JPH0375598A - Ventilator for nuclear reactor containment vessel - Google Patents

Abstract

PURPOSE:To remove a plenty of particles and to reduce the size of device by making steam and large diameter aerosol particles (particles) collide with a trap board and removing them at a pre-stage pat, and by removing small diameter particles through a filter placed at a post-stage part. CONSTITUTION:Upon failure of nuclear reactor, a pat of steam that spouting into a suppression pool 5 from a nuclear reactor containment vessel 1 via a vent tube 4, is condensated, and a part of particles is transferred to water and roved. Moreover, when pressure in the vessel 1 increases, an isolation valve 6 is opened and the pressure in the vessel 1 is released through a containment vessel ventilator A, and, at that tie, flow of the steam and the particles entering into a pre-stage 7 through a piping 11, produces a turbulent flow within a trap board 9 and therewith the steam becomes water droplets, the particles stick to the trap board 9 by colliding inertia, soluble substances dissolve into the water droplets and insoluble substances are discharged together with the water stream and collected in a central pipe 10 and returned to the vessel 1 through piping 13. Furthermore, particles which are not caught 9 at the pre-stage 7 are removed through a filter 12 at a post-stage 8, and remaining gases are discharged out to the environment through piping 11b, a valve 6 and an offgas treatment system.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention removes water vapor and aerosol particles containing highly concentrated radioactive materials released from a reactor pressure vessel during an accident, and improves the environment outside the reactor containment vessel. The present invention relates to a device that minimizes the amount released into the air.

[Conventional technology] The conventional technology is “containment vessel J with filter vent device”.
(R,O,5chlueter and R,P,
Schumitz.

“Filtered Vented Contains
ent”+Fourth Workshop on C
integrity, Jun
e 15.1988. ), in order to prevent damage to the reactor containment vessel due to an increase in the internal pressure of the reactor containment vessel during an accident, a filter is installed to remove water vapor and aerosol particles of radioactive substances released from the reactor pressure vessel into the reactor containment vessel during an accident. After venting through a vent distom and removing aerosol particles of highly concentrated radioactive materials with a filter, they were released into the environment outside the reactor containment vessel.

[Problems to be Solved by the Invention] However, with the above-mentioned prior art, there are problems in that when a large amount of water vapor and aerosol particles are released, the device becomes large in order to prevent clogging of the filter, and the radioactive aerosol particles disintegrate. There is a problem that the temperature of the filter due to heat) t.

The purpose of the present invention is to be able to remove a large amount of aerosol particles without worrying about filter clogging and temperature rise of the filter due to decay heat of radioactive aerosol particles, and to minimize the amount of radioactive substances released into the environment. Another object of the present invention is to provide a reactor containment vessel venting device that can be made relatively compact.

[Means for Solving the Problems] In order to achieve the above object, the reactor containment vessel venting device of the present invention vents water vapor and aerosol particles containing radioactive materials released from the reactor pressure vessel into the reactor containment vessel. In the first stage of the reactor containment vessel venting system, water vapor and large-sized aerosol particles are collided with a plate to be efficiently removed and returned to the containment vessel in liquid form, and the second stage filter is used to remove small-sized aerosol particles. It is designed to remove particles.

[Operation] Radioactive aerosol particles released from the reactor pressure vessel during an accident are fission products, and the main chemical forms are CsI and Cs.
s0I(, C52C○3. Cs2Te, Te, and most of these particles are water-soluble.

Further, the average particle size of the particles is about 1 μm.

Water vapor and aerosol particles can be removed by a collection plate by inertial collision. The removal efficiency E at this time is proportional to the collision parameter S1--Sx number S. The Stokes number S can be expressed by the following formula.

5ccd”V/D Here, d: particle diameter, V: flow rate, D: flow path diameter.

That is, as shown in FIG. 3, the larger the particle size, the greater the removal efficiency. At the time of venting, the flow velocity (1) can be set to about 200 m/8, so particles with a particle size of 1 μm or more can be removed by inertial collision with a collection plate in the previous stage. The water-soluble aerosol particles passing through the flow path between the collection plates are gradually removed while colliding with the collection plates and dissolved in the condensed water, becoming water droplets. The aerosol particles that have become water droplets are returned to the reactor containment vessel via the return flow path. Aerosol particles that are not water-soluble also collide with the collection plate, are swept away by the condensed water, and return to the reactor containment vessel.

As mentioned above, the radioactive aerosol particles collected on the collection plate by the inertial collision in the previous stage do not remain there but are returned to the reactor containment vessel, so the temperature of the collection plate does not rise significantly due to decay heat. do not have.

Small particles that cannot be removed by inertial collision can be removed by a filter filled with fibers in the subsequent stage. In this case, one particle is captured by the fiber filter by interception and diffusion. The dependence of removal efficiency on particle size is shown in FIG. The radioactive aerosol particles are removed by the inertial collision in the first stage, and there are few small-diameter radioactive aerosol particles entering the second stage, so the temperature of the filter does not rise significantly due to decay heat.

In this way, the containment vessel venting system is a two-stage system, in which water vapor and radioactive aerosol particles are removed and returned to the reactor containment vessel in the first stage, and small-sized aerosol particles are removed in the second stage, thereby reducing the amount of water vapor and radioactive aerosol particles that can be removed from the filter. The amount of radioactive materials released into the environment can be minimized without worrying about clogging or temperature rise of the collection plate or filter due to decay heat.

[Embodiment 1] An embodiment of the present invention will be described below with reference to the upper diagram and FIG. 2. The reactor containment vessel 1 includes a reactor pressure vessel 2 (the reactor core is 3
), a vent pipe 4, and a suppression pool 5, and a containment vessel vent device A and an isolation valve 6 are connected to the outside.

At the time of an accident, water vapor and aerosol particles released from the reactor pressure vessel 2 fill the reactor containment vessel 1 and are then ejected into the suppression boul 5 through the vent pipe 4.

A portion of the ejected water vapor is condensed by the suppression pool water, and a portion of the aerosol particles are transferred into the water and removed by the scrubbing effect. Furthermore, in order to prevent damage to the g-reactor reactor containment vessel 1 when the pressure inside the containment vessel increases,
The isolation valve 6 is opened to release the pressure inside the reactor containment vessel l via the containment vessel vent device A.

Figure 2 shows the structure of the containment vessel vent system A.

The containment vessel vent system A is divided into a front stage 7 and a rear stage 8, and in the former stage, a concave-convex collection plate 9 is provided with a slope and is spirally attached to a central pipe 10. The flow of water vapor and aerosol particles that entered the front stage 7 from the containment vessel l through the piping 11a becomes turbulent in the spiral flow path formed between the uneven plates 9, and the aerosol particles collide with the plates 9 due to inertial collision. adhere to. At this time, the water vapor also condenses due to collision with the plate 9 and becomes water droplets.

Among the aerosol particles attached to the plate 9, water-soluble particles dissolve in water droplets, and insoluble particles are swept away by the water droplets and collected on the collection plate 9.
It flows down from above, passes through the hole 10' in the central pipe 10, collects in the central pipe 10, and returns to the containment vessel 1 through the pipe 13. The height of the front stage 7 is higher than the highest level of the pool water 5 in the containment vessel 1 to prevent backflow. Aerosol particles that are not collected at the front stage 7 of the containment vent system are removed at the rear stage 8 by a filter 12 filled with glass fiber, etc., and the remaining gas is passed from the pipe 11b to the isolation valve 6 and the off-gas treatment system to the environment. is released.

In this example, aerosol particles and water vapor are removed in two stages, and in particular, radioactive aerosol particles are removed in the first stage and returned to the containment vessel together with the water droplets.

Therefore, the amount of radioactivity released into the environment can be minimized.

Another structural example of the containment pen 1 to the device will be explained with reference to FIG. This containment vessel venting device includes a front stage 7 consisting of a lattice-like plate (5) for separating air and water and a concave-convex collection plate 9 installed spirally with an outward downward slope on the air collection pipe 14; The rear stage 8 consists of a filter connected to the upper part of the filter.The filter of the rear stage 8 is filled with glass fiber or the like.

When the internal pressure of the containment vessel 1 increases and the isolation valve 6 is opened, a flow of water vapor and aerosol particles is introduced through the plumber ↓a to the containment vessel pen 1 to the front stage 7 of the device. The large-sized water vapor collides with the grid plate 15 for steam/water separation, becomes water droplets, and returns to the containment vessel 1 via the pipe 13b. The remaining water vapor and aerosol particles flow between the spirally arranged uneven plates 9 and are removed by inertial collision. The aerosol particles adhering to the uneven plate 9 are dissolved in water droplets or washed away, flow down on the collection plate 9, pass through holes 9' provided at the periphery of the collection plate 9, and flow down along the inner wall of the cylinder of the front stage 7. , returns to the containment vessel l through the pipe 13a or 13b. Non-condensable gas and small-sized aerosol particles that are not collected by the collection plate 9 are introduced into the filter 8 through the air collection pipe 14. Here, the aerosol particles are removed and the non-condensable gas is released from pipe 11b to the environment via an off-gas treatment system.

In this embodiment, the water droplets and radioactive aerosol particles removed by the uneven plate are efficiently returned to the containment vessel l along the inner wall of the front stage 7 of the containment vessel vent device.

In this embodiment as well, there is no need to worry about clogging of the filter or rise in temperature of the collection plate or filter due to decay heat. Also, the release of radioactivity into the environment is minimized.

Furthermore, if a hydrogen adsorbent such as palladium is attached to the glass fiber that is the filler of the filter, hydrogen generated in the accident can be collected. Furthermore, heat dissipation fins may be attached to the outer wall of the containment vessel vent device described above.

Further, the containment vessel vent device may be installed inside the reactor containment vessel.

Another embodiment of the present invention will be described with reference to FIG.

The containment vent system A is connected to the reactor containment vessel 1 by two interlocked isolation valves 6 .

In the event of an accident, when the pressure inside the containment vessel increases, the isolation valve 6 is simultaneously opened to release the pressure inside the reactor containment vessel 1 via the containment vessel vent device A, thereby preventing damage to the reactor containment vessel 1. . The structure, operation, and effects of the containment vent device are similar to those of the previous embodiment.

[Effects of the Invention] Since the present invention has the structure as described above, water vapor and high concentration radioactive aerosol particles generated in the reactor containment vessel during an accident are prevented from clogging the filter and increasing temperature due to decay heat. Large amounts can be removed without worry, and the amount of radioactive materials released into the environment can be minimized. Moreover, it has the advantage of requiring a relatively small device.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing a reactor containment vent system and a reactor containment vessel according to an embodiment of the present invention, and FIG. 2 is a diagram showing a reactor containment vent system according to the same embodiment. (A) is a schematic sectional view of the front stage, (B) is a schematic sectional view of the rear stage, Figure 3 is a diagram showing the particle size and removal efficiency of aerosol particles, and Figure 4 is a diagram showing the removal efficiency dependence of the fiber filter. Diagram showing gender. FIG. 5 is a schematic cross-sectional view of another embodiment of the reactor containment vent system of the present invention, and FIG. 6 is a schematic cross-sectional view showing the JMT reactor containment vessel and containment vent system in another embodiment of the present invention. It is. ■・Reactor containment vessel 2...Reactor pressure vessel 3...
・Reactor core 4... Vent pipe 5... Suppression pool 6... Isolation valve 7... Containment vessel venting device front stage 8... Containment vessel venting device rear stage 9... Collection plate 10... Central pipe 11a,
llb...Plumber 2...-Fiber filter 13, 1
3 a, 13 b-= Return piping 14... Air collection pipe 15... Air/water separation plate (1 other person) Fig. 3 Fig. 0.01 0.1 Particle size (μm) Fig. 0 .01 0.1 Particle size (μm) Figure

Claims (1)

[Scope of Claims] 1. A collection plate that inertially collides water vapor and radioactive substance aerosol particles flowing from inside the reactor containment vessel, and condensed water collected on the collection plate and dissolved in or condensed in the condensed water. A front stage section that is equipped with a flow path that returns collected material containing radioactive aerosol particles washed away by water into the reactor containment vessel, and a rear stage section that is equipped with a filter that removes radioactive aerosol particles that were not removed in the front stage section. A nuclear reactor containment vessel venting device comprising: 2. The collection plate is composed of a concave-convex plate arranged in a spiral shape so as to form a spiral passage therebetween, and the passage for returning the collected material into the reactor containment vessel is arranged in the spiral shape. 2. The reactor containment vessel venting device according to claim 1, further comprising a flow path for collecting the collected material flowing down on the collecting plate.