JPH06105311B2 - Reactor refueling shihagei device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a reactor refueling shield device installed in a bulkhead portion of a boiling water reactor or the like.

(Prior Art) When the nuclear reactor is shut down and the nuclear fuel is exchanged, the spent fuel having a high radioactivity is set so that it is always moved through an underwater route. For example, as shown in FIG. 4, the upper lids of the reactor containment vessel 1 and the reactor pressure vessel 2 are removed and the reactor well 3 and the fuel storage pool 4 are communicated with each other so that the water surfaces 4A of both are the same. Is filled with water. After that, the spent fuel 8A is carried out from the fuel 8 loaded in the core 7 by using the fuel exchanger 6 which runs on the fuel exchange floor 5 provided above these,
The water is moved and carried into the fuel rack 9 installed in the fuel storage pool 4.

The spent fuel 8A is moved while passing above the bulkhead portion 10 that forms a gap between the upper edge of the open reactor containment vessel 1 and the upper edge of the reactor pressure vessel 2. The member that seals the part 10 in a watertight manner has a structurally small shielding thickness against radiation, and the tip of the spent fuel 8A passes close to it, so if it is left as it is, it will be stored in the reactor. The leakage dose to the internal space 11 of the container 1 may increase, which may hinder other work performed in the internal space 11 at the same time.

In order to improve this problem, a portion of the bulkhead portion 10 above which serves as a passage for the spent fuel 8A, that is, a slot connecting the fuel storage pool 4 and the reactor well 3
A temporary U-shaped shield 13 is installed above the portion adjacent to 12. It should be noted that the U-shaped shield 13 also has a role of protecting damage to the constituent members of the bulkhead portion 10 due to collision if the spent fuel 8A separates from the fuel exchanger 6 and falls while passing therethrough.

The U-shaped shield 13 is a U-shaped outer frame 14 having a bottom portion filled with an appropriate number of lead plates 15 as shown in FIG. 5 and FIG. 6 in an enlarged manner. At the time of replacement, it is hung by using an overhead crane or the like installed in the reactor building and installed across the flange surface 2A of the reactor pressure vessel 2 and the bottom surface 12A of the slot 12.

Since a large number of stud bolts 16 that fasten the upper lid of the reactor pressure vessel 2 are erected on the entire circumference of the flange surface 2A, the stud bolts 16 corresponding to the position where the U-shaped shield 13 is installed. However, as shown in FIG. 7, it is necessary to once remove the required number, for example, six. Stud bolt 16
As shown in FIG. 8, the concave hole 17 provided in the flange surface 2A
Since it is screwed in, the water stopper 18 is attached to the recessed hole 17 from which the stud bolt 16 is removed so that the clad or dust in the water after water filling does not enter, as shown in FIG.

The spent fuel 8A is moved through the concave portion of the U-shaped shield 13. After refueling work, U-shaped shield 13
Is removed and temporarily placed at a designated position on the refueling floor 5. After lowering the water level of the filling water, the water stopper 18 is replaced with the stud bolt 16 again.

(Problems to be Solved by the Invention) According to the above-mentioned shielding means, since the U-shaped shield 13 is a temporary structure, not only extra work time is required for attaching and detaching the U-shaped shield 13 at the time of refueling, but also the U-shape. Since the shield 13 has a clad or the like that has fallen off from the spent fuel 8A during use, it must be decontaminated until the radiation dose drops below a certain value before removal.
In addition, it was necessary to secure a space on the refueling floor 5 for temporary placement after removal.

The present invention provides a reactor refueling shield device that can reduce the number of man-hours required for refueling while maintaining the shielding effect, thereby shortening the time required for periodic inspection of a nuclear power plant including refueling work. The purpose is to do.

[Structure of Invention]

(Means for Solving the Problems) In the present invention, an atom is provided which is installed in the bulkhead portion of a nuclear reactor and has a shield which reduces the amount of leakage radiation from inside the reactor well to the internal space of the reactor containment vessel. The shield device for reactor refueling is provided with a shield body which is always supported by the water sealing member of the bulkhead while maintaining an outer dimension smaller than the distance between the outer wall of the reactor pressure vessel and the reactor containment vessel.

(Operation) Even when the space between the reactor pressure vessel and the containment vessel changes due to temperature fluctuations between the reactor operation and shutdown, the outer dimensions of the shield must exceed this. Since the shield body is not present, the shield body can be permanently installed in the bulkhead body and can be used as it is at the time of refueling performed by shutting down the reactor.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a plan view showing this embodiment, and FIG. 2 is A- in FIG.
It is an A line arrow sectional view.

A well seal bellows 20 is provided over the entire circumference by connecting an outer wall near the upper end of the reactor containment vessel 1 and a concrete body 19 surrounding it, and an inner wall near the upper end of the reactor containment vessel 1. Is provided with a cantilevered girder-shaped bulkhead 21 over the entire circumference, and a fuel exchange bellows 22 is connected between the outer periphery of the upper end of the reactor pressure vessel 2 and the bulkhead 21. Thus, the inside and outside of the reactor containment vessel 1 can be kept watertight with respect to the reactor well 3.

On the flange 2A of the reactor pressure vessel 2 with the upper lid removed,
A large number of stud bolts 16 are erected. Only one of them is shown in FIG.

The upper surface of the bulkhead 21 forms a well platform 23. The upper end 1A of the reactor containment vessel 1 is provided with a grating 24 connected to the outer periphery thereof.

On the upper surfaces of the bulkhead 21 and the refueling bellows 22,
A shield 25 having a fan-shaped planar shape divided into two is provided between opening angles θ centering on a line directed to the slit 12 leading from the center C of the reactor pressure vessel 2 to the fuel storage pool 4. .

The shield 25 is formed by coating a block 26 of lead or the like having a large radiation shielding effect with a liner 27 of, for example, stainless steel, and has a stepped portion whose bottom surface is in contact with the top surfaces of the bulkhead 21 and the fuel exchange bellows 22. An appropriate number of hanging ears 28 are formed on the upper surface and used for mounting, for example, 3
It is provided individually. The upper surface of the shield 25 is preferably a flat surface as it is used as an alternative to the well platform 23, and the hanging ear 28 may be recessed so as not to project on the upper surface. The total size of the gap between the shield 25 and the flange 2A and the gap between the shield 25 and the upper end 1A of the reactor containment vessel 1 is the reactor containment vessel 1 and the reactor pressure vessel 2
Is larger than the difference in the amount of thermal displacement in the radial direction.

The shield 25 does not necessarily need to be installed on the entire surface of the bulkhead 21 or the like, and the above-mentioned opening angle θ is conveniently set to, for example, about 60 degrees, but it is possible to make it smaller than this. Further, the shield 25 may be arbitrarily divided for convenience of manufacture or installation, and is not limited to two divisions. The shield 25 is permanently installed, but if decontamination of the refueling bellows 22 is necessary, for example, the shield ear 28 can be appropriately lifted and removed.

At the time of refueling, the reactor containment vessel 1 and the reactor pressure vessel 2
After removing the upper lids (not shown), the stud bolts 16 close to the slits 12 are large enough to allow the spent fuel 8A to pass through.
For example, three of them are removed and replaced with a separately prepared water shutoff plug 18. After that, if the reactor well 3 and the fuel storage pool 4 are communicated with each other through the opened slit 12 and filled with water, the spent fuel 8A can be carried out immediately. Spent fuel 8A
The fuel is taken out of the reactor pressure vessel 2 by using a fuel exchanger (not shown), passed through the water shut-off plug 18 and above the shield 25 as shown in FIG. 2, and delivered to the fuel storage pool 4.

According to the present embodiment, since the shield 25 is permanently installed regardless of the operation / shutdown of the reactor, temporary work for refueling is unnecessary, and the stud bolt 16 can also pass the spent fuel 8A. It should be removed to the extent. By the way, according to this example, the effect of shortening the working time as shown in Table 1 was obtained.

Furthermore, the shield 25 does not need to be decontaminated every time the fuel is changed, and a temporary storage place is also unnecessary. Further, even if the spent fuel 8A may drop during the fuel exchange, damage to the fuel exchange bellows 22 and the bulkhead 21 can be avoided.

The shield 25 may be permanently attached to the lower surface of the well platform 23 by engaging with the bulkhead 21, as shown in FIG.

〔The invention's effect〕

According to the present invention, it is possible to provide not only the work time at the time of refueling, but also a shielding device for a refueling of a nuclear reactor, which has a remarkable effect of reducing the radiation exposure of workers.

[Brief description of drawings]

1 is a plan view showing an embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA of FIG. 1, and FIG. 3 is a sectional view showing another embodiment of the present invention. FIG. 4 is a cross-sectional view showing a conventional technique, FIGS. 5 and 6 are enlarged front views and side views of the U-shaped shield of FIG. 4, and FIG. 7 is a flange surface of a reactor pressure vessel. FIG. 8 is a plan view showing a part of FIG. 8, FIG. 8 is a cross-sectional view showing a mounted state of a stud bolt, and FIG. 9 is a cross-sectional view showing a mounted state of a water stopcock. 1 ... Reactor containment vessel, 2 ... Reactor pressure vessel 3 ... Reactor well, 10 ... Bulkhead part 11 ... Internal space, 20 ... Well seal bellows 21 ... Bulkhead, 22 ... Fuel Exchange bellows 25 ... Shield body

Claims (1)

[Claims] Claim: What is claimed is: 1. A reactor refueling shield device having a shield body installed in the bulkhead portion of a nuclear reactor for reducing the amount of leakage radiation from inside the reactor well to the internal space of the reactor containment vessel. A reactor refueling shield device provided with a shield body supported by a water sealing member of the bulkhead portion while maintaining an outer dimension smaller than a distance between the outer wall of the reactor pressure vessel and the reactor containment vessel.