JPS6038679B2 - Radioactive contaminated air treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radioactively contaminated air treatment system, and in particular to radioactive contaminated air treatment equipment for treating radioactively contaminated air from inside the primary system when opening the lid of a reactor pressure vessel or opening a turbine casing during periodic inspections of nuclear power generation equipment. The present invention relates to a radioactively contaminated air treatment device suitable for preventing contamination of surrounding areas or surrounding air by radioactively contaminated air.

Conventionally, methods to prevent radioactive contaminated air from dispersing into the surrounding work area when opening the reactor pressure vessel lid or turbine casing have included ventilation using temporary local exhaust fans or existing condenser vacuum pumps. Methods of providing ventilation are generally known. However, in the former case, complete ventilation cannot be expected due to lack of capacity, and in the latter case, only hold-up piping is provided as a radioactivity removal device, which can only be expected for short half-life nuclides. The disadvantage is that the air remaining in the reactor pressure vessel cannot be ventilated during the turbine opening period.

As described above, the conventional apparatus has not been able to fully satisfy the objectives of preventing contamination of the work area and air and reducing radioactivity released into the outdoor environment. The present invention was developed in view of the current situation, and its purpose is to prevent the spread of radioactively contaminated air to the surrounding area when the reactor pressure vessel lid or casing is opened, and to reduce the amount of radioactivity released into the outdoor environment. The purpose of the present invention is to provide an air treatment device capable of reducing radioactive contamination.

The present invention connects one end of the steam piping having the bleed valve to the main steam piping position between the main steam stop valve and the turbine inlet valve, and connects the pond end of the bleed piping to the bleed valve at reactor startup and the condenser. A removal device for removing radioactive substances in contaminated air is installed between the vacuum pump and the reactor startup piping, and between the condenser vacuum pump and the hold-up piping. When the reactor pressure vessel lid or turbine casing is opened, the condenser vacuum pump is started, and the contaminated air in the primary system is aerated through the air piping or the condenser, removing radioactive substances from the contaminated air. The device removes and attenuates the air to produce clean air, which is then exhausted from the exhaust stack.

The invention will be explained below on the basis of illustrated embodiments. The drawing schematically shows a radioactively contaminated air treatment device in a boiling water nuclear power plant, and in the drawing, 1 is a reactor pressure vessel.

This reactor pressure vessel 1 is connected to a turbine 5 via a main steam pipe 4 having a main steam stop valve and a turbine inlet valve 3, respectively, and a lower part of the turbine 5 is connected to a main condenser 6. are doing. The main condenser 6 has a reactor start-up bleed pipe 8 having a reactor start-up air valve 7 as shown in the figure.
One end of the bleed pipe 8 is connected to the condenser vacuum pump inlet pipe 101 on the inlet side of the condenser vacuum pump 9 . By operating the condenser vacuum pump 9, air is extracted from the main condenser 6 and exhausted from the exhaust pipe 12 via the hold-up piping 11. The configuration described above is the same as the conventional one, and in this embodiment, the following configuration is further added. That is, between the condenser vacuum pump 9 and the hold-up piping 11, there is a particle removal filter 13 for removing particulate radioactive substances contained in the contaminated air transferred to the exhaust stack 12, as shown in the figure. Charcoal tower 1 that captures and attenuates gaseous radioactive materials
4 are respectively installed, and the main steam piping 4 position between the main steam stop valve 2 and the turbine inlet valve 3 and the inlet piping 10 interconnect a steam piping 16 having a piping valve 15. has been done.

Next, the effect will be explained. During periodic inspections of nuclear power plants, the lid of the reactor pressure vessel 1 is opened,
Alternatively, the casing of the bin 5 may be opened.

In such a case, the air inside the reactor pressure vessel 1 or the turbine 5 generally has a high radioactivity level, so
Its diffusion poses a problem of contamination of the surrounding work area and the surrounding air. Therefore, when opening the lid of the reactor pressure vessel i, first open the main steam stop valve 2.
Then, the air valve 15 is opened and the turbine inlet valve 3 is closed.

Then, in this state, the condenser vacuum pump 9 is started, and the radioactively contaminated air stagnant in the reactor pressure vessel 1 is removed from the main steam pipe 4.
, the gas pipe 16 , the condenser vacuum pump 9 , the particle removal filter 3 , the charcoal column 14 and the hold-up pipe 11 in order to be discharged from the exhaust pipe 12 to the outside of the system. When you start the lid opening work in this state, the inside of the system from the reactor pressure vessel 1 to the condenser vacuum pump 9 is under negative pressure due to the air capacity of the condenser vacuum pump 9. Surrounding air is sucked into the reactor pressure vessel 1, and as a result, radioactively contaminated air within the reactor pressure vessel 1 is prevented from flowing out and contaminating the surrounding area. Further, particulate radioactive substances contained in the contaminated air transferred to the exhaust stack 12 are removed by a particle removal filter 13, and gaseous radioactive substances are captured and attenuated by a charcoal tower 14. Therefore, the air released from the exhaust stack 12 into the outdoor environment becomes extremely clean. On the other hand, when opening the casing of the turbine 5, the turbine inlet valve 3, bleed valve 15, and reactor startup bleed valve 7 are opened respectively, and the main steam stop valve 2 is closed before the casing is removed. .

When the condenser vacuum pump 9 is started in this state, the radioactively contaminated air remaining in the casing of the turbine 5 and the main condenser 6 is removed from the main steam pipe 4, the yuzu pipe 16, and the condenser vacuum pump 9. , particle removal filter 13, charcoal tower 14
and hold-up piping 11, and a route from main condenser 6 to reactor startup bleed piping 8, condenser vacuum pump 9, particle removal filter 13, charcoal column 14, and hold-up piping 11. Air is bled through the path and discharged from the exhaust stack 12 to the outside of the system.

When the casing of the turbine 5 is removed in this state, the inside of the casing of the turbine 5 and the inside of the main condenser 6 are under negative pressure due to the air pressure of the condenser vacuum pump 9, so the air around the turbine 5 is transferred to the turbine 5. As a result, the radioactively contaminated air in the casing of the turbine 5 and the main condenser 6 will not flow out and contaminate the surrounding area.

In addition, particulate radioactive substances contained in the contaminated air transferred to the exhaust stack 12 are removed from the particle removal filter 1 during the transfer.
3, and the gaseous radioactive substances are captured and attenuated by the charcoal tower 14, so that the air released from the exhaust stack 12 into the outdoor environment becomes extremely clean. The present invention has been described above based on the preferred embodiments. According to the present invention, ventilation is performed using a permanently installed condenser vacuum pump instead of using a temporary local exhaust fan as in the past. No equipment is required, improving work efficiency, and
Sufficient ventilation capacity prevents radioactive contamination of the surrounding work area and the surrounding air when the reactor pressure vessel lid or turbine casing is opened, and complete exhaust ventilation prevents internal radiation exposure of workers.

In addition, a removal device is installed on the outlet side of the condenser vacuum pump, so the air released from the exhaust stack is cleaned.
The release of radioactivity into the outdoor environment, including the exhaust during reactor startup, can be significantly reduced compared to conventional methods.

Further, in the conventional device, it was not possible to ventilate the inside of the reactor pressure vessel when the turbine casing was opened, but ventilation can be easily performed through the air piping.

[Brief explanation of drawings]

The drawing is a system diagram showing an embodiment of the present invention. 1...Reactor pressure vessel, 2...Main steam stop valve, 3...Turbine inlet valve, 4...
・Main steam piping, 5... Turbine, 6... Main condenser, 7... Reactor startup bleed valve, 8...
・Bleed air piping at reactor startup, 9...Condenser vacuum pump, 11...Hold up piping, 12...
Exhaust pipe, 13... Particle removal filter, 14.
...Charcoal tower, 15...Bleed valve, 1
6... Air bleed piping.

Claims (1)

[Scope of Claims] 1. Steam from the nuclear reactor is guided to the turbine through main steam piping each having a main steam stop valve and a turbine inlet valve, and a condenser connected to the turbine at the time of reactor startup. One end of the bleed piping that has a bleed valve in the case where air is bled from the inside by a condenser vacuum pump via a bleed piping at reactor startup that has a bleed valve at reactor startup, and is exhausted from the exhaust stack via a hold-up piping. Connect it to the main steam piping between the main steam stop valve and the turbine inlet valve, and connect the other end of the bleed piping to the reactor startup bleed piping between the reactor startup bleed valve and the condenser vacuum pump. connect to the position,
In addition, a removal device for removing radioactive substances in contaminated air is installed between the condenser vacuum pump and the hold-up piping, and when the reactor pressure vessel lid or turbine casing is opened, the radioactive contaminated air in the system is removed. A radioactively contaminated air processing apparatus characterized in that air is extracted by the vacuum pump, radioactive substances in the contaminated air are removed and attenuated by a removal device, and clean air is exhausted from an exhaust stack. 2. Radioactivity according to claim 1, characterized in that the removal device is composed of a particle removal filter that removes particulate radioactive substances and a Charcoal tower that captures and attenuates gaseous radioactive substances. Contaminated air treatment equipment.