JPH08292293A - Reactor exhaust gas treatment system - Google Patents

Abstract

PURPOSE: To prevent discharge of radioactive fine particles and volatile gas into environment by collecting and removing them separately with a solid fine particles collected by inertial collision. CONSTITUTION: Air is supplied into a building 2 from an air supply facility 3 to prevent such particle as a leaked CsI from being discharged to environment and is exhausted from an exhaust tower 10 by a fan 9 for exhaust gas. The Cs1 particle is sent to an inertia collector via a connection pipe 4. A nozzle plate is installed in the inertia collector and the particle is subjected to inertia collision onto a collection plate 6 after it passes a particle acceleration nozzle 5 and then 50% or more of the entire particle is collected. The particle such as CsI through the inertia collector passes through a connection pipe and 99.99% or higher of the particle through a stainless fiber filter 7 is eliminated. The exhaust gas after the collection is fed to a filter 8 for collecting volatile iodine after that, 99% or higher of the gas-shaped radioactive substance is eliminated by a gas adsorbing agent such as an active carbon, and then the gas is discharged into environment. In this manner, a solid fine particle of a radioactive iodine compound is passed through a nozzle 5 and a filter 7, thus preventing the discharge into environment.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a reactor exhaust gas treatment system.

[0002]

2. Description of the Related Art In the prior art, a gas treatment system is installed so as not to release radioactive substances into the environment even in the event of an accident. In particular, in order to suppress the release of radioactive iodine compounds to the environment, potassium iodide that collects organic iodine and the like in the gas treatment system, activated carbon filter impregnated with organic substances, and high performance to remove dust and the like A (HEPA) filter is used so that the radioactive iodine compound can be collected or adsorbed and removed.

[0003]

The above-mentioned prior art is constructed so that the main component of the radioactive iodine compound is elemental iodine I ₂ , which is not released to the environment.

However, recent findings indicate that iodine is more likely to be released from the fuel as radioactive solid fine particles of cesium iodide than as elemental iodine. Solid particles can be removed with a high-performance filter even with a conventional gas treatment system,
The pressure loss in the filter may be large for a large amount of solid particles. Therefore, a gas treatment system with high collection efficiency is required even for a large amount of solid fine particles.

An object of the present invention is to provide an exhaust gas treatment system capable of coping with changes in the chemical form of radioactive iodine compounds.

[0006]

In order to achieve the above object, the present invention is to increase the inertial force of solid fine particles of a radioactive iodine compound so that the solid particles collide with a collecting plate, or are made of metal with less pressure loss than a HEPA filter. Solid fine particles are ventilated through the fiber filter, and are collected and removed by inertial collision with the metal fiber surface.

[0007]

When solid fine particles of a radioactive iodine compound discharged from the storage container are passed through a nozzle having a small diameter, the streamline on which the particles are mounted changes, and the speed of the particles increases. A collecting plate is installed at a certain distance from the nozzle, and particles having increased inertial force are made to collide with the surface of the collecting plate. Further, by allowing the particles to pass through the metal fiber filter and adhering the particles to the surface by inertial collision or the like, it is possible to collect the particles for a long time using the voids of the filter.

[0008]

EXAMPLES Examples of the present invention will be shown below. FIG. 1 shows a reactor exhaust gas treatment system, which includes a reactor 1, a reactor building 2, an air supply facility 3, a connecting pipe 4, a particle accelerating nozzle 5, a collecting plate 6, a stainless fiber filter 7, and volatile iodine collecting. The exhaust gas filter 8, the exhaust gas fan 9, and the exhaust tower 10. At the time of the accident, Cs with a particle size of 0.3 μm or more from the reactor 1
There is a possibility that radioactive fine particles such as I will be released into the reactor building 2. In order to prevent the release of particles such as CsI to the environment due to the air leak in the reactor building 2, the air is supplied from the air supply facility 3 into the building at a maximum flow rate of 75 m ³ / hr, and the exhaust gas fan is used. 9 is operated to exhaust from the exhaust tower 10. 50 to 10 in the building air 18,000m ³
Ventilate at a rate of 0% / day. CsI particles are connecting pipes 4
It is sent to the inertial collector via the. Inside the inertial collector, a nozzle plate with 200 nozzles with a hole diameter of 0.1 cm is installed, and the particle velocity when passing through the nozzle is 56 m.
/ S. The particle number concentration is 10 ⁸ particles / cm ³ , and the particle size is 0.1.
Even in the case of 3 μm CsI particles, after passing through the nozzle, they collide inertially on a collection plate installed at a distance of 3 mm from the nozzle plate, 50% or more of the particles are collected and the number concentration is 5 × 10 5.
⁷ pieces / cm ³ or less. Particles such as CsI that have passed through the inertial collector are supplied to the filter unit through the connecting pipe. Inside the filter unit, the fiber diameter is 4 μm and the filling rate is 0.
Filled with 00625 stainless fiber filter.
The filter unit has an area of 0.25 m ² and a thickness of 35 cm. After passing through the filter unit, 99.99% or more of particles are removed.

Further, at the time of an accident, a maximum of about 37 kg of radioactive fine particles such as CsI may be released. The porosity of the stainless fiber filter is 99.375%, and the volume of the space inside the filter unit is 0.0869 m ³ . C
Since the density of particles such as sI is about 4.5 g / cm ³ , the total volume is 0.0082 m ³ , which is about 10% of the spatial volume in the filter. Therefore, the filter unit is CsI
Even if all the radioactive fine particles are adsorbed, the pressure loss hardly increases. Further, particles are not emitted from the inside of the filter due to re-scattering. The exhaust gas after collecting the radioactive particulates such as CsI is then sent to the filter 8 for collecting volatile iodine, and 99% or more of the gaseous radioactive substances are removed by a gas adsorbent such as activated carbon, and then released to the environment. To be done. As described above, the solid fine particles of the radioactive iodine compound discharged from the reactor containment vessel according to the present embodiment can be prevented from being discharged into the environment by passing through the nozzle having the small diameter and the stainless fiber filter.

[0010]

According to the present invention, the solid fine particles of the radioactive iodine compound released from the reactor containment vessel can be trapped and removed by adhering to the surface of the trapping material by inertial collision, and the release to the environment. It can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

[Explanation of symbols] 1 ... Reactor, 2 ... Reactor building, 3 ... Air supply equipment, 4 ...
Connection pipe, 5 ... Particle accelerating nozzle, 6 ... Collection plate, 7 ... Stainless fiber filter, 8 ... Volatile iodine collection filter, 9 ... Exhaust gas fan, 10 ... Exhaust tower.

Claims (2)

[Claims] 1. An exhaust gas treatment system for collecting radioactive substances released from a reactor containment vessel, wherein radioactive particulates and a volatile gas are separately collected. 2. An exhaust gas treatment system for separately collecting radioactive fine particles and a volatile gas, wherein the radioactive fine particles are collected and removed by inertial collision.