JPS6357759B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an apparatus for discharging gas within a nuclear reactor containment vessel.

Technical Background of the Invention Generally, in boiling water nuclear power generation equipment,
If a loss of coolant accident is assumed, hydrogen gas may be generated by the reaction between the fuel cladding material (zirconium alloy) and the coolant water. For this reason,
The air in the reactor containment vessel is replaced in advance with an inert gas such as nitrogen gas to maintain the oxygen concentration within the reactor containment vessel within approximately 4% (volume ratio),
It is configured to prevent the reaction between generated hydrogen gas and oxygen.

The reactor containment vessel is provided with an exhaust system for controlling the internal gas composition and pressure. Conventionally, this exhaust system was constructed as shown in FIG. That is, numeral 1 in the figure is a nuclear reactor building, and a reactor containment vessel 2 is housed within this reactor building 1. This reactor containment vessel 2
Dry well 3 and suppression chamber 4
It is formed from. A large-diameter vent pipe 5 communicates with the dry well 3 and suppression chamber 4, respectively. This vent pipe 5 is provided with a pump 6,
It is configured to discharge the gas within the reactor containment vessel 2 to the exhaust stack 7. The vent pipes 5a, 5b communicating with the dry well 3 and the suppression chamber 4 are provided with, for example, large-diameter fully open/fully closed first isolation valves 8a, 8b. Further, an emergency gas treatment facility is provided branching off from the upstream side of the exhaust fan 6, and this emergency gas treatment pipe 10 is connected to the emergency gas treatment facility via filters 12, 12 and exhaust fans 6, 6. and communicates with the exhaust pipe 7. Second isolation valves 9a and 9b are provided upstream of the exhaust fan 6 and on the emergency gas processing pipe 10. In the event that radioactive particles are mixed into the gas in the reactor containment vessel 2, this gas is flowed to the emergency gas treatment pipe 10, the radioactive particles are separated and collected by the filter 12, and only clean gas is left outside. is configured to emit. Further, first isolation valve bypass pipes 4a, 14b are provided to communicate the upstream side and downstream side of the first isolation valves 8a, 8b, and these first isolation valve bypass pipes 14a, 14b are provided.
In the middle, small-diameter fully open/fully closed first isolation valve bypass valves 15a and 15b are provided.

When adjusting the pressure inside the reactor containment vessel 2, these first isolation valve bypass valves 8a, 8
b is opened, and the gas in the reactor containment vessel 2 is discharged through the first isolation valve bypass pipes 14a and 14b.

Problems with the Background Art Incidentally, during manufacturing and periodic inspection of the reactor containment vessel 2, the inside of the reactor containment vessel 2 is pressurized to approximately 4 kg/cm ² and pressure resistance/leakage tests are performed. When the high-pressure gas in the reactor containment vessel 2 is to be discharged after completion of this pressure resistance/leakage test, the conventional exhaust system has the following problems.

When discharging a large amount of high-pressure gas stored in the reactor containment vessel 2, the first isolation valves 8a and 8b are fully opened.
Since it is a fully closed type, when the first isolation valves 8a and 8b are opened, a large amount of high pressure gas flows out to the downstream side. Furthermore, since downstream devices such as the exhaust fan 6 and the filter 12 have low pressure resistance, there is a risk that these devices will be damaged by the large amount of high-pressure gas that flows out.

Second, the first isolation valves 8a, 8b and the second isolation valve 9
When performing a pressure resistance/leakage test on the vent pipe 5 between the vent pipe 5 and the vent pipe 5, when the second isolation valves 9a and 9b are opened, the high pressure gas accumulated in the vent pipe 5 causes the exhaust fan 6 on the downstream side to ..., filter 12,1
There was a problem that damaged the 2nd class.

For this reason, conventionally, when exhausting the high pressure gas in the reactor containment vessel 2 after performing a pressure resistance/leakage test of the reactor containment vessel 2, the first isolation valve bypass valve 1
5a, 15b and the second isolation valves 9a, 9b were opened and closed in a complicated manner, and the high pressure gas was exhausted little by little. For this reason, the exhaust work was extremely inefficient.

Purpose of the Invention The purpose of the present invention is to damage equipment with low pressure resistance downstream of the vent piping when discharging a large amount of high-pressure gas stored in the reactor containment vessel after a pressure resistance/leakage test of the reactor containment vessel. An object of the present invention is to provide an exhaust system for a reactor containment vessel that can efficiently exhaust high-pressure gas without causing any damage.

Summary of the Invention In order to achieve the above object, the present invention includes a vent pipe whose one end is connected to a reactor containment vessel, a first isolation valve provided in the vent pipe, and a a second isolation valve provided, an exhaust fan provided downstream of the second isolation valve to exhaust gas in the reactor containment vessel, a bypass pipe that bypasses the second isolation valve, and this bypass pipe. a bypass valve whose opening degree can be adjusted; a pressure detector that detects the pressure on the downstream side of the second isolation valve; and an opening degree of the bypass valve is adjusted based on a detection signal from the pressure detector. and a control means for controlling the pressure on the downstream side of the second isolation valve to a predetermined pressure or less.

Embodiment of the Invention A first embodiment of the invention will be described with reference to FIG. In the figure, 101 is a nuclear reactor building, and a reactor containment vessel 102 is provided within this reactor building 101. This reactor containment vessel 102 is formed from a dry well 103 and a suppression chamber 104. And this dry well 1
One end of a vent pipe 105 communicates with 03 and the suppression chamber 104, and the other end of this vent pipe 105 communicates with an exhaust pipe 107 outside the reactor building 101. First isolation valves 108a and 108b are provided in a portion of the vent pipe 105 that communicates with the dry well 103 and a portion that communicates with the suppression chamber 104, respectively. Further, an exhaust fan 106 is provided on the downstream side of the vent pipe 105. Also,
An emergency gas processing pipe 110 is provided branching from the upstream side of the exhaust fan 106, and this emergency gas processing pipe 110 communicates with the exhaust pipe 107. And, in the middle of this emergency gas processing piping 110, there is a filter 112 of the emergency gas processing equipment...
Filter isolation valves 113... and exhaust fans 106... are provided. And the exhaust fan 106
Second isolation valves 109a and 109b are provided upstream of the emergency gas processing pipe 110 and in the middle of the emergency gas processing pipe 110, respectively. The first isolation valve 108a, 108
b. The second isolation valves 109a and 109b are large-diameter butterfly valves, and are configured to isolate the inside and outside of the reactor containment vessel 102. and,
Bypassing the upstream and downstream sides of the first isolation valves 108a and 108b, bypass piping 114a and 1
14b is provided, and this bypass piping 114a,
Bypass valves 115a and 115b, which are small-diameter butterfly valves, are provided at 114b. and,
The most downstream isolation valve, that is, the second isolation valve 109a, 1
Bypass pipes 116a and 116b are provided to bypass the upstream and downstream sides of 09b, and the bypass pipes 116a and 116b are provided with opening-adjustable bypass valves 117a and 117b. These opening degree-adjustable bypass valves 117a and 117b are electrically operated globe valves, and the opening degree can be adjusted arbitrarily. In addition, these second isolation valves 109
There are pressure detectors 1 on the downstream sides of a and 109b, respectively.
18a and 118b are provided, and these pressure detectors 118a and 118b detect pressure and convert it into an electrical signal. Electric signals from these pressure detectors 118a and 118b are sent to a control circuit 119. This control circuit 119 transmits a signal to a pressure display 120 to display the pressure on the downstream side of the second isolation valves 109a, 109b, and also displays the pressure on the downstream side of the second isolation valve 109a, 109b.
The pressure on the downstream side of these second isolation valves 109a, 109b is maintained at a predetermined pressure or less by adjusting the opening degrees of the second isolation valves 109a, 117b.

Next, the operation of this first embodiment will be explained. first,
During normal pressure adjustment in the reactor containment vessel 102, the first isolation valves 108a, 108b and the second isolation valve 10
9a, 109b, flow rate adjustment type bypass valve 117
a, 117b and bypass valves 115a, 1
The pressure is adjusted by opening and closing 15b. In addition, when adjusting the oxygen concentration in the reactor containment vessel 102, the first isolation valves 108a, 108b and the second isolation valve 10
9a and 109b are opened to rapidly discharge a large amount of gas.

Next, in the event that radioactive particles are mixed into the gas in the reactor containment vessel 102, the first isolation valve 108a,
108b, the second isolation valve 109b, the filter isolation valve 13... are opened, the gas in the reactor containment vessel 102 flows to the emergency gas processing pipe 110, and the filter 1
12 and 112, radioactive particles are separated and collected, and only clean gas is discharged into the exhaust stack. Then, pressure leakage test (Type A test) of the reactor containment vessel 102
When implementing, first the first isolation valve 108a, 1
08b, the second isolation valves 109a, 109b, bypass valves 115a, 115b, and opening-adjustable bypass valves 117a, 117b are all closed, and the inside of the reactor containment vessel 102 is pressurized to about 4 g/cm ² with nitrogen gas or the like. Perform a pressure leakage test. After the test, the bypass valves 115a and 115b are opened, and the opening-adjustable bypass valves 117a and 117b are slightly opened to drain the gas in the reactor containment vessel 102 to the vent pipe 105.
discharge through. At this time, the valve opening of the opening adjustable bypass valves 117a and 117b is set to the second isolation valve 1.
The pressure on the downstream side of 09a and 109b is adjusted by the control circuit 119 so as to be below a predetermined pressure. After the pressure inside the reactor containment vessel 102 becomes sufficiently low, the first isolation valves 108a, 10
8b and second isolation valves 109a, 109b are opened to discharge the gas. Note that the first isolation valve 108
A pressure leakage test (C type test) between a, 108b and the second isolation valves 109a, 109b is also conducted to discharge gas in the same manner as above.

In this way, by providing the bypass valves 117a, 117b whose opening degree can be adjusted in the bypass pipes 116a, 116b of the second isolation valves 109a, 109b, the pressure on the downstream side of the second isolation valves 109a, 109b can be kept below a predetermined pressure. Therefore, the gas in the reactor containment vessel 102 can be exhausted without damaging the exhaust fan 106, the filter 112, etc. Therefore, the gas in the reactor containment vessel 102 can be exhausted without the need for complicated opening/closing operations of the first isolation valve bypass valves 115a, 115b as in the prior art, thereby significantly reducing the burden on the operator.

In this first embodiment, the second isolation valves 109a, 109b of the conventional exhaust system are bypassed and flow rate regulating bypass valves 117a, 117b are provided, and only minor modifications are made to the existing equipment. It has the advantage of being able to be carried out.

Note that the present invention is not limited to the first embodiment described above.

For example, as in the second embodiment shown in FIG. 109 to bypass piping and flow rate regulating bypass valve 117
may be provided.

Further, the opening degree adjustment of the flow rate regulating bypass valve does not necessarily need to be performed automatically, and may be performed manually.

Effects of the Invention As explained above, the present invention includes a vent pipe whose one end is connected to the reactor containment vessel, a first isolation valve provided on the vent pipe, and a vent pipe provided on the downstream side of the first isolation valve. a second isolation valve; an exhaust fan provided on the downstream side of the second isolation valve to exhaust gas in the reactor containment vessel; a bypass pipe that bypasses the second isolation valve; and a bypass pipe provided in the bypass pipe. a bypass valve whose opening degree can be adjusted; a pressure detector that detects the pressure on the downstream side of the second isolation valve; and adjusting the opening degree of the bypass valve based on a detection signal from the pressure detector; and a control means for controlling the pressure on the downstream side of the second isolation valve to a predetermined pressure or less, so that the pressure inside the reactor containment vessel and the vent pipe is maintained while the pressure on the downstream side of the second isolation valve is kept below the predetermined pressure. Gas can be exhausted, and high pressure gas can be exhausted without damaging equipment provided downstream of the second isolation valve during class A and class C tests.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing a conventional exhaust system for a reactor containment vessel, FIG. 2 is a system diagram showing a first embodiment of the present invention, and FIG. 3 is a system diagram showing a second embodiment of the present invention. be. 101...Reactor building, 102...Reactor containment vessel, 103...Dry well, 104...Suppression chamber, 105...Vent piping,
106...Exhaust fan, 107...Exhaust pipe, 10
8...First isolation valve, 109...Second isolation valve, 11
0...Emergency gas processing piping, 112...Filter, 113...Filter isolation valve, 114...Bypass pipe, 115...Bypass valve, 116...Bypass pipe, 117...Adjustable opening type bypass valve, 11
8...Pressure detector, 119...Control circuit, 120
...Pressure indicator.

Claims (1)

[Claims] 1. A vent pipe whose one end is connected to the reactor containment vessel, a first isolation valve provided on this vent pipe, a second isolation valve provided on the downstream side of this first isolation valve, and this second isolation valve. an exhaust fan provided on the downstream side of the valve to exhaust gas in the reactor containment vessel, a bypass pipe that bypasses the second isolation valve, and a bypass valve provided in the bypass pipe whose opening degree can be adjusted; A pressure detector detects the pressure on the downstream side of the second isolation valve, and an opening degree of the bypass valve is adjusted based on a detection signal from the pressure detector, and the pressure on the downstream side of the second isolation valve is adjusted. 1. An exhaust system for a nuclear reactor containment vessel, comprising a control means for controlling the pressure to a predetermined pressure or less.