JPS597959B2 - Reactor pressure vessel cooling method and reactor pressure vessel cooling device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nuclear reactor pressure vessel, and in particular to a method and method for cooling the reactor pressure vessel for periodic inspection of the reactor and inspection in the event of an abnormality. This relates to a nuclear reactor pressure vessel cooling system.

At nuclear reactors, during periodic inspections and inspections in the event of an abnormality,
After shutting down the reactor, it is necessary to cool the reactor pressure vessel.

For this reason, conventional nuclear reactors are provided with a reactor pressure vessel cooling device that cools reactor water within the reactor to cool the reactor pressure vessel from the inside.

Figure 1 is an explanatory diagram of a conventional reactor pressure vessel cooling system.
1 is the pressure vessel main body, 12 is the pressure vessel upper cover, 21 and 2
2 are a pressure vessel main body 11 and a pressure vessel upper lid 12, respectively.
0 cover, and the main steam isolation valve 3 is installed in the pressure vessel body 11.
2 and a safety valve 33 are installed, and a reactor water suction pipe 41 and a reactor water circulation pump 42 are installed.
, a reactor pressure vessel cooling system having a reactor water cooling heat exchanger 43 and a reactor water return pipe 44 is provided.

Note that 45 is a refrigerant circulation pipe having a refrigerant circulation pump 46, 47 is a return reactor water temperature gauge, 4B is a reactor water cooling heat exchanger bypass pipe, and 49 is a bypass flow rate control valve.

In order to cool a reactor pressure vessel having such a cooling device, the water level of the reactor water in the pressure vessel body 11, which is normally at water level A, is first raised to the water level B in the pressure vessel upper lid 12, and then , reactor water is transferred from the pressure vessel main body 11 to the reactor water suction piping 41
The reactor water is taken out through the reactor water circulation pump 42, guided to the reactor water cooling heat exchanger 43 for cooling, and then returned to the reactor pressure vessel through the reactor water return piping 44 to cool the reactor water, thereby removing the pressure vessel main body 11 and the pressure vessel upper cover. 12 was being cooled.

The cooling method using this reactor pressure vessel cooling system requires raising the water level of the reactor water from the water level A to the water level B in the pressure vessel upper lid 12 and filling the inside of the reactor pressure vessel with reactor water. Reactor water flows into the main steam pipe 31 that guides steam to the turbine, and the inside of the main steam pipe 31 corrodes because the inner pipe wall of the main steam pipe 31 is wetted by this reactor water.

In addition, the main steam pipe 3
1 had the disadvantage of radioactive contamination.

An object of the present invention is to provide a method for cooling a reactor pressure vessel that can cool the entire reactor pressure vessel without causing reactor water to flow into the main steam piping. In the method for cooling a reactor pressure vessel, which is the first invention, the pressure vessel main body and the pressure vessel top cover are respectively covered with a pressure vessel body force bar and a pressure vessel top cover, and the reactor water in the pressure vessel main body is cooled. In a method for cooling a reactor pressure vessel having a flow path, the pressure vessel main body and the pressure vessel top cover are externally cooled by ventilation from the outer periphery, and at the same time, the reactor is cooled in a gas phase part within the top of the reactor pressure vessel. The reactor pressure vessel cooling device, which is the second invention, is characterized in that internal cooling is performed by spraying water. , a reactor pressure vessel cooling device having a flow path for cooling reactor water in the pressure vessel body, a flow path for ventilation cooling the outside of the pressure vessel body and the pressure vessel top cover; and a flow path for cooling the outside of the pressure vessel body and the pressure vessel top cover; The reactor is characterized by being provided with a flow path through which cooled reactor water is sprayed into the gas phase of the reactor.

In other words, the present invention enables the reactor pressure vessel to be cooled by cooling the outside and inside of the reactor pressure vessel in this manner, thereby reducing the reactor pressure while maintaining the reactor water level at the normal water level. This allows the container to be cooled.

Examples will be described below.

FIG. 2 shows the configuration of one embodiment, and the same parts as in FIG. 1 are designated by the same reference numerals.

In this device, between the pressure vessel body 11 and the pressure vessel body force bar 21, the pressure vessel top cover 12 and the pressure vessel top cover 2
A coolant flow path is formed between the pressure vessel body 11 and the pressure vessel upper cover 12 from the outside by a coolant such as air cooled by the pressure vessel cooler.

In Fig. 2, 511 and 512 are coolant suction pipes, and the coolant is guided to the pressure vessel cooler 53 by a coolant circulation machine 52, and the coolant cooled here is passed through coolant return pipes 541 and 542 to the pressure vessel main body. It is returned to the physical strength bar 21 and the pressure vessel top cover 22.

The coolant return pipes 541 and 542 are provided with a coolant flow meter 55, a coolant thermometer 56, and a coolant flow control valve 57, respectively.
The pressure vessel cooler 54 is provided with a cooler bypass pipe 58 and a bypass flow control valve 59, which control the reactor pressure vessel cooling rate and the temperature difference between the inside and outside of the reactor pressure vessel. Control takes place.

Refrigerant is introduced to the pressure vessel cooler 53 through a refrigerant circulation pipe 60, and is circulated by a refrigerant circulation pump 61.
The coolant is cooled by the heat exchange means of the pressure vessel cooler 53.

Additionally, this device is provided with a flow path for spraying reactor water coolant from the pressure vessel upper cover 12 to the gas phase at the top of the pressure vessel, and the reactor water in the pressure vessel main body 11 is transferred to the reactor water suction piping 41.
After being guided to the reactor water heat exchanger 43 by the reactor water circulation pump 42 and cooled, spray is injected from the top of the pressure vessel upper cover 12 through the top spray cooling piping 71 to cool the gas phase from inside the reactor pressure vessel. .

The top spray cooling pipe 11 has a top spray control valve 12.
, a spray flow meter 13, and a spray water temperature gauge 74 are provided, and the reactor water heat exchanger 43 is provided with a reactor water heat exchanger bypass pipe 48.
and a bypass flow rate control valve 49 are provided, and these control the cooling rate of the gas phase portion at the top of the pressure vessel upper lid 12 and the temperature difference between the inside and outside.

Since the cooling device of this embodiment is configured in this way,
When cooling the reactor pressure vessel, without raising the reactor ice water level, it is necessary to cool down not only the pressure vessel main body but also the entire area of the pressure vessel upper cover, which is particularly hot, especially the joint area between the pressure vessel main body and the pressure vessel upper cover. Since the thick portion can be cooled from both the inside and outside, the cooling efficiency is high, rapid cooling is possible, and the temperature difference between the inside and outside of the reactor pressure vessel can be controlled to a small level.

Note that the flow path for ventilation cooling the outside of the pressure vessel body and the pressure vessel top cover can be constructed using an existing pressure vessel body force bar, pressure vessel top cover, or pressure vessel cooler.

FIG. 3 shows still another embodiment, in which the same parts as in FIGS. 1 and 2 are given the same reference numerals, and the difference from the device in FIG. It has a flow path in which water is cooled by reactor water cooled by a reactor water heat exchanger.

In this device, a reactor water return pipe 44 is branched from a top spray cooling pipe 71, and this reactor water return pipe 44 includes a return reactor water flow rate control valve 81, a return reactor water thermometer 41, and a reactor water return pipe 44.
A return reactor water flow meter 82 is installed.

The cooling device of this embodiment can cool both the pressure vessel main body and the pressure vessel top cover both from the inside and outside, and therefore has the highest cooling efficiency.

Figure 4 shows the temperature change in the reactor pressure vessel cooled by the cooling system of the embodiment shown in Figure 3, where the horizontal axis represents reactor cooling time (hr) and the vertical axis represents pressure vessel upper cover temperature ( C)
(If ToJ is set and C raises the vertical water level,
D is a case in which cooling is performed using a conventional cooling system without raising the water level, and is shown for comparison. E is a case in which the reactor ice water level is kept at the normal water level and the reactor water is cooled, and at the same time the reactor water is cooled in the gas phase at the top of the pressure vessel. Play cooling water to cool the reactor pressure vessel from the inside,
Furthermore, temperature changes in the pressure vessel top cover in the case of an example in which the outside of the pressure vessel main body and the pressure vessel top cover are cooled with a coolant are shown.

As is clear from the comparison with curves C and D(!:E) in this figure, the time required for the temperature to reach 50°C, the temperature at which inspection work can be carried out, can be shortened by 100 hours and 40 hours, respectively, and the reactor is shut down for inspection. This has a great effect on shortening the period and improving the operating rate.

Figure 5 shows the change in the temperature difference inside and outside the reactor pressure vessel, with the horizontal axis representing the reactor cooling time (hr) and the vertical axis representing the temperature inside and outside the upper lid of the pressure vessel ('C) (To-T1). (To, T
1 is the temperature of point 00 and point I in Figure 3, respectively.
F is the conventional method of raising the water level, G is the case of cooling with a conventional device without raising the water level, which are shown for comparison, and H is the case of cooling the reactor water while keeping the reactor ice water level at the normal water level. At the same time, the figure shows an example in which the gas phase at the top of the pressure vessel is sprayed to cool it from the inside of the reactor pressure vessel, and the outside of the pressure vessel main body and the pressure vessel top cover are further cooled with a coolant.

As is clear from a comparison of curves F and H in the figure, when the reactor water level is raised and the reactor pressure vessel is cooled from the inside, the temperature difference between the inside and outside of the pressure vessel upper cover becomes 50 to 100°C or more. In contrast, in this embodiment indicated by H, the temperature difference is 50° C. or less, which reduces the thermal stress in the reactor pressure vessel and has a great effect on improving safety.

In addition, when reactor water flows into the main steam piping in a conventional cooling system, eight main steam isolation valves 32 are installed in the main steam piping 31 as shown in FIG. Rapid contact with water causes a sudden change in temperature, causing thermal strain, creating a permanent gap between the valve seat 321 and the valve body 322, which may cause radioactivity leakage from this gap in the event of a nuclear reactor accident. Alternatively, as shown in Fig. 1, several safety valves 33 are installed in the main steam piping 31, which may come into contact with reactor water and cause strain.
A permanent gap is created between the valve seat 331 and the valve body 332, causing steam leakage during normal operation of the reactor.Furthermore, many minute solid metal foreign objects are floating in the reactor water, which causes
Valve sea of main steam isolation valve 32 and safety valve 33} 321
, 331 and the valve bodies 322, 332, damaging the valve seats 321, 331 and causing leakage, all of which are caused by reactor water flowing into the main steam piping due to a rise in the reactor ice water level. Therefore, in the cooling device of the embodiment, all such problems are eliminated.

These effects can be achieved in any of the cooling devices of the above embodiments depending on the respective conditions.

In other words, the reactor pressure vessel can be cooled while the reactor water level remains at the normal water level below the main steam piping, and reactor water can be prevented from flowing into the main steam piping. It can prevent leakage, prevent corrosion of main steam piping, and prevent the spread of radioactivity.
Furthermore, the cooling efficiency is high, rapid cooling is possible, and the temperature difference between the inside and outside of the reactor pressure vessel can be controlled to a small extent, which shortens the reactor shutdown period and reduces thermal stress in the reactor pressure vessel. can be reduced.

Therefore, the safety and operation rate of the power generation plant can be improved.

As described above, the reactor pressure vessel cooling device of the present invention is capable of cooling the entire reactor pressure vessel without injecting reactor water into the main steam piping, and has great industrial effects. .

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the configuration of a conventional reactor pressure vessel cooling system;
2 and 3 are configuration explanatory diagrams of different embodiments of the reactor pressure vessel cooling system of the present invention, and FIGS. 4 and 5 are characteristic diagrams showing the effects in comparison with conventional equipment. FIG. 6 is a partial sectional view of the main steam isolation valve of the reactor pressure vessel, and FIG. 7 is a partial sectional view of the safety valve. 11...Pressure vessel main body, 12...Pressure vessel upper lid, 2
DESCRIPTION OF SYMBOLS 1... Pressure vessel body force bar, 22... Pressure vessel top cover, 31... Main steam piping, 41... Reactor water suction piping, 43... Reactor water cooling heat exchanger, 44...・Reactor water return piping, 511, 512... Coolant suction piping, 53...
- Pressure vessel cooler, 54L542... Coolant return piping, 11... Top spray cooling piping.

Claims (1)

[Claims] 1. A pressure vessel body and a pressure vessel top cover are respectively covered by a pressure vessel body force bar and a pressure vessel top cover,
In the method for cooling a reactor pressure vessel having a flow path for cooling reactor water in the pressure vessel body, the pressure vessel body and the pressure vessel top cover are externally cooled from the outer periphery by ventilation κ, and at the same time, the reactor pressure vessel A method for cooling a nuclear reactor pressure vessel, characterized in that internal cooling is performed by spraying cooled reactor water onto a gas phase within the top. 2 The pressure vessel main body and the pressure vessel top cover are covered with a pressure vessel body force bar and a pressure vessel top cover, respectively,
In the reactor pressure vessel cooling device having a flow path for cooling reactor water in the pressure vessel body, a flow path for ventilation cooling the outside of the pressure vessel body and the pressure vessel top cover, and a flow path inside the top of the reactor pressure vessel. A nuclear reactor pressure vessel cooling device characterized in that a flow path for spraying cooled reactor water is provided in a gas phase part. 3. A flow path for ventilating and cooling the outside of the pressure vessel main body and the pressure vessel top cover is provided between the pressure vessel main body and the pressure vessel body force bar and between the pressure vessel top cover and the pressure vessel top cover. A nuclear reactor pressure vessel cooling system according to claim 2, which is formed in a space of. 4. A flow path for ventilation cooling the outside of the pressure vessel main body and the pressure vessel top cover, a flow path for spraying the cooled reactor water, and a flow path for cooling the reactor water inside the pressure vessel main body are each to be cooled. Cooling rate of parts, and inside,
Claim 2 comprising means for controlling the outside temperature difference
The nuclear reactor pressure vessel cooling system according to item 1 or 3.