JPH11248883A - Radioactive gas waste processing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute to stably control temperature and maintain an efficient system operation without being affected by the failure of peripherals. SOLUTION: To an exhaust gas preheater outlet pipe 9 connecting the primary side 1a of an exhaust gas preheater 1 and an exhaust gas recombiner 2, an electric heater 23 for the pipe is attached. A return pipe 24 connecting the exhaust gas recombiner 2 and the secondary side 1b of the exhaust gas preheater 1 is provided. A gas flow pipe 25 connecting the secondary side 1b of the exhaust gas preheater 1 and the primary side 3a of the exhaust gas condenser 3 is provided. By this, the high temperature exhaust gas generated in the exhaust gas recombiner 2 is again returned to the secondary side 1b of the exhaust gas preheater 1 and made exchange heat to cool the exhaust gas in the secondary side 1b. The cooled exhaust gas flows in the primary side 3a of the exhaust gas condenser 3 and is further cooled. Therefore, the exhaust gas in the primary side 1a is heated by the high temperature exhaust gas having flown in the secondary side 1b of the exhaust gas preheater 1 and so the efficiency of the exhaust gas recombiner 2 can be raised.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiolysis gas (hydrogen /
A radioactive gas waste treatment system with an improved exhaust gas pre-heater and exhaust gas condenser piping system, with a focus on an exhaust gas re-combiner for re-combining oxygen with a catalyst, to enable stable pre-heating. About.

[0002]

2. Description of the Related Art In a boiling water nuclear power plant, steam generated in a nuclear reactor is guided to a turbine and a generator is rotated to generate power. Radioactive exhaust gas from the turbine is supplied to a turbine main body by a radioactive gas waste treatment system. Air is extracted from the condenser by an air extractor and safely processed to reduce radioactivity.

[0003] The radioactive gas waste treatment system generally comprises a turbine main condenser, an air extractor, a recombiner, a dehumidifying dryer, a hold-up tower, and a discharge system device. Through the exhaust stack.

In the exhaust gas recombiner, the radiolysis gas (hydrogen / oxygen) of the reactor water is recombined by a catalyst, and in the hold-up tower, the radioactive fission products are time-decayed by the hold-up effect of activated carbon to reduce radioactivity. Is going on.

Referring to FIG. 2, the outline of a conventional piping system for treating radioactive exhaust gas from an air extractor to a dehumidifying cooler (dehumidifying dryer) will be described. 2, reference numeral 1 denotes an exhaust gas preheater having a primary side 1a and a secondary side 1b, reference numeral 2 denotes an exhaust gas recombiner, and reference numeral 3 denotes an exhaust gas condenser having a primary side 3a and a secondary side 3b. I have.

The exhaust gas preheater 1 is connected to an exhaust gas preheater inlet pipe 4 from an air extractor (not shown) on the primary side 1a,
An in-house steam inflow pipe 6 having a temperature control valve 5 for flowing in-house steam into the secondary side 1b, and an in-house steam return pipe 8 having a drain trap 7 are connected.

[0007] A first temperature sensor 10 is connected to an exhaust gas preheater outlet pipe 9 which connects the exhaust gas preheater 1 and the exhaust gas recombiner 2.
The first temperature sensor 10 is electrically connected to the temperature controller 11, and the temperature controller 11 is electrically connected to the temperature control valve 5.

The exhaust gas recombiner 2 has a short electric heater 12
And a second temperature sensor 13. The electric heater 12 and the second temperature sensor 13 have an electric circuit electrically connected to the temperature switch 14. The exhaust gas recombiner outlet pipe 15 is connected to the primary side 3 a of the exhaust gas condenser 3.

The gas system on the primary side 3a is connected to an exhaust gas condenser outlet pipe 16 connected to a dehumidifying cooler (not shown), the liquid system is connected to a liquid trap 17, and the liquid trap 17 is connected to a main condenser. A liquid outflow pipe 19 having a water level control valve 18 connected to a water device (not shown) is connected to a water level sensor 20. The water level control valve 18 and the water level sensor 20 have an electric circuit that is electrically connected to the water level controller 21. Reactor accessory cooling water piping 22 is connected to the secondary side 3b.

The exhaust gas preheater 1 passes through the primary side 1a the exhaust gas guided from the main condenser by the air extractor and passes through the secondary side 1a.
In this apparatus, the internal steam is ventilated to b and the exhaust gas on the primary side 1a is heated by the heat of the internal steam to increase the efficiency of recombining hydrogen and oxygen in the exhaust gas in the next exhaust gas recombiner 2.

The exhaust gas recombiner 2 is filled with a catalyst, and if water droplets adhere to the surface of the catalyst, the catalytic effect is weakened.
In order to keep the exhaust gas temperature constant, the exhaust gas preheater 1 detects the temperature of the exhaust gas with the first temperature sensor 10 of the exhaust gas preheater outlet pipe 9 and controls the opening of the temperature control valve 5 with the temperature controller 11. The steam flow is adjusted.

Further, condensed water of the in-site steam generated by heat exchange in the exhaust gas preheater 1 is returned to the in-site steam return system via the drain trap 7. The exhaust gas recombiner 2 has a catalyst inside, and is an apparatus that efficiently combines oxygen and hydrogen with the exhaust gas heated by the exhaust gas preheater 1 using the catalyst to reduce the volume of the exhaust gas.

The exhaust gas recombiner 2 detects the temperature in the exhaust gas recombiner 2 by a second temperature sensor 13 and keeps the electric heater 12 by a temperature switch 14 in order to keep the catalyst in the container in a dry state during standby. Is controlling.

In the exhaust gas condenser 3, the high-temperature exhaust gas from the exhaust gas recombiner 15 is passed through the primary side 3a, and the cooling water 22 of the reactor auxiliary equipment is passed through the secondary side 3b to exchange heat. Is a device that condenses the vapor content of the gas and reduces the volume of the flow gas. The hot exhaust gas is cooled by the exhaust gas condenser 3 and the liquid trap
The condensed water condensed in 17 is detected by a water level sensor 20, a water level controller 21 controls a water level control valve 13, and is discharged to a main condenser.

Next, the normal operation of the radioactive gas waste treatment system will be described. The exhaust gas (about 140 ° C) extracted from the main condenser by the air extractor is the primary side 1a of the exhaust gas preheater 1.
To the secondary side 1b,
Heat to ° C. The heated exhaust gas flows into the exhaust gas recombiner 2 and forcibly recombines hydrogen and oxygen in the exhaust gas by a catalytic effect to become a gas containing steam.

When hydrogen and oxygen are combined in the exhaust gas recombiner 2, the temperature in the exhaust gas recombiner 2 rises to about 320 ° C. The high-temperature exhaust gas generated in the exhaust gas recombiner 2 enters the primary side 3a of the exhaust gas condenser 3, and the steam in the exhaust gas is cooled by the cooling water in the cooling water system piping 22 of the reactor auxiliary equipment. Guided to the vessel.

[0017]

However, in the system in which the in-house steam flows into the secondary side 1b and the exhaust gas is preheated (heated) in the primary side 1a of the exhaust gas preheater 1, the failure of the in-house boiler that produces the in-house steam, There is a problem that steam is not supplied due to the influence of peripheral devices such as malfunction of the temperature control valve 5 and failure of the temperature controller 11, and stable temperature control cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has been made stable without being affected by failure of peripheral equipment such as an in-house boiler for generating in-house steam, a temperature control valve, and a temperature controller. An object of the present invention is to provide a radioactive gas waste treatment system capable of controlling temperature and maintaining efficient system operation.

[0019]

According to a first aspect of the present invention, a gaseous waste to be treated extracted from a turbine main condenser by an air extractor flows into a primary side of an exhaust gas preheater and is heated. Radioactive gas waste treatment that removes H ₂ and O ₂ generated by radiolysis of reactor water by using exhaust gas recombiner, flows into exhaust gas condenser, and diverts to dehumidifying cooler and the main condenser In the system, an electric heater for exhaust gas is provided at an exhaust gas preheater outlet pipe communicating the primary side of the exhaust gas preheater and the exhaust gas recombiner, and an outlet side of the exhaust gas recombiner and a secondary side of the exhaust gas preheater are provided. And a gas distribution pipe communicating the secondary outlet of the exhaust gas preheater and the primary side of the exhaust gas condenser is provided.

According to a second aspect of the present invention, there is provided an electric circuit for attaching a temperature switch to the electric heater for piping, attaching a temperature sensor to the exhaust gas preheating outlet piping, and electrically connecting the temperature sensor and the temperature switch. Is provided.

According to a third aspect of the present invention, the cooled exhaust gas passing through the secondary side of the exhaust gas preheater is guided to the primary side of the exhaust gas condenser, and the exhaust gas flowing into the primary side is supplied to the reactor auxiliary. A piping system for cooling with machine cooling water is provided.

According to the first aspect of the present invention, the exhaust gas preheater and the exhaust gas recombiner use the high-temperature exhaust gas generated by the exhaust gas recombiner instead of the in-house steam conventionally used in the exhaust gas preheater. By ventilating the secondary side of the exhaust gas preheater, it exchanges heat with the exhaust gas passing through the primary side, the primary side exhaust gas is heated, and the secondary side exhaust gas is cooled, thus reducing the efficiency of the radioactive gas waste treatment system. Can be improved.

According to the second aspect of the present invention, the electric heater for piping provided at the exhaust pipe of the exhaust gas preheater, which is the inlet pipe of the exhaust gas recombiner, generates a small amount of hydrogen such as at the time of starting the reactor, and recombines the exhaust gas. The exhaust gas can be heated to an appropriate temperature when sufficient waste heat of the vessel is not available and supplied to the exhaust gas recombiner to increase the efficiency of the exhaust gas recombiner.

According to the third aspect of the present invention, the auxiliary water cooling system piping of the secondary reactor of the exhaust gas condenser is incorporated on the primary side, so that the conventional auxiliary equipment is not required and the equipment can be prevented from malfunctioning. Regardless, stable cooling can be performed.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a radioactive gas waste treatment system according to the present invention will be described with reference to FIG. FIG.
2, the same parts as those in FIG. 2 are denoted by the same reference numerals, and the description of the overlapping parts will be omitted.

This embodiment is different from the conventional example shown in FIG. 2 in that, as shown in FIG.
In the exhaust gas preheater outlet pipe 9 that communicates with the exhaust gas preheater 2, a long pipe electric heater 23 is provided, and the outlet side of the exhaust gas recombiner 2 and the secondary side 1b of the exhaust gas preheater 1 are connected. A return pipe 24 is provided, and a gas circulation pipe 25 for connecting the secondary side 1b of the exhaust gas preheater 1 and the primary side 3a of the exhaust gas condenser 3 is provided.

A second temperature switch 26 is electrically connected to the piping electric heater 23, and the second temperature switch 26 has an electric circuit electrically connected to the first temperature sensor 10. Other parts are almost the same as those in FIG.

Next, the operation of the above embodiment will be described.
Exhaust gas preheater 1 uses exhaust gas from the air extractor as primary side 1a.
Through the secondary side 1b instead of in-house steam
The high-temperature exhaust gas generated in the step is passed through the return pipe 24 to perform heat exchange. The exhaust gas recombiner 2 is a device that combines the exhaust gas heated by the exhaust gas preheater 1 with oxygen and hydrogen using a catalyst to reduce the volume of the exhaust gas.

The high-temperature exhaust gas generated in the exhaust gas recombiner 2 is returned to the secondary side 1b of the exhaust gas preheater 1. When the reactor is started, the amount of hydrogen generated is small.
23, a first temperature sensor 10 detects the exhaust gas temperature at the inlet of the exhaust gas recombiner 2, and a second temperature switch 26 controls the pipe electric heater 23 so that the exhaust gas at an appropriate temperature is supplied to the exhaust gas recombiner 2. Can supply.

The short electric heater 12 provided in the exhaust gas recombiner 2 detects the temperature in the container of the exhaust gas recombiner 2 with the second temperature sensor 13 during standby, and turns on the electric heater 12 with the temperature switch 14. Control to keep the catalyst dry at all times.

The exhaust gas condenser 3 vents the exhaust gas heat-exchanged on the secondary side 1b of the exhaust gas preheater 1 into the primary side 3a, and supplies the cooling water of the reactor auxiliary equipment cooling water system pipe 22 to the secondary side 3b. Then, heat exchange is performed, and volume reduction and cooling of the exhaust gas are performed. The condensed water generated by cooling the exhaust gas in the exhaust gas condenser 3 is detected by a water level sensor 29, and the water level controller 21 controls the water level control valve 18.
Is operated to discharge to the main condenser through the liquid outflow pipe 19.

Next, the normal operation of this embodiment will be described. When the amount of hydrogen gas generated at the time of starting the reactor is small, the exhaust gas extracted from the main condenser by the air extractor is not sufficiently heated even if it passes through the exhaust gas preheater 1. Therefore, the temperature of the exhaust gas is raised to about 160 ° C. by the electric heater for piping 23 provided on the exhaust gas preheater outlet pipe 9. Thereby, the efficiency of the recombination of hydrogen and oxygen in the exhaust gas in the exhaust gas recombiner 2 is increased.

When the reactor output reaches the rated output and the amount of generated hydrogen increases, the recombination of hydrogen and oxygen in the exhaust gas recombiner 2 becomes active, the temperature of the exhaust gas recombiner 2 rises, and the exhaust gas preheating The temperature of the exhaust gas flowing into the secondary side of the vessel 1 increases. While the temperature of the exhaust gas rises, the electric heater for piping 23
Is automatically turned OFF, and thereafter, stable heat exchange is performed on the secondary side 1b of the exhaust gas preheater 1 by the waste heat of the exhaust gas recombiner 2.

In an emergency such as when the nuclear reactor is automatically shut down, the electric heater 23 for piping of the exhaust gas recombiner 2 is automatically turned on to perform appropriate temperature control. Exhaust gas recombiner 2
The high-temperature exhaust gas generated in the above is cooled on the secondary side of the exhaust gas preheater 1, flows into the exhaust gas condenser 3,
Is further cooled and condensed, and guided to the next exhaust gas dehumidifying cooler.

According to the present embodiment, the exhaust gas recombiner 2
Does not directly flow into the exhaust gas condenser 3, so that the flow rate of the reactor auxiliary equipment cooling water system can be reduced. Also, by recombining with the exhaust gas recombiner and returning the high temperature exhaust gas to the exhaust gas preheater again and exchanging heat,
Stable preheating can be performed without being affected by troubles of peripheral devices.

[0036]

According to the present invention, heat can be exchanged in the same system by using waste heat of an exhaust gas recombiner for preheating of an exhaust gas preheater, and there is no accessory equipment.
Stable temperature control can be performed without being affected by other factors. Also,
Since the high-temperature exhaust gas is not directly cooled by the exhaust gas condenser, the load on the cooling water system for the reactor auxiliary equipment is reduced, and efficient operation can be continued.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of a radioactive gas waste treatment system according to the present invention.

FIG. 2 is a system diagram for explaining a conventional radioactive gas waste treatment system.

[Explanation of symbols]

1 ... exhaust gas preheater, 1a ... primary side, 1b ... secondary side, 2 ...
Exhaust gas recombiner, 2a ... Primary side, 2b ... Secondary side, 3 ... Exhaust gas condenser, 3a ... Primary side, 3b ... Secondary side, 4 ... Exhaust gas preheater inlet piping, 5 ... Temperature control valve, 6 ... In-plant steam inflow pipe, 7 ... Drain trap, 8 ... In-plant steam return pipe, 9 ...
Exhaust gas preheater outlet piping, 10: first temperature sensor, 11: temperature controller, 12: electric heater, 13: second temperature sensor, 14
… Temperature switch, 15… Exhaust gas recombiner outlet pipe, 16… Exhaust gas condenser outlet pipe, 17… Liquid trap, 18… Water level control valve, 19… Liquid outflow pipe, 20… Water level sensor, 21… Water level controller, 22: Reactor accessory cooling water piping, 23: Electric heater for piping, 24: Return piping, 25: Gas distribution piping, 26: Second temperature switch.

Claims (3)

[Claims] A gas waste to be treated extracted from an air extractor from a main condenser of a turbine flows into a primary side of an exhaust gas preheater to be heated, and the heated exhaust gas is subjected to radiolysis of reactor water by an exhaust gas recombiner. In the radioactive gas waste treatment system which removes H ₂ and O ₂ generated by the gas and flows into the exhaust gas condenser, and is diverted to the dehumidifying cooler and the main condenser, the primary side of the exhaust gas preheater and the exhaust gas A pipe electric heater is provided on an exhaust gas preheater outlet pipe communicating with a recombiner, and a return pipe communicating the outlet side of the exhaust gas recombiner and a secondary side of the exhaust gas preheater is provided. A radioactive gas waste treatment system comprising a gas distribution pipe communicating a secondary outlet and a primary side of the exhaust gas condenser. 2. A temperature switch is attached to the electric heater for piping, a temperature sensor is attached to the exhaust gas preheating outlet piping, and an electric circuit for electrically connecting the temperature sensor and the temperature switch is provided. Claim 1
A radioactive gas waste treatment system as described. 3. A pipe for guiding the cooled exhaust gas passing through a secondary side of the exhaust gas preheater to a primary side of the exhaust gas condenser, and cooling the exhaust gas flowing into the primary side with cooling water for a nuclear reactor auxiliary machine. 2. The radioactive gas waste treatment system according to claim 1, further comprising a system.