JPS61119993A - Vacuum degree controller of main condenser - Google Patents

Abstract

PURPOSE:To make it feasible to maintain the vacuum degree in a main condenser within specified range by a method wherein a feedback piping to feed non-condensing gas processed in an off gas processing system back to a main condenser as well as an ON-OFF valve to be opened and closed by detecting signals from a vacuum degree detector are provided. CONSTITUTION:Non-condensing gas in a main condenser 1 is extracted by an air extractor 2 and after processing by an off gas processing system 3 to be discharged into atmosphere through a stack 4. As soon as the vacuum degree reaches the rated value of main condenser 1, a vacuum degree detector 19 is started to transmit vacuum degree detecting signals to ON-OFF valve 18. The ON-OFF valve 18 is opened to feed the non-condensing gas being discharged into atmosphere so far back to the main condenser 1 through a pressure regulating valve 15 to prevent the main condenser 1 from being excessively vacuumized. As soon as the vacuum degree declines to the specified range, the vacuum degree detector 19 is reset to open the ON-OFF valve 18 so that the non- condensing gas processed by the off gas processing system 3 may discharge into atmosphere through the stack 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a main condenser vacuum level control device for controlling the vacuum level of a main condenser within a specified range in a nuclear power plant.

[Technical background of the invention]

Conventionally, in order to maintain the vacuum level of the main condenser in a nuclear power plant, the non-condensable gas in the main condenser 1 is extracted by an air extractor 2, as shown in Figure 2, and the extracted non-condensable gas is The degree of vacuum in the main condenser 1 is maintained by treating the gas in the off-gas treatment system 3 and then releasing it to the atmosphere through the stack 4.

In the off-gas treatment system 3, the non-condensable gas extracted by the air extractor 2 is first raised in gas temperature by an exhaust gas preheater 5, and then hydrogen molecules and oxygen molecules in the gas are recombined by an exhaust gas recombiner 6. The water is combined and returned to water, and further cooled in the exhaust gas condenser 7. The water cooled in the exhaust gas condenser 7 is returned to the main condenser 1 through a drain pipe (not shown), and only non-condensable gas is The flow rate is set by the flow rate adjustment valve 8 to 4ONm3, which is the design operating flow rate.
/h, r or less and sent to the precooler 9. In the precooler 9, the dew point temperature of the gas is lowered to about -40° C., and then sent to the dryer 10, where the non-condensable gas is dehumidified. The non-condensable gas removed by the dryer 10 is sent to the rare gas hold-up tower 11, where the radioactivity is attenuated over a hold-up time of 40 to 70 hours, and then stacked by the exhaust gas vacuum bomb 12. It is released into the atmosphere through 4.

In addition, when the flow direction of the non-condensable gas flowing into the off-gas treatment system 3 exceeds 4ONrn3/hr, a bypass line 1 provided between the exhaust gas condenser 7 and the flow rate regulating valve 8 is provided.
3, excess gas is returned to the main condenser 1. This bypass line 13 is provided with a 6111 valve 14 and a pressure regulating valve 15, and the pressure regulating valve 15 is activated by the detection signal from the pressure detector 16 provided at the outlet of the exhaust gas condenser 7. The pressure is controlled so that the outlet pressure is OKg/Cm2.

(Problems with the Background Art) By the way, the design operating flow rate of such off-gas treatment system 3 is <4ONm3/hr as described above, but when the plant is in steady operation, the gas flow rate flowing into the off-gas treatment system 3 is Even if the in-leakage to the main condenser 1 is included, it is at most about 1 ONm'/hr. Therefore, during steady operation, the degree of vacuum in the main condenser 1 increases, making it difficult to maintain the rated operating value of 722 mHgVaC, and the main condenser 1 enters a high vacuum state. If the main condenser reaches a high vacuum state, it will lead to deformation of the main turbine body casing, etc.
This may have an adverse effect on the main turbine, and if the flow layer flowing into the off-gas treatment system 3 decreases, the temperature of the precooler 9 and dryer 10 will rise, causing a trip.

When the main condenser 1 reaches a high vacuum like this, conventionally the vacuum breaker valve (not shown) of the main condenser 1 is slightly opened to allow outside air to leak into the main condenser 1. As a result, the degree of vacuum in the main condenser 1 is reduced. However, such an operation is not a normal operation, and if the slightly opened vacuum breaker valve were to fail to close, the degree of vacuum in the main condenser 1 would drop more than expected, and eventually the atomic May lead to furnace scram.

(Object of the Invention) The present invention was made based on the above circumstances, and its purpose is to maintain the degree of vacuum in the main condenser within a specified range and to prevent trips due to a decrease in the flow rate of the off-gas treatment system. An object of the present invention is to provide a vacuum degree control device for a main condenser that can prevent such problems.

[tR requirements for invention]

In order to achieve the above object, the present invention is characterized by having the following configuration. That is, the main condenser vacuum level control device according to the present invention includes: a vacuum level detector that detects the vacuum level of the main condenser; an air extractor that extracts non-condensable gas in the main condenser; an off-gas treatment system that processes the non-condensable gas extracted by the air extractor and releases it to the atmosphere, and a condenser return piping that returns the non-condensable gas treated by the off-gas treatment system to the main condenser; The condenser return pipe is provided with an on-off valve that opens and closes in response to a detection signal from the vacuum level detector.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an off-gas treatment system showing an embodiment of the present invention.
In the J#18 system diagram, the same parts as in Fig. 2 are given the same reference numerals. In the figure, 17 is a condenser return pipe that returns the process gas processed in the off-gas treatment system 3 to the main condenser 1. This condenser return pipe 17 is connected to the vacuum pump 12, four stacks, the isolation valve 14, It is connected between the regulating valves 15. This condenser return pipe 17 is provided with an on-off valve 18, and a vacuum level detector 19 for detecting the vacuum level of the main condenser 1.
It is designed to open and close based on the detection signal from.

Next, the operation of the above embodiment will be explained.

As described above, the non-condensable gas in the main condenser 1 is extracted by the air extractor 2, treated by the off-gas treatment system 3, and then discharged to the atmosphere through the stack 4. air extractor 2
When the degree of vacuum in the main condenser 1 reaches the rated value (722IllImHgVaC) by operating the off-gas treatment system 3,
The vacuum level detector 19 operates and the vacuum level detection signal is output to the open/close valve 1.
Send to B.

The on-off valve 18 is opened by the vacuum level detection signal from this one vacuum level detector, and the non-condensable gas that has been released to the atmosphere is returned to the main condenser 1 via the pressure regulating valve 15. This prevents the main condenser 1 from becoming highly vacuumed. Note that when the on-off valve 18 is open, the pressure on the main condenser 1 side is lower than the pressure on the stack 4 side, so most of the non-condensable gas exhausted from the vacuum exhaust pump 12 goes to the condenser return pipe. 17 and return to the main condenser 1.

In this way, when the degree of vacuum in the main condenser 1 reaches the rated voltage, the on-off valve 18 opens and the non-condensable gas treated in the off-gas treatment system 3 leaks into the main condenser cohesion. The degree of vacuum in the main condenser 1 gradually decreases. When the degree of vacuum in the main condenser 1 falls to within a specified range, one of the vacuum degree detectors is reset and the on-off valve 18 is closed. As a result, the non-condensable gas treated in the off-gas treatment system 3 is released to the atmosphere through the stack 4, and the main condenser 1
The degree of vacuum in the main condenser 1 rises again, but when it reaches the rated voltage, the on-off valve 18 opens again, so that by repeating the above, the degree of vacuum in the main condenser 1 is kept within a certain range.As is clear from the above explanation. According to the present invention, it is possible to maintain the degree of vacuum in the main condenser within a specified range, so it is possible to prevent the main turbine from being adversely affected by the high vacuum of the main condenser, and also to prevent the main turbine from being adversely affected by the high vacuum of the main condenser. Trips can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a schematic system diagram of an off-gas treatment system showing an embodiment of the present invention, and FIG. 2 is a schematic system diagram of a conventional off-gas treatment system. DESCRIPTION OF SYMBOLS 1... Main condenser, 2... Air extractor, 3... Off gas treatment system, 4... Stack, 17... Condenser return piping, 18... Open/close valve, 19... ...Vacuum level detector.

Claims (1)

[Claims] A vacuum level detector detects the degree of vacuum in the main condenser, an air extractor extracts non-condensable gas in the main condenser, and processes the non-condensable gas extracted by the air extractor. an off-gas treatment system that discharges the non-condensable gas to the atmosphere; a condenser return pipe that returns the non-condensable gas treated in the off-gas treatment system to the main condenser; A vacuum degree control device for a main condenser, comprising an on-off valve that opens and closes in response to a detection signal.