JPS61198099A - Transport vessel for radioactive body - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to containers for transporting radioactive objects such as spent nuclear fuel.

(Prior Art) So-called spent fuel that has completed a prescribed combustion process in a nuclear reactor emits strong radiation (gamma rays, neutrons, etc.) and also generates considerable heat through decay.

Therefore, a container for transporting spent fuel, etc. must have a gamma ray and neutron shielding function as well as a heat dissipation function, and the container is provided with heat dissipation fins on its outer surface. However, it is expected that a fire may occur during the transportation of the container, and even in such a case, each shielding function must not be impaired. Polymer compounds containing a large amount of water and hydrogen atoms have excellent neutron blocking properties, and it has been proposed to provide a neutron blocking layer (body) made of a polymer material on the outer circumferential surface of the container.

On the other hand, it has also been proposed to form a neutron barrier layer by sealing an aqueous ethylene glycol solution between an inner shell and an outer shell in the container body.

(Problems to be Solved by the Invention) Among the conventional proposals, the former has the polymeric material of the neutron 1-yield layer located on the outer surface of the container, so it is easily exposed to the flame of a fire accident and the polymeric material is Due to the nature of the molecular material, there was a problem in maintaining the neutron blocking function.

Loading of spent fuel and other materials is carried out underwater and is susceptible to radioactive contamination, which is difficult to remove (decontamination).

Father, in the latter of the above proposals, the pressure in the aqueous solution layer of Tamago Rengelicol tends to become excessive due to heat input during a fire accident, and if a Lavture disk is used to prevent this overpressure, the aqueous solution may leak out. However, the neutron shielding function tends to deteriorate.

(Means and effects for solving the problems) The present invention has been made to solve the above-mentioned problems. A neutron barrier is formed between the intermediate shell and the outer shell, and internal fins are installed radially through the neutron barrier, and heat dissipation fins are protruded from the outer surface of the outer shell. It is characterized by the fact that

According to the present invention, gamma rays and neutrons are shielded by the gamma ray barrier between the inner shell and the intermediate shell and the neutron barrier between the intermediate shell and the outer shell, and the decay heat is transferred to the outside by the radiation fins. released into the air. In this way, the temperature inside the container is maintained properly, and the radiation level outside is also maintained properly.

Heat input in the event of an external fire is transmitted to the intermediate shell side through the internal fins, so the temperature rise in the neutron barrier layer is suppressed.

(Example) The present invention will be described below based on illustrated embodiments.

1 and 2, ring-shaped stainless steel heat dissipation fins 13 are provided on the outer peripheral surface of the outer shell 11 of the container body 10.
is protruded, and furthermore, tranios 715a and 15b for handling are provided.
115CS15d is provided.

The intermediate barrel 19 fixed to the bottom of the outer barrel 11 via a support ring 17 has a disk-shaped bottom plate 21. The intermediate shell 19 extends to the same length as the outer shell 11, and a neutron barrier body (hereinafter referred to as silicone rubber) 23 filled with silicone rubber is formed between them.

A large number of internal copper fins 25 pass through the silicone rubber 23.
is installed between the inner surface of the outer shell 11 and the outer surface of the intermediate shell 19. The internal fins 25 transmit decay heat generated from the spent fuel, which will be described later, to the outside, and the radiation fins 13 further transmit it to the outside atmosphere.

A stainless steel inner body 29 having a bottom plate 27 separated from the bottom plate 21 is surrounded by a lead layer 31 which is a gamma ray shield.
A space or cavity 33 is defined inside to accommodate spent fuel, which is a radioactive substance.

The upper ends of the inner shell 29 and the intermediate shell 19 are connected by a thick ring 35, to which trunnions 37a, 37b are attached, and an outer shell support ring 39 is also fixed.

The ring 35 of the container body 10 defines a cavity 33, which is closed with a lid 40. 36 is a vent valve, 38 is a drain valve, and a thermal bridge 34 is provided on the inner surface of the intermediate body 19 to protrude into the lead layer 31 to promote heat transfer.

3 and 4 show a cross section and a front view of the lid 40, and the lid 40 has a main body 41 made of stainless steel and a rubber
Ring 438N43b and plug 44a, 44
It consists of O-rings 45a and 45b for the same plug. Reference numeral 42 is a hole for inserting a tightening bolt. The outer periphery of the lid 40 is surrounded by a reinforcing ring 51, and when transported on a trailer, an upper buffer 53 and a lower buffer 55 are attached with bolts or the like. These buffer bodies 53 and 55 absorb impact force and protect the container body 10 etc. when the container body 10 or the like is accidentally dropped.

Next, the structure of the storage can 60 placed in the cavity 33 will be explained with reference to FIG.

The storage can 60 shown here stores the leaked spent fuel S.
The can body 61 is made of stainless steel.
, a can lid 62, an upper inner spacer 63, a lower inner can spacer 64, a lower spacer 65, a lower can spacer 66, and water supply and drainage pipes 67a and 67b. The inner can upper spacer 63 is attached to the can lid 62, and the lower part spacer 65 is attached to the lid 40.
The can lower spacers 66 are each fixed to the can body 61 with bolts. The water supply and drainage pipes 678N67b are welded to both ends of the can body 61. Moreover, the can lid 62 includes a main body 62a, an O-ring 62b1, as shown in FIGS. 6, 7, and 8.
Pulp 62C162d, 62e, plug 62g, O-ring 62h, 62i for plug 62g, and hanging handle 6
Consists of 2 j. The inner valves 62C to 62e, the plug 62g, and the hanging handle 62j are welded to the main body 62a. Further, the fuel rod spacer 70 is used to maintain a regular arrangement of the fuel rods when the spent nuclear fuel is stored in the fuel storage container in units of fuel rods.

Next, a procedure for storing the leaked spent fuel S will be explained.

With the upper buffer body 53 not attached and the lid 40 removed, the fuel S is stored in the storage can 60 with the can lid 62 removed inside the container body 10 held vertically, and then, The main body 62 a incorporating the O-rings 62 b, 62 h, and 62 r is fixed to the upper surface of the can main body 61 with a can lid tightening bolt, thereby maintaining the sealing performance of the storage can 60. Confirm the sealing property by using an air valve test (K) that pressurizes the inside of the storage can 60 using the valve 62d.

In addition, replacing the water in the storage can 60 and adjusting the water level are performed using the valve 62.
This is done using C, 62d, and 62e. Valve 62C
, 62e is connected to the water supply and drainage pipe 67a via the plug 62g.
, 67b.

Next, the main body 41 incorporating the O-rings 43a and 43b is fixed to the ring 35 on the upper surface of the container main body 10 with a lid tightening bolt, thereby maintaining the sealing performance of the container main body 10. The sealability of the container body 10 is confirmed by a vacuum leak test using a plug, vent valve 36, and drain valve 38.

Gamma rays emitted from the fuel S are shielded by the lead layer 31, and similarly emitted neutrons are somewhat shielded by water inside and outside the storage can 60, and are mainly shielded by the silicone rubber 23.
be shielded by

The heat emitted from the fuel S is transferred to the water in the storage can 60, the can body 61, the water in the cavity 33, the inner shell 29, the lead layer 31, and the intermediate shell 19.
, the inner fins 25, and the outer shell 11 in this order, and then to the heat radiation fins 13, and then to the outside atmosphere.

Heat is transferred from the lead layer 31 to the intermediate shell 19 fairly well due to the provision of a thermal bridge 34, and the silicone rubber 23 does not become an obstacle to heat transfer.

In addition, if an external fire occurs during transport on the road,
Heat is transferred inward in the opposite direction of the heat transfer path described above.

(Effects of the Invention) According to the present invention, since the internal fins promote heat transfer through the neutron shield, excessive temperature rise of the neutron shield can be suppressed and the shield function can be maintained at all times. In addition, the neutron shielding body is located inside the outer shell, so it is not directly exposed to external fire and is not burned out by heat. The thermal bridge also promotes heat transfer between the lead layer and the intermediate shell, and can maintain a low internal temperature.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a sectional view taken along the n-IT line in FIG. 1, FIG. 3 is a partially enlarged view of FIG. 1, and FIG. Front view corresponding to Figure 5, Figure 1
The partial views of FIG. 6, FIG. 7, and FIG. 8 are partially enlarged views of FIG. 5, respectively. 10. Container body, 11. Outer shell, 13. Radiation fins, 19. Intermediate shell, 23. Silicone rubber, 25. Inner fins, 40. Lid No. 27 Fig. 4 Fig. 3

Claims (1)

[Claims] An inner shell, an intermediate shell, and an outer shell arranged substantially coaxially, a gamma ray shield formed between the inner shell and the intermediate shell, and a neutron shield formed between the intermediate shell and the outer shell. The container body is composed of a body and a large number of heat dissipating fins protruding from the outer peripheral surface of the outer shell, and the storage space in the inner shell is closed by a lid that is attached to and detached from one end surface of the main body, in which the neutron A transport container for radioactive materials, characterized in that a large number of internal fins are installed between the intermediate shell and the outer shell by penetrating the shield body in the radial direction.