JPS592877B2 - Channel boxes for water-cooled nuclear reactors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides channels and
More specifically, the present invention relates to a channel box that ensures safety in the event of a nuclear reactor piping rupture accident.

In conventional boiling water reactors and new converter reactors, channel boxes are used to bind together a large number of fuel rods in the reactor core and to guide cooling water channels to each fuel rod assembly.

In the event of a rupture accident in the reactor's cooling water circulation piping, if a fast upward steam flow continues to occur in this channel box, the cooling water from the emergency core cooling system, which is injected from the top of the reactor core, will Recent research has raised questions about whether or not they can overcome the current and fall into the reactor core and prevent the core from heating up.

This is especially true because the emergency cooling water that accumulates in the channel box above the tie plate, which is installed to secure a large number of fuel rods at the top of the conventional channel box, is flowing into the soil with strong steam coming from below. It is pushed up by the direction flow and becomes difficult to fall below the flow path hole of the tie plate.

The purpose of the present invention is to effectively guide cooling water injected from the top of the reactor core into the reactor core in the event of a pipe rupture accident in a water-cooled nuclear reactor that uses a channel box or something similar. An object of the present invention is to provide a channel box having a structure that ensures safety.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a channel box 10 according to the present invention,
This channel box has an outer box 12 that houses a fuel assembly 11.

In this embodiment, the fuel assembly has a configuration in which fuel rods 13 are arranged in an 8×8 array and their earthwork ends are bound by upper and lower tie plates 14.

The outer box 12 extends both above and below the entire length of the fuel rod 13, and an upper tie plate 1 is located inside the upper extension part.
An inner box 15 having a length extending from the upper surface of the inner box 4 to further upward than the upper end of the outer box 12 is provided.

Only the upper tie plate is shown, but the lower tie plate has the same structure as the upper tie plate.

These tie plates have passage holes 16 on their periphery and in the gaps between the fuel rod arrays.

A passage 17 is provided between the outer box 12 and the inner box 15.

The size of this passage 17 is arbitrary and appropriately determined depending on the predicted state of the pipe rupture accident.

FIG. 2 shows an example in which this inner box is installed adjacent to the outside of the outermost fuel rod array, and the flow passage hole 16 is arranged between the outer flow passage hole 161 located outside of the inner box and the outer flow passage hole 161 located on the inside thereof. It is divided into an inner flow passage hole 162.

Further, the upper end of the inner box 15 is connected to a passage 17 as shown in FIG.
It has a bent portion 18 that is bent outward in the horizontal direction so as to cover the width of the outer box 12, and this bent portion is located above the upper end of the outer box 12.

FIG. 3 shows an embodiment in which the present invention is applied to a boiling water reactor.

For example, if a part of the recirculation system piping 20 or the main steam system piping 21 of a boiling water reactor breaks, the cooling water in the pressure vessel 22 will violently flow out from this rupture part B, and the reactor core 23 will flow out.
Becomes in a state of confusion.

The solid line arrow in Figure 3 is from the lower core 23a to the upper core 23.
b and shows the outgoing flow of water and steam to break B.

At this time, cooling water is injected by the core spray 24 from the upper core 23b.

(Indicated by the dashed arrow in the figure) However, if the channel box does not have the inner box 15 according to the present invention, the injected cooling water that has accumulated all over the upper tie plate 14 will remain in the lower part of the core. The steam generated by the evaporation of the water is pushed up by the strong upward flow, making it almost impossible to enter below the flow path hole 16. On the other hand, the steam cannot rise sufficiently due to the water pressure of the accumulated water and stagnates in the core. fuel rod 1
3 is not cooled well and the temperature continues to rise.

Further, the cooling water having an unsaturated temperature tends to reach the saturated temperature by receiving the heat of the steam on the tie plate.

However, by providing the inner box 15 of the present invention, the cooling water falling from the core spray 24 collects only inside the inner box 15, and does not collect in the passage 17 because it is blocked by the bent portion 18.

Therefore, the steam flow can be easily discharged to the passage 1γ through the outer passage hole 161 on the outer periphery of the tie plate where no water has accumulated, and in exchange, the cooling water can also be easily discharged from the inner box 15 through the inner passage hole 162. It falls and quickly cools down the fuel rods 13.

Moreover, according to the structure of the present invention, there is no steam flow that passes through the inner flow passage hole 162 into the soil through the accumulated water, so that the water accumulated on the tie plate is not heated and remains unsaturated.

Once that unsaturated water enters the core, it condenses the steam existing in the core and reduces the pressure inside the core, so it can be expected that a larger amount of water will be drawn in from the top of the tie plate.

Although the example shown in the present invention is applied to a boiling water reactor, it can also be applied to the upper end of a new type converter reactor or a pressurized water reactor assembly that uses an assembly that does not use a channel box. Therefore, even if the channel box is circular due to the arrangement of the aggregate, it is possible to arrange the inner box concentrically with it.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of the upper part of the channel box according to the present invention, FIG. 2 is a partially sectional view taken along the line A-A in FIG. It is a block diagram when applied to. 12...Outer box, 13...Fuel rod, 15
...Inner box, 17...Aisle.

Claims (1)

[Claims] 1. An outer box which accommodates a fuel assembly formed by arranging a plurality of fuel rods, whose upper and lower ends extend from the upper and lower ends of the fuel rods in the axial direction of the fuel rods, and which is positioned inside the core barrel; an inner box disposed above the fuel assembly inside the box, and between the outer box and the inner box, fluid is allowed to flow from the lower part of the core to the upper part of the core, but not from the upper part of the core to the lower part of the core. A channel box for a water-cooled nuclear reactor, characterized by having a passage formed therein.