JPH10288693A - Purifier of condenser and its operation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively purify radioactive iodine in a condenser prior to the relief of turbine even with the existence of radioactive iodine in the condenser air phase and make the release of radioactive iodine zero by placing an iodine removing filter in the exhaust side of the condenser vacuum pump exhausting the air in the condenser. SOLUTION: Downstream a condenser vacuum pump 6 placed by way of a suction pipe from the condenser 2, an iodine removing filter 10 is placed in parallel to the pipe. A recirculation pipe 15 circulates gas after processing from the filter 10 outlet to the condenser 2. After shutting down the plant, opening a condenser vacuum breaker valve 9 and introducing air into the condenser 2 to be atmospheric pressure, inside of the condenser is again degassed to vacuum by a vacuum pump. In the condenser vacuum raising operation, an inlet valve 11 and outlet valve 12 are opened and a bypass valve 10 is closed, the exhaust gas of the vacuum pump 6 is passed through the iodine removing filter 10 and the radioactive iodine exhausted from the condenser 2 is absorbed in the filter 10 and released out of a stack 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a condenser purification system and a method for operating the same in a boiling water reactor facility.

[0002]

2. Description of the Related Art FIG. 2 schematically shows a conventional condenser and vacuum pump equipment, which will be described below with reference to FIG.

[0003] In the boiling water reactor facility, a system is used in which the turbine 1 is directly driven by steam generated in the reactor to generate power. If radioactive iodine is present in the reactor water, a part of the steam is generated. At the same time, it flows into the turbine 1 and the condenser 2. During the operation of the plant, these are extracted by the air extractor 3, and after the radioactive iodine and the rare gas are sufficiently attenuated in the gas waste treatment system 4, they are released to the environment from the exhaust stack 5.

[0004] When the plant is stopped, a very small amount of radioactive iodine is present in the gas phase of the condenser. After confirming that the emission amount is sufficiently low by the main exhaust pipe monitor via, the release is managed from the exhaust pipe.

On the other hand, when starting up the reactor, the steam generated in the reactor is condensed in the condenser 2, so that the condenser 2 must be kept at a vacuum (about -700 mmHg). Therefore, when starting up the plant, the condenser vacuum pump 6 for degassing the condenser gas phase part is required to make the condenser and the turbine system piping vacuum before starting the nuclear reactor. A vacuum pump 6 is installed from the condenser gas phase through an intake pipe 7, and the exhaust gas is guided to an exhaust pipe 5 through a particle removal filter 8. When radioactive iodine is present in the condenser, the radioactive iodine in the condenser is exhausted through the condenser vacuum pump 6, and the emission amount is sufficiently low in the main exhaust pipe monitor. Controlled release from the stack while confirming that.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the amount of radioactive iodine released from the ventilation system to the environment when the turbine is released even when radioactive iodine is present in the condenser gas phase. Therefore, prior to opening the turbine, the radioactive iodine in the condenser should be effectively purified.

[0007]

According to the present invention, there is provided an iodine removal filter installed in parallel with a pipe on the downstream side of a condenser vacuum pump installed from a condenser gas phase through an intake pipe. Install. Then, a recirculation pipe for circulating the treated gas to the condenser through the valve from the iodine filter outlet side is installed.

[0008] With the condenser purifier constructed as described above, the inside of the condenser can be degassed to a vacuum state without releasing radioactive iodine to the environment. By circulating the water from the circulation pipe to the condenser, the inside of the condenser can be scavenged and purified.

[0009]

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

FIG. 1 shows an embodiment of the present invention.

When the operation of the plant is stopped to check the turbine, etc., the condenser vacuum release valve 9 is opened to allow the air to flow into the condenser 2 and to set the inside of the condenser 2 to the atmospheric pressure. State,
Thereafter, the casing of the turbine 1 is opened. At this time,
In order to prevent radioactive iodine existing in the condenser 2 from being released from the open condenser, radioactive iodine in the condenser 2 and the secondary system piping and equipment is released before opening. It is desirable to remove them.

FIG. 3 shows an outline of the secondary piping and equipment of the boiling water reactor equipment. As shown in this figure, many pipes and equipment such as a main steam pipe 17, a bleed pipe 18, a moisture separator 19, a cross-around pipe 20 and the like are connected to the condenser 2, and most of them are connected when the plant is stopped. The tip is closed by closing the valve. Therefore, when air is introduced into the condenser gas phase to bring the condenser to atmospheric pressure, the gaseous radioactive iodine that was present in the condenser at the time of vacuum decreases in volume as the pressure rises, These tips are pushed to the corners of the secondary pipe in a closed state. Therefore, before scavenging and purifying the condenser and secondary piping before opening the condenser, radioactive iodine in the piping is effectively removed if only the condenser gas phase is scavenged. This is not possible, and this diffuses into the condenser gas phase for a long time after the turbine is released, and becomes a release source for releasing iodine from the turbine opening into the building.

As a means for effectively removing and purifying radioactive iodine remaining in these pipe tips and equipment, after the plant is stopped, the condenser vacuum release valve 9 is opened and air is introduced into the condenser 2. , And then the condenser vacuum release valve 9 is closed again, and the condenser vacuum pump 6 is operated, and the condenser 2 is evacuated to a vacuum of about -700 mmHg. I care. By making the inside of the condenser 2 vacuum, the air at the tip of the secondary system piping and the equipment also expands with the decompression, and radioactive iodine in the piping and equipment flows out to the gas phase part of the condenser 2. come. In this condenser vacuum rising operation, the inlet valve 11 and the outlet valve 12 are opened, the bypass valve 13 is closed, and the exhaust of the vacuum pump 6 is made to pass through the iodine removal filter 10. After the discharged radioactive iodine is adsorbed on the iodine removal filter 10, the radioactive iodine is discharged from the exhaust stack 5.

After the condenser is evacuated and the pipes and radioactive iodine are discharged from the apparatus, the condenser vacuum release valve 9 is opened again, and air is injected into the condenser 2 to recover the condenser. Bring water and secondary piping equipment to atmospheric pressure. Then, with the inlet valve 11 opened, the outlet valve 12 closed, and the recirculation valve 14 opened, the condenser vacuum pump 6 is operated, and the gas flows out to the condenser 2 gas phase due to the system vacuum rise. After the radioactive iodine is adsorbed by the iodine removal filter 8, it is returned to the condenser 2 gas phase again by the recirculation pipe 15. During this operation, the gas waste is prevented from being in a negative pressure state in the condenser 2 and the radioactive iodine in the condenser 2 is prevented from leaking into the turbine building from a gap such as a shaft portion of the turbine 1. By operating the treatment system blower 16, the air in the condenser is sucked into the gaseous waste treatment system 4, and the inside of the condenser 2 is maintained at a slightly negative pressure.

By repeating the operation of increasing the vacuum in the condenser, injecting air, and recirculating the filter, radioactive iodine retained in the condenser and the secondary piping is adsorbed by the iodine removal filter. FIG. 4 shows a flowchart of an example of the condenser purification operation when the iodine concentration in the reactor water increases.

[0016]

In the above embodiment, the example in which the iodine removal filter is provided as a permanent installation has been described.
The iodine removal filter 10 can be shared by a plurality of plants by making the 2 and the recirculation valve 14 a flange structure and making the iodine removal filter portable equipment. FIG. 5 shows an example of a portable iodine removal filter. This equipment removes the mist of the gas flowing from the intake port 21 by a demister and drys it by an electric heater 23, and then removes iodine and particulate radioactive substances by a charcoal filter 24 and a HEPA filter 25. The purified gas is returned to the equipment. This equipment is demister 2
2, electric heater 23, charcoal filter 24 and HE
Each of the PA filters 25 has a separable flange structure so that the wheels can be easily attached and moved. Further, the equipment is provided with a control panel 27 for an electric heater, a charcoal filter 24, and a differential pressure gauge 28 for monitoring a differential pressure across the HEPA filter 25.

[Brief description of the drawings]

FIG. 1 is a system diagram showing claim 1 of the present invention.

FIG. 2 is a system diagram showing a conventional condenser vacuum pump facility.

FIG. 3 is a system diagram showing a condenser and a secondary piping device of a conventional example.

FIG. 4 is a flowchart showing the operation procedure of condenser purification and turbine opening when iodine concentration in reactor water increases according to the present invention.

FIG. 5 is an explanatory view showing a portable iodine filter as another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Turbine, 2 ... Condenser, 3 ... Air extractor, 4 ... Gas waste treatment system, 5 ... Exhaust pipe, 6 ... Condenser vacuum pump, 7
... intake pipe, 8 ... particle removal filter, 9 ... condenser vacuum release valve, 10 ... iodine removal filter, 11 ... inlet valve, 12
... Outlet valve, 13 ... Bypass valve, 14 ... Recirculation valve, 15 ...
Recirculation piping, 16: Gas waste treatment system blower.

Claims (3)

[Claims] In a boiling water nuclear power plant, a condenser purifying device is provided with an iodine removal filter on the exhaust side of a condenser vacuum pump for exhausting gas in the condenser. 2. A condenser purifying apparatus according to claim 1, further comprising a pipe for circulating exhaust gas from said iodine removal filter to a gas phase portion of said condenser via an isolation valve. 3. The method according to claim 1, wherein when the concentration of iodine in the condenser rises when the reactor is shut down, the inside of the condenser is vacuum-raised before the turbine casing is opened, and the iodine is broken after the vacuum break. An operation method of a condenser purifying apparatus that repeats recirculation operation of a removal filter.