JP2001147295A - Radiation attenuation facility - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure security of workers outside the radiation control zone and surrounding public even for the case of rare accidents discharging radiation such as neutron and gamma ray by applying the facility to ones treating radioactive materials and ensure practicality by facilitating maintenance for confirming the radiation shielding function and suppressing the cost low. SOLUTION: In a zone protected from radiation source or radiation, a radiation protection wall is arranged. The radiation protection wall is desirably constituted by filling water inside a casing and so any horizontal direction can be seen through directly and free passing is maintained. A function attenuating exposure dose at the outside below an allowed level is given for the case of discharge of radiation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation attenuating facility, and more particularly to a preferable technique for preventing radiation exposure in the event of a radiation emission accident.

[0002]

2. Description of the Related Art The following techniques are known as related techniques for attenuating radiation. (A) Technical Example 1: Japanese Patent Application Laid-Open No. 10-300880, "Nuclear Power Plant and Radioactive Waste Treatment Facility with Radiation Shielding Outer Wall" (B) Technical Example 2: Japanese Patent Application Laid-Open No. 10-221489, "Radiation Shielding Facility" (C) Technical Example 3: Japanese Patent Application Laid-Open No. H10-121777, "Radiation Shielding Outer Wall and Construction Method" (D) Technical Example 4: Japanese Patent Application Laid-Open No. H06-294895, "Radiation shielding structure""

[0003] Technical example 1 is a technique in which the outer periphery of a nuclear power plant is surrounded by a radiation shielding wall made of heavy concrete. As a preferred embodiment, the outer peripheral wall is formed as a multi-layer structure, and water or high water content is absorbed in a gap portion. The gamma ray and the neutron ray are shielded by a multi-wall by filling with a hydrophilic resin. Technical example 2 is a technology in which a shielding door is detachably attached to the opening of a maze in a bent state, and makes it easy for people and equipment to enter and exit. In the third technical example, a radiation source is housed in an underground structure to enhance the radiation shielding property and to make the outer wall thin. In Technical Example 4, an assembling ceiling panel, a wall panel, and a lead plate are installed around a radiation source to facilitate assembly, disassembly, and extension / renovation.

[0004] On the other hand, at about 10:35 am on September 30, 1999, at a uranium fuel processing company in Tokai-mura, Ibaraki Prefecture, a serious accident in which nuclear fission reached criticality occurred, and neutrons and gamma rays were emitted from the boundary of the facility. Was released to the outside. It is estimated that this radiation-emitting accident has resulted in 69 radiation-exposed individuals, and that some have exceeded annual allowable doses.

[0005]

The above-mentioned technical examples 1 to 4
Is a radiation shielding (attenuating) function within a limited area, but is not a nuclear power plant or a storage facility for high-level radioactive materials, that is, various facilities that handle nuclear fuel and general radioactive materials It cannot be said that it has applicability to. In addition, in facilities where fission is not predicted to reach criticality in advance, such as the uranium fuel processing company mentioned above, even if dare to apply technology and remodel the facility, it will require a lot of cost and practicality. The problem of being damaged remains.

[0006] The present invention has been made in view of the above circumstances, and achieves the following objects. (1) To ensure the safety of workers inside and outside the facility and the surrounding residents, even in the event of a radiation accident such as neutron radiation or gamma radiation. (2) Improve applicability to most facilities that handle radioactive materials. (3) To facilitate confirmation and maintenance of the facility's radiation shielding function. (4) To keep costs low and secure practicality, and to make it possible to quickly implement the existing facilities. (5) To maintain the damping performance at the worst radiation release in nuclear power plants and uranium fuel processing facilities, eliminate the need for evacuation by radiation release alone, and maintain the normal environmental continuity. (6) To reduce the impact on the living environment and natural environment around the facility. (7) To facilitate conversion in the event of a disaster such as an earthquake.

[0007]

According to the present invention, a technique is employed in which a radiation protection wall is arranged so as to surround a radiation source or a region or facility to be protected from radiation. The radiation protection wall is installed in a state where the radiation source and the area outside the radiation source are partitioned, and if there is a partition wall between the radiation source and the area outside the radiation source, the radiation protection wall is formed along the partition wall and the radiation generation area. If there is a target building containing the source, or if there is a target building to protect the internal environment from radiation, it is placed along its outer wall. On the radiation protection wall,
A water layer having a radiation attenuating function is erected on the way in the radial direction and at least in the horizontal direction. The water layer is preferably formed by filling the inside of the casing with water, and in any horizontal direction, in a non-linear state in which it is not possible to directly see through the inside and outside, and the entry and exit of people and equipment. A traffic path having a permissible free traffic is added. The thickness of the water layer is set such that a function of attenuating the external exposure dose to an allowable amount or less when radiation is emitted in an emergency is provided. It is desirable that the water layer is provided with a liquid level gauge for constantly detecting the liquid level from the side, and the water layer is provided with a water intake means in an emergency other than a radiation leak accident, When the water is needed or depleted, the radiation level is measured and sufficiently confirmed to be below the allowable value before being used as a water supply source. If the location of the radiation source is such that it can be installed below the surface of the ground, or if it is a location that can be buried around the facility, a large depression is formed and the radiation source is placed inside it. Is applied, and furthermore, the depression is made to have a lining or an inner surface waterproof so as to be able to store water. A water storage pool is provided around the upper part of the depression, and a technology is employed in which water is caused to flow down by using a head in an emergency to submerge the radiation source. In each such technique, the water itself is used as a neutron or gamma ray attenuator, primarily due to its thickness and the presence of hydrogen atoms, so that the radiation dose is attenuated, preferably to a degree that does not matter for acceptable limits. Is set to

[0008]

FIG. 1 to FIG. 5 show a first embodiment of a radiation attenuation facility according to the present invention. In the figure,
Symbol A is a radiation source, B is an outer area, C is a target building, D is a partition wall, E is a control room, and G is the surface of the earth (or road).
It is.

In the first embodiment, the radiation attenuating wall 1 is arranged so as to divide a target building C containing the radiation source A and an outer area B to be protected from radiation. .

The radiation attenuating wall 1 is, as shown in FIG.
Along the outer wall surface of the target building C and the inner wall surface of the radiation attenuating wall 1, it is installed so as to cover them and as shown in FIG.

As shown in FIG. 2, a number of passages 2 are provided at important points of the partition wall D and the radiation attenuating wall 1 in order to allow people to enter and exit and to carry in and out equipment. .

The passage 2 is selected to be a non-linear shape such as a bent state so that it cannot be seen through an arbitrary linear direction intersecting the radiation attenuating wall 1. As shown in FIG. 5, a required number of gates 3 are installed on a part of the partition wall D and the radiation attenuation wall 1. For this reason, at a place where the passage 2 is required, a part of the radiation attenuation wall 1 is H-shaped, L-shaped, I-shaped, as shown in FIGS.
It is deformed into a shape, a crank shape, etc., and is set in a partially overlapping state.

The radiation attenuating wall 1 is formed by filling a casing 11 made of stainless steel or the like with fresh water to form a water layer 12 having a desired thickness in order to attenuate radiation to a required dose level. Is set to The water layer 12 is interposed in any radiation direction, when the radioactive material is in a critical state while being housed in the target building C, or outside the target building C. And partition wall D
Even in the event of an unexpected accident, such as when radiation is emitted when exposed inside the
Care should be taken to have a function of attenuating the exposure dose to an allowable amount or less, that is, a sufficient radiation attenuation function. The water level X of the water layer 12 arranged along the inner surface of the radiation attenuation wall 1
Is also set to be higher than the radiation source A.

In the embodiment shown in FIG. 2, the radiation attenuating wall 1 and the traffic path 2 in a bent state are also installed at the entrance 13 of the target building C, and the corner inside the target building C is provided. An auxiliary water layer 12 for enhancing the radiation attenuating function is provided in the portion.

On the other hand, as shown in FIG. 1 and FIG. 3, various facilities for setting the water level X and improving the usability are added to the water layer 12.

In a facility surrounded by the partition wall D and the radiation attenuation wall 1, a water supply tank 22 mounted on a gantry 21 is provided.
Is installed, connected to the inside of the casing 11 of the radiation attenuation wall 1 by a water supply pipe 23, and inside and outside of the partition wall D, a siphon type (communication type) liquid for constantly measuring the water level X of the water layer 12. A position indicator 24 is arranged, and a gas phase portion of the water layer 12 includes:
Respirator 25 is connected. The water level of the water supply tank 22 is set so as to be higher than the water level X of the water layer 12, and care is taken so that a head difference H is formed between them in a steady state. In FIG. 1, reference numeral 26 denotes a control valve, which includes a valve operated by remote control, a valve operated manually, or a valve provided with these.

A water storage tank 27 for draining water from the water layer 12 is disposed below the radiation attenuating wall 1. The water storage tank 27 has a transfer pump 28 for sucking and transferring the stored water. , A purifying system 29 for purifying water, a water intake means 30 for taking out purified water, and a drainage system 31 for discharging surplus water.

Further, the water supply tank 22 is provided with a water supply system 41 and a water supply pipe 42 for supplying water such as water supply.
A extraction pipe 43 for extracting and using water, and a branch pipe 44 for connecting the water intake means 30 and the water supply pipe 42 are arranged.

In the first embodiment of the radiation attenuating facility having such a configuration, even if a radiation emission accident from the radiation source A occurs, the radiation attenuating wall 1 outside the target building C and the partition The radiation is attenuated twice with the radiation attenuating wall 1 provided adjacent to the wall D, and the radiation dose to the outer zone B is significantly smaller than the allowable limit. At this time, by setting the radiation attenuation wall 1 higher than the radiation source A, it is possible to prevent radiation leakage to the living area.

Whether or not the water layer 12 of the radiation attenuating wall 1 maintains a sufficient radiation attenuating function can be constantly checked inside and outside the radiation attenuating wall 1. In other words, anyone can check from the ground surface (road) G at any time without entering the facility by the liquid level gauge 24 installed outside the partition wall D.

The water stored in the water layer 12 of the radiation attenuation wall 1 can be used as a water supply source in the event of an earthquake or fire. Unless a radiation leak accident occurs from the target building C, the water layer 1 on the inner surface of the partition wall D
Although no radiation is applied to 2, the water layer 12 may be in a state in which organic matter such as slime has been mixed due to long-term storage. When the water is needed or depleted, the transfer pump 28 is operated to transfer the water in the water storage tank 27 to the purification system 29 to purify the water.
It is desirable to take out a part of the water and check the water quality and the degree of radiation contamination one by one or at any time, and confirm the safety such as being below the allowable value before using the water storage .

In the first embodiment described above, the radiation source A is housed in the target building C.
Even when the target building C is an evacuation site in the event of a radiation emission accident, that is, when installing the target building C in an area or facility that should be protected from radiation, radiation from a distant radiation source A is The radiation attenuation wall 1 can attenuate the radiation to below an allowable limit.

FIG. 6 shows a second embodiment of the radiation attenuation facility according to the present invention. 6, reference numeral 51 denotes a depression, 52 denotes a water storage pool, 53 denotes a bridge, 54 denotes a maintenance road, and 55 denotes a protection wall.

In the second embodiment, a large concave portion 51 is formed in a portion lower than the ground surface G, and a target building for accommodating the radiation source A is formed at the bottom of the concave portion 51. An object C is installed, and a water storage pool 52 is installed around the upper opening of the depression 51 so as to surround it, and a radiation attenuating wall 1 is installed outside thereof and around the target building C. Is done. In the water storage pool 52, a bridge 53 is installed so as to connect the inside and the outside area B, and the bottom of the recess 51 and the bridge 53 are connected via a maintenance road 54 in a spiral state and an inclined state. Connected to the maintenance road 54, a protection wall 55 having a function such as a guardrail is installed. The recess 51 is set to be able to store water by waterproofing the lining and the inner surface.

The second embodiment shown in FIG. 6 is excellent in applicability to the case where the target building C is a facility that handles a large amount of radioactive materials, such as a nuclear power plant, and is capable of normal radiation attenuation and radiation. The shielding is performed by a target building C such as a reactor building. In addition, as shown in FIG. 6, the radiation attenuating wall 1, the soil, the storage pool 52, the soil and the radiation attenuating wall 1 are interposed in quadruple and fivefold around the target building C, as shown in FIG. The radiation emission towards the area B is significantly lower. Even if it is assumed that a serious radiation accident would occur such that the internal facilities of the target building C would run away, the thickness of water and soil itself and the presence of hydrogen atoms would attenuate neutrons and gamma rays and reduce radiation dose. Can be reduced to a degree that does not cause a problem with respect to the allowable limit.

By adopting such a configuration, it is possible to effectively increase safety against radiation accidents. However, in the case of a serious accident such as a long-term emission of radioactive materials, It is also possible to take measures such as causing the water in the water storage pool 52 to flow down by using the head and guiding the target building C to a submerged state to minimize damage.

[Other Embodiments] The present invention includes the following techniques. a) The partition wall D and the radiation attenuating wall 1 are installed closely. b) Casing 1
(1) The constituent material is optional. Also, the casing 11
Is formed of a soft material, and the water layer 12 is provided between frames and plates. c) Install the radiation attenuation wall 1 inside or outside the target building C or the partition wall D. Or install radiation attenuation wall 1 on both.

[0028]

According to the radiation attenuation facility according to the present invention, the following effects can be obtained. (1) If a radiation protection wall with sufficient radiation attenuation function is installed between the radiation source and the protected area, radiation accidents such as neutron rays or gamma rays should occur. However, it is possible to ensure the safety of workers inside and outside the facility and the local residents. (2) Since the technology forms the water layer along the wall of the target building or the partition wall, it can be applied to most facilities that are easy to construct and handle radioactive materials. (3) The technology to display the liquid level of the water layer is adopted, and the radiation shielding function of the facility can be freely checked at any time just by visual observation, and the drop of the liquid level is detected by detecting Maintenance can be performed promptly. (4) Since the radiation shielding function is a technology that sets the thickness of water, it is necessary to suppress cost increases and secure practicality, take measures against existing facilities promptly, and improve soundness. Can be. (5) This technology predicts the worst radiation emission accidents in nuclear power plants and uranium fuel processing facilities, and sets radiation attenuation performance. This prevents radiation exposure to outsiders and ensures You can maintain your life and behavior. (6) This is a technology for significantly reducing the amount of radiation emitted to the periphery of the facility from an allowable limit, and can reduce the influence on the living environment and the natural environment so that there is no substantial effect. (7) The water layer can be easily diverted as a water storage facility in the event of a disaster such as an earthquake, so that an emergency water source can be secured.

[Brief description of the drawings]

FIG. 1 is a connection diagram illustrating a first embodiment of a radiation attenuation facility according to the present invention.

FIG. 2 is a plan view showing a first embodiment of the radiation attenuation facility according to the present invention.

FIG. 3 is a front sectional view showing the first embodiment of the radiation attenuation facility according to the present invention.

FIG. 4 is a plan view showing an embodiment near the front of the partition wall and the radiation attenuation wall in FIG. 2;

FIG. 5 is a plan view showing an embodiment in the vicinity of corners of a partition wall and a radiation attenuation wall in FIG. 2;

FIG. 6 is a front sectional view showing a second embodiment of the radiation attenuation facility according to the present invention.

[Explanation of symbols]

 A Radiation source B Outer area C Target building D Partition wall E Management room G Ground surface (or road) 1 Radiation attenuation wall 2 Passageway 3 Gate 11 Casing 12 Water layer 13 Doorway 21 Mounting base 22 Water tank 23 Water supply pipe 24 Liquid Position meter 25 Respirator 26 Control valve 27 Water storage tank 28 Transfer pump 29 Purification system 30 Water intake means 31 Drainage system 41 Water supply system 42 Water pipe 43 Extraction pipe 44 Branch pipe 51 Depression 52 Water storage pool 53 Bridge 54 Maintenance road 55 Protection wall X Water level H Head difference

Claims (6)

[Claims] 1. A radiation attenuating wall (1) installed in a state where a radiation source (A) and an outer area (B) are partitioned, and the radiation attenuating wall has water having a radiation attenuating function. A radiation attenuating facility in which the layer (12) is erected in a state of being interposed in the radial direction. 2. A water layer (1) on a radiation attenuation wall (1).
The radiation attenuating facility according to claim 1, wherein 2) is formed by filling a casing (11) with water. 3. The radiation attenuating facility according to claim 1, wherein the radiation attenuating wall (1) is provided with a traffic passage (2) in a non-transparent state inward and outward. 4. A liquid level meter (24) for constantly detecting a liquid level from a side in the water layer (12).
The radiation attenuation facility according to 2 or 3. 5. The radiation attenuating facility according to claim 1, wherein the water layer (12) is provided with a water intake means (30) used for purposes other than a radiation leakage accident. 6. A radiation attenuating facility comprising: a depression (51) for accommodating a radiation source (A) therein; and a water storage pool (52) provided around the depression to attenuate radiation. .