JPH03215792A - Nuclear reactor containment - Google Patents

Abstract

PURPOSE:To suppress the inflow of uncondensed gas into an isolation condenser at the time of a main vapor tube rupture accident and to perform efficient decay heat removal by providing the dry well side opening part of a pressure suppression bent tube almost at the height of a main vapor tube. CONSTITUTION:The dry well side opening part of the pressure suppression bent tube 9 is provided almost at the height of the main vapor tube 2 and the dry well side discharge port of a vacuum breakdown value 10 which connects a dry well 8 and a dry well 7 is provided below the dry well 7. Then noncompressive gas present nearby the main vapor tube 2 in a main vapor tube rupture accident moves to the wet well 8 through the bent tube 9 having an opening almost at the height of the main vapor tube 2 together with vapor flowing in the dry well 7 together with a rupture opening. Further, even when the vacuum breakdown valve 10 which connect the dry well 7 and wet well 8 is opened, the noncompressive gas in the wet well 8 is discharged at the lower part of the dry well 7. The noncompressive gas is prevented from flowing in the isolation condenser.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a reactor containment vessel for a nuclear power plant.

(Prior Art) An emergency condenser (isolation condenser) has been proposed as a system for removing decay heat without using dynamic equipment such as pumps in the event of a nuclear reactor accident. As shown in FIG. 2, this system is built into a containment vessel 13 consisting of a dry well 7 and a wet well (not shown). A steam supply pipe 3 branched from the main steam pipe 2 is connected to the inlet side of a heat exchanger tube 4 housed in a condensate tank 6 or a pool, and an outlet side of the heat exchanger tube 4 is connected to one end of a return pipe 5. The other end is connected to the reactor pressure vessel 1.

Therefore, the steam generated in the reactor pressure vessel 1 passes through the steam supply pipe 3 branched from the main steam pipe 2 to the condensation tank 6.
heat transfer tubes 4 housed in a pool. While the steam passes through the heat exchanger tube 4, heat is transferred between the tank water or the pool water through the heat exchanger tube wall, and the steam is condensed into condensed water, which is returned by gravity to the reactor through the return pipe 5. It is refluxed into the pressure vessel 1.

This system can be expected to have high operational reliability because it does not use dynamic equipment such as pumps.

(Problem to be Solved by the Invention) However, in the event that a rupture accident occurs in the main steam pipe 2, the non-condensable gas present in the dry well 7 will pass through the ruptured main steam pipe 2 and When it flows into the ration condenser, there is a problem that the condensed heat transfer in the wall soil of the heat exchanger tubes 4 is deteriorated. The deterioration of heat transfer due to non-condensable gas has the disadvantage that even the presence of even a small amount of non-condensable gas significantly inhibits heat transfer.

By the way, when the mass percentage of non-condensable gas is 10% of the total steam, the heat transfer coefficient is about 20% of that without non-condensable gas.
It has been experimentally confirmed that the deterioration of Therefore, in order to prevent deterioration of the heat removal characteristics of the isolation condenser, it is desirable to prevent non-condensable gas from flowing into the isolation condenser as much as possible.

The present invention was made in view of the above circumstances, and its purpose is to suppress the inflow of non-condensable gas into the isolation condenser in the event of a main steam pipe rupture accident, and to provide an atomic system for efficiently removing decay heat. The objective is to provide a reactor containment vessel.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention condenses steam generated in a nuclear reactor during a nuclear reactor accident through a steam supply pipe branched from a main steam pipe. An isolation condenser is installed inside as a decay heat removal system, which is configured so that the condensed water is guided to a heat transfer tube housed in a tank and circulated by gravity into the reactor while the steam passes through the heat transfer tube. In the contained reactor containment vessel, an opening on the dry well side of a pressure suppression vent pipe that connects the wet well and dry well in the containment vessel is disposed near the height of the main steam pipe, and the wet well and the dry well are connected to each other. The dry well side exhaust port of the vacuum breaker valve connecting the wells is installed at the bottom of the dry well.

(Function) According to the present invention, non-condensable gas existing near the main steam pipe at the time of a main steam pipe rupture accident forms an opening near the height of the main steam pipe together with steam that flows into the dry well through the rupture port. Since the non-condensable gas flows into the wet well through a pressure suppression vent pipe, it is possible to suppress the amount of non-condensable gas flowing into the isolation condenser. In addition, even if the isolation condenser continues to cool the dry well, and the dry well pressure drops below the wet well pressure, and the vacuum breaker valve connecting the dry well and wet well opens, the Since the non-condensable gas is released to the lower part of the dry well, it is possible to prevent the non-condensable gas released into the dry well through the vacuum breaker valve from flowing into the isolation condenser.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention.

As shown in the figure, the inside of the containment vessel 13 is composed of a dry well 7 and a wet well 8.

On the dry well 7 side, a steam supply pipe 3 branched from the main steam pipe 2 connected to the reactor pressure vessel 1 is connected to the inlet side of a heat transfer tube 4 housed in a condensate tank 6 or pool, and this The outlet side of the heat pipe 4 is connected to one end of a return pipe 5, and the other end is connected to the reactor pressure vessel 1. 11 is a return pipe valve. Furthermore, on the wet well 8 side, the suppression pool 12 and the dry well 7 are in communication via a vent pipe 9, but the dry well side opening of the pressure suppression vent pipe 9 is located near the height of the main steam pipe 2. The dry well side exhaust port of the vacuum breaker valve 10 that connects the wet well 8 and the dry well 7 is installed in the lower part of the dry well 7.

Next, the operation of this embodiment will be explained.

In the unlikely event that a rupture accident occurs in the main steam pipe 2, most of the non-condensable gas present in the upper part of the dry well 7 will flow out from the reactor pressure vessel 1 to the dry well 7 within several tens of seconds after the main steam pipe 2 ruptures. The steam passes through the pressure suppression vent pipe 9 and is transferred to the wet well 8. This has also been confirmed by analysis using the detailed thermal hydraulic analysis code TRAC-BWR.

That is, in the analysis system shown in Fig. 3, the dry well is divided into 6 nodes (Ringl-Level.Ri).
ng2-Lutll to Levtl5), and the node where the broken main steam pipe and vent pipe opening are the same (Rin
FIG. 4 shows the distribution of non-condensable gas partial pressure in the dry well 7 when main steam pipe rupture analysis is performed in the analysis system connected to g2Level5). As can be seen from this figure, the dry well node (Ring2-Lev
In el5), it can be seen that the non-condensable gas partial pressure rapidly decreases in a period of about several tens of seconds after the pipe ruptures, and the amount of non-condensable gas present decreases.

Therefore, when the valve 11 of the return pipe 5 is opened to remove decay heat, the non-condensable gas in the steam flowing from the upper part of the dry well 7 into the heat transfer tube 4 through the broken main steam pipe 2 is The content is small, and the deterioration of heat transfer within the heat transfer tubes 4 due to the non-condensable gas is only slight.

In addition, cooling of the dry well 7 by the isolating condenser progresses, and the dry well pressure drops below the wet well pressure, and the vacuum breaker valve 10 opens and the non-condensable gas in the wet well 8 is released from the wet well 8. Even when returning to the dry well 7, since the dry well side opening of the vacuum breaker valve 10 is open to the lower part of the dry well, the concentration of non-condensable gas near the main steam pipe break opening leading to the isolation condenser will be reduced. has almost no effect, and the effect on the performance of the isolation capacitor is also small.

[Effects of the Invention] As explained above, in the reactor containment vessel of the present invention, when an isolation condenser is used as a decay heat removal system in a reactor accident, the main cause of the deterioration of the heat removal performance of the isolation condenser is When a steam pipe breaks,
It is possible to suppress the inflow of non-condensable gas into the heat transfer tubes and prevent a significant drop in the heat removal performance of the isolation condenser.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a block diagram of a conventional isolation condenser, Fig. 3 is an analysis noding diagram of the detailed thermal hydraulic analysis code TRAC-BWR, and Fig. 4 is a block diagram of the TRAC-BWR. - It is a distribution map of the non-condensable gas partial pressure in a dry well calculated by BWR. 1...Reactor pressure vessel 2...Main steam pipe 3...Steam supply pipe 4...Heat transfer tube 5...Return pipe 6...Condensate tank 7...Dry well 8...・Wet well 9...Pressure suppression vent pipe 10...Vacuum break valve 11...Return pipe valve 12...Subpression pool 13...Reactor containment vessel (8733) Agent Patent attorney Sho Inomata Akira (and others)
1 person) 't' letter: 3I2・Tame (sec) younger brother 4th ward

Claims (1)

[Claims] (1) Steam generated in the reactor during a nuclear reactor accident is guided to the heat transfer tube housed in the condensation tank through a steam supply pipe branched from the main steam pipe, and while the steam passes through the heat transfer tube, In a reactor containment vessel in which an emergency condenser configured to circulate condensed water back into the reactor by gravity is stored inside as a decay heat removal system, a wet well and a dry well in the containment vessel are connected. The dry well side opening of the pressure suppression vent pipe is arranged near the height of the main steam pipe, and the dry well side exhaust port of the vacuum breaker valve connecting the wet well and the dry well is arranged at the bottom of the dry well. A nuclear reactor containment vessel characterized by: