FR2687829A1 - AUTOMATIC VENT FILTERS. - Google Patents

Abstract

A containment enclosure comprising a nuclear reactor and an automatic vent filter including a housing (10) having an inlet (11) inside the enclosure (28) and an outlet (14) outside the enclosure. enclosure, a chamber (18) dividing the housing (10) into upstream and downstream sections, and comprising at least one inertial separator (17) having an inlet (19), a fluid outlet (20) and a contaminating agent outlet (22) leading inside the chamber, the latter also having an outlet (27) in which a pump (26) is provided for sucking the contaminating agent with a view to discharging it into the chamber.

Description

"Automatic vent filters".

  The invention relates to automatic vent filters and these filters when incorporated into a containment containing a nuclear reactor. Such enclosures may contain,

  intermittently, fluid & higher pressure

  lower than normal, containing contaminants.

  In order not to damage the enclosure, it is necessary to relieve the pressure of the fluid towards the atmosphere, but to try and ensure as much as possible that the

  contaminants are not purged with the fluid.

  An example of such a situation is to prevent the escape of irradiating material and contaminating particles from a nuclear power plant.

  in the event of a reactor failure

  torers, such as pressurized water nuclear reactors, are housed in concrete constructions, known as containment chambers, the purpose of which is to retain any radioactive material near the reactor In the case of a nuclear accident, such as the melting of the reactor core, it is likely

  that extremely high temperatures will be generated

  drées inside the reactor In order to control such an accident, water is sprayed on the enclosure of

  containment to provide cooling The temperature

  erosion and evaporation of water have the effect of increasing

  ment the gas pressure in the enclosure In order to prevent the rupture of this one, a vent is installed to allow the gas to be evacuated at a certain 2 - pressure below the explosion pressure of

  the enclosure As the explosion pressure is typical-

  1 twist of 12 bar g, the wind is usually

  designed to operate at pressures of the order of 5-

  7 bar g. It is desirable that such a vent should adapt to the interior of the containment so that the danger of irradiation is controlled in an area which has a high capacity of contaminating agent, since the level of agent contaminant cannot be predicted from

precisely.

  It has been proposed to provide a bar filter

  laugh in such a vent A barrier filter is a

  filter which presents a barrier to the passage of particles

  them through the filter Such a filter can be formed for example of a fibrous material However, such barrier filters have the problem that they are easily blocked by particles (they have a low capacity of contaminating agent) and that '' such a blockage would lead to a possible overpressure

  of the containment This may in a certain

  taine measure be mitigated by increasing the size of such a barrier filter, but there are

  obviously limits & an acceptable size.

  According to a first aspect of the invention, there is provided a confinement enclosure containing a nuclear reactor and an automatic vent filter comprising a housing having an inlet inside the enclosure and an outlet outside the enclosure for the passage of the fluid through it, a chamber being provided in the housing and dividing the housing into upstream and downstream sections, the chamber comprising at least one inertial separator having an inlet communicating with the upstream end of the housing, an outlet from fluid communicating with a downstream end of the housing and an outlet for contaminating agent leading inside 3 - the chamber, the chamber also having an outlet in which is provided a pump intended to extract the contaminating agent from the chamber in view to evacuate it to

  inside the containment.

  3 Like, following any accident

  tooth, the gas in the containment is heavy-

  ment contaminated with radioactive particles, the vent

  must filter this gas to eliminate the danger of

  We can therefore ask such a filter to be passive, because current supplies can

be broken by the accident.

  The housing may have, located between the chamber and the outlet of the housing, a converter intended to convert the kinetic energy of the fluid

  passing through the housing into an energy which

  drags the pump so that the fluid loaded with contaminating agent and penetrating through the entrance to the housing is separated from the contaminating agent by the separator and this agent is released by the pump, the flow of the

  fluid downstream of the chamber causing the

weaver to feed the pump.

  In this way, blockage is avoided since the contaminating agent is continuously removed from the separator by the pump. No external current source is required, however, since the energy

  kinetics of the gas is used to drive the pump.

  According to a second aspect of the invention, there is provided an automatic vent filter comprising a housing having an inlet and an outlet for the passage of the fluid through it, a chamber provided in the housing and dividing the housing into upstream sections and downstream, the chamber comprising at least one inertial separator having an inlet communicating with the upstream end of the housing, a fluid outlet communicating with the downstream end of the housing and an outlet of contaminating agent leading to the interior of the chamber, the 4 - housing having, located between the chamber and the outlet of the housing, a converter for converting kinetic energy of the fluid in the housing into energy which drives a pump so that fluid loaded with contaminating agent and penetrating into the entry of the housing is separated from the contaminating agent by said at least one separator, the contaminating agent being removed by the pump, the flow of the fluid downstream of the chamber

  driving the converter & supply the pump.

  o 10 According to a third aspect of the invention,

  there is a process for the separation of contaminated agents

  fluids from a fluid, comprising passing the fluid through an inertial separator to separate the contaminant from the fluid and then passing the fluid through a converter to convert the kinetic energy of the fluid to energy driving a pump, the pump acting to extract the contaminant separated from the separator and

go to an evacuation.

  The following consists of a more detailed description

  detailed embodiments of the invention, to

  using examples, and with reference to the an-

  attached. Figure 1 shows an elevational view

  front of an automatic vent filter.

  FIG. 2 represents a sectional view,

  along line II-II of Figure 1.

  Figure 3 is a view similar to the

  figure 2, but it illustrates the additional panels

  coalescer res / mist eliminator.

  Figure 4 is a partial sectional view of a second form of automatic vent filter

  incorporating a first form of an ejector pump.

  FIG. 5 represents a view in partial section of a third embodiment of the filter - automatic vent comprising a second form of

ejector pump.

  Referring to both Figures 1 and 2, the vent filter includes a housing 10 which may for example be made of a sheet of light stainless steel which is completely airtight

  by watertight seals

  ment 10 has a rectangular inlet 11 followed by a conduit 12 which is reduced in cross section to be connected to a tube 13 whose downstream end forms a

exit 14.

  Two rectangular panels 15, 16, parallel-

  the but spaced, are mounted in the inlet 11 of the housing 10 to divide the housing into upstream and downstream parts The edges of the panels 15, 16 are completely

  made airtight by the adjacent housing.

  The panels 15, 16 and the part of the housing situated between them form a chamber 18 A large number of inertial separators 17 are arranged inside the chamber which extends between the panels, 16 As can be seen on FIG. 2, each separator comprises a tube having an inlet 19 which opens onto the upstream panel 15 and an outlet 20 which opens onto the downstream panel 16 The inlets 19 and the

  outputs 20 are welded to the associated panels 15, 16.

  Each inertial separator 17 comprises a tube and a

  swirl generator arranged at 21 inside

  rieur du tube An outlet for contaminating agent 22 leads inside the chamber 18 at an intermediate point between the inlet 19 and the outlet 20 of each separator

inertial 17.

  The inertial separator 17 can take any suitable form. Such a separator

  inertial is sold by Pall Corporation under the name

  commercial nation of CENTRISEP and it is described in British patents 1,236,941 and 1,207,208 In a 6 - such separator, a mixture of fluid / contaminant entering the tube is influenced by the generator

  which causes the vortex mixture to

  lonner and which therefore provides a centri-

  contamination of the contaminant This has the effect of

  pick up the contaminating agent in an annular space adjacent to the internal surface of the tube The outlet 22 is dimensioned so as to remove from this annular zone the fluid / contaminating agent while the remaining fluid

  in the center of the tube (containing no contaminating agent

  minant) passes through outlet 20 of the tube.

  Note that the size and perfor-

  mance of the inertial separator 17 will be arranged for

  meet the expected operating requirements.

  A kinetic energy converter 23 is mounted in the tube 13 and it comprises a turbine 24 driven by a fluid and connected to one end of a drive shaft 25 The drive shaft 25 passes through the conduit 12 ( with suitable seals to prevent a passage of the contaminating agent in the conduit 12) and it carries at its opposite end a pump in the form of a propeller 26 The propeller 26 is located in the sealed outlet passage 27 leading from

chamber 18 towards an evacuation.

  In service, the filter is mounted for example on a wall 28 of a confinement enclosure, such as a chamber where a nuclear reactor (not shown) is housed. The outlet 14 of the tube 13 is connected to a

orifice 29 in the wall.

  While the pressure inside

  the containment remains at atmospheric pressure

  or close to it, the filter is inactive.

  If, however, the pressure increases above a predetermined level, explosive discs or valves located in the inlets of the inertial separators 17 open and allow a flow of fluid through 7 - through the separators 17 The turbine 24 begins to operate, therefore starting the propeller 26 The fluid inside the containment, which

  is usually air, going, given the difference

  rence of pressure between the inside and the outside of the containment, pass through the inertial separators 17 o the contaminating agents are separated by centrifugal forces and eliminated by a current of expulsion air created by a pressure d suction provided by the propeller 26, passing inside the chamber

18 and through the outlet passage 27.

  During this operation, the duct 12 performs a function of controlling the distribution of the air flow through the panels 15, 16 to obtain a uniform flow by separator 17 By reducing its cross section in the downstream direction, the duct 12 accelerates the air flow to provide the correct velocity vector suitable for the turbine 24 It also decelerates the air flow from the

  turbine 24 with minimum pressure loss.

  The conduit 12 includes slopes of straight

  swims to collect any liquid that passes into the housing 10 and directs it to the outlet passage 27 via a connected expulsion hole, which is provided between the conduit 12 and the passage 27 The flow through this hole is induced by a small differential

  pressure between the conduit 12 and the passage 27.

  In order to reduce the volume of liquid passing through the housing 10 and leaving the housing 10, coalescers / mist eliminators can be

  places upstream and / or downstream of the chamber 18.

  An example of this is shown in Figure 3 o the common parts between Figures 3 and 2 are indicated with the same reference numerals and

will not be described in detail.

8 -

  In this example, two coalescers /

  steam sensors 30, 31 are provided, one upstream of the separators 17 and the other downstream of the separators 17, at

  inside the chamber 12 Each coalescer / eliminated

  steam generator 30, 31 comprises a frame 32 holding upstream and downstream screens 33, 34 between which is interposed a wire mesh mattress 35 having a predetermined density and thickness.

  wire can for example be between 0.1 and 0.3 mm.

  The lower point of the chassis 32 is connected to a conduit

  36 uai leads to exit 27.

  The upstream coalescer / fume eliminator 30 is connected to the conduit 12 by a cover 37 which is provided with holes, one of which is shown at 38 to allow the fluid to flow towards the separators 17 in the case where the coalescer / fog eliminator is blocked by

the contaminating agent.

  In service, the water and the air laden with contaminating agent hits the coalescer / eliminator of fog upstream 30, small droplets of water strike the wires and condense into larger droplets which pass downward through the wires. direction of the conduit 36 from which they are expelled in the passage 27 by the pressure differential created by the propeller 26 In this way, the volume of water passing to the separators

17 is significantly reduced -

  The downstream coalescer / fume eliminator 31 works in the same way, removing water from

  the air passing from the separators 17 to the chamber 12.

  The use of coalescing / eliminating panels

  fogging 30, 31 can provide efficiency

  overall water removal of 99.6% or more.

  The outlet passage 27 is designed to efficiently collect the air and the contaminating agent coming from the chamber 18 and to ensure that a good distribution of the air flow is obtained at the propeller 26 with the minimum drop pressure and with the minimum risk of low flow areas where the contaminating agent can be deposited This outlet 27 can be connected to a conduit which directs the fluid and the contaminating agent to a corner of the containment o of the fluid is static and consequently the fluid and the particles can be evacuated with the minimum risk of being reintroduced by the filter This duct can therefore be designed to decelerate the flow of air in order to recover the kinetic energy and to provide a deflection system to retain

  maximum contaminant in the correct location.

  A filter, such as that described above with reference to the drawings, can operate for example

  at a pressure of 1.8 bar and above and at temperatures

  air tures up to 3000 C For a distribution of dust with an average size of 7 micrometers, 92% of the dust particles can be separated from the air Efficiency of water separation

  between 60 and 90% can also be obtained.

  The pressure drop across the housing is minimal and remains constant during operation, thus eliminating the risk of

  overpressure in the containment.

  There are a certain number of modifications which can be made to the filter. A second chamber formed by two panels and the housing 20 can be provided downstream from the first chamber 18, by including additional inertial separators,

  arranged like the inertial separators 17 described above

  top The second bedroom can have a connected outlet

when passing propeller 27.

  The inertial separators of the second chamber can have different characteristics

  inertial separators 17 of the first chamber 18.

  - Propeller 26 can be replaced by

  sweeping fans, or air ejectors

  award-winning or water / oil jet pumps powered from an external power source Two such proposals are shown in Figures 4 and S and they

  will now be described in more detail.

  The parts common to Figures 1 to 3 and Figures 4 and 5 have been given the same reference numbers and they

will not be described in detail.

  In the embodiment of Figure 4, the turbine 24, the propeller 26 and the drive shaft 25 which connects them are removed The outlet passage 27

  is formed by a chamber 45 from which comes an ejection tube

  vertical tor 46 which ends in a divergent outlet 47 A conduit 48 terminates inside the chamber in a nozzle 49 which is directed into the tube 46 The conduit 48 is connected to a source 50 of a gas or liquid under high pressure (which can be air or water). In service, the fluid from the source emerges from the nozzle 49 and creates a pressure zone

  reduced in room 45 This sucks the contaminated agent

  nant separated by separators 17 and water from

  coalescers / fog eliminators 30, 31, where these

  The contaminating agent and the water are entrained in the fluid flow from the nozzle 49 and they pass with the fluid through the tube 46 and the

  exit 47 to the containment.

  The embodiment according to Figure 5

  is similar except that the ejection tube

  tor 46 and divergent outlet 47 are arranged horizontally

  The nozzle 49 is connected to a source 51 of pressurized liquid / gas mixture which, in service, leaves via the nozzle at a sonic or supersonic speed to produce a low pressure zone in the chamber II and cause the contaminant and the water and the

  pass through the containment.

12 -

Claims (13)

  1 Containment enclosure comprising a nuclear reactor and an automatic vent filter comprising a housing (10) having an inlet (11) inside the enclosure (28) and an outlet (14) outside the enclosure for the passage of fluid through it, a chamber (18) provided in the housing (10) and dividing the housing (10) into upstream and downstream sections, the chamber (18) comprising at least one inertial separator (17) having an inlet (19) communicating with the upstream end of the housing (10), a fluid outlet (20) communicating with a downstream end of the housing and   a contaminant outlet (22) leading to the interior   the chamber (18), the chamber (18) also having an outlet (27) in which a pump (26) is provided for sucking the contaminating agent from the chamber (18)   view of the evacuation inside the confines of the confines   is lying. 2 containment enclosure according to claim 1, characterized in that the housing (10) comprises,   located between the chamber (18) and the exit (14) of the lodge   a converter (24) for converting kinetic energy of the fluid in the housing (10) into energy which drives the pump (26) so that fluid laden with contaminant enters the inlet (11) of the housing is separated from the contaminating agent by said at least one separator (17), the contaminating agent being evacuated by the pump (26) in the confinement enclosure, the flow of the fluid downstream of the chamber (18 ) causing the converter (24) to activate the pump (26).   3 Automatic vent filter comprising a housing (10) having an inlet (11) and an outlet (14) for the passage of fluid through it, a chamber   (18) provided in the housing (10) and dividing the accommodation   13 - ment (10) in upstream and downstream sections, the Chamber (18) comprising at least one inertial separator (17) having an inlet (19) in communication with the upstream end of the housing (10), a fluid outlet ( 20) communicating with a downstream end of the housing (1 o) and an outlet of contaminating agent (22) leading to the interior of the chamber (18), the housing (10) comprising, located between the chamber (18) and the outlet (14) of the housing, a converter (24) for converting kinetic energy of the fluid in the housing (10) into energy which drives a pump (26) so that the fluid loaded with contaminating and penetrating agent in the housing entrance (10) is separated from the contaminating agent by said at least one separator (17), the contaminating agent being removed by the pump (26), 1 flow of fluid   downstream of the chamber (18) causing the convert-   sor (24) to activate the pump (26).   4 Automatic vent filter according to one   either of claims 2 and 3, characterized in that   that the converter comprises a turbine (24) driven in rotation by the fluid, the rotation of the turbine   (24) being used to drive the pump (26).   Automatic vent filter according to claim 4, characterized in that the rotation of the turbine (24) rotates a shaft (25) which, at its end opposite the turbine (24), is connected to the   pump (26) so as to drive the pump (26).   6 Automatic vent filter according to claim 4, characterized in that the turbine (24) is connected to an electric generator whose output   is connected to an electric motor which drags the pump (26).   7 automatic vent filter according to claim 4, characterized in that the turbine (24) is connected to a fluid compressor having an outlet 14 - of compressed fluid connected to a fluid motor intended to drive the pump (26).   8 Automatic vent filter according to one   any of claims 4 to 7, characterized in   S that the housing (10) comprises a tubular section (13), the turbine (24) being mounted in this tubular section (13), a downstream end of this section   tubular forming the outlet (14) of the housing.   9 Automatic vent filter according to claim 1 and comprising an energy source external connected to the pump.   Automatic vent filter according to claim 9, characterized in that the pump is a fluid ejector pump (49) connected to a source of pressurized fluid (50).   11 Automatic vent filter according to one   any one of claims 1 to 10, characterized in   that the chamber (18) is formed of two panels, parallel-   but spaced (15, 16), which lie in respective planes normal to the direction of flow of the   fluid through the housing, said at least one separation   inertial sensor (17) extending between these panels (15 16). 12 Automatic vent filter according to claim 11, characterized in that a large number   inertial separators (17) are provided, the separations   tors extending in parallel between them panels (15, 16).   13 Automatic vent filter according to one   any one of claims 1 to 12, characterized in that   at least one inertial separator (17) comprises a tube forming the inlet (19) and the fluid outlet (20) and a swirl generator arranged inside the tube to provide a centrifugal force to the fluid and to the contaminant entering the tube so that the contaminant flows into an annular section -   radially external to the tube, the outlet of contaminated agent   (22) eliminating the fluid and the contaminating agent from this section while the rest of the fluid leaves the tube through the fluid outlet (20).   14 Automatic vent filter according to one   any of claims 11 to 13 and comprising a   second chamber located downstream of the first chamber and formed by two panels, parallel but spaced, which lie in respective planes normal to the   I O direction of flow of the fluid through the housing   at least one additional inertial separator extending between an inlet formed in an upstream panel and an outlet formed in a downstream panel, the second chamber leading to the outlet of the first chamber mentioned.   Automatic vent filter according to one   any of claims 1 to 8, characterized in   that the pump comprises a centrifugal impeller (26).   16 Automatic vent filter according to one   any one of claims 1 to 15, characterized in that   that a mist eliminator (30) is provided in the housing (10) upstream of the chamber (18) to separate   water from the fluid entering the housing (10).   17 Automatic vent filter according to one   any one of claims 1 to 15, characterized in that   that a mist eliminator (31) is provided in the housing (10) downstream of the chamber (18) to separate   the fluid water leaving the chamber (18).   18 Process for the separation of contaminated agents   nants from a fluid, comprising passing the fluid through an inertial separator to separate the contaminant from the fluid and then passing the fluid through a converter to convert kinetic energy from the fluid to energy for drive a pump, the pump acting to suck 16 - the contaminant separates by the separator and to   pass the contaminating agent towards an evacuation.