JPS60230095A - Housing device for cask - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a container for storing nuclear fuel, and particularly to an apparatus for further storing a container for storing spent nuclear fuel.

Nuclear power plants produce spent nuclear fuel, which contains a large amount of so-called "dead ash" that emits strong radiation. In addition, this spent nuclear fuel also spreads high heat, so unless some measure is taken, the container containing the spent nuclear fuel will become extremely hot and extremely dangerous.

On the other hand, this spent nuclear fuel contains unburned uranium-235.
Since uranium-238 contains plutonium-239, which is produced by absorbing neutrons in the reactor, the newly produced plutonium is recovered and reprocessed.

For this reason, spent nuclear fuel is stored in special containers (casks) in order to safely and reliably transport it from nuclear power plants to reprocessing plants.

Figure 1 shows the structure of this cask. [Symbol in the figure] indicates the main body of the cask, which is a large one with a length of 5m to 6m, and caps 2 on both ends that also function to absorb shock.
and 3 are attached, and a large number of fins 4 for 1Lt release are formed on the outer cylinder 8 of the body part other than the cap attachment part. 5 is an inner cylinder, and a fuel basket 7 having a fuel assembly 6 is disposed inside the inner cylinder 5, and water is injected into this part. 9 is a lead shield, and 10 is a lid.

The cask with the above structure is tightly sealed to prevent radioactivity from leaking outside, and the container itself is so strong that it can be dropped onto concrete from a height of several meters without causing any problems. There is. For this reason, the cask is extremely large and heavy compared to its internal storage capacity, weighing approximately 75 tons. Such casks are transported to their destinations by heavy goods transport vehicles or ships, and as mentioned above, casks have extremely strict and strong construction in preparation for accidents.

However, in the unlikely event that an accident occurs, it is inevitable that it will have a major impact on the environment. That is, (1) If the seal of the cask is damaged or the valve malfunctions, contaminated water with high concentration of radioactivity inside the cask will flow out.

(2) Since the inside of the cask is at a high temperature due to the heat generated by the spent fuel, contaminated water leaks and contaminated steam is released into the atmosphere, raising the risk of internal radiation exposure to humans.

(3) It is conceivable that a fire may occur due to a car collision during transport of the cask, but in such a case, delays in extinguishing the fire could rapidly worsen the situation.

In consideration of the above points, a method has been considered in which the cask is further accommodated in a container and transported in order to prevent damage due to impact during transportation and to prevent rust from forming on the cask.

However, this container merely houses the cask, and in most cases it will not be used if the cask is damaged or if there is a major threat to it, such as by fire.
I was helpless.

This invention was constructed in view of the above-mentioned problems,
It is an object of the present invention to provide a container that safely and reliably accommodates not only used fuel but also unused fuel.

In short, this invention installs devices such as water leakage detectors and neutron detectors inside the container to detect accidents caused by damage to the cask, as well as devices that can safely hold the cask against external threats such as fire. be.

Examples of the present invention will be described below.

In Figures 2 to 4, 11 is a main body of a cask storage device (container) that houses the cask 1, and the casters are disposed diagonally at a certain angle inside the container 1, and are made to move outward by convection of water inside the container. This is to ensure effective heat transfer. The storage capacity of water in the cask is approximately 1.5 m8 in the case of spent fuel of a pressurized water reactor (PWR), and approximately 2.1 m3 in the case of a boiling water reactor (BWR). . Reference numeral 12 denotes a tray disposed at the bottom of the container body, and in the event that contaminated water leaks from the cask, the tray accommodates the contaminated water and prevents it from flowing outside.

Reference numeral 13 denotes a water leakage detector installed in this tray, and is configured so that, for example, a circuit is activated when it comes into contact with water leakage, and a signal is sent to the alarm 14. In this case, it is preferable to install the water leakage detector at the lowest part of the tray so that water leakage can be detected as soon as possible.

Reference numeral 15 denotes a fire extinguishing agent tank, and a flame detector (not shown) installed inside and outside the container opens the valve of the N' cylinder in the tank, and the gas pressure causes the foam extinguisher 1 to be fired through the nozzle 16.
Inject from. In this case, it is more effective to apply a foaming resin to the surface of the container body 1. This resin foams due to the heat of the flame and forms a heat insulating layer, which prevents the transfer of heat. For example, if it is applied to the container surface to a thickness of 8 mm, the flame will spread it to about 40 mm. It expands and serves as a heat insulator. According to experiments conducted by the inventors, a cask coated with resin to this thickness has passed a fire resistance test at 800° C. for 30 minutes.

Reference numeral 17 denotes a blower, which directs heat dissipated from the cask by a drive device (for example, a small gasoline engine) 18 to an exhaust port 19. , e't:. 20
is a generator, which is driven by a drive device 18, charges a battery (not shown), and supplies electricity to each device inside the container. Further, in the event that the drive device 18 stops, the generator may be operated as a motor from an external power source to continue operating the blower. Further, it will be safer if a means is provided to transmit the decrease in fuel in the drive device to the outside.

21 is a gamma ray detector, 22 is a neutron detector, and both detectors constantly input the detection results to the recording device 23, and if an amount exceeding a set value is detected, a signal is sent to the alarm device 14. to issue a warning. In this case, the reason why both detectors are placed above cask 1, which is arranged diagonally, is that air bubbles (voids) generated in the water inside the cask will concentrate in this area, reducing the shielding effect and reducing the radiation dose. This is because it becomes the largest.

A temperature detector 24 is attached to the outside of the cask, detects the humidity on the outside of the cask, constantly inputs the detection results to the recording device 23, and also sends an alarm to the alarm device 14 when the temperature exceeds a set value. It sends a signal and issues an alarm. As the temperature sensor, a thermocouple such as a Kromel-Hunstankun is suitable.

Reference numeral 25 denotes a shielding tank formed on the container ceiling surface, that is, the upper part of the cask arrangement part.In order to enhance the shielding effect, it is preferable to form it into a substantially saddle shape so as to partially cover the upper surface of the cask (see Fig. 4). ). For this reason, the entire container is also formed into a kamabot shape as shown in FIG. Shield tank 25
A radiation shielding material, such as a mixture of boron water and antifreeze (to prevent freezing in winter), is injected into the inside.

In addition, in this case, a meltdown section 27 made of a material that melts at a preset temperature is formed on a part of the ceiling surface 26 that forms the bottom of the tank, and the cask surface temperature becomes abnormal due to a fire or the like. If it rises to , this meltdown part 2'! The material melts down and sprays shielding water onto the cask surface. When this tank is formed and the tank thickness is 600 mm, γ rays are attenuated to about - and neutrons are attenuated to about I AOo, 0000. Further, the weight of the shielding water in this case is approximately 11 tons.

Next, in FIGS. 3 and 4, an air intake port 28 is formed at the bottom of the container l, through which air is exhausted and taken in by the aforementioned blower. Further, doors 29 and 30 are attached to these exhaust ports and intake ports, respectively, so that they can be sealed in case of an accident or when transporting an empty cask. 31 is an opening/closing lever for the door 29. 32 is a meter panel that can monitor the radiation dose, cask temperature, etc. from the outside of the container; 33 is a hook retaining fitting that is attached with consideration to hanging the container.

Note that when transporting empty casks, there is no need to consider heat dissipation, so the door is sealed as described above to protect the casks from rain, snow, and salt. In this case, it is more effective to place a cartridge type desiccant 40 in the container. For example, if the desiccant is silica gel, 15 kg of this silica gel is effective for approximately 6 months.

FIG. 5 shows another embodiment of the invention. In the case of this embodiment, skirt portions 34 are attached to both sides of the upper end of the container 11 in the longitudinal direction, so that the container can be easily moved and unloaded by a transport vehicle 35 whose loading platform can be raised and lowered. In other words, the loading platform 3 is moved by the hydraulic jack 37 or the like.
After lowering the transport vehicle 6 to the position 36 and placing it in the space below the container 11, the loading platform 36 of the transport vehicle is raised to support the load of the container and transport the container to a predetermined location. Place the containers in the opposite order as above. With this configuration, there is no need to suspend the container with a crane for loading and unloading onto the transport vehicle.

Although the present invention has been described above using the case of transporting spent nuclear fuel as an example, it is not limited thereto, and can also be effectively used for storing containers for transporting unused nuclear fuel.

By implementing this invention, containers for storing spent nuclear fuel, etc. can be transported safely and reliably.

Can be stored.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of a cask for storing spent fuel, FIG. 2 is a vertical sectional view showing the internal structure of a cask storage device according to the present invention, and FIG. 3 is a perspective view of the cask storage device. FIG. 4 is a front view of the cask storage device, and FIG. 5 is a front view of the cask storage device showing another embodiment. 1... Cask 11... Cask accommodation device 13... Water leak detector 15... Fire extinguishing agent tank 16... Nozzle 17... ...Blower 1
8... Drive device 20... Generator 21
... R-ray detector 22 ... Neutron detector 24 ... Temperature detector 25 ... Shielding tank 27 ... Meltdown section 34 ...Skirt part 35 ...Transportation vehicle 3rd
Figure 11 Fourth cause Figure 5

Claims (1)

[Scope of Claims] 1. A water leakage detector that houses a cask for storing spent nuclear fuel, etc., and has a heat exhaust device that discharges heat emitted from the cask to the outside. A cask storage device characterized by being equipped with at least one of a gamma ray detector, a neutron detector, a cask temperature detector, and a fire extinguishing device. 2. The cask storage device according to claim 1, characterized in that a shielding tank injected with a radiation-shielding material is formed on the ceiling of the storage device above the cask arrangement portion. 3. A meltdown section made of a material that melts at a predetermined temperature is formed in the shielding tank, and when the cask temperature rises above the set value, radiation is shielded from the cask through the meltdown section. Configured to spray material lf-, jl-? A cask storage device described by the Momoshima Tonas Softsha Packer for mine fence scraps. 4. The cask storage device according to claim 2, wherein the shielding tank is formed into a substantially saddle shape so as to cover a part of the cask. 5. The cask housing device according to claim 2, wherein the radiation shielding material is boron water or boron water to which antifreeze is added. 6. The cask storage device according to claim 1, wherein at least one of the outer surface and the inner surface of the device is coated with a material that foams under high heat to form a heat insulating layer. 7. A skirt portion is formed at the lower end of the device, so that the device body can be easily transported and installed by combining it with a carrier that moves up and down the loading platform. cask storage equipment. 8. The cask storage according to claim 1, wherein the fire extinguishing device includes a fire extinguishing agent tank that discharges a fire extinguishing agent at a predetermined temperature, and fire extinguishing agent injection nozzles arranged at a plurality of locations within the device. Device. 9. The cask according to claim 1, wherein at least one of the gamma ray detector and the neutron detector is disposed near a portion of the obliquely disposed cask where voids are concentrated. Containment device. ], 0. The heat exhaust device consists of a drive device and a blower operated by this drive device, and a generator is attached to this drive device to supply power to each device.When the drive device is stopped, the generator is turned on by an external power source. The cask storage device according to claim 1, characterized in that the cask storage device is configured so that the drive device can continue the heat exhausting operation.