JPH04104087A - Apparatus for suppressing discharge of radioactivity at time of accident - Google Patents

Abstract

PURPOSE:To suppress the discharge quantity of radioactivity to environment effectively by providing a combined filter of a metal fiber filter and an activated carbon fiber filter in a reactor on the way of piping. CONSTITUTION:When a severe accident exceeding the planning standard of a reactor container is generated, a large amount of a radioactive substance is discharged to the dry well 4 of a reactor container 3. At this time, the greater part of the granular (aerosol-like) radioactive substance is removed by the metal fiber filter 21 composed of a stainless steel fiber provided in a vent pipe 9 and further reduced by scrubbing. When the pressure in the reactor container further rises and there is the possibility of the damage of the reactor container 3, the radioactive substance such as iodine suspended in vent gas is passed through a metal fiber filter 19 and an activated carbon fiber filter 20 and the granular radioactive substance is collected by the former and gaseous radioactive iodine is collected by the latter.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an accident radioactivity release control system that minimizes the amount of radioactive materials released into the environment during an accident at a nuclear power plant.

(Prior Art) A conventional system for suppressing the release of radioactive substances into the environment during an accident at a nuclear power plant will be described with reference to FIG.

As shown in FIG. 2, radioactive materials released from the reactor core 1 in the event of an accident are released from the reactor pressure vessel 2 to the dry well 4 or urinary well 5 of the reactor containment vessel 3. In this case, a portion of the radioactive material is plated out or fallen out onto the inner wall or floor surface of the dry well 4 or wet well 5. Among the remaining radioactive substances, iodine, which has a particularly large effect on the human body (internal exposure), is handled by the containment vessel spray system (dry well spray system 7 or wet well spray system 72) and electric valve 12, which are engineering safety equipment. ．． ．． After the amount of iodine released from the containment vessel 3 is suppressed to a large extent by an emergency gas treatment system (SGTS) 11 consisting of a 12□ and an activated carbon filter, the iodine is released into the environment through the stack 10. A part of the radioactive material released from the containment vessel 3 is also plated out or fallen out within the nuclear power building 8.

Further, a suppression pool 6, which is a pressure suppression equipment in the containment vessel 3, also suppresses the release of radioactive substances present in the dry well 4 through a vent pipe 9 by scrubbing.

On the other hand, in European countries such as France, West Germany, and Sweden, in anticipation of an accident in which the design pressure of the containment vessel 3 is exceeded (severe accident), sandbed filters and Containment vessel vent filter equipment 13 consisting of a metal fiber filter, scrubber, etc. is provided. In other words, in the event of an accident, the gas inside the containment vessel is vented from the wet well 5 via the electric valve 142, and the wet well 5 is flooded by the cooling containment vessel spray before the internal pressure of the containment vessel rises and reaches the failure pressure of the containment vessel. In such a case, the electric valve 14. The gas in the containment vessel is vented through the reactor, and at the same time as the pressure inside the containment vessel is reduced, most of the radioactive substances such as iodine are removed by the vent filter equipment 13, and then released from the stack 10, greatly reducing the amount of radioactive substances released into the environment. suppress.

(Problem to be solved by the invention) Conventional engineering safety equipment functions very effectively against accidents that do not exceed the design pressure of the containment vessel (design basis accidents); There is a problem in that the effectiveness of suppressing radioactive substances is greatly reduced in the event of an accident (an accident that causes damage to the containment vessel: severe accident).

The present invention was made to solve the above problems, and
The purpose is to provide a radioactivity release control system in the event of an accident that can significantly suppress the amount of radioactive material released into the environment with a relatively small system even in the event of an accident that exceeds the design standards of the containment vessel. be.

[Configuration of the Invention (Means for Solving the Problems) In order to achieve the above object, the radiation release control system in the event of an accident of the present invention has the following features: Install an electric valve, air-operated valve, or manual valve on the gas vent piping that passes through the upper flange of the reactor containment vessel to the stack, and install a combination of metal fiber filters such as stainless steel and activated carbon fiber filters in the reactor building along the piping. It is characterized by being equipped with a filter.

(Function) According to the present invention, even in the event of an accident that exceeds the design standards of the containment vessel, the effect of trapping radioactive materials by the stainless steel and metal fiber filters in the vent pipe inside the containment vessel and the gas vent inside the containment vessel and Due to the radioactive material collection effect of the combined filter system of a metal fiber filter such as stainless steel and an activated carbon fiber filter, it is possible to reduce the internal pressure of the containment vessel (prevent damage) and significantly suppress the amount of radioactive material released into the environment. .

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

FIG. 1 shows a configuration diagram of an embodiment of the present invention.

As shown in FIG. 1, from the dry well 4 and wet well 5 of the reactor containment vessel 3 to the containment vessel vent piping 16
．． 15, and each pipe has an electric valve 17. ．． 17
A remote control valve such as □ or a manual valve is provided. In the middle of the containment vessel vent piping in the reactor building up to stack 10, there is a metal fiber filter 1 made of stainless steel.
A combination filter consisting of a filter 9 and an activated carbon fiber filter 20 is provided. Further, a lubricant disk 18 is provided in the wet well piping 15 depending on the case.

Furthermore, a metal fiber filter 21 made of stainless steel or the like is provided in the vent pipe 9 and filled in a housing.

In the unlikely event that a severe accident that exceeds the design standards of the containment vessel occurs, a large amount of radioactive material will be released from the reactor core 1 through the reactor pressure vessel 2 into the triwell 4 of the containment vessel 3, causing pressure inside the containment vessel to rise. When the water rises, it is scrubbed into the suppression pool 6 through the vent pipe 9. At this time, most of the radioactive substances in the form of particles (aerosols) are removed by a metal fiber filter 21 made of stainless steel or the like provided in the vent pipe 9, and further reduced by scrubbing. However, depending on the degree of the accident, the pressure inside the containment vessel may further increase and the containment vessel 3 may be damaged. etc., and vent the gas to reduce the pressure inside the containment vessel. Then, radioactive substances such as iodine floating in the vent gas are vented through the metal fiber filter 19 and the activated carbon fiber filter 20, with the former mainly removing the radioactive substances in the form of particles (aerosol), and the latter mainly removing the radioactive iodine in the form of gas. Collect. The remaining gas containing a small amount of radioactivity is released from the stack 10.

In addition, if the containment vessel is sprayed from a water source other than the suppression pool water at the time of an accident, the inside of the wet well will be flooded, so close the electric valve 171 etc., open the electric valve 171 through the containment vessel vent piping 16 from the dry well 4,
Vent the gas. In addition, when the rupture desk 18 is provided, the electric valve 172 is opened in advance and the rupture desk set pressure is set lower than the bursting pressure of the containment vessel so that the rupture desk 18 is not damaged before the containment vessel 3 is damaged. The char disk 18 is destroyed and the gas is vented through this destruction port. If wet well 5 is flooded, electric valve 1
Close 7□.

In addition, in the above embodiment, the electric valve 17. ．． 172 is activated, but if the power supply is lost, the same operation can be performed using a manual valve or the like.

In addition, in the above-mentioned embodiment, an example was shown in which a metal fiber filter made of stainless steel or the like was provided in the vent pipe inside the containment vessel, but this system is not necessarily applicable in cases where the radioactive material trapping effect is not so required. Not required.

Here, the metal fiber filter 19 used in this system
．． For example, 21 is made of stainless steel, and the fiber diameter is 2 to 4 μm.
It is sufficient if the packing density is about 50 to 100 mg/cm3 and the thickness is about several tens of centimeters, and the filter size is about one to several meters for the former, and about the diameter of a vent pipe for the latter. .

"Effects of the Invention" As explained above, according to the present invention, even in the event of an accident that exceeds the design standards of the containment vessel, the radioactive material collection effect of the metal fiber filter made of stainless steel or other material in the vent pipe inside the containment vessel is effective. The radioactive substance collection effect of the gas vent inside the containment vessel and the combined filter system of a metal fiber filter such as stainless steel and an activated carbon fiber filter reduces the internal pressure of the containment vessel and the environment of radioactive substances such as particulate radioactive substances and gaseous iodine. In addition, since the conventional emergency gas treatment system and the containment vessel vent filter are combined into one system, the system can be made simpler and smaller, and the cost can be reduced. It can also be down.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional radiation release control system in the event of an accident. 1...Reactor core 2...Reactor pressure vessel 3...Reactor containment vessel 4...Dry well 5...Wet well 6...Suppression pool 71...Dry well spray system 7□...Wet Well spray system 8...Nuclear power building 9...-Vent pipe 10...Stack 11...Emergency gas treatment system 12, . 122...Electric valve 13...Containment vessel vent filter equipment 14, . 142
・Electric valve 15, 16... Throat piping 17, .. to containment vessel. 17.・・Electric valve 18・・Loveture disk 19.21 ・Metal fiber filter 20・Activated carbon fiber filter (8733) Representative/patent attorney Yoshiaki Inomata (and others)
1 person)

Claims (1)

[Claims] The gas vent piping from both the dry well and wet well of the reactor containment vessel to the stack through the upper flange of the reactor containment vessel is equipped with an electric valve, air-operated valve, or manual valve, and the reactor A radioactivity release control system in the event of an accident, characterized by a combination filter of a metal fiber filter and an activated carbon fiber filter installed inside the building.