WO2004038267A1

WO2004038267A1 - Flow control device

Info

Publication number: WO2004038267A1
Application number: PCT/IB2003/004412
Authority: WO
Inventors: Frank Curtolo; Kurt Karl Prinsloo
Original assignee: Pebble Bed Modular Reactor (Proprietary) Limited
Priority date: 2002-10-25
Filing date: 2003-10-06
Publication date: 2004-05-06
Also published as: WO2004038267B1; AU2003264779A1

Abstract

This invention relates to a flow control device (10) which includes a housing (400) defining a chamber into which at least two spaced apart passages (402) extend. The device (10) further includes a valve member (40) having a body (42) mounted for angular displacement within the chamber, the body defining an inlet opening (44), an outlet opening (46) and a flow passage (48) connecting the two in flow communication. The body (42) of the valve member (40) is angularly displaceable between a first position, in which the inlet and outlet openings (44, 46) are in register with the passages(402), and a second position, in which at least one of the inlet and outlet openings (44, 46) is out of register with the associated passage (402). At least one seal member (66, 68) is mounted on the body (42) at a position spaced from the inlet and outlet openings (44, 46). The at least one seal member (66, 68) is displaceable relative to the body (42), between a retracted position, and an extended position.

Description

FLOW CONTROL DEVICE

THIS INVENTION relates to a nuclear power plant. More particularly it relates to a flow control device, for use in controlling the flow of spheres and gas along a sphere flow path.

Nuclear reactors of the pebble bed type employ spherical fuel elements. The fuel elements are graphite spheres, typically of about 60 mm in diameter, which are loaded with uranium. The pebble bed reactor also makes use of graphite spheres, i.e. without uranium, as moderator elements.

In the context of this specification, both the fuel elements and the moderator elements are referred to as "spheres".

To optimise burn-up of fuel, the spheres are typically cycled through the reactor a number of times. Accordingly, a nuclear plant incorporating a pebble bed nuclear reactor typically also includes a fuel handling and storage system which permits the recycling of fuel elements and, if desired, moderator elements, through the reactor. The fuel spheres and, if applicable, the moderator spheres, are conveyed along a sphere flow path, to, for example, an inlet in the reactor or storage vessel in the sphere flow path, partly by gravity but predominantly using gas under pressure.

According to one aspect of the invention, there is provided a flow control device which includes a housing defining a chamber into which at least two spaced apart passages extend; a valve member having a body which is mounted for angular displacement within the chamber, the body defining an inlet opening, an outlet opening and a flow passage connecting the inlet opening in flow communication with the outlet opening, the body of the valve member being angularly displaceable relative to the housing between a first position, in which the inlet and the outlet openings are in register with the passages of the housing to connect them in flow communication, and a second position, in which at least one of the inlet and outlet openings is out of register with the associated passage; and at least one seal member which is mounted on the body for displacement therewith, the seal member being mounted on the body at a position spaced from the inlet and outlet openings and being displaceable relative to the body, at least when the body is in its second position, between a retracted position, in which it is clear of the housing, and an extended position, in which it is in sealing contact with the housing.

The at least one seal member may be positioned such that when the body is in its first position the seal member is out of register with the passages and when the body is in its second position the seal member is in register with at least one of the passages.

The at least one seal member may be biassed towards its retracted position and may be displaceable between its retracted position and its extended position only when the body is in its second position.

The inlet opening, outlet opening and flow passage may be circular, to pass spheres conveyed in a fluid stream therethrough. More particularly, the inlet and outlet openings and flow passage may be configured to pass spheres having a diameter of about 60 mm therethrough, that is, the diameter of the inlet and outlet openings and flow passage may be greater than 60 mm.

The flow control device may include actuating means for actuating displacement of the at least one seal member between its retracted and its extended positions. The actuating means may include a cam arrangement.

The flow control device may include a rotatable drive shaft which is disengageably engageable with the body by means of a clutch arrangement, the drive shaft also driving the cam arrangement.

The cam arrangement may include a cam-formation on the drive shaft.

The clutch arrangement may drivingly connect the body to the drive shaft so that, as the drive shaft is displaced from a first, or rest, position to an intermediate position, the body is displaced from its first position to its second position, and when the shaft is in its intermediate position the clutch arrangement disengages the drive connection between the shaft and the body such that displacement of the shaft beyond its intermediate position causes displacement of the at least one seal member from its retracted position, towards which it is resiliently biassed, to its extended position.

The at least one seal member may include a base which is connected to the body for displacement relative thereto and a floating member which defines a sealing face and which is urged into abutment with the base. The base and the floating member may have complementary abutment surfaces, at least one of which is curved such that relative displacement of the base and floating member results in the one abutment surface rolling over the other and inhibits the abutment surfaces sliding relative to one another.

The flow control device may include two opposed sealing faces which are angularly displaceable as a unit. The sealing faces may furthermore be laterally displaceable between their extended and retracted positions as a unit.

According to another aspect of the invention, there is provided a flow control device which includes a valve member having a body defining an inlet opening, an outlet opening spaced from the inlet opening and a flow passage connecting the inlet opening and the outlet opening in flow communication; and at least one angularly displaceable seal member mounted on the body at a position spaced from the inlet and outlet openings, and being displaceable relative to the body between a retracted position and an outwardly displaced extended position in which it is sealingly seatable on a complementary valve seat.

According to still another aspect of the invention, there is provided a fluid flow line, which includes at least two flow line elements; and a flow control device as hereinbefore described connecting the flow line elements together.

According to yet another aspect of the invention, there is provided a nuclear power plant having a nuclear reactor of the pebble bed type and an element handling system for transporting spherical fuel and/or moderator elements, the element handling system including at least one flow control device as hereinbefore described.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings.

In the drawings,

Figure 1 shows a longitudinal sectional view of a flow control device in accordance with the invention;

Figure 2 shows a longitudinal sectional view of part of the flow control device of Figure 1 ; Figure 3 shows a longitudinal sectional view of part of another flow control device in accordance with the invention;

Figure 4 shows a side view of the flow control device of Figure 3; Figure 5 shows a stepped cross-sectional view through the flow control device of Figure 2 taken along the line A-A (ie. with the device in an open position);

Figure 6 shows a stepped cross-sectional view, similar to that of Figure 5, through the flow control device of Figure 2 with the shaft rotated through an angle of 90 degrees;

Figure 7 shows a cross-sectional view through the flow control device of Figure 2 taken along the line B-B with the shaft rotated through 90 degrees;

Figure 8 shows a cross-sectional view through the flow control device of Figure 2 taken along the line C-C with the shaft rotated through 90 degrees; Figure 9 shows a stepped cross-sectional view through the flow control device of Figure 2 (taken along the line A-A) with the shaft rotated through 180 degrees; Figure 10 shows a longitudinal sectional view through the flow control device of Figure 3 with the shaft rotated through 90 degrees in a clockwise direction from the open position;

Figure 11 shows a longitudinal sectional view through the flow control device of Figure 3 with the shaft rotated through 180 degrees in a clockwise direction from the open position;

Figure 12 shows a schematic diagram of the valve member of the flow control device of Figure 3 as viewed in the direction of the arrow D with the two opposed co-axial passages extending into the chamber of the flow control device indicated;

Figure 13 shows a schematic diagram of the flow control device of Figure 12 with the shaft rotated 180 degrees in an anti-clockwise direction; and

Figure 14 shows a schematic diagram of the flow control device of Figure 12 with the shaft rotated 180 degrees in a clockwise direction.

In Figures 1 to 4 of the drawings, reference numeral 10 refers generally to a flow control device in accordance with the invention. The flow control device 10 includes a housing 400 defining a chamber into which at least two spaced apart passages 402 extend. The device 10 further includes a valve member 40. The valve member 40 has a body 42 defining an inlet opening 44, an outlet opening 46 spaced from the inlet opening 44 and a flow passage 48 connecting the inlet opening 44 and the outlet opening 46 in flow communication. In the embodiment of the invention shown in Figures 1 and 2 of the drawings, two opposed co-axial passages extend into the chamber of the housing, the inlet opening 44 and outlet opening 46 being spaced such that the flow passage 48 defines a straight-through passage 50 in the body 42. In the embodiment of the flow control device shown in Figures 3 and 4 of the drawings, three passages extend into the chamber of the housing, two opposed co-axial passages and one passage at right angles to the two opposed passages, the inlet opening 44 and the outlet opening 46 being spaced such that the flow passage 48 interconnecting the two defines a right-angled passage 52. The inlet and outlet openings 44,46 and flow passage 48 are shaped and dimensioned to, in use, pass fuel and/or moderator spheres, typically having a diameter of about 60mm, with clearance therethrough.

The body 42 is roughly rectangular in cross-section having longitudinally spaced ends 58, 70 and opposed sides 54 (in which the inlet opening 44 is defined), 56 and 67, 69 extending between the ends 58, 70, the sides 54, 56 being arcuate. In the embodiment of Figures 1 and 2 of the drawings, the outlet opening 46 is defined in the side 56 of the body 42. In the embodiment of Figures 3 and 4 of the drawings, the outlet opening 46 is defined in the end 70 of the body 42.

The flow control device 10 includes a rotatable drive shaft 18 which is disengageably engageable with the body 42 by means of a clutch arrangement, as described in more detail below. The drive shaft 18 is housed within a shaft housing 14 having a central circular cylindrical cavity/bore 16 shaped and dimensioned to accommodate the drive shaft 18 with clearance therein. The drive shaft 18 is mounted for rotation in the housing 14 between two bearing arrangements 20, 22 located at or near longitudinally spaced ends 17, 19 of the shaft 18. The bearing arrangement 20 is retained in position between the shaft 18 and the housing 14 at the end 17 of the shaft 18 by means of a lock ring 25 which is bolted to the housing 14 at a longitudinally spaced end 24 of the housing 14.

The shaft 18 tapers to become of reduced diameter about halfway along its length (Figure 1 ). The bore 16 is similarly of stepwise-reduced diameter. An annular tapering recess 26 is defined in the housing 14 at a junction between regions of larger and reduced diameter of the bore 16, to permit a small degree of longitudinal displacement of the shaft 18 relative to the housing 14.

The lock ring 25 has a pair of diametrically opposed recesses 30 defined on an inner surface 32 thereof (see Figures 5, 6, 8 and 9), which recesses 30 are shaped and dimensioned to accommodate part of a rolling element 28 of circular cross-section therein.

An internally splined annular locating ring 34 (Figures 5 to 9) is connected to the shaft 18, at its end 17, which end 17 is externally splined, and is retained in longitudinal position on the shaft 18 by means of a key element 36 which extends transversely through the shaft 18 and ring 34 and projects laterally outwardly from the locating ring 34 at diametrically opposed positions. The locating ring 34 is connected to the shaft 18 so as to be receivable with clearance within the lock ring 25 such that the laterally outwardly projecting portions of the key element 36 are closely spaced to the inner surface 32 of the lock ring 25. A pair of diametrically opposed recesses 37, shaped and dimensioned to accommodate part of a rolling element 28 of circular cross-section therein and complementary to the recesses 30 of the lock ring 25, is defined in an outer surface 39 of the locating ring 34.

A cam 38 having a hole defined centrally therein and being internally splined is mounted to the end 17 of the shaft 18 at a position spaced longitudinally outwardly from the bearing arrangement 20 and lock ring 25.

The body 42 is mounted at its end 58 to the end 17 of the shaft 18 via a bearing arrangement 60 (Figures 1 and 2). Two pairs of diametrically opposed ring segments 62, 64 (one segment of each of which pairs is shown in Figures 5, 6, 8 and 9) depend downwardly from the body 42 at its end 58, each ring segment 62, 64 being spaced radially inwardly of an arcuate side 54, 56 of the body 42. Ring segments 62, 64 of different pairs are spaced to accommodate a rolling element 28 therebetween. The valve member 40 is mounted to the shaft 18 such that the ring segments 62, 64 are received in the clearance space between the lock ring 25 and the locating ring 34 and such that ring segments 62, 64 of each pair are disposed on opposite sides of the key element 36. A rolling element 28, in the form of a cylindrical roller, is received between each set of two adjacent ring segments 62, 64.

The valve member 40 further includes two seal members, in the form of cylinder segments 66, 68 (Figures 1 and 2), which are mounted to the opposed sides 67, 69 of the body 42 at the end 70 of the body 42 spaced from the shaft 18. The seal members 66, 68 are resiliently biassed towards a rest/retracted position, in which they lie flush against the sides 67, 69, by blade springs 72 (Figure 2), by which the cylinder segments 66, 68 are connected to the body 42.

Each cylinder segment 66, 68 is comprised of an inwardly disposed base member 74 (Figure 2) of roughly U-section, and a floating member 75 comprising an outwardly disposed first sealing element 76 and a second sealing element 80 disposed between the base member 74 and the first sealing element 76 and urged into abutment with the base member 74. The first sealing element defines a ringlike sealing face 78 which is curved to conform to the shape of a seat on the housing (not shown) of the device 10, against which seat it seals, as described below. Each cylinder segment 66, 68 is connected to the body 42 for displacement relative thereto via the base member 74 of the relevant segment 66, 68, which in turn is connected to the second sealing element 80, also of roughly U-section, by means of two clip rings 82,84, received in complementary annular-segment spaced grooves defined in the second sealing element 80. The first sealing element 76 is positioned in a complementary recess in the second sealing element 80, such that it stands slightly proud of the sealing element 80, and is retained thereon by retaining pins 86, 88. An outwardly disposed surface 90 of each base member 74 is contoured to complement an inner surface 92 of the associated second sealing element 80 of the relevant floating member 75 which it abuts, each of the two abutment surfaces 90,92 being generally curved/rounded with the surface 92 having a smaller radius of curvature than the surface 90. A clearance space 94 is defined between the two abutment surfaces 90, 92 to permit of relative displacement of the second sealing element 80, and first sealing element 76 inlaid therein, and the base member 74. By virtue of the curved surfaces 90,92, relative displacement between the base member 74 and sealing element 80 will be as a result of the surfaces 90,92 rolling over one another. This avoids sliding contact between the surfaces 90,92 which can result in cold welding in a helium atmosphere.

A laterally outwardly displaceable cam-follower 110 is mounted to a free end 112 of each base member 74, spaced from the blade spring 72, and is configured in use to follow a profile of the cam 38, thereby to displace the seal members 66, 68 laterally outwardly into a sealing position, as described in more detail below. Each cam-follower 110 is mounted for rotation by means of a bearing arrangement 111 (Figures 5 to 7 and 9) to a short projection 403 from the end 112 of the relevant base member 74. A stop formation 96 is defined at the end 70 of the body 42 for, in use, abutting against a complementary head stop 711 (see, eg., Figure 4) defined on a manifold or other block to which the flow control device 10 is mounted.

Reference is made to Figure 5 of the drawings which shows relative positions of parts of the flow control device 10 in accordance with the invention when the flow control device 10 is in an open position, i.e. when spheres conveyed in the gas stream are permitted to flow through the flow passage 48 of the device 10. In the open position, each cylinder segment 66, 68 is in a retracted position against the associated side 67, 69 of the body 42. The shaft 18 and valve member 40 are engaged by means of the cylindrical rollers 28 which are held captive between the ring segments 62, 64 within the recesses 37 of the locating ring 34.

In Figures 6 to 8 of the drawings, the shaft 18 is rotated from the open position through 90 degrees in an anti-clockwise direction (as can best be appreciated from the position of the key element 36 relative to Figure 5). The valve member 40 is also rotated through 90 degrees in an anticlockwise direction by the shaft 18. In this way, opposed sealing faces 78 defined on the first sealing elements 76 of each cylinder segment 66, 68 are displaced angularly through 90 degrees. In this position, the sealing faces 78 are disposed in the sphere flow path, each adjacent to a complementary valve seat (not shown) provided in the sphere flow path, for example, on the housing forming part of the device 10 in alignment with its two opposed coaxial passages. In this position the flow control device 10 is closed but not sealingly closed, or isolated, such that sphere flow through the device 10 is inhibited, since the flow passage 48 extends transversely to the normal sphere flow path, but gas leakage around the valve member 40 may still occur. The stop formation 96 defined on the body 42 abuts a head stop of the block to which the device 10 is mounted such that the valve member 40 with its pairs of downwardly depending ring segments 62, 64 is stopped at a position in which the recesses 37 accommodating the cylindrical rollers 28 are in register with the recesses 30 of the lock ring 25 (see Figure 8).

^" Continued rotation of the shaft 18 causes the rollers 28 to be displaced radially outwardly in the direction of the arrows 409, respectively (Figure 6), into the recesses 30 of the lock ring 25, thereby to disengage the valve member 40 and shaft 18. The cam 38 is now rotated with the shaft 18 relative to the cam followers 110 mounted to the base members 74, which are stationary. The cam 38 thereby displaces the base members 74 laterally outwardly via the cam followers 110, until the sealing faces 78 are seated on their complementary valve seats (not shown) when the shaft 18 has been rotated through a full 180 degrees from the open position. The device 10 is now in a sealingly closed position or isolated/condition (see Figure 9).

The device 10 is returned to an open position by reversing a direction of rotation of the drive shaft 18, i.e. the shaft 18 is rotated clockwise through 90 degrees such that the base members 74 and sealing faces 78 are retracted and so that a small leak flow of gas is established around the valve member40. The valve member 40 is re-engaged by the clutch arrangement, comprising the rollers 28, lock ring 25 and locating ring 34, when the key element 36 drives each ring segment 64 to displace each roller 28 into the recess 37 of the locating ring 34. Further rotation of the shaft 18 through to 180 degrees in a clockwise direction rotates the valve member 40 through 90 degrees thereby angularly to displace the sealing faces 78 out of the flow path and bring the flow passage 48 into register with the flow path to open the device 10. As can best be seen from Figures 3 and 4 and 12 to 14 of the drawings, the device 10 of this embodiment of the invention includes three seal members 66, 68 and 120, the seal member 120 being disposed on the side 56 of the body 42 and being laterally displaceable between a retracted position and an outwardly displaced sealing position, towards which it is displaced under the influence of springs 122 and differential pressure.

In the case of this embodiment of invention, which is intended in use to provide a means of changing direction of gas flow, rotation of the shaft 18 in a reverse (i.e. clockwise) direction through/past the open position (see Figure 12) (gas flow is indicated by arrows 407), through 270 degrees from the isolated position (see Figure 13), displaces the valve member 40 through to 180 degrees from the isolated position (Figure 9) to a position in which the device 10 is closed, the seal member 120 being closed under action of the springs 122, and sphere flow is inhibited whilst gas flow is obstructed but leak flow (indicated by the arrow 405) may occur (see Figure 10).

Rotation of the shaft 18 through a further 90 degrees in a clockwise direction (i.e. to a position 360 degrees from the isolated position of Figure 9) rotates the valve member 40 through 270 degrees from the isolated position of Figures 9 and 13, which corresponds to a position 180 degrees from the open position (see Figures 11 and 14). In the open position (Figure 5), the inlet opening 44 is in flow communication with a gas supply thereby to connect an overhead outlet manifold 130, to which the vertical outlet opening 46 in the end 70 of the body 42 is connected, in flow communication with the gas supply. When in the position 180 degrees from the open position (Figure 12), the inlet opening 44 of the valve member 40 is connected in flow communication with an inlet manifold (not shown) and functions as an outlet, the outlet opening 46 then functioning as an inlet through which gas from the overhead outlet manifold 130 flows to the inlet manifold thereby to purge the system. In this position, the stop formation 96 again abuts the head stop defined on the outlet manifold.

Typically, the embodiment of the device 10 shown in Figures 1 and 2 of the drawings will find application as a safety valve, in the case of failure of part of the element handling system and/or a repair valve for isolating at least part of the element handling system. It is envisaged that two such devices/valves 10 will be placed one behind the other between the nuclear reactor and element handling system, one to serve as back-up valve in a case of failure or during replacement of the other valve 10.

The Inventors believe that the device 10 in accordance with the invention will permit obstacle-free connection of sphere conveying channels defining the sphere flow path as well as selective gas-tight closure of said channels for pressures ranging from about 1 bar (or 100 kPa) to about 100 bar (or 10 000 kPa). Such gas-tight closure will facilitate safe isolation of a failed part of the element handling system as a result of, for example, pipe breakage, at pressures of up to about 85 bar. It is believed that the device 10 will allow for gas flow obstruction within about 3,5 seconds and leak-flow cut-off (i.e. isolation) within about a further 3,5 seconds.

The Inventors believe that the device 10 will be readily maintainable by, for example, removal and replacement of the cam 38 without requiring replacement of the entire shaft 18. Furthermore, it is believed that the provision of retractable/expandible sealing faces 78 will alleviate the problems associated with sliding engagement of parts during relative rotation thereof, more particularly, the attendant effect of cold welding of surfaces in the presence of Helium gas.

Claims

CLAIMS:

1. A flow control device which includes a housing defining a chamber into which at least two spaced apart passages extend; a valve member having a body which is mounted for angular displacement within the chamber, the body defining an inlet opening, an outlet opening and a flow passage connecting the inlet opening in flow communication with the outlet opening, the body of the valve member being angularly displaceable relative to the housing between a first position, in which the inlet and the outlet openings are in register with the passages of the housing to connect them in flow communication, and a second position, in which at least one of the inlet and outlet openings is out of register with the associated passage; and at least one seal member which is mounted on the body for displacement therewith, the seal member being mounted on the body at a position spaced from the inlet and outlet openings and being displaceable relative to the body, at least when the body is in its second position, between a retracted position, in which it is clear of the housing, and an extended position, in which it is in sealing contact with the housing.

2. A flow control device as claimed in Claim 1 , in which the at least one seal member is positioned such that when the body is in its first position the seal member is out of register with the passages and when the body is in its second position the seal member is in register with at least one of the passages.

3. A flow control device as claimed in Claim 2, in which the at least one seal member is biassed towards its retracted position and is displaceable between its retracted position and its extended position only when the body is in its second position.

4. A flow control device as claimed in any one of Claims 2 to 4, inclusive, in which the inlet opening, outlet opening and flow passage are circular, to pass spheres conveyed in a fluid stream therethrough.

5. A flow control device as claimed in Claim 4, in which the diameter of the inlet and outlet openings and flow passage is greater than 60 mm.

6. A flow control device, as claimed in any one of the preceding claims, which includes actuating means for actuating displacement of the at least one seal member between its retracted and its extended positions.

7. A flow control device as claimed in Claim 6, in which the actuating means includes a cam arrangement.

8. A flow control device as claimed in Claim 7, which includes a rotatable drive shaft which is disengageably engageable with the body by means of a clutch arrangement, the drive shaft also driving the cam arrangement.

9. A flow control device as claimed in Claim 8, in which the cam arrangement includes a cam-formation on the drive shaft.

10. A flow control device as claimed in Claim 9, in which the clutch arrangement drivingly connects the body to the drive shaft so that, as the drive shaft is displaced from a first, or rest, position to an intermediate position, the body is displaced from its first position to its second position, and when the shaft is in its intermediate position the clutch arrangement disengages the drive connection between the shaft and the body such that displacement of the shaft beyond its intermediate position causes displacement of the at least one seal member from its retracted position, towards which it is resiliently biassed, to its extended position.

11. A flow control device as claimed in any one of the preceding claims, in which the at least one seal member includes a base which is connected to the body for displacement relative thereto and a floating member which defines a sealing face and which is urged into abutment with the base.

12. A flow control device as claimed in Claim 11 , in which the base and the floating member have complementary abutment surfaces, at least one of which is curved such that relative displacement of the base and floating member results in the one abutment surface rolling over the other and inhibits the abutment surfaces sliding relative to one another.

13. A flow control device as claimed in any one of the preceeding claims, which includes two opposed sealing faces which are angularly displaceable as a unit.

14. A flow control device as claimed in Claim 13, in which the sealing faces are laterally displaceable between their extended and retracted positions as a unit.

15. A flow control device which includes a valve member having a body defining an inlet opening, an outlet opening spaced from the inlet opening and a flow passage connecting the inlet opening and the outlet opening in flow communication; and at least one angularly displaceable seal member mounted on the body at a position spaced from the inlet and outlet openings, and being displaceable relative to the body between a retracted position and an outwardly displaced extended position in which it is sealingly seatable on a complementary valve seat.

16. A fluid flow line, which includes at least two flow line elements; and a flow control device as claimed in any one of Claims 1 to 15, inclusive, connecting the flow line elements together.

17. A nuclear power plant having a nuclear reactor of the pebble bed type and an element handling system for transporting spherical fuel and/or moderator elements, the element handling system including at least one flow control device as claimed in any one of Claims 1 to 15, inclusive.

18. A flow control device as claimed in Claim 1 or Claim 15, substantially as herein described and illustrated.

19. A fluid flow line as claimed in Claim 16, substantially as herein described and illustrated.

20. A nuclear power plant as claimed in Claim 17, substantially as herein described and illustrated.

21. A new flow control device, a new fluid flow line or a new nuclear power plant, substantially as herein described.