7 provided at a position higher than the air supply port 6. It has a structure to discharge.

The concrete cask 2 has a concrete container 3 and a concrete lid 8, and is configured as an unsealed structure having a shielding function.

The canister 4 is made of metal, for example, stainless steel. For example, the spent fuel is stored in a cylindrical container with a bottom, and a double cover of the inner cover plate and the outer cover plate is attached by welding and sealed. It has a structure.

The canister 4 is also charged with a partition 11 having a honeycomb structure, which is also called a basket made of stainless steel, for example, and spent fuel, which is a radioactive substance, is inserted into each section of the partition 11.

The canister 4 has a sealed structure by welding to prevent the enclosed radioactive material from leaking to the outside, and is also enclosed with an inert gas having a thermal conductivity higher than that of the outside air, so that the spent fuel in the canister 4 is used. The structure is such that the decay heat of the is transferred to the canister 4 via the basket 11 and the inert gas.

As the inert gas sealed in the canister 4, an inert gas having a higher thermal conductivity than the outside air (usually air), generally helium (He) is preferably used, but other inert gases. May be used.

The canister 4 is sealed after the initial internal pressure is made negative. The pressure in the canister 4 is not limited to a specific value as long as it is a negative pressure (that is, less than 1 atm), and specifically, for example, any of the range of about 0.1 to 0.8 atm. It is conceivable that it will be set to that value.

Since the initial internal pressure of the canister 4 is negative, if the sealing structure of the canister 4 is damaged, the outside air is sucked into the canister 4 from the outside (in other words, an in leak occurs).

The canister 4 is placed on the support legs 9 and housed in the concrete container 3.

The upper opening of the concrete container 3 is closed by the concrete lid 8.

A distribution space 10 through which the internal cooling outside air 5 flows is provided between the canister 4 and the concrete container 3. In relation to this structure, an air supply port 6 leading to the distribution space 10 is provided at the bottom of the concrete container 3, and an exhaust port 7 communicating with the distribution space 10 is provided at a position near the upper end of the concrete container 3.

With the above structure, the outside air naturally convects as the internal cooling outside air 5 through the air supply ports 6 and the exhaust ports 7 provided above and below the concrete cask 2, and the spent fuel in the canister 4 is transferred to the internal cooling outside air 5. The decay heat of the concrete is removed.

Although the air supply port 6 and the exhaust port 7 are generally provided so as to open on the peripheral surface of the concrete cask 2, the air supply port 6 opens on the bottom surface of the concrete cask 2 / concrete container 3, for example. It may be provided, or the exhaust port 7 may be provided so as to open on, for example, the upper surface (in other words, the top surface) of the concrete cask 2 / concrete lid 8.

Then, the detection method of sealing loss of the canister of the present embodiment, the bottom temperature of the canister 4 that the internal pressure is a negative pressure greater inert gas thermal conductivity than the outside air is sealed T _B, the lid temperature T _T and determining when a change exceeds a predetermined threshold in at least one temperature of the side wall temperature T _S occurs, the Inriku to the interior of the outside air of the canister 4 is impaired sealing structure of the canister 4 is generated I try to do it. In this specification, the predetermined threshold value is not limited to a specific value, and is appropriately set to an appropriate value based on, for example, numerical analysis or experiment on an assumed actual machine or actual fluctuation of outside air temperature. It is a thing.

Here, as the temperature to be monitored, the bottom temperature T _B, the lid temperature T _T, and although either good sidewall temperature T _S, may be used in combination with other temperature used not only alone, preferably it is a combination of the most significant temperature changes bottom temperature T _B or bottom temperature T _B and the other showing the temperature, these not particularly limited, may be used the temperature of all the sites, when Depending on the case, it may be a combination thereof. For example, bottom temperature T _B of the canister 4, the lid temperature T _T, and the temperature difference _{ΔT BS (= T B -T S} ) between any two temperatures of the side wall temperature _{T S, ΔT TS (= T} T -T _S), and Inriku to the interior of _{ΔT BT (= T B -T T} ) sealing structure of the canister 4 when a change exceeds a predetermined threshold has occurred impaired by the outside air of the canister 4 is generated You may decide. Further, it may be determined that the sealing structure of the canister is impaired when the temperature difference between the bottom temperature and the side wall temperature, which causes a large temperature change, is changed, and more preferably, the bottom temperature and the lid temperature of the canister. It may be determined that the sealing structure of the canister is impaired when the temperature rises above a predetermined threshold and the side wall temperature falls below a predetermined threshold.

The method for detecting the loss of seal of the canister can also be carried out by the device for detecting the loss of seal of the canister according to the present invention. The canister seal loss detection device of the present embodiment detects the loss of the seal structure of the canister 4 vertically stored in the concrete cask (concrete storage container) 2 from the outside air together with the used fuel. a canister 4 is large inert gas is sealed besides the internal pressure of the thermal conductivity is a negative pressure, the first temperature sensor 13A for measuring the bottom temperature T _B of the canister 4, the lid temperature T _T of the canister 4 second temperature sensor 13B, and a temperature sensor at least one of the third temperature sensor 13C for measuring the sidewall temperature T _S of the canister 4, any temperature sensor 13A for measuring the, 13B, as measured by 13C When at least one temperature measurement value data is input and the input measurement value changes beyond a predetermined threshold, the sealing structure of the canister 4 is damaged and the outside air leaks into the inside of the canister 4. Has a seal loss determination unit 16a for determining that has occurred.

Here, the combination of sealing loss determination unit 16a, a bottom temperature T _B, using lid temperature T _T, and any temperature of the side wall temperature T _S alone or a temperature difference or other temperature among a plurality of temperature When the temperature exceeds a predetermined threshold value and changes occur, it is determined that the sealing structure of the canister 4 is impaired and an in-leak of outside air into the canister 4 has occurred. That is, most combinations of a large bottom shows the temperature change temperature T _B or bottom temperature T _B and other temperatures are preferred, these not particularly limited, may be used the temperature of all the sites, when Depending on the case, it may be a combination thereof. For example, sealing loss determination unit 16a, a bottom temperature T _B of the canister 4, the temperature difference [Delta] T _BS between any two temperatures of the lid temperature T _T, and the side wall temperature T _S, [Delta] T _TS, predetermined to [Delta] T _BT When a change occurs beyond the threshold value of, it may be determined that the sealing structure of the canister 4 is impaired and an in-leak of outside air into the canister 4 has occurred. Further, sealing loss determination unit 16a also may be determined that the sealed structure of the canister has been compromised when a large change in the temperature difference between the bottom temperature T _B and the side wall temperature T _S to produce temperature change occurs , more preferably when the bottom temperature T _B and the lid temperature T _T rises above the predetermined threshold and the side wall temperature T _S of the canister is reduced beyond a predetermined threshold value, it determines that the sealing structure of the canister is compromised You may.

As the first to third temperature sensors 13A, 13B, 13C, temperature measuring means such as a thermocouple or a thermistor can be used. Although it is desirable that the first to third temperature sensors 13A, 13B, and 13C measure the surface temperature of the canister by directly contacting the surface of the canister 4 in order to further increase the detection sensitivity of the loss of sealing property of the canister 4. In some cases, a non-contact thermometer may be used to measure the temperature of the surface of the canister 4 or the temperature in the immediate vicinity of the surface.

According to the findings of the inventors, the initial internal pressure of the canister 4 is negative and the outside air is an inert gas having a higher thermal conductivity than air, for example, the outside air moves into the canister 4 from a state where the canister 4 is filled with helium gas. If you Inriku, the pressure increase in the interior of the canister 4 (in other words, pressure changes directed from a negative pressure to the atmospheric pressure (1 atm)) with the, while the canister bottom temperature T _B and the canister lid temperature T _T rises The canister side wall temperature T _S decreases.

The mechanism of the temperature change that occurs in the canister 4 is that the outside air, that is, the air, which has a small thermal conductivity due to an in-leak, is mixed in the inert gas atmosphere with a large thermal conductivity, and the heat removal effect is obtained as the thermal conductivity decreases. This is due to the decrease and the temperature of the spent fuel in the canister 4 rising. Accordingly, the temperature T _B of the bottom of the canister 4 in contact with the spent fuel is increased.

Further, since the mixed outside air has a higher density than the inert gas (specifically, air has a higher density than helium), the outside air collects in the lower space inside the canister 4, while the inert gas is in the canister. It will accumulate in the upper space inside 4. Thus, transmitted heat of the spent fuel temperature increases are to cover the canister 4 through a good inert gas thermal conductivity, it is considered to be raised canister lid temperature T _T.

Further, the canister bottom temperature T _B and the canister lid temperature T _T increases with Inriku. On the other hand, the calorific value per se of the spent fuel from not change basically before and after Inriku, canister sidewall temperature T _S is considered to decrease relatively.

Here, according to the inventor's knowledge, when the gas inside the canister and the gas outside the canister are the same, for example, when air is sealed inside the canister, when leakage occurs when the inside of the canister is pressurized, the canister Although the bottom temperature T _B is the canister lid temperature T _T while increasing decreases, the canister when air outside air Inriku occurs is mixed into the canister 4 is a canister bottom temperature T _B decreases in the negative pressure state Meanwhile canister lid temperature T _T in is increased. That is, a phenomenon called canister bottom temperature T _B is and rises canister lid temperature T _T increases, the thermal conductivity Inriku canister is from the negative pressure state of the inert gas atmosphere is generated than inert gas This is a phenomenon peculiar to the case where air as a small outside air is mixed, and is a previously unknown finding.

Incidentally, as the pressure increases toward the atmospheric pressure inside the canister 4 after Inriku, canister bottom temperature T _B and the temperature difference [Delta] T _BS of the canister side wall temperature _{T S (= T B -T S} ) and the canister bottom temperature T _B and the temperature difference _{ΔT BT (= T B -T T} ) of the canister lid temperature T _T increases.

The canister bottom temperature T _B, although the temperature at any position of the bottom of the canister 4 is may be used are measured, the temperature change in the bottom surface 4B of the canister when the outside air Inriku occurs center of the bottom surface 4B Since it is the largest at the position, it is preferable that the temperature at the center position 4Bc of the bottom surface 4B in the horizontal plane direction is measured and used (FIGS. 2A and 2C).

The canister lid temperature T _T, although the temperature at any position of the lid of the canister 4 is may be used is measured, the upper surface of the lid of the canister when the outside air Inriku occurs (hereinafter, the top surface 4T Since the temperature change in (referred to as) is the largest at the center position of the top surface 4T, it is preferable that the temperature of the center position 4Tc of the top surface 4T in the horizontal plane direction is measured and used (FIGS. 2A and 2B).

The canister sidewall temperature T _S, although the temperature at any position of the side wall of the canister 4 is may be used are measured, the outer surface of the side wall of the canister when the outside air Inriku occurs (hereinafter, the side peripheral surface 4S Since the temperature change in the side peripheral surface 4S in the vertical direction is often the largest at the central position or around the central position, the temperature at the central position 4Sc in the vertical direction of the side peripheral surface 4S or its surroundings is high. It is preferably measured and used (Fig. 2A). Incidentally, canister bottom temperature T _B and the structure of each degree / balance and canister structures 4 of the rise of the canister lid temperature T _T, a temperature change in the side peripheral surface 4S of the canister 4 is maximized position side It may deviate from the central position 4Sc in the vertical direction of the peripheral surface 4S.

Based on the findings of the above inventors, by observing at least one of the temperatures I to III below for the canister 4 in the vertical position and monitoring whether or not the temperature changes with time. , It becomes possible to determine whether the sealed structure of the canister 4 is maintained or damaged, that is, to detect an outside air in-leak in the canister 4.
I) canister bottom temperature T _B (Note that rises by Inriku)
II) canister lid temperature T _T (Note that rises by Inriku)
III) canister sidewall temperature T _S (Incidentally, reduced by Inriku)

Here, the canister lid temperature T _T, not only the surface temperature of the canister lid itself, influenced by the canister lid temperature T _T (in other words, the temperature varies with a change in the canister lid temperature T _T) space And the temperature of the member may be included. Specifically, opposite the lid of the canister 4, the temperature of the space or members affected by the canister lid temperature T _T with the top surface 4T of the bottom surface 8B and the canister 4 of the concrete cask 2 concrete lid 8 is used For example, the bottom surface temperature of the concrete lid 8 of the concrete cask 2, that is, the bottom surface temperature of the concrete lid _TLB may be used. Therefore, the canister lid temperature T _T, in addition to the temperature of the lid of the canister 4, affected canister lid temperature T _T with the top surface 4T of the bottom surface 8B and the canister 4 of the concrete cask 2 concrete lid 8 space And the temperature of the member Specifically, for example, the temperature of the bottom surface of the concrete lid _TLB is included. Since the natural convection of the internal cooling outside air 5 in the space between the bottom surface 8B of the concrete lid 8 of the concrete cask 2 and the top surface 4T of the canister 4 is small, the above-mentioned space and the members in contact with the space are the canister lid temperature. susceptible to the influence of _T T.

Based on the findings of the above inventors, and by observing at least one of the following temperature differences from i to iii regarding the canister 4 in the vertical position, whether or not the temperature difference changes with time is determined. By monitoring, it becomes possible to determine whether the sealed structure of the canister 4 is maintained or damaged, that is, to detect an outside air in-leak in the canister 4. It is considered that the following orders of i, ii, and iii correspond to the order of good sensitivity to outside air in-leak, and further correspond to the order of advantage in detecting outside air in-leak.
i) the canister bottom temperature T _B and the temperature difference [Delta] T _BS of the canister side wall temperature T _S
ii) Temperature difference between canister lid temperature T _T and canister side wall temperature T _S ΔT _TS
temperature difference [Delta] T _BT and iii) the canister bottom temperature T _B and the canister lid temperature T _T

When the temperature difference between the two temperatures with respect to the canister 4 is used, the change in the outside air temperature is canceled out from the two temperatures that fluctuate under the influence of the change in the outside air temperature. It is less susceptible and accurate judgments can be made.

Further, the larger the negative pressure degree of the initial internal pressure of the canister 4 (that is, the lower the initial internal pressure), the larger the inflow amount of the outside air (air) having a small thermal conductivity due to the in-leak, so that after the in-leak (in other words, in other words, progresses in Inriku) the degree of temperature rise of the spent fuel in the canister 4 increases (see FIG. 21), Thus, each section temperature for a canister 4 T _B, T _T, T change in _S width and the temperature difference ΔT _BS , ΔT _TS , and ΔT _BT increase.

Incidentally, the degree of temperature rise of the spent fuel of a negative圧度is too large canister 4 after Inriku large initial pressure of the canister 4, and each unit temperature for the canister 4 T _B, T _T, the variation width of T _S and the temperature difference [Delta] T _BS, [Delta] T _TS, the variation width of [Delta] T _BT is advantageous for detection of the outside air Inriku the larger (in other words, the detection sensitivity is improved) but, these units the temperature _{T B,} T T, T _S Ya The magnitude of the change in temperature difference ΔT _BS , ΔT _TS , and ΔT _BT is the result of reflecting the magnitude of the temperature change in the spent fuel. Therefore, if necessary, the allowable temperature rise of the spent fuel in the canister 4 can be increased. The degree of negative pressure of the initial internal pressure is set after considering the degree.

The detection device for the loss of seal of the canister may be realized by executing a predetermined program on the computer.

The canister loss-sealing detection device 15 includes, for example, a control unit 16 (specifically, a CPU; that is, a central processing unit), a storage unit 17, an interface 18, and a display unit 19 as shown in FIG. It can be realized by executing the program stored in the storage unit 17 at least in the provided computer.

The control unit 16 of the computer as the detecting device 15 of the sealing loss of the canister, by the program is executed, the temperature sensors 13A, 13B, bottom temperature T _B of the canister 4 that has been input from 13C, the lid temperature T _T, and sealing loss determination unit 16a that performs determination of the sealing structure of the canister 4 is impaired configured when a change exceeds a predetermined threshold in at least one temperature of the side wall temperature T _S occurs. The measured value data of the first temperature sensor 13A, the second temperature sensor 13B, and the third temperature sensor 13C are input to the computer via the interface 18, and the input measured values change with time. Whether or not it is present is determined by the seal loss determination unit 16a.

Further, sealing loss determination unit 16a of the present embodiment, the bottom temperature T _B, as described above, with the lid temperature T _T, and one of the temperature of the side wall temperature T _S alone, their temperature is a predetermined threshold value When a change occurs beyond the above, it is judged that the sealing structure of the canister 4 is damaged and an in-leak of the outside air into the inside of the canister 4 occurs, but the temperature is not particularly limited to this and the temperature of all parts is determined. may be used, or may be used in combination with the temperature difference or other temperature between combinations thereof i.e. a plurality of temperature, bottom temperature more preferably indicates the greatest change in temperature T _B or bottom temperature T _B Judgment is made from the temperature change obtained from the combination of and other temperatures. For example, the control unit 16 of the computer, by the program is executed, the temperature of the bottom of the canister 4 T _B, the temperature difference [Delta] T _BS between any two temperatures of the lid temperature T _T, and the side wall temperature T _S , ΔT _TS , ΔT _BT may be determined that the sealing structure of the canister 4 is impaired and an in-leak of the outside air into the canister 4 occurs when the change occurs beyond a predetermined threshold value.

Further, sealing loss determination unit 16a also may be determined that the sealed structure of the canister has been compromised when a large change in the temperature difference between the bottom temperature T _B and the side wall temperature T _S to produce temperature change occurs , more preferably when the bottom temperature T _B and the lid temperature T _T rises above the predetermined threshold and the side wall temperature T _S of the canister is reduced beyond a predetermined threshold value, it determines that the sealing structure of the canister is compromised You may.

Then, when the measured value exceeds a predetermined threshold value and changes with time, the detection device 15 causes, for example, display on the display unit 19 that the sealing structure of the canister 4 has been damaged, or Issue an alarm, etc.

According to the findings of the inventors, when the internal gas of the canister 4 is air, the temperature of the spent fuel drops slightly, but it is an inert gas (specifically, for example). , Helium), the temperature of the spent fuel drops dramatically. The temperature of the spent fuel and the surface temperature of the canister 4 hardly depend on the degree of negative pressure (specifically, in the range of about 0.1 to 0.8 atm). Therefore, setting the initial internal pressure of the canister 4 to a negative pressure does not pose any problem from the viewpoint of managing the decay heat of the spent fuel stored in the canister 4.

Further, since the initial internal pressure of the canister 4 is negative, even if the sealing structure of the canister 4 is damaged, the internal gas containing radioactive substances is used without being immediately released to the external environment. Since the phenomenon that the temperature of the fuel rises occurs, it is possible to detect the occurrence of an outside air in-leak in the canister 4 while preventing the release of the internal gas containing radioactive substances to the outside environment. Therefore, for example, the transportation regulations in the sealing design standard of the radioactive material transport container in Japan and the US standard (specifically, US NRC NUREG-1536 "Standard Review Plan for Sport Feel Dry Stage Stages at a General License") It is not necessary to consider the permissible leakage amount as specified by (that is, by what Pa the leakage must be detected).

Further, as a case where the radioactive substance is released to the outside environment, it is conceivable that the internal pressure of the canister 4 becomes atmospheric pressure and the gas inside the canister 4 is replaced with the outside gas, that is, the outside air. However, since stress corrosion cracking (SCC) usually occurs at the welded part at the bottom of the canister 4, even when cracks due to stress corrosion cracking occur and the in-leakage of the outside air progresses to atmospheric pressure, the outside air When the density of the inert gas in the canister 4 is smaller than the density of the outside air sucked into the canister 4, the sucked outside air accumulates in the lower space in the canister 4, while the inert gas is in the canister. Accumulates in the upper space inside 4. Therefore, it is considered that the amount of the internal gas, that is, the inert gas, replaced with the external gas, that is, the outside air by molecular diffusion is extremely small in the cracked portion, and therefore the release of the internal gas containing radioactive substances to the external environment is suppressed. Be done.

<< Second embodiment: Horizontal canister >>
4 to 6 show a method for detecting a canister seal loss and a second embodiment of a canister seal loss detection device according to the present invention. In this embodiment, the description of the same configuration as that of the vertical canister of the first embodiment will be omitted.

In the present embodiment, the case of the storage facility 21 in which the canister 24 is stored in the concrete silo 22 in a horizontal position, which is also called a concrete silo type, will be described.

The storage facility 21 takes in the internal cooling outside air 25 for cooling the canister 24 housed in the concrete storage 23 of the concrete silo 22 from the air supply port 26, and is provided at a position higher than the air supply port 26. It has a structure for discharging from 27.

The concrete silo 22 has a concrete storage 23 and a concrete lid 28, and is configured as an unsealed structure having a shielding function.

The configuration of the canister 24 (specifically, metal, double lid, partition / basket charging, sealing structure by welding, filling of inert gas, initial internal pressure is negative, etc.) is the same as in the first embodiment described above. Is.

The canister 24 is placed on a rail-shaped support stand 29 and housed in the concrete storage 23.

The side opening of the concrete storage 23 is closed by the concrete lid 28.

A distribution space 30 through which the internal cooling outside air 25 flows is provided between the canister 24, the concrete storage 23, and the concrete lid 28. In relation to this structure, an air supply port 26 leading to the distribution space 30 is provided at the bottom of the concrete storage 23, and an exhaust port 27 communicating with the distribution space 30 is provided at the ceiling of the concrete storage 23. Be done.

With the above structure, the outside air naturally convects as the internal cooling outside air 25 through the air supply port 26 and the exhaust port 27 provided above and below the concrete silo 22, and the spent fuel in the canister 24 is transferred to the internal cooling outside air 25. The decay heat of the concrete is removed.

Then, the detection method of sealing loss of the canister of the present embodiment, the bottom temperature of the canister 24 that the internal pressure is a negative pressure greater inert gas thermal conductivity than the outside air is sealed T _HB, the cover temperature T _HT The sealing structure of the canister 24 is impaired when at least one of the lower side wall temperature _{THSL in} the horizontal position and the upper side wall temperature _THSU in the horizontal position changes beyond a predetermined threshold. Therefore, it is determined that an in-leak has occurred inside the canister 24 of the outside air.

Here, as the temperature to be monitored, the bottom temperature T _HB of the canister 24, the lid temperature T _HT, sidewall lower temperature T _HSL, and may be any of the at least one temperature of the side wall upper temperature T _HSU, alone may be used not in combination with other temperature just used, preferably a combination of the most significant temperature changes bottom temperature T _B or bottom temperature T _B and the other showing the temperature, in particular limited to these The temperature of all parts may be used, and in some cases, a combination thereof may be used. For example, bottom temperature T _HB of the canister 24, the lid temperature T _HT, the temperature difference [Delta] T _HBT between any two temperatures of the side wall lower temperature T _HSL, and upper side wall temperature _{T HSU (= T HB -T HT} ) _{, ΔT HBSU (= T HB -T} HSU), ΔT HSLT (= T HSL -T HT), sealing the canister 24 when a change exceeds a predetermined threshold occurs in _{ΔT hSLU (= T HSL -T HSU} ) It may be determined that the structure is damaged and an in-leak of the outside air into the canister 24 has occurred. Moreover, even if determined that the sealing structure of the canister when a change in temperature difference is caused between the bottom temperature T _HB and the lid temperature T between _HT or sidewall upper temperature T _HSU make a big change in temperature is compromised good to, more preferably when the bottom temperature T _HB and sidewall lower temperature T _HSL rises above the predetermined threshold and the lid temperature T _HT and sidewall upper temperature T _HSU of the canister 24 is reduced beyond a predetermined threshold value , It may be determined that the sealing structure of the canister is impaired.

The method for detecting the loss of seal of the canister can also be carried out by the device for detecting the loss of seal of the canister according to the present invention. The canister seal loss detection device of the present embodiment detects the loss of the seal structure of the canister 24 housed in the concrete silo 22 in a horizontal position, and has a higher thermal conductivity than the outside air together with the used fuel. large canister 24 inert gas, which is a sealed besides negative pressure, the first temperature sensor 33A for measuring the bottom temperature T _HB of the canister 24, the second temperature sensor 33B for measuring the lid temperature T _HT, at least one temperature sensor of the fourth temperature sensor 33D for measuring the sidewall upper temperature T _HSU in the third temperature sensor 33C and horizontal orientation, to measure the sidewall lower temperature T _HSL in horizontal posture, When at least one temperature measurement value data measured by any of the temperature sensors 33A, 33B, 33C, 33D is input and the input measurement value changes beyond a predetermined threshold value, the canister 24 It has a seal loss determining unit 36a for determining that the sealing structure is impaired and an in-leak into the inside of the canister 24 of the outside air has occurred.

Here, the seal loss determination unit 36a uses any one of the bottom temperature _THB , the lid temperature _THT , the side wall lower temperature _THSL , and the side wall upper temperature _THSU alone, or is a temperature between a plurality of temperatures. When used in combination with a difference or other temperature, when those temperatures change beyond a predetermined threshold, the sealing structure of the canister 24 is impaired and an in-leak of outside air into the canister 24 occurs. I try to judge. That is, a bottom temperature _THB showing the largest temperature change or a combination of the bottom temperature _THB and another temperature is preferable, but the temperature is not particularly limited to these, and the temperature of all parts may be used. Depending on the case, it may be a combination thereof. For example, sealing loss determination unit 36a, a bottom temperature T _HB of the canister 24, the lid temperature T _HT, the temperature difference [Delta] T _HBT between any two temperatures of the side wall lower temperature T _HSL and sidewall upper temperature T _HSU, [Delta] T _{When the HBSU} , ΔT _HSLT , and ΔT _HSLU change beyond a predetermined threshold value, it may be determined that the sealing structure of the canister 24 is impaired and an in-leak of outside air into the canister 24 has occurred. Further, sealing loss determination unit 36a, the sealing structure of the canister when a change in temperature difference is caused between the bottom temperature T _HB and the lid temperature T _HT or between the side wall upper temperature T _HSU and make a big temperature change may be determined that the impaired, more preferably bottom temperature T _HB and sidewall lower temperature T _HSL rises above the predetermined threshold and the lid temperature T _HT and sidewall upper temperature T _HSU predetermined threshold canister 24 It may be determined that the canister's sealing structure has been impaired when it drops beyond.

The first to fourth temperature sensors 33A, 33B, 33C, 33D are the same as the temperature sensors of the first embodiment, and the description thereof will be omitted.

According to the findings of the inventors, when the initial internal pressure of the canister 24 is negative and the thermal conductivity is filled with an inert gas, for example, helium gas, which is larger than the outside air, for example, air, the outside air becomes the canister due to the loss of sealing of the canister 24. When Inriku to 24, by heat removal effect with a decrease in the thermal conductivity is reduced, also the canister sidewall lower temperature T _HSL with canister bottom temperature T _HB rises increases, while the canister lid temperature T _{As HT} decreases, the canister side wall upper temperature _THSU also decreases.

In the canister 24 in the horizontal position, the bottom of the canister is one end in the horizontal direction, and the canister lid is the other end in the horizontal direction. That is, the canister bottom temperature T _HB corresponds to the temperature of the spent fuel and the areas of bottom basket is in contact with vertical canister 4, the canister lid temperature T _HT becomes vertical lid of the canister 4 Corresponds to the temperature of the part.

Further, the canister side wall lower temperature _THSL is the temperature of the portion of the side wall of the horizontally placed canister 24 that is lower than the horizontal plane Hp passing through the center of the canister 24.

Further, the canister side wall upper temperature _THSU is the temperature of the portion of the side wall of the horizontally placed canister 24 that is above the horizontal plane Hp passing through the center of the canister 24.

Similar to the first embodiment, the temperature change of the canister 24 causes a decrease in thermal conductivity because outside air (air) having low thermal conductivity is mixed in the inert gas atmosphere having high thermal conductivity due to in-leakage. Along with this, the heat removing effect is reduced, and the temperature of the spent fuel in the canister 24 rises.

Then, the heat of the spent fuel is contacted (in particular, metal-to-metal contact) because it is the most carried by the canister sidewall lower temperature T _HSL increases in the canister bottom temperature T _HB and horizontal orientation, the canister lid temperature T _HT And the canister side wall upper temperature _THSU in the horizontal position decreases.

The canister bottom temperature T _HB, although the temperature at any position of the bottom of the canister 24 may be used is measured, the temperature at the bottom of the outer surface of the canister when the outside air Inriku occurs (i.e., bottom surface) Since the change is greatest at the center position of the bottom surface, the vertical surface of the bottom surface of the canister 24 in the horizontal position on one end surface (that is, the bottom surface 24HB) in the axial direction (that is, the horizontal direction H) of the canister 24. It is preferable that the temperature at the center position 24HBc in the direction Vp is measured and used (FIGS. 5A and 5C).

The canister lid temperature T _HT, although the temperature at any position of the lid of the canister 24 may be used is measured, the outer surface of the lid of the canister when the outside air Inriku occurs (i.e., top surface ) Is the largest at the center position of the top surface, so that the lid of the canister 24 in the horizontal position has the other end surface (that is, the top surface) in the axial direction (that is, the horizontal direction H) of the canister 24. It is preferable that the temperature at the central position 24HTc in the vertical facing direction Vp of 24HT) is measured and used (FIGS. 5A and 5B).

As the canister side wall lower temperature _THSL , the temperature at any part of the side wall of the canister 24 in the horizontal position, which is lower than the horizontal plane Hp passing through the center of the canister 24, may be measured and used. Although not, the temperature of the lowermost 24HSL (in other words, the lowermost bottom) of the outer surface of the side wall (that is, the side peripheral surface 24HS) at the central position 24HSLc in the horizontal direction H or its surroundings is measured and used. Is preferable (Fig. 5A). Incidentally, the configuration of the structure of the degree / balance and canister 24 between the drop and the respective increase of the canister bottom temperature T _HB and canister lid temperature T _HT, the outer surface of the side wall of the canister 24 (i.e., the side peripheral surface 24hs) The position where the temperature change is greatest may deviate from the central position 24HSLc in the horizontal direction H of the lowermost 24HSL of the side peripheral surfaces 24HS.

As the canister side wall upper temperature _THSU , the temperature at any part of the side wall of the canister 24 in the horizontal position, which is above the horizontal plane Hp passing through the center of the canister 24, may be measured and used. Although not, the temperature of the uppermost 24HSU (in other words, the top) of the outer surface (that is, the side peripheral surface 24HS) of the side wall of the canister 24 in the horizontal position is measured at the central position 24HSUc in the horizontal direction H. It is preferably used (Fig. 5A).

Based on the findings of the above inventors, by observing at least one of the temperatures I to IV below for the canister 24 in the horizontal position and monitoring whether or not the temperature changes with time. , It becomes possible to determine whether the sealed structure of the canister 24 is maintained or damaged, that is, to detect an in-leak in the canister 24.
I) canister bottom temperature T _HB (Note that rises by Inriku)
II) Canister lid temperature T _HT (It will decrease due to in-leakage)
III) horizontal orientation of the canister sidewall lower temperature T _HSL (Note that rises by Inriku)
Canister sidewall of IV) horizontal posture upper temperature T _HSU (Note, reduced by Inriku)

Based on the findings of the above inventors, and by observing at least one of the following temperature differences from i to iv regarding the canister 24 in the horizontal position, whether or not the temperature difference changes with time is determined. By monitoring, it becomes possible to determine whether the sealed structure of the canister 24 is maintained or damaged, and to detect in-leakage in the canister 24.
i) the temperature difference [Delta] T _HBT of the canister bottom temperature T _HB and canister lid temperature T _HT
ii) Temperature difference between canister bottom temperature T _HB and canister side wall top temperature T _HSU ΔT _HBSU
temperature difference [Delta] T _HSLT and iii) the canister sidewall lower temperature T _HSL and canister lid temperature T _HT
iv) Temperature difference between canister side wall lower temperature T _HSL and canister side wall upper temperature T _HSU ΔT _HSLU

Since the degree of increase in the canister bottom temperature T _HB and the canister sidewall lower temperature T _HSL is different, the temperature difference [Delta] T _HBSL the canister bottom temperature T _HB and the canister sidewall lower temperature T _HSL is observed whether the changes over time It may also be monitored, and since the degree of reduction of the canister lid temperature T _HT and canister side wall upper temperature T _HSU different, temperature difference [Delta] T _HTSU the canister lid temperature T _HT and canister side wall upper temperature T _HSU is It may be observed and monitored for changes over time.

When the temperature difference between the two temperatures with respect to the canister 24 is used, the change in the outside air temperature is canceled out from the two temperatures that fluctuate under the influence of the change in the outside air temperature. It is less susceptible and accurate judgments can be made.

Further, the larger the negative pressure degree of the initial internal pressure of the canister 24 (that is, the lower the initial internal pressure), the larger the inflow amount of the outside air (air) having a smaller thermal conductivity than the canister internal gas due to the in-leak. (With other words, with the progress of Inriku) the degree of temperature rise of the spent fuel in the canister 24 is increased, Therefore, each part temperature T _HB relates canister 24, T _HT, T _HSL, variation of T _HSU Ya The temperature differences ΔT _HBT , ΔT _HBSU , ΔT _HSLT , and ΔT _HSLU increase.

Incidentally, the degree of temperature rise of the spent fuel in the canister 24 after the negative圧度higher the outside air Inriku large initial pressure of the canister 24, and, each portion temperature _{T HB, T HT, T HSL} , changes in T _HSU it is advantageous to detect the width and the temperature difference _{ΔT HBT, ΔT HBSU, ΔT HSLT} , the Inriku enough variation width of [Delta] T _hslU large impaired sealing structure of the canister 24 to the interior of the outside air of the canister 4 is generated (in other words, the detection sensitivity is improved) but, these units the temperature _{T HB, T HT, T HSL} , T HSU and the temperature difference _{ΔT HBT, ΔT HBSU, ΔT HSLT} , the change of [Delta] T _hslU magnitude of spent fuel Since this is a result that reflects the magnitude of the temperature change, the negative pressure degree of the initial internal pressure is set as necessary after considering the degree of the allowable temperature rise of the spent fuel in the canister 24.

The detection device for the loss of seal of the canister may be realized by executing a predetermined program on the computer.

The canister loss-sealing detection device 35 includes, for example, a control unit 36 (specifically, a CPU; that is, a central processing unit), a storage unit 37, an interface 38, and a display unit 39, as shown in FIG. It can be realized by executing the program stored in the storage unit 37 at least in the provided computer.

When a program is executed in the control unit 36 of the computer as the detection device 35 for the loss of sealing of the canister, the bottom temperature _THB and the lid temperature of the canister 24 input from the temperature sensors 33A, 33B, 33C, and 33D are executed. Loss of sealing that determines that the sealing structure of the canister 24 has been impaired when at least one of the T _HT , lower side wall temperature T _HSL , and upper side wall temperature T _HSU changes beyond a predetermined threshold. The determination unit 36a is configured. The measured value data of the first temperature sensor 33A, the second temperature sensor 33B, the third temperature sensor 33C, and the fourth temperature sensor 33D are input to and input to the detection device / computer 35 via the interface 38. The seal loss determination unit 36a determines whether or not the measured value exceeds a predetermined threshold and changes with time.

Here, the seal loss determination unit 36a uses any one of the bottom temperature _THB , the lid temperature _THT , the side wall lower temperature _THSL , and the side wall upper temperature _THSU alone, or is a temperature between a plurality of temperatures. When used in combination with a difference or other temperature, when those temperatures change beyond a predetermined threshold, the sealing structure of the canister 24 is impaired and an in-leak of outside air into the canister 24 occurs. I try to judge. At this time, although most combinations of a large bottom shows the temperature change temperature T _B or bottom temperature T _B and other temperatures are preferred, these not particularly limited, it may be used the temperature of all the sites, In some cases, it may be a combination thereof. For example, sealing loss determination unit 36a, a bottom temperature T _HB of the canister 24, the lid temperature T _HT, the temperature difference [Delta] T _HBT between any two temperatures of the side wall lower temperature T _HSL and sidewall upper temperature T _HSU, [Delta] T _{When the HBSU} , ΔT _HSLT , and ΔT _HSLU change beyond a predetermined threshold value, it may be determined that the sealing structure of the canister 24 is impaired and an in-leak of outside air into the canister 24 has occurred. Further, sealing loss determination unit 36a, the sealing structure of the canister when a change in temperature difference is caused between the bottom temperature T _HB and the lid temperature T _HT or between the side wall upper temperature T _HSU and make a big temperature change may be determined that the impaired, more preferably bottom temperature T _HB and sidewall lower temperature T _HSL rises above the predetermined threshold and the lid temperature T _HT and sidewall upper temperature T _HSU predetermined threshold canister 24 It may be determined that the canister's sealing structure has been impaired when it drops beyond.

Then, when the measured value exceeds a predetermined threshold value and changes with time, the detection device 35 causes, for example, display on the display unit 39 that the sealing structure of the canister 24 has been damaged, or It issues an alarm.

According to the findings of the inventors, as described above, the presence of an inert gas such as helium in the canister 24 dramatically lowers the temperature of the spent fuel, and the spent fuel Since the temperature and the surface temperature of the canister 24 are almost independent of the degree of negative pressure (see FIG. 22), setting the initial internal pressure of the canister 24 to a negative pressure is a used product stored in the canister 24. From the viewpoint of fuel decay heat management, there is no problem.

According to the canister seal loss detection method and the canister seal loss detection devices 15 and 35 configured as described above, when the canister seal loss occurs, an in-leak occurs in an inert gas atmosphere having a high thermal conductivity. By mixing outside air with low thermal conductivity, that is, air, the heat removal effect decreases as the thermal conductivity decreases, and the temperature of the spent fuel in the canister 4 rises. Since it is accompanied by a phenomenon, it is possible to accurately detect that the sealing structure of the canisters 4 and 24 is impaired. Therefore, it is possible to improve the usefulness and reliability as a method for detecting the loss of sealing property in the canister 4 in the vertical posture and the canister 24 in the horizontal posture.

Further, even if the sealing structure of the canisters 4 and 24 is damaged, the temperature of the spent fuel rises without immediately releasing the internal gas containing radioactive substances to the outside environment. It is possible to detect the occurrence of an outside air in-leak in the canister 24 while preventing the release of the internal gas containing radioactive substances to the outside environment. Therefore, it is not necessary to consider the allowable leakage amount.

Although the above-described embodiment is an example of a suitable mode for carrying out the present invention, the embodiment of the present invention is not limited to the above-mentioned one, and the present invention is not limited to the above-mentioned embodiment and does not deviate from the gist of the present invention. The invention can be modified in various ways.

For example, in the above-described embodiment, the case where the present invention is applied to the concrete cask type storage facility 1 whose schematic structure is shown in FIG. 1 and the concrete silo type storage facility 21 whose schematic structure is shown in FIG. 4 is taken as an example. However, the specific configuration / structure of the storage facility to which the present invention can be applied is not limited to the examples shown in FIGS. 1 and 4, and various storage facilities in which the canister is stored in a vertical position and the like. The present invention is applicable to various storage facilities in which the canister is stored in a horizontal position.

Further, in the above-described embodiment, the change in the surface temperature of any part of the canisters 4 and 24 or the change in the temperature difference between the plurality of parts is focused on, but the surface temperature of each part of the canisters 4 and 24 is focused on. A difference from a temperature other than the above may be used. Specifically, above-described units temperature T _B of the canister 4, 24, ..., and T _HSU, outside air taken in the fifth temperature sensor 13E provided in the air supply port 6, 26 of the concrete cask 2 / concrete silo 22 The difference from the temperature of (called the supply air temperature T _IN ) may be used. Each section temperature particular bottom temperature T _B of the canister 4, 24, T _HB, and sidewall lower temperature T _HSL is influenced by the temperature of the internal cooling ambient air 5, 25 vary with changes in ambient temperature during the day It is easy and fluctuates regardless of the loss of sealing properties of the canisters 4 and 24 (specifically, the occurrence of in-leakage). Therefore, by using the difference between the temperature of each part of the canisters 4 and 24 and the supply air temperature, the fluctuation of the temperature of the internal cooling outside air 5 and 25 due to the change of the outside air temperature from the fluctuation of the temperature of each part of the canisters 4 and 24 is used. Can be offset and removed. Specifically, for example, since the vertical bottom temperature T _B of the canister 4 is particularly susceptible to the influence of the temperature inside the cooling ambient air 5, the temperature difference between the canister bottom temperature T _B and the supply air temperature T _IN over time By monitoring whether or not the temperature changes to, it may be determined whether or not the sealed structure of the canister 4 is maintained or damaged, that is, the outside air in-leak in the canister 4 may be detected.

Further, in the above-described embodiment, the surface temperature of each part of the canister is measured, and when the measured value exceeds a predetermined threshold value by utilizing the fluctuation of the measured temperature itself, the sealing structure of the canister is impaired. It is determined that an in-leak of the outside air has occurred inside the canister, but it is not particularly limited to this, and other physical phenomena caused by the temperature change caused by the in-leak of the outside air into the canister, for example, a change in the heat flux. Or a change in the internal index temperature may be detected to determine the loss of sealing. Especially bottom temperature T _B of the canister 4, since greatly affected by the supply air temperature T _IN, by mitigating the effects of supply air temperature T _IN, using a temperature change of the bottom temperature T _B of the canister 4, It is preferable to detect the leak with high accuracy. For example, determine the heat flux through the canister bottom from the bottom temperature T _B and the supply air temperature T _IN of the canister 4, method to estimate the change in the canister internal pressure due Inriku from the change, or a stainless steel plate of the canister bottom from inside canister pass, under conditions that are heat flux emitted to the ambient air is constant, we obtain the index temperature T _H of the inner canister, the change from a change in the temperature difference between the canister internal index temperature T _H and the bottom temperature T _B of the canister internal pressure It is possible to guess.

[How to find heat flux]
FIG. 23 shows the temperature boundary conditions at the bottom of the canister. Canister bottom surface in contact with the outside air, because it is heated, so that the heat transfer heat flux q _c by natural convection occurs. Although heat is also dissipated by heat conduction from the canister mount, the heat flux at the center position of the bottom of the canister is evaluated here. Therefore, since the plate thickness of the bottom of the canister is sufficiently thin compared to the distance from the center of the bottom to the contact point between the gantry and the bottom of the canister, it is assumed that the influence of heat conduction due to contact does not reach the center position of the bottom of the canister to be evaluated. .. The relationship between these heat fluxes is shown in Equation 1 below.

For the heat transfer coefficient ha on the air side, the natural convection heat transfer correlation equation of the downward heating circular flat plate is used from the heat transfer handbook (heat transfer engineering data revised 5th edition, Japan Opportunity Society, 2009).
Therefore,

Than,

Here, L (canister diameter) was set to 0.4064 m.

FIG. 24 shows the relationship between the difference in heat flux calculated for the leak test case from the initial 0.1 atm helium and the internal pressure of the canister. It can be seen that Δq _B (= q _B − q _B0 ) in the figure increases as the internal pressure increases.

[How to find the index temperature in the canister]
With canister bottom center temperature _{T B} and the supply air temperature _{T IN,} obtaining the index temperature _{T H} of the inner canister. As a so-called inverse problem, boundary conditions are obtained using known temperature data. The heat flux given from the inside of the canister to the bottom of the canister is considered to be the heat flux due to convection in addition to the heat flux transmitted by heat conduction from the heating element inside the canister and the radiant heat flux. The heat flux that combines these is called q _I. To do. Furthermore, the heat flux is assumed at the bottom close proximity to the inner canister, the index temperature T _H of the helium is provided by heat conduction.

FIG. 25 shows the heat flow and boundary conditions from the inside of the canister to the bottom of the canister and released to the atmosphere.

Heat flows from the inside of the canister to the atmosphere (air) through the stainless steel plate at the bottom of the canister. Here, helium index temperature at a location remote height l _H is the immediate vicinity of the canister bottom inner as T _H, the heat flux q _I as shown in Equation 4 heat is transferred by heat conduction to the stainless steel plate Assume. In the stainless steel plate, heat is transferred by the heat conduction shown in Equation 5. Further, the heat transfer between the stainless steel plate and air is transferred by the heat transfer and radiant heat shown in Equation 6. Here, it is assumed that heat dissipation due to heat conduction through the canister mount has no effect at this point. Therefore, the heat flux q _I and q _S are expressed by the following equations, respectively.

Now, since the heat flux inside the canister, the stainless plate at the bottom of the canister, and the heat flux that passes through the bottom of the canister and is released to the standby are the same, q _{I =} q _{S =} q _B is established. Thus, to clear the T _BI three formulas above, the following equation and obtaining a T _H.

Helium index temperature T _H in the vicinity of the bottom canister, as shown in Equation 7, and be represented using T _B and T _IN. l _H is a value arbitrarily determined in the range extremely close to the inner bottom of the canister, and here, l _H = 0.01 m is set.
_Further, T H -T _B will Equation 8.

Temperature variation from the measurement start point, _{T H} '-T _B' is

Will be.

_{T H} '-T _B' in leak test cases from the initial 0.1atm helium and shows the relationship between the canister internal pressure in FIG. 26. The value of T _{H '-T} B' in the figure, with increase in the internal pressure, it is seen that the rise.

The meanings of the symbols in Equations 1 to 9 are as follows.
l _H: distance from the canister bottom to the observation point of helium temperature _{T H} (m)
l _s : Canister bottom thickness (m)
λ _H : Thermal conductivity of helium (W / m / ° C)
λ _s : Thermal conductivity of stainless steel (W / m / ° C)
λ _a : Thermal conductivity of air (W / m / ° C)
q _I : Heat flux from helium in the canister to the bottom of the canister (W / m ² )
q _S : Heat flux passing through the bottom surface of the canister (W / m ² )
q _B : Heat flux from the bottom of the canister to the air (W / m ² )
h _a: heat transfer coefficient between the canister bottom and air (W / ^{m 2} / ℃)
T _H: canister near the bottom of the helium temperature (℃)
T _BI : Canister bottom bottom temperature (° C)
T _B: canister bottom external temperature (℃)
T _IN : Supply air temperature (° C)
Gr _l : Grashof number (-)
β: Coefficient of thermal expansion of air (1 / K)
ν _a : Dynamic viscosity coefficient of air (m ² / s)
g: Gravitational acceleration (m / s ² )
Nu _a : Nusselt number on the air side (-)
Pra _a : Prandtl number of air (-)
L: Representative length (m) (Here, it is the canister diameter. It was set to 0.4064 m.)
C1: Correction coefficient

Further, when the temperature difference between the surface temperature of each part of the canister and the other temperature is used and the temperature difference exceeds a predetermined threshold value, the sealing structure of the canister is impaired and the outside air canister is used. It may be determined that an in-leak has occurred inside. For example, when the lid temperature T _T of the vertical canister 4 and the internal temperature T _LM of the concrete lid 8 of the concrete cask 2 are combined and the temperature difference exceeds a predetermined threshold value, the sealing structure of the canister 4 is formed. You may decide that it has been damaged. The internal temperature T _LM of the concrete lid 8 is measured by the sixth temperature sensor 13F which was charged to e.g. in a concrete cask 2 concrete lid 8. According to this technique, since the internal temperature T _LM of the concrete cask 2 concrete lid 8 which varies with and much slowly a time delay with respect to the change of the lid temperature T _T of the canister 4, the outside air Inriku occurs in the canister 4 Then, when the lid temperature T _T of the canister 4 changes, the difference between the lid temperature T _{T of the} canister 4 and the internal temperature T _LM of the concrete lid 8 of the concrete cask 2 increases. Therefore, it can be determined that the sealing structure of the canister 4 is impaired when the temperature difference between them changes beyond a predetermined threshold value. Further, the canister lid temperature T _T include the temperature of the bottom surface of the concrete lid 8 of the concrete cask 2. Therefore, the temperature of the bottom surface of the concrete cover 8 while changing relatively quick response to changes in the cover temperature T _T of the canister 4, the internal temperature T _LM canister 4 of the concrete lid 8 cover the temperature T _T and concrete lid Since the temperature of the bottom surface of the concrete lid 8 changes slowly and with a time delay, the sealing structure of the canister 4 changes when the temperature difference between the bottom surface temperature of the concrete lid 8 and the internal temperature _TLM changes. It can also be judged that it has been damaged.

<< Verification example >>
An example of a test conducted for verifying the validity of the method for detecting the loss of sealing of the canister according to the present invention will be described with reference to FIGS. 7 to 21. Note that FIGS. 7 and 8 are schematic views for showing the temperature measurement position together with the schematic structure of the model of the storage facility used in this verification example, and the dimensional relationship of each part is accurately matched with the actual dimensional relationship. It is not a representation.

In this verification example, a model 51 of a storage facility in which the canister is stored in a vertical position in the cask is used (FIGS. 7 and 8), and an in-leak from a state where the initial internal pressure of the canister is negative. The test was carried out.

The model 51 of the storage facility was composed of a canister model 54 and a cask model 52 covering the canister model 54 in a vertical position. The cask model 52 and the canister model 54 are formed to a scale of 1 / 4.5 of the assumed actual machine, and have four air supply ports 56 near the lower end of the cask model 52 and four positions near the upper end. It was configured to have an exhaust port 57. Reference numeral 60 in the figure is a space communicating with the air supply port 56 and the exhaust port 57, and is a distribution space through which the internal cooling outside air 55 flows.

The cask model 52 was formed into a cylindrical shape having the following dimensions.
・ Outer diameter: 766 mm
-Height: 1271.7 mm
・ Diameter of hollow part: 451 mm

The canister model 54 was made of stainless steel and was formed into a cylindrical shape having the following dimensions.
・ Outer diameter: 406.4 mm
・ Height: 1043 mm
・ Body plate thickness: 4.5 mm
・ Thickness of top lid and bottom plate: 40 mm

The top lid of the canister model 54 was welded to the body. The bottom plate had a flange structure that could be opened and closed, and was bolted after being sealed with a metal gasket.

A pipe penetrating the bottom plate of the canister model 54 was attached, and a valve 64 was provided for the pipe, and the valve 64 was used when filling the canister model 54 with gas and during an in-leak test.

Twelve heating elements 62 simulating spent fuel were installed in the canister model 54. The heating element 62 has a diameter of 16 mm and a length of 16 mm around a rod-shaped heater (specifically, having a non-heating portion having a diameter of 16 mm and a length of 900 mm and an upper end side of 100 mm and a lower end side of 80 mm). It was configured to have a structure in which six 885 mm solid aluminum pipes were arranged. The amount of heat generated by the rod-shaped heater can be adjusted by changing the voltage with a transformer.

The heating element 62 was placed in a basket 61 having an internal dimension of 71 mm × 71 mm in each of the partitioned sections. A cross-shaped fixing jig was provided on the upper part of the basket 61, and each heating element 62 / rod-shaped heater was arranged and fixed in the center of each section of the basket 61.

The heat of the rod-shaped heater of the heating element 62 is transmitted through the surrounding aluminum pipe, and the entire heating element 62 is heated and the bottom of the canister model 54 is also heated.

A gap of 30 mm was provided between the lid of the canister model 54 and the upper end of the basket 61.

Thermocouples were installed and the temperatures of the canister model 54 were measured at multiple locations. The temperature measurement positions were set as follows (FIGS. 7 and 8). The names in parentheses below are the names of the temperatures measured at that position.
Canister models lid top (i.e., top surface) temperature of the center position in the horizontal plane direction of (canister lid temperature T _T)
Canister model of the sidewall of the outer surface (i.e., the side peripheral surface) temperature of the center position in the vertical direction (the canister sidewall temperature T _S)
Canister model bottom lower surface (i.e., bottom surface) temperature of the center position in the horizontal plane direction of (canister bottom temperature T _B)

The model 51 of the storage facility used in this verification example was designed in consideration of the similarity law of heat flow in the canister, and is configured to match the number of Rayleighs (Ra * number) in the canister between the actual machine and the model. Was done.

The amount of heat generated from the heating element 62 in the test was set so as to match the surface heat flux of the canister between the actual machine and the model. Specifically, as a test in which the calorific value in the actual machine corresponds to 10 kW, the calorific value in the model was set to 494 W so that the surface heat flux of the canister was matched between the actual machine and the model (however, the voltage). Some fluctuations occurred due to fluctuations).

The canister model 54 was set to gradually fill the inside with helium (He), which is an inert gas, from a vacuum state so that the initial internal pressure becomes a predetermined negative pressure value.

Three internal pressures of 0.8 atm, 0.5 atm, and 0.1 atm were set as the conditions for the initial internal pressure of the canister model 54.

Then, an in-leak test was carried out from the state where the initial internal pressure of the canister model 54 was negative to 1 atm.

In the test in this verification example, helium is used as the initial filling gas in the canister model 54, and air having a thermal conductivity lower than that of helium is mixed in at the time of in-leak. The state in which helium is used as the initial filling gas is a condition smaller than the Ra * number of the actual machine, and the temperature gradient tends to be smaller than that of the actual machine. Furthermore, even when air is mixed in, it is more difficult for the model to have a temperature gradient than when air is mixed in the actual machine. Therefore, it was considered that the test results were underestimated. ..

The situation where an in-leak occurred from the state where the initial internal pressure of the canister model 54 was negative pressure (specifically, 0.8 atm, 0.5 atm, 0.1 atm) to 1 atm was simulated (note that). , initial filling gas is sucked air is ambient air into the canister model 54 is helium), the canister lid temperature T _T accompanying the change in pressure in the canister model 54, canister bottom temperature T _B, and the canister sidewall temperature T _S The results shown in FIGS. 9 (initial internal pressure: 0.8 atm), FIG. 10 (initial internal pressure: 0.5 atm), and FIG. 11 (initial internal pressure: 0.1 atm) were obtained.

9, from the results shown in FIG. 10, and 11, for the case the negative pressure level of the initial internal pressure of both, with the pressure increase towards the atmospheric pressure from the negative pressure, with the canister bottom temperature T _B is increased canister sidewall temperature T _S while also increasing the canister lid temperature T _T was confirmed to be slightly reduced.

The reason why the above temperature change appears is considered as follows. That is, since air having a small thermal conductivity is mixed in the helium atmosphere having a large thermal conductivity due to an in-leak, the heat removing effect is reduced as the thermal conductivity decreases, and the temperature of the heating element 62 in the canister model 54 rises. Rose.

Then, with increasing temperature of the heating element 62 within the canister model 54, the temperature T _B of the bottom of the canister model 54 in contact with the heating element 62 rises.

Further, since the mixed air has a higher density than helium, the air collects in the lower space in the canister model 54, while the helium collects in the upper space in the canister model 54. Accordingly, it communicated to the lid of the canister Model 54 thermal heating element 62 whose temperature is increased through a good helium thermal conductivity, the canister lid temperature T _T also increased.

Also, the minute that a canister bottom temperature T _B and the canister lid temperature T _T rises in Inriku, calorific value itself of the heating element 62 itself because it is the same before and after Inriku, canister sidewall temperature T _S is decreased.

Regarding the results shown in FIGS. 9, 10 and 11, each part of the canister model 54 (specifically, the lid (center position of the top surface), the side wall (the vertical center position of the side peripheral surface), and the bottom (bottom surface). the center position)) each, negative圧度another each part temperature T _T of the initial internal pressure of the canister model 54, T _S, is organized the amount of change T _B results shown in FIG. 12 were obtained.

From the results shown in FIG. 12, it was confirmed that the canister lid temperature T _T and the canister bottom temperature T _B increase and the canister side wall temperature T _S decreases regardless of the degree of negative pressure of the initial internal pressure.

From the results shown in FIG. 12, also, the negative圧度initial internal pressure is large (i.e., the initial pressure is low) as the respective units temperature T _T, T _S, that changes the width of the T _B increases were confirmed. This is because the larger the negative pressure of the initial internal pressure of the canister model 54, the larger the inflow of air with a small thermal conductivity due to the in-leak. Therefore, the canister model 54 after the in-leak (in other words, with the progress of the in-leak). It was considered that this was because the degree of temperature rise of the heating element 62 inside was increased.

9, 10, and with the results are used to indicate 11, the canister bottom temperature T _B and the canister lid temperature T _T and the temperature difference [Delta] T _BT of (= T _B -T _T due to pressure changes; "bottom - cover The amount of change in (referred to as "temperature difference ΔT _BT ") is shown in FIG. 13 (initial internal pressure: 0.8 atm), FIG. 14 (initial internal pressure: 0.5 atm), and FIG. 15 (initial internal pressure: 0.1 atm). Results were obtained.

From the results shown in FIGS. 13, 14, and 15, it was confirmed that the change width of the bottom-lid temperature difference ΔT _BT increases as the pressure increases from the negative pressure to the atmospheric pressure.

Further, FIGS. 9, 10, and the result is used as shown in FIG. 11, the temperature difference ΔT _BS (= T _B -T _S the canister bottom temperature T _B and the canister side wall temperature T _S due to pressure changes; "bottom -Regarding the amount of change in (referred to as "side wall temperature difference ΔT _BS "), FIG. 16 (initial internal pressure: 0.8 atm), FIG. 17 (initial internal pressure: 0.5 atm), and FIG. 18 (initial internal pressure: 0.1 atm). The results shown in are obtained.

From the results shown in FIGS. 16, 17, and 18, it was confirmed that the change width of the bottom-side wall temperature difference ΔT _BS increases as the pressure increases from the negative pressure to the atmospheric pressure.

Regarding the results shown in FIGS. 9, 10, and 11, and FIGS. 16, 17, and 18, the bottom-side wall temperature difference ΔT _BS and the canister bottom temperature T are obtained according to the degree of negative pressure of the initial internal pressure of the canister model 54. The changes in _B and the canister lid temperature T _T were arranged and the results shown in FIG. 19 were obtained.

From the results shown in FIG. 19, regardless of the level of negative圧度initial internal pressure, the bottom - the variation width of the side wall temperature difference [Delta] T _BS is the largest, then it was confirmed that a large variation of the canister bottom temperature T _B.

From the results shown in Figure 19, also the negative圧度initial internal pressure is large (i.e., the initial pressure is low) as a bottom - side wall temperature difference [Delta] T _BS, canister bottom temperature T _B, and none of the canister lid temperature T _T It was confirmed that the range of change was large.

The temperature of the heating element 62 was measured before and after the in-leak, and the results shown in FIG. 20 were obtained for the temperature of the heating element 62 before the in-leak according to the degree of negative pressure of the initial internal pressure of the canister model 54. The results shown in FIG. 21 were obtained with respect to the degree of temperature rise of the heating element 62 (that is, when the internal pressure of the canister model 54 leaked from the initial internal pressure to 1 atm). Specifically, the temperature of the heating element 62 is the temperature at the center position in the vertical direction of the surface of the rod-shaped heater constituting the heating element 62.

From the results shown in FIG. 20, it was confirmed that the temperature of the heating element 62 before the in-leak hardly depended on the degree of negative pressure of the initial internal pressure.

Further, from the results shown in FIG. 21, it was confirmed that the temperature of the heating element 62 before and after the in-leak increases as the degree of negative pressure of the initial internal pressure increases (that is, the initial internal pressure decreases).

From the above results, when the initial internal pressure of the canister is negative, the sealing structure of the canister is impaired and in-leakage occurs, which causes the initial internal pressure to be negative, depending on the location of the canister. It was confirmed that a peculiar temperature change occurs.

Therefore, after making the initial internal pressure of the canister negative, the temperature related to the canister is observed, and the change in temperature at each location and the change in temperature difference at each location are monitored, based on the tendency and degree of change. It was confirmed that it is possible to determine whether the sealed structure of the canister is maintained or damaged, and to detect in-leakage in the canister.

1 Storage facility (concrete cask type)
2 Concrete cask 3 Concrete container 4 Canister (vertical posture)
5 Internal cooling Outside air 6 Air supply port 7 Exhaust port 8 Concrete lid 9 Support legs 10 Distribution space 11 Honeycomb structure partition (basket)
13A 1st temperature sensor 13B 2nd temperature sensor 13C 3rd temperature sensor 13E 5th temperature sensor that measures the air supply temperature at the air supply port 13F 6th temperature sensor 15 Canister seal loss detector 16 Control Part 16a Seal loss judgment part 17 Storage part 18 Interface 19 Display part 21 Storage equipment (concrete silo type)
22 Concrete silo 23 Concrete storage 24 Canister (horizontal position)
25 Internal cooling Outside air 26 Air supply port 27 Exhaust port 28 Concrete lid 29 Support stand 30 Distribution space 31 Honeycomb structure partition (basket)
33A 1st temperature sensor 33B 2nd temperature sensor 33C 3rd temperature sensor 33D 4th temperature sensor 33E 5th temperature sensor that measures the supply air temperature at the air supply port 35 Canister seal loss detector 36 Control Part 36a Seal loss judgment part 37 Storage part 38 Interface 39 Display part 51 Storage equipment model 52 Cask model 54 Canister model 55 Internal cooling outside air 56 Air supply port 57 Exhaust port 60 Flow space 61 Honeycomb structure partition (basket)
62 Heating element 64 Valve 101 Canister 102 Cask body 103 Air flow path 104 Cooling air 105 Air inlet 106 Air outlet

Claims (20)

In a method of detecting the loss of the sealing structure of a canister that is vertically stored in a concrete cask.
In the canister, an inert gas having a thermal conductivity higher than that of the outside air is sealed together with the spent fuel, and the internal pressure is negative.
Sealing of the canister, characterized in that it is determined that the sealing structure of the canister is impaired when at least one of the bottom temperature, the lid temperature and the side wall temperature of the canister changes beyond a predetermined threshold value. How to detect loss. When the bottom temperature and the lid temperature of the canister rise above a predetermined threshold value and the side wall temperature falls below a predetermined threshold value, it is determined that the sealing structure of the canister is impaired. The method for detecting a loss of sealing of a canister according to claim 1. When the temperature difference between the bottom temperature, the lid temperature, and the side wall temperature of the canister exceeds a predetermined threshold value, the sealing structure of the canister is impaired. The method for detecting a loss of sealing of a canister according to claim 1, wherein the determination is made. When the temperature difference between the bottom temperature of the canister and the temperature of the outside air taken into the concrete cask changes beyond a predetermined threshold value, it is determined that the sealing structure of the canister is impaired. The method for detecting a loss of sealing of a canister according to claim 1. When the temperature difference between the lid temperature of the canister and the internal temperature of the concrete lid of the concrete cask changes beyond a predetermined threshold value, it is determined that the sealing structure of the canister is impaired. The method for detecting a loss of sealing of a canister according to claim 1. When the heat flux calculated from the bottom temperature of the canister and the temperature of the outside air taken into the concrete cask or the estimated index temperature in the canister changes beyond a predetermined threshold, the sealing structure of the canister is impaired. The method for detecting a loss of sealing of a canister according to claim 1, wherein it is determined that the concrete has been removed. In a device that detects the loss of the sealing structure of a canister that is vertically stored in a concrete cask.
A canister in which an inert gas having a higher thermal conductivity than the outside air is sealed together with the spent fuel and the internal pressure is negative.
A temperature sensor that measures at least one of the canister bottom temperature, lid temperature, and side wall temperature, and
It has a seal loss determination unit that determines that the sealing structure of the canister is damaged when the measured value data from the temperature sensor is input and the input measured temperature value changes beyond a predetermined threshold value. A detection device for loss of seal in a canister. All measured values of the bottom temperature, the lid temperature and the side wall temperature of the canister are input from the temperature sensor to the seal loss determination unit, and the lid temperature and the side wall temperature of the canister set a predetermined threshold value. The canister seal loss detection device according to claim 7, wherein when the side wall temperature rises above and the side wall temperature falls below a predetermined threshold value, it is determined that the sealing structure of the canister is impaired. The temperature sensor inputs measured value data of at least two of the bottom temperature, the lid temperature, and the side wall temperature of the canister from the temperature sensor, and the temperature difference between the two temperatures is input to the seal loss determination unit. The canister seal loss detection device according to claim 7, wherein it is determined that the sealing structure of the canister is damaged when a change occurs in excess of a predetermined threshold value. Furthermore, it is equipped with a temperature sensor that measures the temperature of the outside air taken into the concrete cask.
The measured value data of the bottom temperature of the canister and the temperature of the outside air taken into the concrete cask is input to the sealing loss determination unit, and the difference between the bottom temperature of the canister and the temperature of the outside air is predetermined. The canister seal loss detection device according to claim 7, wherein it is determined that the sealing structure of the canister is impaired when a change occurs beyond the threshold value of. Further, it is equipped with a temperature sensor that measures the internal temperature of the concrete lid of the concrete cask.
The measured value data of the lid temperature of the canister and the internal temperature of the concrete lid is input to the seal loss determination unit, and is determined by the difference between the lid temperature of the canister and the internal temperature of the concrete lid. The canister seal loss detection device according to claim 7, wherein it is determined that the sealing structure of the canister is impaired when a change occurs beyond the threshold value of. Furthermore, it is equipped with a temperature sensor that measures the temperature of the outside air taken into the concrete cask.
The measured value data of the bottom temperature of the canister and the temperature of the outside air taken into the concrete cask is input to the sealing loss determination unit, and the bottom temperature of the canister and the outside air taken into the concrete cask are input. The canister according to claim 7, wherein when the heat flux calculated from the temperature or the estimated index temperature in the canister changes beyond a predetermined threshold, it is determined that the sealing structure of the canister is damaged. Seal loss detector. In a method of detecting the loss of the sealing structure of a canister that is horizontally stored in a concrete silo.
In the canister, an inert gas having a thermal conductivity higher than that of the outside air is sealed together with the spent fuel, and the internal pressure is negative.
When the bottom temperature of the canister, the lid temperature, the lower side wall temperature in the horizontal position, and the upper side temperature in the horizontal position change at least one temperature exceeding a predetermined threshold value, the canister A method for detecting a loss of sealing of a canister, which is characterized by determining that the sealing structure of the canister is damaged. When the bottom temperature and the side wall lower temperature of the canister rise above a predetermined threshold and the lid temperature and the side wall upper temperature fall above a predetermined threshold, the sealing structure of the canister is impaired. The method for detecting a loss of sealing of a canister according to claim 13, wherein a determination is made. When the temperature difference between any two temperatures of the bottom temperature, the lid temperature, the side wall lower temperature and the side wall upper temperature of the canister exceeds a predetermined threshold value, the canister The method for detecting a loss of sealing of a canister according to claim 13, wherein it is determined that the sealing structure has been damaged. In a device that detects the loss of the sealing structure of a canister that is stored horizontally in a concrete silo.
A canister in which an inert gas having a higher thermal conductivity than the outside air is sealed together with the spent fuel and the internal pressure is negative.
A temperature sensor that measures at least one of the bottom temperature of the canister, the lid temperature, the lower side wall temperature in the horizontal position, and the upper side wall temperature in the horizontal position.
When at least one temperature measurement value data from the temperature sensor is input and the input measurement temperature value changes beyond a predetermined threshold value, it is determined that the sealing structure of the canister is damaged. A detection device for loss of sealing of a canister, which comprises a determination unit. The temperature sensor inputs the measured value data of the bottom temperature, the lid temperature, the side wall lower temperature, and the side wall upper temperature from the temperature sensor, and the canister bottom temperature and the side wall lower part are input to the seal loss determination unit. The claim is characterized in that when the temperature rises beyond a predetermined threshold and the lid temperature and the side wall upper temperature fall below a predetermined threshold, it is determined that the sealing structure of the canister is impaired. 16. The canister loss detection device according to 16. The temperature sensor inputs measured value data of at least two of the bottom temperature, the lid temperature, the side wall lower temperature, and the side wall upper temperature from the temperature sensor, and the two temperatures are input to the seal loss determination unit. The device for detecting a loss of sealing of a canister according to claim 16, wherein it is determined that the sealing structure of the canister is impaired when the difference between the two is changed beyond a predetermined threshold. A canister comprising the detection device for loss of sealing of the canister according to any one of claims 7 to 12 and claims 16 to 18. A concrete storage facility comprising the canister according to claim 19.