JPH0760196B2 - Radioactive gas waste treatment equipment - Google Patents

Description

Description: [Object of the Invention] (Field of Industrial Application) The present invention relates to a radioactive gas waste treatment apparatus in a nuclear power plant, and more particularly to improvement of hydrogen and oxygen injection control system.

(Prior Art) Generally, in a boiling water nuclear power plant, a radioactive gas waste treatment device is installed in the plant so that the radioactivity of the radioactive gas waste generated in the plant is sufficiently attenuated and then released into the atmosphere. I have to.

In a nuclear power plant, hydrogen gas (H ₂ ) is used in the primary system such as water supply in order to prevent stress corrosion cracking of the primary system of the nuclear reactor, prolong the life of highly irradiated materials in the reactor, and improve reliability. It is injected and combined with the oxygen gas (O ₂ ) generated by the radiolysis of the core in the core to generate water to reduce the dissolved oxygen in the reactor water and suppress the radiolysis of the reactor water to reduce hydrogen gas and I try to suppress the generation of oxygen gas.

By the way, when hydrogen gas is injected into the primary system piping, the hydrogen gas in the gaseous waste consists of the injected amount and the radiolytically decomposed part, and the oxygen gas is radiolyzed into the main condenser. The hydrogen gas and the oxygen gas do not exist in a stoichiometric amount ratio because they consist of the leaked amount.

Therefore, in the radioactive gas waste treatment device, a line for supplying oxygen gas is provided on the upstream side of the recombiner, and the equivalent amount of oxygen gas is supplied to recombine hydrogen gas.

FIG. 2 shows a conventional radioactive gas waste treatment device of this type, which is designed to attenuate the radioactivity of the radioactive gas waste from the primary reactor system.

The reactor primary system is configured by sequentially connecting a turbine 3, a turbine condenser 4 and a condensate purification device 5 to a reactor pressure vessel 1 via a closed loop primary system pipe 2, and the primary system pipe 2 is The main steam pipe 2A and the water supply pipe 2B are provided, and the turbine condenser 4 is connected with a radioactive gas waste treatment device.

As shown in FIG. 2, this radioactive gas waste treatment device includes an air extractor 7, a recombiner 8, a condenser 9, a plurality of rare gas holdup towers 10, a vacuum pump 11, and a stack via a pipe 6. It is configured by connecting 12 in sequence. A hydrogen supply device 13 is connected to the water supply pipe 2B via a hydrogen injection pipe 14, and an oxygen supply device 15 is connected to the upstream side of the recombiner 8 via an oxygen injection pipe 16.

In the above-described configuration, the hydrogen gas injected from the hydrogen supply device 13 into the water supply pipe 2B, together with hydrogen and other gases generated by the radiolysis of water in the reactor pressure vessel 1, the main steam pipe 2A, the turbine condenser 4 The air is extracted by the air extractor 7 via the and is introduced to the radioactive gas waste treatment device.

On the other hand, the oxygen gas from the oxygen supply device 15 is supplied to the oxygen injection pipe 16
Is injected into the upstream side of the recombiner 8 through the re-combiner 8, and hydrogen and oxygen are recombined in the recombiner 8. Then, the recombined hydrogen and oxygen are removed as water in the condenser 9.

The radioactive noble gas from which the water has been removed is subjected to radioactivity attenuation treatment in the noble gas hold-up tower 10, and after the radioactivity is sufficiently attenuated, it is released to the atmosphere from the stack 12 via the vacuum pump 11.

(Problems to be solved by the invention) In the conventional radioactive gas waste treatment device having the above configuration, this is applied to, for example, a boiling water nuclear power plant of 800,000 KWe class, and the hydrogen concentration in the feed water is 2 ppm. If you try to, if the main condenser leaks inlet air quantity and 30 Nm ³ / h, amount of hydrogen injection from the hydrogen supply device 13 is 100 Nm ³ / h, the oxygen injection amount from the oxygenator 15 50 Nm ³ It becomes / h, both of which are large, and when the injection control is not appropriate, it becomes a big problem.

That is, at the start of hydrogen injection, if the start of oxygen injection is delayed from an appropriate time, the hydrogen concentration on the downstream side of the recombiner 8 may fall within the explosion range (4 to 75 vol%), and conversely, If the start of oxygen injection is earlier than the appropriate time, there is a risk that a gas having a processing capacity of the rare gas holdup column 10 will flow.

Further, at the time of stopping the hydrogen injection, if the oxygen injection stop is delayed from an appropriate time, there is a possibility that a gas having a processing capacity of the rare gas hold-up column 10 may flow, and conversely, the oxygen injection stop may be delayed from an appropriate time. If it is advanced, the hydrogen concentration on the downstream side of the recombiner 8 may fall within the explosion range (4 to 75 vol%).

The present invention has been made in consideration of the above points, and provides a radioactive gas waste treatment device capable of achieving hydrogen explosion-proof measures during hydrogen injection and at the time of hydrogen injection stop, and maintaining the function of a rare gas retention capacity. With the goal.

[Structure of Invention]

(Means for Solving Problems) According to the present invention, a flow system for detecting the flow rate of radioactive rare gas from a condenser is provided on the upstream side of a rare gas holdup column, and hydrogen and oxygen supply devices are provided. A controller for controlling injection of hydrogen and oxygen based on a signal from the flow meter is provided.

(Operation) In the radioactive gas waste treatment device according to the present invention, the flow rate of the radioactive noble gas from the condenser is detected by the flow meter, and the hydrogen and oxygen controllers are controlled by the signal from the flow meter. To be done. Then, the start and stop times of hydrogen and oxygen injection and the injection amount are controlled. For this reason, it is possible to maintain hydrogen explosion-proof measures and rare gas retention functions when hydrogen is injected or stopped.

(Embodiment) An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, reference numeral 1 is a reactor pressure vessel, and the reactor pressure vessel 1 is provided with a main steam pipe 2A and a water supply pipe 2B through a primary system pipe 2 forming a closed loop, a turbine 3, The turbine condenser 4 and the condensate water purification device 5 are sequentially connected to form a reactor primary system. A radioactive gas waste treatment device is connected to the turbine condenser 4 of the primary reactor system.

As shown in FIG. 1, this radioactive gas waste treatment device re-combines the air bleeder 7 that bleeds the exhaust gas from the reactor pressure vessel 1 through the turbine condenser 4 and the bleed gas and oxygen. Recombiner 8, condenser 9 for condensing and removing recombined water, plural noble gas holdup towers 10 for attenuating radioactive noble gas from this condenser 9, after the radioactivity is sufficiently attenuated The vacuum pump 11 for sucking the noble gas and the stack 12 for discharging the noble gas from the vacuum pump 11 to the atmosphere are continuously formed through the pipe 6. A hydrogen supply device 13 is connected to the water supply pipe 2B via a hydrogen injection pipe 14, and an oxygen supply device 15 is connected to the upstream side of the recombiner 8 via an oxygen injection pipe 16.

The above configuration is basically the same as that of the conventional radioactive gas waste treatment device, and in this embodiment, the following configuration is further added.

That is, on the upstream side of the rare gas holdup tower 10, a flow meter 17 for detecting the flow rate of the rare gas from the recombiner 8 side is installed as shown in FIG. 1, and the injection pipes 14 and 16 are provided.
In this case, adjusting valves 18 and 19 for controlling the injection amount are installed, respectively. Both of the adjusting valves 18 and 19 are controlled by a signal from the flow meter.

Next, the operation of this embodiment will be described.

The radioactive gas waste treatment device according to the present embodiment, for example, 80
When it is applied to a boiling water nuclear power plant of 10,000 KWe class and the hydrogen concentration in the feed water is to be set to 2 ppm, the rare gas hold-up tower 10 processing capacity is 30 Nm ³ / h, and the main condenser leakage air amount is Ten
If it is Nm ³ / h, the processing capacity margin of the rare gas holdup tower 10 is 30−10 = 20 Nm ³ / h.

The hydrogen injected into the water supply pipe 2B is treated with radioactive hydrogen waste by the air extractor 7 through the main steam pipe 2A and the turbine condenser 4 together with hydrogen generated by the radiolysis of water in the reactor pressure vessel 1. Although it is led to the device, it corresponds to the processing capacity margin of the rare gas hold-up column 10 so that the hydrogen concentration does not fall within the explosion range (4 to 75 vol%) on the downstream side of the recombiner 8. 20 Nm ³ / h of oxygen is injected from the oxygen supply device 15 to the upstream side of the recombiner 8. At the same time or after this, 40 Nm ³ / h equivalent to the injected oxygen amount
The hydrogen is injected into the water supply pipe 2B from the hydrogen supply device 13 by the signal from the flow meter 17.

As a result, the injected oxygen and its equivalent hydrogen are recombined in the recombiner 8 and removed as water in the condenser 9. Therefore, the flow meter 17 again shows the condenser leaked air amount of 10 Nm ³ / h. So, repeat the above operation,
The regulating valve 18 is fixed when the hydrogen injection amount reaches 100 Nm ³ / h. As a result, the hydrogen concentration on the downstream side of the recombiner 8 does not fall within the explosion range (4 to 75 vol%), and moreover the gas exceeding the processing capacity of the rare gas hold-up tower 10 does not flow, and the water supply is reduced. It is possible to set the hydrogen concentration in the inside to 2 ppm.

On the other hand, in the case of stopping the hydrogen injection, after stopping the hydrogen from the hydrogen supply device 13, the signal from the flow meter 17 indicates that the processing capacity of the rare gas hold-up tower 10 is 30 Nm ³ / h,
The regulating valve 19 is driven to stop the oxygen injection from the oxygen supply device 15. As a result, the hydrogen concentration on the downstream side of the recombiner 8 does not fall within the explosion range (4 to 75 vol%),
Moreover, it is possible to stop the hydrogen injection without flowing a gas exceeding the processing capacity of the rare gas holdup column 10.

The above operation is generally shown as follows.

That is, the processing capacity of the rare gas hold-up tower 10 is XNm ³
/ h, main condenser leakage entering air amount xNm ³ / h, if the final amount of hydrogen injection into feedwater and ANm ³ / h, the main condenser leakage incoming air quantity X nm ³
/ h is detected by the flow meter 17, and the signal from the flow meter 17 drives the regulating valve 19 to inject (X−x) Nm ³ / h oxygen to the upstream side of the recombiner 8.

Simultaneously with or after this, the regulating valve 18 is driven by the signal from the flow meter 17, and 2 (X−x) Nm ³ / h of hydrogen is injected into the water supply pipe 2B. This allows the injected oxygen and
This and the equivalent amount of hydrogen are recombined by the recombiner 8 to become water, and the indication of the flow meter 17 becomes xNm ³ / h again.

After that, the above operation is repeated, and when the hydrogen injection amount from the hydrogen supply device 13 becomes ANm ³ / h, the adjusting valve 18 is fixed.

On the other hand, when stopping the hydrogen injection, first, the hydrogen supply device
Hydrogen injection from 13 was stopped, then flow meter 17 indicated
The signal that reaches xNm ³ / h drives the regulating valve 19 to stop the oxygen injection from the oxygen supply device 15.

In this way, based on the signal from the flow meter 17, each regulating valve 18,1
Since 9 is controlled, it is prevented that the inlet side of the recombiner 8 is always in the oxygen rich state and the hydrogen concentration is in the explosion range on the downstream side of the recombiner 8. Further, it is also possible to prevent the gas from flowing beyond the processing capacity of the rare gas holdup tower 10.

〔The invention's effect〕

As described above, the present invention controls the injection of hydrogen and oxygen based on the rare gas flow rate signal on the upstream side of the rare gas hold-up tower. It is possible to prevent the hydrogen concentration on the side from being within the explosion range, or to prevent a gas having a processing capacity or more from flowing into the rare gas holdup column. Therefore, hydrogen can be safely treated to improve the reliability of operation, and at the same time, the increase of radioactivity released to the environment can be prevented.

[Brief description of drawings]

FIG. 1 is a system diagram of a radioactive gas waste treatment device showing an embodiment of the present invention, and FIG. 2 is a system diagram of a conventional radioactive gas waste treatment device. 1 ... Reactor pressure vessel, 2B ... Water supply pipe, 4 ... Turbine condenser, 7 ... Air extractor, 8 ... Recombiner, 9 ... Condenser, 10 ... Rare gas hold-up tower , 13 …… Hydrogen supply device, 14 …… Hydrogen injection pipe, 15 …… Oxygen supply device, 16 ……
Oxygen injection pipe, 17 …… Flowmeter, 18, 19 …… Regulator valve.

Claims (3)

[Claims] 1. A hydrogen supply device for injecting hydrogen into a water supply pipe of a reactor pressure vessel, an air bleeder for bleeding exhaust gas from the reactor pressure vessel through a main condenser, and oxygen for this bleed gas. An oxygen supply device for supplying, a recombiner for recombining the extracted gas and oxygen, a condenser for condensing the recombined water, and a rare gas holdup tower for attenuating radioactive rare gas from the condenser. In the radioactive gas waste treatment device comprising and, on the upstream side of the rare gas holdup tower,
A radioactive gas waste characterized in that a flow meter for detecting the flow rate of the radioactive noble gas is provided, and each of the supply devices is provided with a controller for controlling the injection of hydrogen and oxygen based on a signal from the flow meter. Processing equipment. 2. A controller for controlling injection of hydrogen and oxygen based on a signal from a flow meter, a hydrogen injection amount adjusting valve for controlling the injection amount of hydrogen from the hydrogen supply device, and an injection amount of oxygen from the oxygen supply device. The radioactive gas waste treatment device according to claim 1, further comprising an oxygen injection amount adjusting valve for controlling the above. 3. The processing capacity of the rare gas hold-up tower is XN,
The oxygen injection amount control valve injects (X-x) N oxygen to the upstream side of the recombiner, where xN is the leaked air amount of the main condenser and AN is the final hydrogen injection amount into the feed water. The hydrogen injection amount control valve is operated to inject 2 (X-x) N hydrogen into the water supply pipe.
The radioactive gas waste treatment device according to the item.