JP3002431B2 - High capacity and low head loss suction strainer for nuclear reactors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a suction strainer for filtering water from a nuclear emergency shutdown water source.

[0002]

2. Description of the Related Art FIG. 35 is a schematic view of a conventional truncated cone strainer, and FIG. 36 is a schematic view of a conventional (current) stacked disk strainer in which an inner core having a uniform and constant inner radius is formed. That is, in FIGS. 35 and 36,
2 shows two types of conventional general suction strainers.

The frustoconical strainer 10 of FIG. 35 has a porous surface 12, a centerline 14 (x-axis 18), and an inner radius r (x) 16 between the centerline 14 and the porous surface 12.
The truncated cone strainer 10 is relatively inexpensive and has a simple structure. However, with respect to the amount of fine particles (debris) such as fibrous particles that can be accumulated (removed) while maintaining a low head loss, the performance of the truncated cone strainer 10 is as follows.
Has limitations. That is, compared to other types of strainers, the surface area is small for the volume occupied by the strainers.

The stacked disk strainer 20 shown in FIG.
Is an improvement of the truncated cone strainer 10 of FIG. 35, which increases the surface area for accumulating fine dust within the same overall volume or envelope. The stacked disk strainer 20 has a porous surface 22, a center line 2
4 (x-axis 28) and an inner radius r (x) 26 between the centerline 14 and the innermost surface 26. The filtration area of the conventional stacked disk strainer 20 of FIG. 36 can be arbitrarily increased by reducing the disk separation distance and disk thickness and increasing the number of applicable disks in a given volume. is there. Thus, measurement of strainer performance can be performed by dividing the filtration area by the strainer volume, especially when comparing in terms of strainer volume.

FIG. 37 (an explanatory view of a conventional truncated cone strainer in which the approach flow rate Ua changes along the length direction) and FIG. 38 (shows an insert that makes the approach flow rate Ua more uniform along the length direction) As shown in FIG. 37, which is different from FIG. 37, a conventional conventional strainer is designed in consideration of the inflow velocity of a nearby fluid. That is, in the conventional strainer 30 shown in FIG. 37, in a typical situation, the approach flow velocity is large near the intake port, and rapidly decreases as the distance from the intake port increases. The strainer 30 includes a porous cylindrical outer surface 32, a truncated cone bottom 34, a centerline 38 (x-axis), and an inner radius r between the cylindrical outer surface 32 and the centerline 38.
(X) 36. The strainer flange 40
It is connected to the flange 42 of the pump intake. In addition, the approach flow velocity Ua44 shows the maximum value at the position closest to the flanges 40 and 42.

[0006] Alternatively, as in another conventional strainer 50 shown in Fig. 38, there is one in which the internal structure is changed and an insert is provided. The strainer 50 has a porous surface 52, a truncated cone bottom 54, a centerline 58 (x-axis), and an inner radius r (x) 56 between the centerline 58 and the porous surface 52. The strainer flange 60 is connected to the flange 62 of the pump intake. Cylindrical insert 6
6 is arranged inside the strainer 50. While the insert 66 improves the uniformity of the entry flow rate Ua 64, it may introduce another problem.

[0007]

SUMMARY OF THE INVENTION With respect to the design and performance characteristics of strainers according to the prior art, "Burns & Low Incorporated", published in June 1980 by "POWER MAGAZINE", Inc. Roe, Inc., RT Richards, “New Ideas For CylindricalPipe Inta, New Ideas for Cylindrical Pipe Intakes to Help Reduce Fish and Larval Killing.
kes Can Help to Reduce Fish and Larvae Kills) "
It can be found that a valuable study has been made in a paper with the name of. This paper also discusses, among other things, the optimal design characteristics of a conventional strainer with a porous surface similar to the apparatus shown in FIGS. 37 and 38 above.

The above-mentioned patent documents disclose attempts to improve a strainer for an emergency nuclear cooling water tank. For more information, see "Strainer for water filtration for emergency cooling systems in nuclear power plants.
R FILTERING WATER TO AN EMERGENCY COOLING SYSTEM I
NA NUCLEAR POWER PLANT) "
U.S. Pat. Nos. 5,453,180 and 5,539, assigned to "Vattenfall Utveckling AB", located in Alvkarleby, Sweden.
See No. 790. In particular, US Pat. No. 5,539,79
No. 0 discloses in FIG. 2 an apparatus similar to the conventional strainer disclosed in FIG. 37 herein.

[0009] US Patent No. 4,42,897 describes a general state of the related art relating to stacked strainers.
No. 1,646 (see especially FIGS. 2 to 5), U.S. Pat.
No. 26,900, U.S. Pat. No. 4,783,262, U.S. Pat. No. 4,818,402 (see FIGS. 3 to 13), U.S. Pat. No. 4,842,739, U.S. Pat.
No. 2, and U.S. Pat. No. 5,520,805.

[0010] These patent documents do not disclose a stacked disk strainer having a tapered central core suitable for use in a nuclear reactor. Further, as patent documents relating to the laminated filter, US Pat. No. 4,594,162 and US Pat.
No. 12, and U.S. Pat. No. 5,376,278.

[0011] These patent documents disclose a multi-stage disk-shaped surface. However, the structure is substantially different from the present invention, and no reference is made to the benefits obtained by having a tapered central core.

US Pat. No. 4,738,778 discloses a zigzag filter element. This filter element is suitable for certain applications, but not for reactor suction lines.

Finally, problems with particular disk designs,
For example, patents relevant only to the problems associated with multistage disk filters include U.S. Pat. No. 4,549,963, U.S. Pat. No. 4,637,877, and U.S. Pat.
No. 2,420 exists.

As described above, even if it is assumed that the prior art is individually adopted or combined, as the distance from the intake increases, the inner diameter of the core is tapered, and the core is tapered. Suitable suction strainers do not appear to be disclosed.

The present invention has been made in view of such problems of the prior art, and has a high capacity and low head loss suction strainer for a nuclear reactor (filtering water from an emergency shutoff water source of a nuclear reactor). The purpose is to provide.

[0016]

SUMMARY OF THE INVENTION The present invention is, generally, a stacked strainer for use in an emergency shutdown pool of a nuclear reactor, wherein the inner radius is varied (decreased) according to the distance from the water inlet. I do. The strainer is attached to the suction pipe of the suction pump, and has an optimized shape to minimize the head loss and maximize the amount of fine dust accumulation in an arbitrary volume. Also,
The reason for reducing the inner radius with distance from the water inlet is to maintain a constant fluid flow rate throughout the central core region. Constant core flow minimizes head loss and pressure drop. This is because, in the region with the highest flow velocity, the flow of the internal fluid is very much affected by the non-recoverable head loss. Around the central core are arranged a plurality of stacked porous disks of varying inner diameter. The thickness of the disk can be constant or can be varied according to the distance from the water intake. The size of the perforations or holes provided in each disc is such that fines are prevented from passing through the strainer and that the fluid can pass very easily. The disk separation distance is usually set to a fixed value,
It is also possible to vary according to the characteristics of the dust being filtered. Similarly, the outer diameter of the disk is also typically set constant, but can be varied to keep the core flow rate constant.

In a preferred embodiment of the strainer according to the invention, the disk separation distance is constant and the disk thickness increases with distance from the intake, while the inner radius decreases with distance from the intake. I do. The inner radius can be decreased linearly, exponentially, or linearly thereafter, as the distance from the intake increases. The outer diameter can be similarly constant,
Although preferred, it can be reduced according to the distance from the water intake, depending on the conditions. This configuration is most advantageous in situations where it is desirable to minimize the load on the intake flange. Further, in another embodiment of the strainer according to the present invention, not a disk having a constant thickness, but a taper (tapered) disk.

Since the flow velocity is substantially constant throughout the core, there is no significant pressure drop along the centerline, and the pressure drops at the individual disks are substantially the same. This also maximizes the strainer capability, since the rate of increase of the fines deposited on each disk is approximately the same. This feature
This is important for strainers used only in emergency applications. That is, as long as it is recognized as described above, it is not considered that the present invention described herein is suggested or disclosed even if the above-mentioned prior arts are individually adopted or combined.

[0019]

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

FIG. 1 is a perspective view, partially in section, of a strainer according to the invention (in which the inner radius decreases, the disk thickness increases, and the disk separation distance is constant over the entire length, according to the distance from the water intake); 2 is a partial cross-sectional perspective view of the strainer of FIG. 1 with a changed aspect ratio, FIG. 3 is a partial cross-sectional perspective view of the strainer of FIG. 1 with a changed aspect ratio,
FIG. 4 is a front partial cross-sectional view of the strainer of FIG. 1, showing parameters used for description, and FIG. 5 is an explanatory diagram for explaining parameters U, Ua, Uc, Ud related to FIG. Note that, with regard to the reference numerals in the description, the similar numbers are used to identify similar members according to different drawings which explain the present invention.

The suction strainer (preferred embodiment) 100 of the present invention shown in FIG. 1 has a plurality of stacked porous disks 102a-102f. Disk 10
2a to 102f have an inner radius r as shown in FIG.
(X) and the thickness t (x) have changed. That is, the suction strainer 100 includes a plurality of stacked disks 102a.
〜１０102f. Each disk 102a-102
f denotes the interlocked upper surfaces (first surfaces) 112a to 112f
And lower surfaces (second surfaces) 116a to 116f and outer surfaces (third surfaces) 114a to 114f. Each disk 1
02a to 102f have facing surfaces 118a to 118e separated from an adjacent disk. Inward facing 11
8a to 118e have a radius r about the center line 104.
(X) defines a tapered central core having 106;

The suction strainer 100 has a central core 105 that is symmetric about a centerline 104, also referred to as the x-axis.
have. This is because the embodiment 100 is optimally defined as a cylindrical unit. One end of the central core 105 is attached to an intake port of a normal suction pump by a flange 110, and the other end is bounded by the plate 108. According to a preferred embodiment of the present invention, the inner radius r (x) decreases with distance from the intake (or strainer flange), while the thickness t (x) of the disks 102a-102f increases from the intake. It increases with distance. This maximizes the amount of fines (debris) such as fibrous particles that can accumulate, and minimizes the head loss of the suction strainer within a given overall size or within a given envelope.

The suction strainer of the present invention is formed to have a low aspect ratio as shown in embodiment 120 of FIG. 2 or a high aspect ratio as shown in embodiment 140 of FIG. It is possible. The low aspect ratio embodiment 120 of FIG. 2 has three disks 122a-122c. Also, in the low aspect ratio embodiment 120, the inner radius r (x) 126 measured with reference to the center line 124 is gradually changing.
The center core 125 is widest near the suction flange 130 and borders the end plate 128. The low aspect ratio embodiment 120 uses a small number of disks 122a
１２２122c, but the individual disks can also have a relatively large outer diameter.

On the other hand, a high aspect ratio embodiment 140
Has a very large number of disks 142a-142f, but individual disks may have a smaller outer diameter than disks 122a-122c of low aspect ratio embodiment 120 of FIG. Accordingly, the low aspect ratio embodiment 120 is relatively low and squat compared to the long and thin high aspect ratio embodiment 140. Therefore, as a result, the inner radius r (x) 14 of the central core 145 of the high aspect ratio embodiment 140
6 is more progressively changing about the x-axis 144 relative to the end plate 148 from the intake flange 150.

The suction strainer 100, which is a preferred embodiment of the present invention, preferably has a strainer flange 1
3/16 inch zigzag center (stag except 10)
1/8 inch round hole (roun) formed on the gered center
d hole). In other words, the perforated plate material is
a-112f, lower surfaces 116a-116f, and outer surfaces 114a-114f.

FIGS. 4 and 5 show terms and parameters used to describe the geometry of the suction strainer and associated flow field. In particular, the symbols shown in FIG. 4 are: R = outer radius r (0) = strainer base radius r (L) = inlet flange radius t (L) = minimum disk thickness L = strainer length l = disk separation distance Is defined.

An important feature of the assembled strainer 100 according to the preferred embodiment of the present invention is to minimize head loss and collect fine dust in areas where the flow velocity U is low. That is, it is known that the pressure drop caused by passing through the fine dust layer (debris bed) occurs in proportion to the flow velocity, that is, the square of the flow velocity passing through the fine dust layer.

Therefore, the flow velocity is calculated by the formula (Uc>Ud>
U). In addition, the central region 10 of the core
5, the maximum flow velocity (core flow velocity) is denoted by Uc, and the strainer surfaces 112a to 112 determine the deposition speed of fine dust.
e, 114a-114e, 116a-116d, 118
The flow rate across the a-118d is denoted by the symbol U, from the stacking discs 102a-102e to the central core 105 of the strainer.
Is denoted by Ud.

One of the primary objectives of the present invention is to minimize the acceleration of fluid inside strainer 100 in areas of high flow velocity. Therefore, the group of internal geometries described by the function r (x) is limited to keep the maximum flow rate Uc constant or nearly constant.
As a result of this new approach, the pressure drop along center line 104 is zero or nearly zero. In addition, by adjusting the thickness t (x) of the disks 102a to 102e, the core inflow velocity Ud can be controlled.
The mixing and acceleration losses as fluid enters the central core 105 of the strainer 100 are small. Flow velocity Ud / U
The ratio of c can be controlled independently for each disk.

The radius r (x) 106 of the central core region is x
It changes in the direction 104 and has a linear or exponential relationship, or a linear and then exponential relationship. Therefore, the radius r (x) 106 is minimum at the furthest distance from the suction source, i.e., the intake flange 110. This relationship is represented by the core flow velocity Uc in the x direction 104,
Core inflow velocity U flowing from each disk into core 105
d, and helps to maintain a constant flow rate into each disk. The result of this new structure is that as long as the core flow velocity Uc in the core region remains constant, the parameter x
As the volume increases toward the intake flange 110, the volume or mass flow will increase. Although the preferred embodiment suction strainer 100 is shown in FIG. 1, it will be appreciated that the present invention need not be limited to the external shapes or ratios shown in FIG. For example, as shown in FIGS. 2 and 3, the aspect ratio can be high or low.

The thickness t of each of the disks 102a to 102f
(X) changes corresponding to the inner radius r (x) 106, and the ratio of the inner transverse disk area at the interface between the disk area and the core area 105, that is, 2πr (x) t (t), is , Constant and equal for all disks. The head loss associated with fluid entering the core flow away from each of the disks 102a-102f is essentially independent of the position of the individual disks. Fluid flowing into the core 105 from the disks 102a-102f changes direction at approximately the same angle. Each disk 10
Maintaining the same rotational (geometric) configuration for 2a-102f minimizes overall mixing and rotational losses associated with strainer 100. Core flow velocity U
This feature, coupled with keeping c constant, minimizes strainer head loss and helps to achieve the target distribution of fine dust loads in the absence of fine dust, so that fine dust loads are present. Minimize head loss in situations.

The flow velocity U passing through the disk surface is almost constant. However, because the area of the disks 102a-102f varies as a function of x, the inflow velocity Ua for the strainer 100 shown in FIG. 5 will be non-uniform. The present invention has this non-uniform approach velocity Ua,
It is possible to distribute the fine dust optimally and to obtain the minimum head loss. The present invention uses the volume between the disks 102a to 102f to deposit fine dust at the same speed without causing excessive head loss. For example, if 20% of the separation distance between the disks 102a and 102b is blocked, the separation distance between the other disks is also 20%.
% Is clogged.

In the suction strainer 160 of another embodiment of the present invention shown in FIG. 6, the disk thickness t (x) is constant and independent with respect to the x-axis 160. That is, the thicknesses of the disks 162a to 162e are equal, and the equations (t (a) = t (b) = t (c) t = (d) =
t (e)). In the suction strainer 160, the flow velocity Ud varies with respect to the parameter x, while the core flow velocity Uc around the center line 164.
Is kept constant. Center line 164 and interior surface 170
The radius r (x) 166 between a-170d varies exponentially with respect to the parameter x. Specifically, the radius r
(X) 166 decreases away from the pump intake flange and approaches end plate 162. Therefore, the inflow velocity Ua increases in proportion to the distance from the intake flange. Although the outer radius is shown as being constant in the embodiment 160 in FIG. 6, the suction strainer according to the present invention
It will be understood that the outer diameter or ratio need not be limited to conform to this. This suction strainer 160 is considered to be more suitable for applications where head loss is not important.

FIG. 7 is a front partial sectional view of another strainer in which the inner radius decreases linearly with distance from the water intake. In this embodiment 180, the center line 18
4 and the inner surfaces 190a-1 of the disks 182a-182e.
The inner radius r (x) 186 between 90 d increases linearly as the distance from the pump inlet flange increases and approaches the end plate 188. Also, as in the case of the suction strainer 160 described above, the disks 182a to 182
The thickness of e is constant, and the equation (t (a) = t (b) = t)
(C) The relationship of t = (d) = t (e)) is satisfied.
The suction strainer 180 has a low head loss because the inner radial shape is an approximate value, but does not achieve the minimum head loss. However, the inflow velocity Ua (x) 192 is non-uniform and decreases when the inner radius r (x) 186 approaches the end plate 188 corresponding to the distance from the pump intake flange. The suction strainer 180 can more easily achieve manufacturing and maintaining the target non-uniform entry flow velocity Ua. Note that the outer radius need not be constant, and the present invention is not limited to the outer diameter or ratio shown in FIG. The above embodiments can be represented by mathematical relationships. Some of this relationship will be described with reference to another embodiment below.

According to the preferred embodiment of the suction strainer 100 of the present invention, the relationship between the inner radius r (x) and the distance along the strainer axis 10 is determined by the following equation.

[0036]

(Equation 5)

The above parameters are defined as R = outer radius r (0) = strainer base radius r (L) = inlet flange radius t (L) = minimum disk thickness L = strainer length l = disk separation distance Is done.

The thickness t (x) of the disks 102a to 102f is determined by the following equation.

[0039]

(Equation 6)

However, in order to manufacture at low cost,
It is desirable to fix the disk thickness t (x) to a constant value t (c) and keep the core flow velocity Uc constant. Under these conditions, the inner radius r (x) of the disk is determined by the following equation.

[0041]

(Equation 7)

The relational expression of the number of disks N in such an embodiment is given by (N = L / (l + t)). When the flow velocity U passing through the strainer surface is constant and not a function of the parameter x, the core inflow velocity Ud is a function of the distance from the strainer and changes according to the following equation.

[0043]

(Equation 8)

Another embodiment, that is, one in which the core flow rate Uc and the core inflow velocity Ud are kept constant while the flow velocity U passing through the strainer surface can be varied along the strainer axis, is represented by the following equation: It is obtained by designating the inner radius r (x).

[0045]

(Equation 9)

The number N of disks when the disk thickness t (x) is constant is determined from the equation (N = L / (l + t)). In addition, the flow velocity passing through the strainer surface changes according to the distance along the strainer axis represented by the following relational expression.

[0047]

(Equation 10)

FIG. 8 shows a factor describing the group of inner radii r (x) of the preferred embodiment shown in FIG.
It is a graph explaining. That is, the normalized inner radius r as a function of the distance x from the normalized intake
5 is a graph of (x) showing a plurality of curves based on different base sizes and outer radii of the disk. When the disk thickness t (x) is kept constant and the core inflow velocity Ud is not constant, the inner radius r (x) group is represented by the graph shown in FIG. 7 is a graph of the normalized inner radius r (x) as a function of the normalized distance x from the inlet for the strainer of FIG. 6 with the distance from the inlet and thus the inner radius changing exponentially. 3 shows multiple curves based on different base sizes and outer radius of the disc. When the flow velocity passing through the strainer surface can be changed according to the distance along the strainer, the radius r (x) in the strainer changes linearly as shown in FIG. 7 is a graph of the normalized inner radius r (x) for the strainer of FIG. 7 where the inner radius varies linearly with distance from the inlet, with respect to a function of the normalized distance x from the inlet. 3 shows a plurality of curves based on different base sizes and outer radius of the disc. FIGS. 8 to 10 show a part of the shape variation range, and the present invention can employ a different design input.

When the above design factors are used, the design parameters of the suction strainer are as follows: R (outer radius) = 1.66 feet (50.6 cm) r (0) (strainer base radius) = 3 inches (7.6 cm) ) R (L) (inlet flange radius) = 1 foot (30.5 cm) t (L) (minimum disk thickness) = 0.375 inch (0.953 cm) L (strainer length) = 4 feet (122 cm) with a geometric constraint that l (disk separation) = 2 inches (5.1 cm).

This strainer has a surface area of 273 square feet (25.4 m ² ) and has 18 disks with a profile as shown in FIG. 11 (enlarged cross section of the strainer of FIG. 1). . The manufacturing dimensions are shown in FIG.
FIG. 12 is a table giving detailed dimensions of the strainer of FIG.
Is shown. FIG. 13 is an enlarged sectional view of the strainer of FIG. 6 in which the inner radius changes exponentially according to the distance from the water intake. This means that the disc thickness t (x) is constant (t =
1.8 inches (4.6 cm) and keeping the flow rate U through the strainer surface constant,
All design parameters are the same as above. In this design, the design cross section will vary and have a surface area of 210 square feet (19.5 m ² ).

Further, the disc thickness t (x) is kept constant (t =
If all the design parameters were the same as above, except that they were kept at 1.8 inches (4.6 cm) and the core inflow velocity Ud was constant, the design cross section would be as shown in FIG.
(The enlarged sectional view of the strainer in FIG. 7 in which the inner radius changes linearly in accordance with the distance from the water intake). According to this embodiment, the strainer surface changes according to the parameter x and the strainer area is
It will have a surface area of 207 square feet (19.2 m ² ).

Taking into account the dynamic load on the strainer, the strainer area is shown in FIG. 15 (partial sectional view of another strainer according to the invention, from the intake to minimize the hydrodynamic moment of the suction flange. (The outer radius of the disk is reduced according to the distance of (1)), it is desirable to dispose it next to the intake flange 21 as shown in the embodiment 150. In this embodiment, the inner radius r (x) between the inner surfaces 212a to 212d of the disks 202a to 202e is given by the following equation.

[0053]

[Equation 11]

The outer radius of the suction strainer 200 is determined from the equation (R (x) = r (x) + s). Note that the parameter s is, as shown in FIG.
02a to 202e. This disk thickness varies according to the following equation.

[0055]

(Equation 12)

In the suction strainer 200, the flow velocity U
c, Ud, U are substantially constant and the inner radius r (x) between the centerline 204 and the inner surfaces 212a-212d is
It varies according to the distance from the intake flange 210 and decreases as the end plate 208 is approached. Note that the disk thickness t (x) is not constant, and the suction strainer 20
The outer diameter of 0 decreases with distance from the intake flange 210.

FIG. 16 is a partial sectional view of another strainer (stacked taper disk strainer) according to the present invention, wherein the thickness of the disk is not constant. The suction strainer 300 is different from the embodiment 100 in that
a to 114f are not provided. That is, the suction strainer 300 has a plurality of tapered disks 302a to 302f around the center line 304. The suction strainer 300 has a strainer intake flange 310 located opposite the distal end plate 308. Each of the tapered disks 302a to 302f has an upper surface (a first surface).
Surfaces) 312a to 312f and a lower surface (second surface) 316a
316e, which are mutually adjacent to the edge 31
4a to 314f.

FIG. 17 is an explanatory view showing terms for explaining parameters related to the stacked taper disk strainer of FIG. 16, and FIG. 18 is a parameter U related to the stacked taper disk strainer of FIGS. 16 and 17. , Ua, Uc, Ud.
In other words, the terms for describing the geometric arrangement of the strainer 300 and the flow of the fluid are described in FIGS. 17 and 18.

The inner radius r (x) 306 and the thickness of the disk can be varied in the manner described above to maximize the amount of fines that can be deposited and to reduce the head loss at an arbitrarily set overall size or envelope volume. It is possible to minimize it. An important feature of the taper strainer, which is intended to minimize head loss, is to collect fine dust in a low flow rate region. This is because it is known that the pressure drop caused by passing through the fine dust layer occurs in proportion to the flow velocity, that is, the square of the flow velocity passing through the fine dust layer. Therefore, the flow velocity is calculated by the formula (Uc> Ud)
> U). The symbol Uc indicates the maximum flow velocity existing in the central region of the strainer (core). The symbol U indicates the flow velocity through the surface of the strainer and the fine dust layer deposited on the surface. The symbol Ud is
It refers to the flow velocity (core inflow velocity) of the fluid flowing away from the stacking disc and into the central region 305 of the strainer 300. The primary purpose of the embodiment 300 with a tapered disk is to minimize acceleration of the fluid inside the strainer 300 in high flow velocity regions. Therefore,
The internal (geometric) arrangement described by the function r (x) is chosen so that the core flow velocity Uc can be kept constant or almost constant. With this feature, strainer 3
The pressure drop across the 00 axis 304 will be zero or nearly zero. Further, by adjusting the thickness t (x) of the disk, the flow velocity Ud of the fluid leaving the disk is controlled, and the mixing and acceleration loss when the fluid flows into the central core 305 of the strainer 300 is reduced. Can be.

The radius r (x) of the central region 305 of the core is
Depending on the parameter x, it can change linearly, exponentially, or linearly to exponentially, and decrease as it moves away from the intake flange 310. This helps to ensure a constant core flow Uc in the x direction, a constant flow Ud flowing from the disk into the core 305, and a constant flow U flowing into the disk. As a result of the characteristic structure of this embodiment 300, the volume (or mass) flow rate increases with the parameter x toward the intake flange 310 even though the flow velocity in the central region 305 of the core remains constant. It increases as one moves away from the distal end plate 308. Although a preferred embodiment 300 of the tapered plate type according to the present invention is shown in FIG. 16, the present invention need not be limited to the external shapes or ratios shown there. Disks 302a-30
3f tapers, as shown, and each has a tip 314a-314f, however, for structural and flow reasons, a slight minimum thickness can be employed.

The thickness t of the disks 302a to 303f
(X) varies corresponding to the inner radius r (x) 306, but the ratio of the internal transverse disk area at the interface between the disk area and the core area 305, that is, 2πr (x) t (x), is constant. And is equal for all disks.
The head loss associated with the fluid leaving the disks 302a-302f and entering the core flow (core flow rate Uc) is essentially independent of its location on the strainer 300. Fluid flowing into the core from the disks 302a-302f rotates (turns) at approximately the same angle. Maintaining a geometrically approximate rotation angle minimizes mixing and rotation losses in the strainer 300. This feature, which is associated with keeping the core flow velocity Uc constant, minimizes the strainer head loss in the absence of fine dust and helps achieve the target distribution of fine dust load, thereby reducing the fine dust load. Minimize head loss in existing situations.

Disk surfaces 312a to 312f and 31
The flow rates passing through 6a to 316e are almost constant. However, the strainer 30 does not
Since the area of 02f changes as a function of the parameter x, the approach flow velocity Ua becomes non-uniform (forms a non-uniform approach flow velocity) as shown in FIG. Due to this non-uniform inflow velocity, the fine dust is optimally distributed in the strainer 300 and a minimum head loss is established. That is, the strainer 300 accumulates fine dust without forming an excessive head loss by utilizing the volume between the disks.
The fluctuation of the inner radius r (x) is caused by the discs 302a to 302f.
Is dependent on the disk thickness t (x). When the thickness t (x) of the disc is
If less than the nominal separation d (x), the square of the radius r (x) changes exponentially in the x direction. If the disk thickness t (x) is greater than or equal to the nominal separation d (x), the radius r (x) varies linearly with respect to the parameter x. The thickness of the disk is the intake flange 3
As one moves away from 10, it increases.

FIG. 19 is a partial sectional front view of a stacked taper disk strainer whose inner radius decreases exponentially with distance from the water intake. In this embodiment, the strainer 320 sets the disk thickness t (x) to the inner radius r.
(X) is constant and independent of the parameter x. In this case, the flow velocity U changes with respect to the parameter x, but keeps the core flow velocity Uc and the core inflow velocity Ud from the disk to the core constant. Note that the radius r (x) changes exponentially with respect to the parameter x. As in the embodiment 300 in which the disk thickness changes, the outer radius of the embodiment 320 does not need to be constant, and is not limited to the outer shape or ratio shown in FIG. It is considered that the strainer 320 is suitable for an application in which the internal head loss is not critical.

If the flow velocity Ud is variable and the flow velocity U and Uc are constant, the square of the inner radius r (x) varies exponentially with respect to the parameter x. Embodiments 300 and 3
20 has a similarly varying inner radius r (x). In other words, the inner radius r (x) is similarly changed to a preferable ratio corresponding to a region where the thickness is larger than the nominal separation distance and a preferable region corresponding to an area region where the thickness is smaller than the nominal separation distance. The speed Ud can be obtained.

FIG. 20 is a partial sectional front view of a stacked taper disk strainer whose inner radius decreases linearly with distance from the water intake. In the strainer 340 according to this embodiment, the inner radius r (x) changes linearly with respect to the parameter x. As in the embodiment 300 in which the disk thickness changes, the outer radius of the embodiment 320 does not need to be constant, and is not limited to the external shape or ratio shown in FIG.

FIG. 21 is a partial sectional front view of a stacked taper disk strainer in which the internal disk angle α is constant. In other words, the strainer 350 according to another embodiment of the present invention having a tapered disk is constant (αa
= Αb = αc = αd). In the case where the flow velocities U and Ud are variable, the radius r
(X) varies linearly and exponentially with respect to the parameter x. Since the profile in the inner radial direction is an approximate value, the strainer 350 does not reach the theoretical minimum head loss, but achieves a near level.
However, the strainer 350 is easy to manufacture, while maintaining a target non-uniform entry flow velocity. In addition, the outer radius of Embodiment 350 does not need to be constant, and is different from the outer shape or ratio shown in FIG.
Not limited.

The parameters defining the preferred embodiment 300 (with a tapered disk) are: R = outer radius r (x) = inner radius r (0) = strainer base radius r (L) = inlet flange radius t ( L) = minimum disk thickness at inner radius (t (x) <l) L = strainer length l (x) = disk separation α = angle of upper and lower surfaces of strainer with respect to a vertical plane with respect to center line x ( Internal disk angle).

In these dimensions, the relationship between the inner radius r (x) of the disk and the distance along the strainer axis x can be calculated by the following equation.

[0069]

(Equation 13)

The thickness t (x) of the disk is determined by the following equation.

[0071]

[Equation 14]

When the function t (x) is larger than the initial value of the parameter l, it is determined from the relational expression (l = t (x)).

In order to manufacture the disk at a low cost, it is desirable to set the disk thickness to a constant value for the inner radius and a constant value smaller than the inner radius for the outer radius to maintain a constant core flow velocity Uc. Under such conditions, the inner radius r (x) of the disk is given by the following equation when the flow velocity Ud is constant.

[0074]

(Equation 15)

When the flow velocity U is constant, it is given by the following equation.

[0076]

(Equation 16)

Further, the number N of disks in the present embodiment is given by a relational expression (N = L / l). Alternatively, a constant core flow velocity Uc can be maintained by maintaining a constant internal disk angle α. In this alternative embodiment, when the flow velocity Ud is constant, the inner radius changes according to the following equation.

[0078]

[Equation 17]

However, when the flow velocity U is constant, the inner radius changes according to the following equation.

[0080]

(Equation 18)

The disk thickness t (x) is expressed by the relational expression (t) when the internal disk angle α is a value shown in FIG.
(X) = 2 (R−r (x)) tan α).

To explain the principle obtained in the present invention, FIG. 22 shows an inner radius r (x) group in the embodiment 300 (having a tapered disk). However, the relational expression (t (x) <l) is satisfied. That is,
FIG. 22 shows a stacked taper disc strainer,
FIG. 5 is a graph of normalized inner radius r (x) as a function of normalized distance x from intake, showing multiple curves based on different base sizes and outer radius of the disc. Also, the disk thickness is kept constant (t (x) = t
(C)) FIG. 23 shows a group of inner radii r (x) when the flow velocity Ud leaving the disk is not constant.
In other words, FIG. 23 shows the normalized normalized function of the distance x from the normalized intake in a stacked taper disc strainer where the disk thickness is constant and the inner radius varies exponentially with distance from the intake. Inner radius r
5 is a graph of (x) showing a plurality of curves based on different base sizes and outer radii of the disk.

FIG. 24 shows a linearly changing inner radius r (x) group in the case where the flow velocity passing through the strainer surface can be changed with respect to the distance along the strainer. That is, in FIG. 24, the disk thickness is substantially constant,
FIG. 4 is a graph of normalized inner radius r (x) as a function of normalized distance from inlet x for a stacked taper disc strainer whose inner radius varies linearly with distance from the inlet; 3 shows a plurality of curves based on the base size and the outer radius of the disc. Therefore, in the embodiment in which the change of the inner radius is changed linearly from exponential, the curves shown in FIGS. 22 and 24 can be combined. FIGS. 25 and 26 have a constant internal disk angle α, and the flow velocities Ud and U are each kept constant.
The change in the inner radius with respect to the parameter x is shown. That is, FIG. 25 is a graph of the normalized inner radius r (x) with respect to the function of the normalized distance x from the intake port when the internal disk angle α and the flow velocity Ud are constant, and FIG. 4 is a graph of the normalized inner radius r (x) as a function of the normalized distance x from the intake at a constant disk angle α and flow velocity U. As described above, FIGS. 22 to 26 show a part of the shape range of the embodiment according to the present invention, and the present invention can apply different design settings.

Embodiment 300 with Tapered Disk
According to the above design principle, R (outer radius) = 1.66 feet (50.6 cm) r (0) (strainer base radius) = 3 inches (7.6 cm) r (L) (inlet flange radius) = 1 foot (30.5 cm) t (L) (minimum disc thickness) = 0.375 inch (0.953 cm) L (strainer length) = 4 feet (122 cm) l (disk separation) = 2 inches (5 .1 cm) are used to construct the design parameters.

The strainer 300 has a surface area of 336 square feet (31.2 m ² ) and has 24 disks. The cross section is shown in FIG. 27 (an enlarged cross-sectional view of the stacked taper disk strainer of FIG. 16). The manufacturing dimensions are shown in FIG. 28 (a chart giving detailed dimensions of the stacked taper disk strainer of FIG. 27).

FIG. 29 is an enlarged sectional view of an embodiment in which the minimum thickness is increased (having a tapered disk). In this strainer, the portion where the radius r (x) changes linearly is increased. 16 is an enlarged sectional view of the stacked taper disk strainer of FIG.
As the change in (x) approaches the suction flange (water intake), it changes to a linear change.

FIG. 30 shows a linearly changing radius r (x).
FIG. That is, it is an enlarged sectional view of the stacked taper disk strainer in which the inner radius decreases linearly and the disk thickness is substantially constant according to the distance from the water intake port. FIG. 31 shows an exponentially changing radius r (x).
It is an expanded sectional view of. That is, it is an enlarged cross-sectional view of the stacked taper disk strainer in which the inner radius decreases exponentially according to the distance from the water intake and the disk thickness is substantially constant. FIG. 32 is an enlarged sectional view of the embodiment with a constant internal disk angle α. That is, it is an enlarged sectional view of the stacked taper disk strainer in which the internal disk angle α and the flow velocity Ud are substantially constant.

An advantage of the preferred embodiment 100 and the embodiment 300 (having a tapered disk) is that the pressure drop across each disk 302a-302f is the same and each disk 302a-302f has Accumulates. Thus, fines accumulate similarly on each disk over time. FIG. 33 is an explanatory diagram showing a typical tapered disk and related terms. That is, it is an explanatory diagram for explaining parameters and terms used for calculating the pressure drop and the deposition of the fine dust layer.

The amount of fine dust deposited on the disk is Ml = Tlρl2π (R ² −rl ² ), and the deposition rate is dMl / dθ = CUdtl2πrl. The symbol C is the weight concentration of fine dust per unit volume of the fluid around the strainer, and the symbol θ is time.

Head loss Δhl when passing through fine dust layer
Is linearly proportional to the fine dust thickness Tl and the flow velocity Ul passing through the fine dust layer, and the relational expression is Δhl = kUITl (k is a constant). Note that Ul is related to Ud that is independent of time, and the relational expression is Ul2π (R ² −rl ² ) = UdT12πrl.

Further, by substituting this equation into the above head loss equation and integrating the generation amount (yield) with respect to time,
The relational expression is: Δhl = (kUDrl ² tl ² Cθ) / (ρl (R ² −
rl ² ) ² ).

Therefore, the parameters k, Ud and ρ
If 1 is the same for all disks, the head loss is the same for each disk. This is because the thickness and radius of each disc, relations, according ^{tn ~ (R 2 -rn 2)} / rn, in order to change.

FIG. 34 is a partial cross-sectional perspective view of a strainer having support plates equally spaced between stacked tapered disks. By adding the external supports 378a to 378e as shown in the drawing, it is possible to improve the structural strength of the strainer and to reduce the head loss passing through the fine dust layer. Although the external supports 378a-378e are shown as applied to the embodiment 360, those skilled in the art will appreciate that other embodiments can be used as well. . The strainer 360 according to the present embodiment.
Has a plurality of tapered disks 362a to 362f. Each tapered disk 362a-362f has an upper surface 372a-372f and a lower surface 376a-376e. The strainer 360 also has an x-axis 364 and an inner radius r (x) 366 that decreases with distance from the intake flange 370. End plate 368 defines the distal end of intake flange 370. External support 3
78a-378e are preferably plates parallel to the center line 364. Also, the external supports 378a to 378
e can have another structural member, such as a rod. The space between the external supports 378a to 378e is reduced. That is because the small strainer radius prevents fine dust from being densely deposited (filled). Loose deposition (rough filling) reduces the pressure drop. The number and spacing of the external supports 378a-378e depend on the dust packing characteristics and the inherent structural strength of the strainer 360.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art can make various modifications to the structure and components of the present invention without departing from the spirit and scope of the invention.

[0095]

As described above, according to the present invention, the inner radius r (x) between the center line of the central core and the plurality of stacked porous disks is changed according to the distance from the water intake. Therefore, low head loss can be achieved while having high capacity.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional perspective view of a strainer according to the present invention.

FIG. 2 is a partial cross-sectional perspective view of strainers having different aspect ratios.

FIG. 3 is a partial sectional perspective view of strainers having different aspect ratios.

FIG. 4 is a front partial sectional view of the strainer of FIG. 1;

FIG. 5 is an explanatory diagram for explaining symbols U, Ua, Uc, and Ud.

FIG. 6 is a partial front sectional view of another strainer.

FIG. 7 is a front partial sectional view of another strainer.

FIG. 8 is a normalized graph related to an inner radius r (x).

FIG. 9 is another normalized graph for the inner radius r (x).

FIG. 10 is another normalized graph for the inner radius r (x).

FIG. 11 is an enlarged sectional view of the strainer of FIG. 1;

FIG. 12 is a chart giving detailed dimensions of the strainer of FIG. 11;

FIG. 13 is an enlarged sectional view of the strainer of FIG. 6;

FIG. 14 is an enlarged sectional view of the strainer of FIG. 7;

FIG. 15 is a partial sectional view of another strainer according to the present invention.

FIG. 16 is a partial sectional view of another tapered disk strainer.

FIG. 17 is an explanatory diagram showing terms for explaining parameters.

FIG. 18 is an explanatory diagram for explaining parameters.

FIG. 19 is a partial sectional front view of another tapered disk strainer.

FIG. 20 is a partial sectional front view of another tapered disk strainer.

FIG. 21 is a partial sectional front view of another tapered disk strainer.

FIG. 22 is another normalized graph for the inner radius r (x).

FIG. 23 is another normalized graph for the inner radius r (x).

FIG. 24 is another normalized graph for the inner radius r (x).

FIG. 25 is another normalized graph for the inner radius r (x).

FIG. 26 is another normalized graph for the inner radius r (x).

FIG. 27 is an enlarged sectional view of the tapered disk strainer of FIG.

FIG. 28 is a chart giving detailed dimensions of the tapered disk strainer of FIG. 27.

FIG. 29 is an enlarged sectional view of the tapered disk strainer of FIG.

FIG. 30 is an enlarged sectional view of another tapered disk strainer.

FIG. 31 is an enlarged sectional view of another tapered disk strainer.

FIG. 32 is an enlarged sectional view of another tapered disk strainer.

FIG. 33 is an explanatory diagram for describing a method of calculating a pressure drop and a fine dust layer deposition.

FIG. 34 is a partial cross-sectional perspective view of a strainer having a support plate.

FIG. 35 is a schematic view of a conventional truncated cone strainer.

FIG. 36 is a schematic view of a conventional stacked disk strainer.

FIG. 37 is an explanatory view of a conventional truncated cone strainer.

FIG. 38 is an explanatory view of another conventional truncated cone strainer.

[Explanation of symbols]

 L: Strainer length, l: Disk separation distance, R: Outer radius, r (x): Inner radius, r (0): Strainer base radius, r (L): Inlet flange radius, t (L) ... ( Minimum) disk thickness, U: external fluid flow rate, Ua: entry flow rate, Ud: core inflow flow rate, Uc: core flow rate, α: internal disk angle.

────────────────────────────────────────────────── ─── front page continued (51) Int.Cl. ⁷ identifications FI G21F 9/06 521 G21C 19/30 D ( 73) patentee 597044944 Building 9A, James Forrestal Campus, P rinceton New Jerse y 08543, U . S. A. (72) Inventor Andrew E. Kaufman Line 172, West Windsor, New Jersey 08690, West Windsor 172 (56) References JP-A-9-329683 (JP, A) JP-A-9-122408 (JP, A) JP-A-2-6808 (JP, A) JP-A-64-7115 (JP, A) JP-A-64-4210 (JP, A) JP-B-63-52528 (JP, B2) JP-A-8-504271 (JP, A) JP-A-61-21 501437 (JP, A) US Pat. No. 4,434,091 (US, A) US Pat. No. 4,421,646 (US, A) US Pat. No. 4,726,900 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G21C 15/18 B01D 29/39 B01D 35/02 G21C 9/004 G21C 19/307 G21F 9/06 521 JICST file (JOIS) WPI (DIALOG)

Claims (19)

(57) [Claims] 1. A suction strainer for filtering water from an emergency cutoff water source of a nuclear reactor, comprising: a water intake, a plurality of stacked porous disks, and a center provided on the disk and having a center line and communicating with the water intake. A minimum inner radius r between the center line and the disk.
(X) is the distance from the intake suction strainers, characterized and this <br/> to decrease. Wherein a thickness of said disc, suction strainer of claim 1, characterized in that the distance from the intake, changes. 3. The thickness of the disk increases as the distance from the intake increases.
The suction strainer according to claim 2 . 4. The disk has a first surface substantially facing in the direction of the water intake, and a second surface connected to the first surface and substantially facing away from the water intake. The suction strainer according to claim 3 , wherein: 5. A strainer having a third surface annularly connected to the first surface and the second surface, the third surface having a maximum outer diameter of the strainer from the center line defining a vertical direction x. The suction strainer according to claim 4 , wherein 6. The suction strainer according to claim 5 , wherein the outer diameter of the disc is substantially constant along a length of the strainer determined with respect to the center line. 7. The suction strainer according to claim 5 , wherein an outer diameter of the strainer changes according to a distance along the center line. 8. A suction strainer according to claim 6 , further comprising reinforcement means disposed between said disks for providing additional structural support to the strainer. 9. The suction strainer according to claim 4 , wherein the disk has a tapered cross-sectional shape. 10. The suction strainer according to claim 5 , wherein the inner radius r (x) decreases exponentially as the distance from the water intake increases. 11. The suction strainer according to claim 5 , wherein the inner radius r (x) decreases linearly as the distance from the water intake increases. 12. The flow rate of water supplied from an emergency shutoff water source of the reactor and passing through the central core, wherein the inner radius r
The suction strainer according to claim 4 , wherein the suction strainer is substantially constant regardless of a change in (x). 13. The suction strainer according to claim 5 , wherein the inner radius r (x) decreases substantially linearly and then exponentially as the distance from the water intake increases. 14. The suction strainer according to claim 9 , wherein the inner radius r (x) decreases exponentially as the distance from the water intake increases. 15. The suction strainer according to claim 9 , wherein the inner radius r (x) decreases linearly as the distance from the water intake increases. 16. The suction strainer according to claim 9 , wherein the inner radius r (x) decreases substantially linearly and thereafter exponentially as the distance from the water intake increases. 17. The suction strainer according to claim 9 , wherein the square of the inner radius r (x) changes exponentially as the distance from the water intake increases. 18. The parameter is defined as: R = outer radius r (0) = strainer base radius r (L) = inlet flange radius t (L) = minimum disk thickness L = strainer length l = disk separation distance Thus, the relationship between the inner radius r (x) of the disk and the distance along the center line is given by the following equation: And the thickness t (x) of the disk is given by the following equation: The suction strainer according to claim 5 , characterized in that: 19. Signs: R = outer radius r (x) = inner radius r (0) = strainer base radius r (L) = inlet flange radius t (L) = minimum disk thickness at inner radius L = strainer Length l (x) = disc distance [t (x) <l] α = angle of upper and lower surfaces of strainer with respect to vertical to centerline x (internal disk angle) U = flow velocity of external fluid Ua = ingress By defining the flow velocity Ud = core inflow velocity Uc = core flow velocity, the relationship between the inner radius r (x) of the disk and the distance along the center line is given by the equation: And the thickness t (x) of the disk is given by: 10. The suction strainer according to claim 9 , wherein: