JP2590164B2 - Spent fuel storage device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for enclosing fuel used in a nuclear reactor such as a nuclear power plant, shielding radiation, and storing the same.

[Prior Art] FIGS. 4 and 5 show examples of the prior art. FIG. 4 is a perspective sectional view of a shielding module formed of concrete for accommodating a canister filled with spent fuel, and FIG. 5 is the above shielding module. 3 is a longitudinal sectional view of a portion including the canister of FIG. 4 and 5, reference numeral 51 denotes a shielding module, 52 denotes a shielding plate, 53 denotes a canister, 55 denotes an air inlet for cooling, and 56 denotes an air outlet for cooling. At first, water pools were the main method of storing fuel used in nuclear reactors.However, due to the large initial investment costs and the high cost of water-cooling-related ordinary expenses, special methods for storing fuel were subsequently used. A method of storing a steel cask for transportation without a cooling system has been considered.

However, the storage method using a steel cask for transportation requires an auxiliary shielding device to shield gamma rays and neutrons from spent fuel in the storage building, or a large number of expensive steel casks are required. Problems such as an increase in cost have occurred. 4th-5th
The figure shows a storage method using a conventional shielding module 51 manufactured to address these problems.

The spent fuel taken out of the reactor is stored in a canister 53 provided in a transport cask in a reactor fuel pool facility, and is carried out with a radiation shield attached as necessary. The carried out canister 53 is dehydrated and dried after the blind plate is attached by welding, and further filled with an inert gas to maintain the airtightness. The canister 53 whose storage state has been completed by the above procedure is attached with a cask lid in a state of being stored in the transport cask, and is carried into the spent fuel storage by a trailer.

A shielding module 51 made of concrete having the structure shown in FIGS. 4 and 5 is previously provided in the fuel storage. After the loaded canister 53 is positioned in front of the shielding module 51, the insertion device causes the shielding module to be positioned.
The shielding plate 52 is inserted into the inside of 51 and sealed.

Since the spent fuel removed from the reactor generates heat for a long period of time, if the heat removal is insufficient, an increase in temperature may cause damage to the radiation sealing mechanism or damage to the spent fuel itself, which may lead to accidents. There is. Therefore, maintaining the heat removal capability is the most important matter in ensuring the safety of the storage device.

FIGS. 4 and 5 show an example in which the canister is cooled by natural circulation of air. The shielding module accommodating the canister 53 is made of concrete, and has a cooling air inflow hole 55 formed at the lower part of the front wall. A buffer room made of concrete is formed at an opening of the air inlet 55 in the shielding module 51. An outflow hole for air is formed in the peripheral wall of the buffer chamber, so that the cooling air that has flowed in from the air inflow hole 55 can freely flow into a space formed below the spent fuel storage space, and Is formed in a maze shape to prevent radiation in the spent fuel storage space from leaking outside.

The cooling air flowing from the air inlet 55 enters the buffer chamber, enters the lower part of the fuel storage space via the inlet formed in the peripheral wall of the buffer chamber, and is inserted into the upper part of the fuel storage space. After passing around 53, the shielding module
The air flows out from an air outflow hole 56 formed at the upper part of 51.

Since the spent fuel in the canister 53 taken out of the reactor, carried in, and inserted generates decay heat over a long period of time, the temperature inside the canister is about 400 ° C, and the temperature on the outer wall of the canister is about 200 ° C. It is rising. Therefore, the cooling air that has flowed into the fuel storage space rises in temperature by contacting the canister, decreases in specific gravity, rises, and flows out of the upper air outlet 56 to the outside.

Thus, even in the storage device for spent fuel by the conventional shielding module formed of concrete,
The canister containing the spent fuel is stored, shields radiation, and contacts the canister by forming cooling air inlet and outlet holes at the lower and upper parts of the shielding module to form air flow passages. Due to the generation of an ascending air current accompanying an increase in the temperature of the air, it was possible to remove heat from the canister and the spent fuel sealed in the canister by natural circulation of the air.

[Problems to be Solved by the Invention] However, in the shield module for storing spent fuel formed by the above-mentioned conventional concrete, an inlet for cooling air and an internal buffer chamber are inside the shield module. As a result, the structure of the shielding module becomes complicated, which increases the number of manufacturing steps and makes it difficult to inspect products to ensure safety.
It was difficult to contact the upper canister at a uniform flow rate and flow rate, and there was a problem that the canister was not cooled uniformly.

In addition, since the inner surface of the shielding module comes into contact with the radiant heat from the outer wall of the canister and the cooling air that has been heated by contacting the canister, the temperature of the concrete increases, and the soundness of the concrete may be impaired. Was.

[Means for Solving the Problems] The above problems are solved by the spent fuel storage device described in the claims. (1) It is made of concrete, has an internal space for storing spent fuel inside, has an opening that can be closed by a shielding plug at the front, and connects the internal space and the outside at the top. A shield module for storing spent fuel having a plurality of cooling air outflow holes communicating with each other, and an open space communicating with the cooling air inflow hole at a lower part, and a concrete module pad for supporting and mounting the shielding module. Has a cooling air inflow hole opening in the storage, a cooling air outflow hole opening in the shielding module internal space, and a cooling air flow passage communicating the cooling air inflow hole and the cooling air outflow hole. Before the shielding module is constructed, the upper part is opened and formed and the cooling air flow passage is formed with a radiation shielding barrier part. The structure of the concrete module pad and the shielding module can be simplified by dispersing and sharing the functions of shielding radiation and equalizing the flow rate of cooling air to the heating element. Spent fuel storage device.

(2) Between the position of the inner surface of the shielding module facing the side of the spent fuel canister and the outlet of the cooling air outflow hole, it comes into contact with the storage container for storing the spent fuel canister, and A heat-shielding separator is provided to prevent the cooling air having the raised height from directly contacting the inner wall of the shielding module, and to prevent the inner wall of the shielding module from directly receiving the radiant heat from the outer surface of the high temperature storage container. (1) The spent fuel storage device according to (1), wherein low-temperature cooling air before contacting with the storage container and raising the temperature is allowed to flow between the module and the separator.

[Operation] A shielding module made of concrete for storing spent nuclear fuel (hereinafter simply referred to as a concrete module) is replaced with a preformed concrete module pad (hereinafter simply referred to as a concrete pad). ). The concrete module has a space for storing the canister filled with spent fuel inside, the canister loading opening at the front can be closed by a shielding plug, and the canister storage space and the outside can be closed at the top. And a plurality of cooling air outflow holes communicating with the cooling air inflow holes.

In the concrete pad made of concrete in which the concrete module is disposed, a cooling air inflow hole that opens into a storage and a cooling air flow passage that communicates the internal open space of the concrete module are formed. A maze-shaped barrier made of concrete is formed inside the cooling air flow section of the concrete pad to prevent radiation from the canister filled with spent fuel from leaking to the outside. The cooling air flow passage in the concrete pad is formed in an open state.

Therefore, in the spent fuel storage device using the concrete module, the concrete pad is manufactured in advance when the upper part is in an open state, and since the structure is simple, the cost can be reduced, and the inspection of the main part can be performed. It can be easily and completely implemented, and it can be said that the cooling air flow passage in the concrete pad and the open space under the concrete module have a simple structure without any obstacles, so that canister cooling air can be uniformly supplied. Has advantages.

In addition, between the inside of the concrete module, which faces the horizontal side of the spent fuel canister, and the outlet of the cooling air outlet, it contacts the storage container that contains the spent fuel canister, and the temperature rises. A heat shielding separator is arranged to prevent the cooling air having the raised height from directly contacting the inner wall of the shielding module and to prevent radiant heat from the outer surface of the storage container, and the separator between the inner surface of the concrete module and the separator is provided. By allowing low-temperature cooling air to flow freely before contacting the storage container during heating, the inner surface of the concrete module comes into contact with the radiant heat from the outer wall of the canister and the cooling air heated by contacting the canister. This prevents the concrete temperature from rising and impairing the soundness of the concrete.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an internal space for storing spent fuel, a cooling air outlet hole communicating the space with the outside, and an open space communicating with the cooling air inlet hole at the bottom according to the present invention. FIG. 2 is a longitudinal sectional view of a concrete module for storing spent fuel and a concrete pad for fixing the concrete module, FIG. 2 is a sectional view taken along line aa of FIG. 1, and FIG. 3 is a concrete module and concrete. FIG. 3 is a conceptual diagram illustrating a temperature distribution of each part of a pad. 1 to 3, 1 is a concrete module, 2 is a shielding plug, 3 is a canister, 4 is a storage container, 5 is an air inlet, 6 is an air outlet, 7 is a used fuel assembly, 8 is a separator. , 9 are concrete pads.

The spent fuel taken out of the reactor is stored in a canister 3 installed in a transport cask in a reactor fuel pool facility, and is carried out with a radiation shield attached as necessary. The carried-out canister 3 is dehydrated and dried after the blind plate is attached by welding, and further filled with an inert gas to maintain the airtightness. The canister 3 whose storage state has been completed by the above procedure is attached with a cask lid in a state of being stored in the transport cask, and is carried into the spent fuel storage by a trailer.

A concrete module 1 having the structure shown in FIGS. 1 to 3 is installed in the fuel storage in advance. After the loaded canister 3 is positioned in front of the concrete module 1, it is inserted into a metal plate-made canister storage container 4 previously installed in the concrete module at a predetermined interval from the inner wall of the concrete module. . After insertion of the canister, a sealing lid is attached to the storage container 4 by welding or bolts, the inside of the storage container 4 is evacuated, and an inert gas is injected into the vacuum portion to seal the container. Thereafter, the shielding plug 2 is installed at the entrance, and the storage operation is completed.

Since the spent fuel removed from the reactor generates heat for a long period of time, if the heat removal is insufficient, an increase in temperature may cause damage to the radiation sealing mechanism or damage to the spent fuel itself. There is. Therefore, maintaining the heat removal capability is the most important matter in ensuring the safety of the storage device. FIGS. 1 to 3 show examples of cooling of the spent fuel canister 3 housed in the concrete module by natural circulation of air.

The air flowing from the cooling air inflow hole 5 formed in the concrete pad 9 passes through a maze-shaped barrier portion for preventing radiation leakage at the entrance portion of the concrete pad 9, and the cooling air formed upward in an open state. Enter the flow passage. A concrete module 1 for housing the canister 3 is provided above the concrete pad.

The concrete module 1 has a space for accommodating a canister 3 in which a spent fuel assembly 7 is sealed, and a front opening of the canister 3 for carrying in the canister 3 is a shielding plug 2.
The upper part has a plurality of air outlets communicating with the space of the canister 3 and the outside, and the lower part has an open space communicating with the cooling air inlet.

The cooling air that has flowed into the open cooling air flow passage of the concrete pad 9 diffuses in the upper open space, contacts the outer wall of the storage container 4 that surrounds the canister 3 at a uniform speed, and exchanges heat. To lower the temperature of the outer wall of the storage container 4, the cooling air itself rises in temperature to reduce the specific gravity, and naturally rises, and flows out of the upper air outflow hole 6.

When the inner wall of the concrete module 1 receives the radiant heat from the high-temperature canister in which the spent fuel is filled, in addition to the contact with the cooling air whose temperature has increased, the temperature of the concrete may increase, and the deterioration may occur. is there.

In order to prevent this, in the present invention, as shown in FIGS. 2 and 3, the cooling air outflow hole is formed on the inner surface of the concrete module 1 from the peripheral wall of the canister 3 housing portion located on the horizontal side of the spent fuel canister 3. A separator 8 is provided at a predetermined distance from the peripheral wall over the entire surface up to the outlet end of the concrete module 1, and a concrete pad 9 is provided between the provided separator 8 and the inner wall of the concrete module 1.
And the low-temperature air before contacting the storage container 4 and raising the temperature can flow.

This prevents the inner wall of the concrete module 1 from coming into contact with the cooling air whose temperature has risen, thereby preventing the temperature from rising. In addition, the concrete module 1 receives the radiant heat from the outer surface of the storage container 4 that stores the canister 3 in which the spent fuel is filled, and This prevents the soundness of the module 1 from being impaired.

FIG. 3 is a structural conceptual diagram showing the temperature distribution of each part of the concrete module 1 and the concrete pad 9 when the above-mentioned separator 8 is provided. In FIG. 3, t ₁ is the maximum temperature of the center of the spent fuel assembly, t ₂ is the maximum temperature of the trunk of the canister 3, t ₃ is the maximum temperature of the trunk of the storage container 4, and t ₄ is the maximum temperature of the concrete pad inlet. Cooling air temperature,
t ₅ is the cooling air temperature of the cooling air outflow portion of the concrete module, t ₆ the cooling air temperature, t ₇ flowing out from the gap between the inner wall and the separator 8 of the concrete module 1 is the highest portion temperature of the concrete module 1.

In this embodiment, when t = 400 ° C. and t ₄ = 35 ° C., t ₂
= 190 ° C., t ₃ = 140 ° C., t ₅ = 70 ° C., t ₆ <70 ° C., t ₇ <70 ° C., and the concrete module 1 can always maintain a safe temperature.

[Effects of the Invention] As is apparent from the above embodiment, the present invention, when constructing a concrete module for storing spent fuel in a nuclear reactor spent fuel storage, first requires radiation shielding together with the concrete module. A concrete pad that distributes and distributes the function of equalizing the flow rate of cooling air to the heating element will be constructed.

The concrete pad has a cooling air inflow opening that opens into the storage, a cooling air flow passage that communicates with the interior space of the concrete module in an open state, and a maze-shaped radiation leakage prevention barrier is provided in the cooling air flow passage. It has a very simple structure.

Since the construction of the concrete pad is performed before the concrete module is constructed above, the production is extremely easy, and each part can be sufficiently inspected and the production cost can be reduced. .

The concrete module constructed on the concrete pad has an internal space for storing spent fuel in a central part, a cooling air outflow hole communicating the internal space with the outside at an upper part, and a lower part at a lower part. Has an open space leading to a cooling air flow passage formed in the concrete pad,
It is constructed on a pre-constructed concrete pad as a foundation.

Since the concrete module has a simple structure, the production cost can be kept low, and the inspection of the main part at the time of production can be made easy and complete. In addition, since the lower part of the concrete module is an open space having a sufficient volume, there is an effect that cooling air can be uniformly flowed into the spent fuel storage portion and cooling can be efficiently performed.

In addition, a separator disposed between the position facing the horizontal side of the spent fuel canister and the outlet of the cooling air outlet hole on the inner surface of the concrete module, and a storage container containing the spent fuel canister, The cooling air whose temperature has been increased by contact is prevented from directly contacting the inner wall of the shielding module and is not radiated from the outer surface of the storage container, thereby preventing the inner surface integrity of the concrete module from being impaired. It becomes possible.

In addition, since the module has a simple structure as described above, a large number of shielding modules can be provided at once, or can be added sequentially, and the installation work is easy.

Furthermore, it is also possible to prefabricate the concrete pads and concrete modules and to carry the concrete pads and concrete modules manufactured efficiently and accurately at the factory to the site and install them, which can further facilitate the construction of the storage facility. . In addition, by manufacturing concrete pads and concrete modules in a factory, manufacturing costs can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 3 show an embodiment of the present invention, and FIG. 1 shows a longitudinal section of a storage container, a concrete module and a concrete pad in a state in which a canister filled with spent nuclear fuel is stored. FIG. 2 is a sectional view taken along line aa in FIG. 1, and FIG. 3 is a conceptual diagram showing the temperature distribution of each part of the concrete module and concrete pad. 4 and 5 show examples of the prior art. 1 ... concrete module, 2 ... shielding plug, 3
... Canister, 4 ... Storage container, 5 ... Air inlet hole, 6 ... Air outlet hole, 7 ... Fuel assembly, 8 ... Separator, 9 ... Concrete pad, 51 ...
Shield module, 52… Shield plate, 53… Canister, 55… Air inlet,
56 ... Air outlet.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihisa Tanaka 2-4-2, Minamisuna, Koto-ku, Tokyo Kawasaki Heavy Industries, Ltd. Tokyo Design Office (56) References JP-A-58-63895 (JP, A) JP-A-61-17996 (JP, A) JP-A-63-30791 (JP, A) JP-A-62-147000 (JP, U)

Claims (2)

(57) [Claims] 1. An interior space for storing spent fuel, which is formed of concrete, an opening which can be closed by a shielding plug at a front portion, and the interior space and the outside at an upper portion. A shield module for spent fuel storage having a plurality of cooling air outlet holes communicating with each other and an open space below the cooling air inlet hole, and a concrete module pad for supporting and mounting the shielding module, Has a cooling air inflow opening opening in the storage, a cooling air outflow opening opening in the shielding module internal space, and a cooling air flow passage communicating the cooling air inflow opening and the cooling air outflow opening. Before the installation of the shielding module, the upper part is opened and formed, and a barrier part for radiation shielding is formed in the cooling air flow passage. The structure of the concrete module pad and the shielding module is simplified by dispersing and sharing the functions of shielding radiation and equalizing the flow rate of cooling air to the heating element.
A spent fuel storage device, which can be separately constructed and sequentially constructed. 2. A storage container for accommodating a spent fuel-filled canister between an inner surface of the shielding module and a position facing the side of the spent fuel-filled canister to an outlet of a cooling air outlet. A heat shielding separator is provided to prevent the cooling air, whose temperature has been raised, from coming into direct contact with the inner wall of the shielding module, and to prevent the inner wall of the shielding module from directly receiving radiant heat from the outer surface of the high-temperature storage container. The spent fuel storage device according to claim 1, wherein the low-temperature cooling air before the temperature rises by contacting the storage container between the shielding module and the separator is made freely.