JPS60202390A - Core cooling device for emergency - 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 Application of the Invention] The present invention relates to loss of coolant accident (LOCA) in a boiling water nuclear reactor.
Related to the emergency core cooling system that occasionally cools the reactor core.

[Backbone of the invention] Figure 1 shows a boiling water reactor, and in the event of an LOC
In order to sufficiently cool the core in case A is assumed, an emergency core cooling system, a high-pressure water injection system 1, and a core spray system 2 are installed. Core spray is for core 3 and shroud head 4
It is set between 0 and 0.

FIG. 2 shows the Overherd Radspancher method. The coolant is sent from the spray pipe to the main header pipe 5 along the side wall of the shroud, followed by the main header pipe 6, and sprayed onto the fuel assembly 8 from a plurality of spray nozzles 7.

The core spray system 2 is a system that cools the core by spraying water directly from above in the event of a LOCA where the core is exposed, such as a major rupture in the re-vti ring pipe.

On the other hand, if the coolant injection pipe height is near the top of the core,
In the event that the core spray pipe 10 self-ruptures, the coolant inside the shroud will be released through this injection pipe, and the self-rupture will cause serious consequences as one of the eight ECC systems has already lost its functionality. I would like to give it to you.

However, the capacity of the emergency core cooling system is designed to ensure sufficient core cooling even in such cases.

[Purpose of the invention]

The present invention improves safety against self-rupture of the spray piping by increasing the height of the spray header pipe in a spray system that cools the entire reactor core during LOCA, and reduces the required capacity for spray cooling. The entire purpose is to streamline the process.

[Source of invention]

The present invention has been experimentally confirmed that when spray water is injected into the 8 o'clock LOC, there is a tendency for coolant to fall into the peripheral bypass area. Then, each cha/
This takes into consideration the fact that a coolant is injected into the ball.

[Embodiments of the invention]

Next, a third embodiment of the emergency core cooling system according to the present invention will be described.
This will be explained with reference to the drawings and FIG.

I) Configuration of Embodiment In the emergency core cooling system of the present invention, as shown in FIG. It is the highest in the upper shroud 4 (2f from the top of the fuel rods)
Water is injected directly into the reactor core at a position greater than or equal to t.

1i>Phenomenon of core cooling during LOCA Figure 4 shows the behavior within the fuel assembly 8 when the core spray system of the present invention is activated during LOCA.

Spray water 1 is generated by blowing up steam 11 from the reactor core.
2 is at the top of the fuel assembly, and then begins to fall into the core bypass section 13 due to the dynamic pressure of the spray water.

As a result, when the core bypass section becomes full of water, coolant is injected into each chicken channel as an overflow.

111) Effect Implementation of the present invention has the following effects.

(a) By spraying the reactor core directly from the outlet of the spray piping, the differential pressure generated in the piping is smaller than when water is injected from the conventional piping through the header and from the nozzle. Furthermore, the water head pressure of the pump for pumping out the coolant is also reduced.

(b) In place of the conventional header and nozzle placed inside the shroud head, there is only one pipe, which simplifies the furnace internal structure.

(C) As shown in Figure 5, the required amount of spray hi can be reduced by increasing the elevation of the outlet of the spray pipe.

〔Effect of the invention〕

According to the present invention, a predetermined safety is ensured and the r
+fi Since hatching can be achieved, it greatly contributes to cost reduction. Additionally, safety can be further improved against self-rupture of the spray piping.

[Brief explanation of drawings]

g (Figure 51 shows the current boiling water reactor, Figure 2 shows the over-rad spanner system, and Figure 3 shows the boiling water reactor adopting the emergency core cooling system of the present invention. Figure 4 is a diagram showing the behavior of the coolant in the fuel assembly,
FIG. 5 shows a diagram of the relationship between the required amount and the elevation of the spray piping.

Claims (1)

[Scope of Claims] 1. An emergency core cooling system characterized by being capable of directly injecting coolant into an upper plenum inside a shroud in the event of a reactor coolant loss accident in a light water reactor. 2. Claim 1: Emergency core cooling system-18, characterized in that the number of coolant injection ports is one, and the height of the injection pipe is set at least 2 ft higher than the top of the core. 3. Patent In claim 2 or 3, the injection pipe for the cooling moon is passed through the shell of the shroud head body to the position where it enters from the vessel, and is further extended vertically to the top of the core above the upper plenum. Yo! An emergency core cooling system that injects water into the reactor core from a height of 112 feet or more.