JPS62278490A - Biological shield wall activation preventive structure - 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 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a radiation prevention structure for a concrete structure surrounding a nuclear facility, particularly a reactor pressure vessel or a reactor containment vessel.

[Conventional technology]

When a nuclear power plant reaches the end of its operating life, its obsolete equipment is removed and it is dismantled. During the dismantling process, remote-controlled equipment must be used to dismantle one piece of equipment that has become radioactive due to radioactivity or radioactive contamination unique to nuclear power plants, and to dispose of these waste materials in order to reduce radiation exposure for workers. This is a big difference from the case of general structures that are not radioactive. In particular, the biological wall around the reactor containment vessel is an architectural structure reinforced with a large amount of reinforcement, and efficient dismantling techniques have not yet been established.

In the case of boiling water reactor equipment, the activated part of the biological barrier wall is limited to the inner surface near the height of the reactor core. Demolition operation equipment will be installed, and a cutting machine such as a diamond drill or core drill will be suspended in the space inside the biodestructive wall to cut out the radioactive concrete inside.

By the way, the work of cutting out the surface of a raw wall that has been strongly reinforced with reinforcing bars requires large-scale mechanical equipment, as well as floating dust (radioactivity contained in the object to be cut) during cutting. Countermeasures (also found in dust).

This type of technology also required safety equipment, such as suspending cut pieces from high places, and also required large-scale work safety equipment to ensure radiation exposure for workers. Examples include JP-A-56-57989 and JP-A-57-59194.

[Problem that the invention seeks to solve]

In the conventional technology, when dismantling biodegradable walls, a large-scale remote-controlled machine is used to remove radioactive concrete, which requires a large amount of money and time.
r? It is necessary to take it out as a block about the size of a corner.

The bio-jahei wall is an important architectural structure that houses the nuclear reactor, so in Japan, which is a land-farming country, it is reinforced with steel bars, especially in warehouses, which makes it difficult to cut and remove the part. I take it as a thing.

In order to solve this problem, it is necessary to prevent the activation of biodeflection walls, make it possible to use the same means and construction methods as for other general structures, and make cheap and efficient demolition work possible. good.

An object of the present invention is to provide an inexpensive and effective radiation prevention structure for biological walls.

[Means for solving problems]

Activation of the biological wall is caused by neutron beams from the core of the reactor, and its range is centered at the height of the reactor core.

The top and bottom are about 6 meters each, and the depth is 10 to 20 a1. Therefore, if neutron shielding material corresponding to the concrete activation thickness is placed offset from the center of the reactor relative to the biological shielding wall, the biological shielding wall can be prevented from activation.

Polymer materials such as plastics are about 2 times cheaper than concrete.
Because it has a reliable neutron blocking effect, it is possible to effectively block neutrons by installing a plastic material with a thickness approximately half the thickness of the radioactive concrete on the biological wall surface or the outer surface of the atomic containment vessel. This objective will be achieved.

In addition, the barrier material can be easily peeled off from the biological barrier wall or the reactor containment vessel, making it easy to selectively remove the radioactive portion during disassembly.

[Effect]

Neutron beams generated in the core of a nuclear reactor have high energy, pass through reactor pressure vessels, etc., and reach biological walls. At this time, the neutron beam is scattered by the structures through which it passes and consumes energy, but roughly speaking, the intensity distribution of the neutron beam attenuates within a circle around the reactor core.

Therefore, the activation of the biological wall is also limited to the area close to the core of the reactor. In the present invention, the biological wall was placed inside the wall (on the reactor side). The neutron barrier material attenuates the neutron beam to the biological barrier wall.

This reduces the activation of biological walls by neutrons to a negligible level.

〔Example〕

Prior to a detailed explanation of the present invention, in order to facilitate understanding thereof, an outline of the structure of a conventional boiling water nuclear power generation facility will first be explained with reference to FIGS. 5 and 6. FIG. 6 is an enlarged view of the problematic biological wall.

In these figures, 1 is the reactor building, 2 is the reactor containment vessel, 3 is the reactor pressure vessel, 4 is the reactor shield wall, and 5 is the reactor containment vessel.
is the reactor pedestal, 6 is the biological shield wall, and 7 is the activation part of the biological shield wall. The biological wall is approximately 2
It is a concrete structure that is strongly reinforced with steel bars and has a thickness of 10 to 20 am.

In order to prevent activation of a reinforced concrete part, the surface of the biological barrier wall can be covered with a material that has a shielding efficiency comparable to the activation depth of the part.

7th Wi shows the shielding effect of plastic materials such as polyethylene and Visco material in comparison with concrete and reinforcing steel. As shown in the same figure, polyethylene can achieve a shielding effect of about 10 (3 oa) equivalent to 2 oa of concrete. In the case of Visco, the number is approximately 151.A specific example of a structure in which a plastic material is installed on the surface of a wall that is not suitable for living bodies is shown below.

Figure 1 shows an example in which a lubricating material is attached to the surface of a living limp wall. The neutron barrier material 8 is fixed to the biological barrier wall 6 by adhesive or bolting. Figure 3A shows an example of bolting a barrier material to a biological barrier wall.The neutron barrier material 8 is made of a material with a high barrier effect, such as a shaped plastic material, and is fixed at a constant pitch. It is fixed with a mounting bolt 9 provided on the living room wall 6.

During disassembly, the lumber is removed by loosening the bolts.
The remaining living wall 6 will be dismantled using normal construction methods as a general structure whose activation can be ignored.

FIG. 2 shows an example in which a barrier material 8 is provided on the outside of the reactor containment vessel 2 by adhesive or the like. Installation of shiyahei materials,
In addition to gluing or bolting the shaped reinforcement material as in the case of attaching it to a biological barrier wall, as shown in FIG. It is also possible to install it in the reactor containment vessel 2 and support it thereby.

FIG. 4 shows an example of using the stiffener material 8 and the support frame 11 as the construction form for the living wall 6 to further improve the efficiency of construction, and concrete for the living wall 6. At the time of pouring, conventional methods.

In place of the shielding body 8 in FIG. 4, a steel plate liner with a thickness of 1/2 inch is used, and in this example, it is possible to efficiently deal with the problem by replacing the iron plate liner with the shielding material 8.

〔Effect of the invention〕

According to the present invention, in addition to greatly streamlining the dismantling work of biological walls during the dismantling and removal of nuclear power generation facilities, the use of large-scale remote vibration equipment for cutting and removing radioactive concrete parts can be avoided. can.

Furthermore, as shown in the embodiment, if the timber is also used as a form for pouring concrete into a living wall, the overall cost efficiency can be further increased.

[Brief explanation of drawings]

Figures 1 and 2 are conceptual diagrams of one embodiment of the present invention, Figures 3 and 4 are partial cross-sectional views showing an embodiment of how to attach shingles, and Figures 5 and 6 are The figure is a schematic cross-sectional view of a boiling water reactor building, and FIG. 7 is a diagram of the neutron deflection effect of various materials. 1... Reactor building, 2... Reactor containment vessel, 3...
・Reactor pressure vessel, 4...Reactor shield wall, 5...
・Reactor pedestal, 6... Living wall, 8...
・Shiyahei material, 9...Mounting bolt, 1o...Mounting bracket, 11...Support frame.

Claims (1)

[Claims] 1. A bioshield wall activation prevention structure characterized by installing a shielding material for neutron shielding near the height of the reactor core between the bioshield wall and the containment vessel.