GB2578965A - A blowdown apparatus, a steam generator and a nuclear reactor arrangement - Google Patents

Abstract

A steam generator 26, especially for a nuclear reactor, comprises a tube-sheet 32 having a plurality of apertures 34A, 34B, a plurality of U-shaped, straight or helical steam generator tubes 36, each steam generator tube 36 having a first end located in one of the apertures 34A in the tube-sheet 32. A blowdown apparatus 50 is arranged adjacent to but spaced from the tubesheet 32. The blowdown apparatus 50 comprising at least one sinuous pipe 52, each sinusoidal pipe 52 is arranged to pass between a plurality of adjacent steam generator tubes 36 and each sinuous pipe 52 extends around a portion of the perimeter of a plurality of U-shaped steam generator tubes 36. Each sinuous pipe 52 has a plurality of longitudinally spaced apertures 54 and each aperture 54 is angled towards the tube-sheet 32 and/or a steam generator tube 36. The blowdown arrangement 50 provides more even removal of crud from the tube-sheet 32.

Description

A BLOWDOWN APPARATUS, A STEAM GENERATOR AND A NUCLEAR

REACTOR ARRANGEMENT

Field of the Disclosure

The present disclosure concerns a blowdown apparatus for a steam generator for a nuclear reactor arrangement.

Background of the Disclosure

In a steam generator, steam is generated by boiling feed water. The feed water contains chemical impurities either added to maintain water chemistry or corrosion products from the internals of the steam generator and/or other parts of the nuclear reactor arrangement. As the steam is generated these chemical impurities remain in the steam generator and begin to concentrate. These chemical impurities tend to settle around areas of low flow rate within the steam generator, e.g. on flat surfaces. This is particularly problematic on the surface of the tube-sheet at the base of the steam generator. The steam generator comprises a tube-sheet and a plurality of U-shaped steam generator tubes. The tube-sheet has a plurality of apertures extending there-through and a first end of each steam generator tube locates in one of the apertures in the tube-sheet and a second end of each steam generator tube locates in one of the apertures in the tube-sheet. These concentrated chemical impurities eventually result in a crud, or sediment, that is very high in sulphates and other corrosive compounds that may cause premature failure of the steam generator tubes and/or the tube-sheet resulting in either unplanned shut down of the nuclear reactor arrangement, leakage of water from the primary circuit into the secondary circuit of the nuclear reactor arrangement or in extreme circumstances total failure of the steam generator, requiring replacement.

Currently a pipe, known as "a blow-down pipe" is installed in the centre of a bundle of steam generator tubes of the steam generator. The blow down pipe is arranged to continuously suck the concentrated water across the tube-sheet and out of the steam generator. However, this system does not affect all areas of the tube-sheet evenly and leaves areas of the tube-sheet that have concentrations of chemical impurities that may cause degradation of the steam generator tubes.

US3916844 discloses an arrangement in a flow down the steam generator is forced to the centre of the tube-sheet to remove sediment, or crud, build up. However, this is still subject to the above issues and results in reduced flow of water through the steam generator and limits efficiency.

Summary of the Disclosure

According to a first aspect of the present disclosure there is provided a steam generator comprising a tube-sheet having a plurality of apertures, a plurality of steam generator tubes, each steam generator tube having a first end located in one of the apertures in the tube-sheet and a blowdown apparatus, the blowdown apparatus being arranged adjacent to but spaced from the tube-sheet, the blowdown apparatus comprising at least one sinuous pipe, each sinuous pipe being arranged to pass between a plurality of adjacent steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each aperture being angled towards the tube-sheet and/or a steam generator tube.

The steam generator may comprise a plurality of U-shaped steam generator tubes, each U-shaped steam generator tube having a first end located in one of the apertures in the tube-sheet and a second end located in a further one of the apertures in the tube-sheet, the blowdown apparatus comprising at least one sinuous pipe, each sinuous pipe being arranged to pass between a plurality of adjacent U-shaped steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of U-shaped steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each aperture being angled towards the tube-sheet and/or a U-shaped steam generator tube.

The steam generator may comprise a plurality of straight steam generator tubes, each straight steam generator tube having a first end located in one of the apertures in the tube-sheet and a second end located in a respective one of a plurality of apertures in a further tube-sheet, the further tube sheet being arranged above the tube-sheet, the blowdown apparatus comprising at least one sinuous pipe, each sinuous pipe being arranged to pass between a plurality of adjacent straight steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of straight steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each aperture being angled towards the tube-sheet and/or a straight steam generator tube.

The steam generator may comprise a plurality of helical steam generator tubes, each helical steam generator tube having a first end located in one of the apertures in the tube-sheet and a second end located in a respective one of a plurality of apertures in a further tube-sheet, the further tube sheet being arranged above the tube-sheet, the blowdown apparatus comprising at least one sinuous pipe, each sinuous pipe being arranged to pass between a plurality of adjacent helical steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of helical steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each aperture being angled towards the tube-sheet and/or a helical steam generator tube.

Each sinuous pipe may be spaced from the tube-sheet and each sinuous pipe is 20 spaced from the U-shaped steam generator tubes.

The blowdown apparatus may comprise a cruciform pipe, an annular pipe and a plurality of sinuous pipes, the annular pipe is connected to the cruciform pipe, each sinuous pipe is connected at one end to the cruciform pipe and is connected at an opposite end to the annular pipe, each sinuous pipe being arranged to pass between a plurality of adjacent U-shaped steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of U-shaped steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each apertures being angled towards the tube-sheet and/or a U-shaped steam generator tube.

The blowdown apparatus may comprise a cruciform pipe and a plurality of sinuous pipes, each sinuous pipe is connected at one end to a first limb of the cruciform pipe and is connected at an opposite end to a second limb of the cruciform pipe, the second limb of the cruciform pipe is arranged perpendicularly to the first limb of the cruciform pipe, each sinuous pipe being arranged to pass between a plurality of adjacent U-shaped steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of U-shaped steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each apertures being angled towards the tube-sheet and/or a U-shaped steam generator tube.

The blowdown apparatus may comprise an annular pipe and a plurality of sinuous pipes, each sinuous pipe is connected at one end to the annular pipe and is connected at an opposite end to the annular pipe, each sinuous pipe being arranged to pass between a plurality of adjacent U-shaped steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of U-shaped steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each apertures being angled towards the tube-sheet and/or a U-shaped steam generator tube.

The cruciform pipe may be aligned with perpendicular diameters of the tube-sheet.

The apertures in the tube-sheet may be arranged in rows and columns. The rows and columns may be arranged perpendicularly.

The at least one sinuous pipe may be oval or ellipsoidal in cross-section. The major dimension of the sinuous pipe may be arranged perpendicularly to the tube-sheet. The annular pipe may be oval or ellipsoidal in cross-section. The major dimension of the annular pipe may be arranged perpendicularly to the tube-sheet. The cruciform pipe may be oval or ellipsoidal in cross-section. The major dimension of the cruciform pipe may be arranged perpendicularly to the tube-sheet. The apertures in the sinuous pipe may have different diameters or different cross-sectional areas.

The at least one, or each, sinuous pipe may be manufactured by additive layer manufacturing. The at least one, or each, sinuous pipe may be manufactured by powder bed laser deposition, direct laser deposition, selective laser sintering etc. The at least one, or each, sinuous pipe may be a serpentine pipe or a sinusoidal pipe. The at least one, or each, sinuous pipe may be a pipe with many curves arranged along its length. The at least one, or each, sinuous pipe may be a pipe in which the curves are in opposite directions along its length, e.g. the pipe curves alternately in opposite directions. The curves of the at least one, or each, sinuous pipe may be arranged in a plane parallel to the plane of the tube-10 sheet.

It may be possible to simply have at least one sinuous pipe fluidly connected to a pipe fluidly connected to a filter. The pipe may have a pump to supply water there-through from the sinuous pipe to the filter. The filter may be arranged to supply filtered water to a water supply. The water supply may supply water as the secondary fluid to the secondary circuit of the steam generator.

The tube-sheet may be arranged horizontally.

According to a second aspect of the present disclosure there is provided a nuclear reactor arrangement comprising a nuclear reactor and a steam generator comprising a tube-sheet having a plurality of apertures, a plurality of steam generator tubes, each steam generator tube having a first end located in one of the apertures in the tube-sheet and a blowdown apparatus, the blowdown apparatus being arranged adjacent to but spaced from the tube-sheet, the blowdown apparatus comprising at least one sinuous pipe, each sinuous pipe being arranged to pass between a plurality of adjacent steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each aperture being angled towards the tube-sheet and/or a steam generator tube.

The steam generator may comprise a plurality of U-shaped steam generator tubes, each U-shaped steam generator tube having a first end located in one of the apertures in the tube sheet and a second end located in a further one of the apertures in the tube-sheet, and a blowdown apparatus, the blowdown apparatus being arranged adjacent to but spaced from the tube-sheet, the blowdown apparatus comprising at least one sinuous pipe, each sinuous pipe being arranged to pass between a plurality of adjacent U-shaped steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of U-shaped steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each apertures being angled towards the tube-sheet and/or a U-shaped steam generator tube.

The steam generator may comprise a plurality of straight steam generator tubes, each straight steam generator tube having a first end located in one of the apertures in the tube-sheet and a second end located in a respective one of a plurality of apertures in a further tube-sheet, the further tube sheet being arranged above the tube-sheet, the blowdown apparatus comprising at least one sinuous pipe, each sinuous pipe being arranged to pass between a plurality of adjacent straight steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of straight steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each aperture being angled towards the tube-sheet and/or a straight steam generator tube.

The steam generator may comprise a plurality of helical steam generator tubes, each helical steam generator tube having a first end located in one of the apertures in the tube-sheet and a second end located in a respective one of a plurality of apertures in a further tube-sheet, the further tube sheet being arranged above the tube-sheet, the blowdown apparatus comprising at least one sinuous pipe, each sinuous pipe being arranged to pass between a plurality of adjacent helical steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of helical steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each aperture being angled towards the tube-sheet and/or a helical steam generator tube.

The skilled person will appreciate that except where mutually exclusive, a feature described in relation to any one of the above aspects may be applied mutatis mutandis to any other aspect. Furthermore, except where mutually exclusive any feature described herein may be applied to any aspect and/or combined with any other feature described herein.

Brief description of the Drawings

Embodiments will now be described by way of example only, with reference to the Figures, in which: Figure 1 is a sectional side view of a nuclear power plant having a steam generator according to the present disclosure.

Figure 2 is a sectional side view of a steam generator having a blowdown 15 apparatus according to the present disclosure.

Figure 3 is an enlarged plan view of a tube-sheet and the blowdown apparatus according to the present disclosure for the steam generator shown in figure 2.

Figure 4 is a further enlarged plan view of a portion of the tube-sheet and the blowdown apparatus of the steam generator shown in figure 2.

Figure 5 is an enlarged cross-sectional view though the tube-sheet and the blowdown apparatus of the steam generator shown in figure 2.

Figure 6 is a perspective view of a sinuous pipe of the blowdown apparatus.

Figure 7 is an enlarged plan view of a tube-sheet and another blowdown apparatus according to the present disclosure for the steam generator shown in 30 figure 2.

Figure 8 is an enlarged plan view of a tube-sheet and a further blowdown apparatus according to the present disclosure for the steam generator shown in figure 2.

Detailed Description

Figure 1 shows a nuclear power plant 10 comprising a nuclear reactor 12, a reactor vessel 16 surrounding the nuclear reactor 12 and a primary shield 18 surrounding the reactor vessel 16. The nuclear reactor 12 comprises reactor fuel elements 14. A further wall 20 surrounds the primary shield 18, a containment vessel 22 surrounds the further wall 20 and a building wall 24 surrounds the containment vessel 22. The primary shield 18 at least forms a ring around the reactor vessel 16. The reactor vessel 16 comprises a main portion 17 and a lid, or closure head, 19. The nuclear power plant 10 also comprises a primary circuit 25, a steam generator 26, a secondary circuit 27, a turbine 28 and an electrical generator 29. The primary fluid in the primary circuit 25 is heated by the nuclear reactor 12. The primary fluid flows through a pipe 25A from the nuclear reactor 12 to the steam generator 26 where it heats the secondary fluid in the secondary circuit 27. The primary fluid in the primary circuit 25 flows through pipe 25B from the steam generator 26 back to the nuclear reactor 12. The heated secondary fluid in the secondary circuit 27 flows through the pipe 27A to and drives the turbine 28 which in turn drives the electrical generator 29 to generate electricity. For example the primary fluid is water, the secondary fluid is water, the heated secondary fluid is steam and the turbine 28 is a steam turbine 28. Alternatively, the turbine 28 may provide drive for other purposes. The nuclear reactor 12 may be any type of pressurised water reactor (PWR). There may be a pressuriser if the nuclear power plant 10 comprises a pressurised water reactor. The nuclear reactor 12 may be a small modular reactor (SMR) for example for producing up to 600 MWe, producing up to 500 MWe, e.g. 220 to 440 MWe.

The steam generator 26, as shown more clearly in figure 2, comprises an outer shell, or vessel wall, 30, a tube-sheet 32 having a plurality of apertures 34 and plurality of U-shaped steam generator tubes 36. The outer shell 30 is generally cylindrical with domed ends. The tube-sheet 32 is arranged at a bottom region of the outer shell 30 and is spaced from the bottom of the outer shell 30 and a splitter wall 38 extends from the tube-sheet 32 to the bottom of the outer shell 30 to divide the interior of the outer shell 30 below the tube-sheet 32 into a first chamber 40 and a second chamber 42. The first chamber 40 is fluidly connected to the pipe 25A to receive primary fluid from the nuclear reactor 12 and the second chamber 42 is fluidly connected to the pipe 25B to supply primary fluid back to the nuclear reactor 12. Each U-shaped steam generator tube 36 has a first end located in one of the apertures 34A in the tube-sheet 32 and a second end located in a further one of the apertures 34B in the tube-sheet 32. The apertures 34A and 34B in the tube-sheet 32 are arranged in rows and columns. The rows and columns are arranged perpendicularly. The apertures 34A in the tube-sheet 32 are fluidly connected to the first chamber 40 and the apertures 34B in the tube-sheet 32 are fluidly connected to the second chamber 42 to allow the primary fluid to flow from the first chamber 40 through each of the U-shaped steam generator tubes 36 and back to the second chamber 42 to define a portion of the primary circuit 25 within the steam generator 26. The U-shaped steam generator tubes 36 are located above the tube-sheet 32. A wrapper, a cylindrical wall, 44 is arranged concentrically within the outer vessel 30 and is arranged around and spaced from the U-shaped steam generator tubes 36. The wrapper 44 is also spaced from the outer shell 30 to define an annular passage, a downcomer passage, 46 and the bottom of the wrapper 44 is spaced longitudinally, or axially, from the tube-sheet 32. A feed water manifold 48 is arranged in the outer vessel 30 and is fluidly connected to a pipe 27B supplying secondary fluid, water, to the feed water manifold 48. The tube-sheet 32 is generally arranged horizontally and each U-shaped steam generator tube 36 has a first portion extending vertically upwardly to a 180° bend and a second portion extending vertically from the 180° bend back to the tube-sheet 32.

In operation the primary fluid is supplied through the primary circuit 25 from the nuclear reactor 12 through the pipe 25A to the steam generator 26, and the primary fluid flows sequentially flows through the first chamber 40, the U-shaped steam generator tubes 36, the second chamber 42 and then flows back to the nuclear reactor 12 through the pipe 25B. The secondary fluid, water, is supplied through the pipe 27B from a water supply to the feed water manifold 48 and the water flows through, down, the annular passage 46 and then the water flows through, up, the chamber within the wrapper 44 and over the U-shaped steam generator tubes 36. The water flowing through the chamber within the wrapper 44 is heated by the primary fluid flowing through the U-shaped steam generator tubes 36 to generate steam. The steam rises to the top of the outer vessel 30 and then flows through the pipe 27A to the steam turbine 28.

The steam generator 26 also comprises a blowdown apparatus 50. The blowdown apparatus 50, shown more clearly in figures 3 to 6, is arranged adjacent to but spaced from the tube-sheet 32. The blowdown apparatus 50 is arranged above the tube-sheet 32. The blowdown apparatus 50 comprises at least one sinuous pipe 52, each sinuous pipe 52 is arranged to pass between a plurality of adjacent U-shaped steam generator tubes 36 and each sinuous pipe 52 extends around a portion of the perimeter, or periphery, of a plurality of U-shaped steam generator tubes 36. Each sinuous pipe 52 has a plurality of longitudinally spaced apertures 54 and each aperture 54 is angled towards the tube-sheet 32 and/or a U-shaped steam generator tube 36. Each sinuous pipe 52 is spaced from the tube-sheet 32 and each sinuous pipe 52 is spaced from the U-shaped steam generator tubes 36.

The blowdown apparatus 50 also comprises a cruciform pipe 56, an annular pipe 58 and a plurality of sinuous pipes 52. The annular pipe 58 is connected to the cruciform pipe 56 and each sinuous pipe 52 is connected at one end to the cruciform pipe 56 and is connected at an opposite end to the annular pipe 58. Each sinuous pipe 52 is arranged to pass between a plurality of adjacent U-shaped steam generator tubes 36 and each sinuous pipe 52 extends around a portion of the perimeter, or periphery, of a plurality of U-shaped steam generator tubes 36. Each sinuous pipe 52 has a plurality of longitudinally spaced apertures 54 and each aperture 54 is angled towards the tube-sheet 32 and/or a U-shaped steam generator tube 36. The cruciform pipe 56 is aligned with perpendicular diameters of the tube-sheet 32.

The at least one, or each, sinuous pipe 52 is oval or ellipsoidal in cross-section as shown in figure 5. The major dimension of the at least one, or each, sinuous pipe 52 is arranged perpendicularly to the tube-sheet 32. The annular pipe 58 is oval or ellipsoidal in cross-section. The major dimension of the annular pipe 58 is arranged perpendicularly to the tube-sheet 32. The cruciform pipe 56 is oval or ellipsoidal in cross-section. The major dimension of the cruciform pipe 56 is arranged perpendicularly to the tube-sheet 32. The apertures 54 in the at least one, or each, sinuous pipe 52 may have different diameters or different cross-sectional areas. The annular pipe 58 and/or the cruciform pipe 56 may have apertures angled towards the tube-sheet 32 and/or a U-shaped steam generator tube 36.

The blowdown apparatus 50 also comprises at least one pipe 60, a pump 62, a filter 64 and a further pipe 66. The at least one pipe 60 is fluidly connected to the cruciform pipe 56, or the annular pipe 58, and the pipe 60 is also fluidly connected to the filter 64. The at least one pipe 60 is fluidly connected to the annular pipe 58 in this example. The pump 62 is provided in the pipe 60 to pump water through the pipe 60 to the filter 64 and then filtered water from the filter 64 through the pipe 66 to the water supply.

In operation the at least one, or each, sinuous pipe 52 sucks crud, or sediment, off the surface of the tube-sheet 32 through the apertures 54 in the sinuous pipe, or sinuous pipes, 52. The pump 62 in the pipe 60 provides suction to suck the crud through the apertures 54 in the sinuous pipes 52, the cruciform pipe 56 and/or the annular pipe 58 and then through the pipe 60 to the filter 64. The filter 64 removes the crud, the sediment, from the water and returns cleaned water to the water supply via the pipe 66.

The sinuous pipes 52 snake between the U-shaped steam generator tubes 36 to ensure even coverage of the entire tube-sheet 32. The sinuous pipes 52 have a series of apertures 54 that are tailored in size, cross-sectional area, and in location through Computational Fluid Dynamics (CFD). Computational Fluid Dynamics (CFD) is performed in an iterative manor to ensure a maximum flow rate through the sinuous pipes 52 in areas that are shown to be either stagnant or of minimum flow velocity during normal operation of the steam generator 26.

This is unique for individual steam generator 26 designs due to the multitude of factors that affect secondary fluid flow characteristics during operation, such as U-shaped steam generator tube 36 size, density of U-shaped steam generator tubes 36, water chemistry, temperature regime etc. The iterative process would ensure that increasing flow to a specific area of the tube-sheet 32 does not add a stagnant area to another area of the tube-sheet 32. The intent is to provide an even flow rate across the whole of the tube-sheet 32. Hence, there are apertures 54 across the whole of the sinuous pipes 52 with extra apertures 54 and/or apertures 54 with large cross-sectional area where the CFD shows that there is a requirement for extra flow due to stagnation. The blowdown apparatus 50 is tolerant of a certain amount of blockage and may be cleaned during an outage by passing fluid in the opposite direction through the blowdown apparatus 50 or may be cleaned mechanically through access holes in the steam generator 26.

The connection of the sinuous pipes 52 to the cruciform pipe 56 and the perimeter pipe 58 provides support to the sinuous pipes 52 and also allows additional flow through the sinuous pipes 52. The whole of the blowdown apparatus 50 may be tack welded to the tube-sheet 32 for support or may be additively manufactured directly onto the tube-sheet 32. The sinuous pipes 52 may have a convoluted and complex design with multiple connection points to each-other to ensure structural rigidity and so that the sinuous pipes 52 support each other.

Another blowdown apparatus 50A according to the present disclosure is shown in figure 7 and comprises a cruciform pipe 56 and a plurality of sinuous pipes 52. The at least one pipe 60 is fluidly connected to the cruciform pipe 56 in this example. Each sinuous pipe 52 is connected at one end to a first limb 56A of the cruciform pipe 56 and is connected at an opposite end to a second limb 56B of the cruciform pipe 56. The second limb 56B of the cruciform pipe 56 is arranged perpendicularly to the first limb 56A of the cruciform pipe 56. Each sinuous pipe 52 is arranged to pass between a plurality of adjacent U-shaped steam generator tubes 36 and each sinuous pipe 52 extends around a portion of the perimeter of a plurality of U-shaped steam generator tubes 36. Each sinuous pipe 52 has a plurality of longitudinally spaced apertures 54 and each aperture 54 is angled towards the tube-sheet 32 and/or a U-shaped steam generator tube 36. The cruciform pipe 56 is aligned with perpendicular diameters of the tube-sheet 32. The apertures in the tube-sheet 32 are arranged in rows and columns. The rows and columns are arranged perpendicularly. The blowdown apparatus 50A works in substantially the same way as the blowdown apparatus in figures 2 to 6.

The at least one, or each, sinuous pipe 52 may be circular, square, rectangular, triangular or generally polygonal in cross-section. The at least one, or each, sinuous pipe 52 may be oval or ellipsoidal in cross-section. The major dimension of the at least one, or each, sinuous pipe 52 may be arranged perpendicularly to the tube-sheet 32. The at least one, or each, sinuous pipe 52 may have portions which have different cross-sectional shapes, e.g. one or more oval portions and one or more circular portions. The cruciform pipe 56 may be circular, square, rectangular, triangular or generally polygonal in cross-section. The cruciform pipe 56 may be oval or ellipsoidal in cross-section. The major dimension of the cruciform pipe 56 may be arranged perpendicularly to the tube-sheet 32. The cruciform pipe 56 may have portions which have different cross-sectional shapes, e.g. one or more oval portions and one or more circular portions. The apertures 54 in the sinuous pipe 52 may have different diameters or different cross-sectional areas. The at least one, or each, sinuous pipe 52 may be manufactured by additive layer manufacturing. The at least one, or each, sinuous pipe 52 may be manufactured by powder bed laser deposition, direct laser deposition, selective laser sintering etc. A further blowdown apparatus 50B according to the present disclosure is shown in figure 8 and comprises an annular pipe 58 and a plurality of sinuous pipes 52. The at least one pipe 60 is fluidly connected to the annular pipe 58 in this example. Each sinuous pipe 52 is connected at one end to the annular pipe 58 and is connected at an opposite end to the annular pipe 58. Each sinuous pipe 52 is arranged to pass between a plurality of adjacent U-shaped steam generator tubes 36 and each sinuous pipe 52 extends around a portion of the perimeter of a plurality of U-shaped steam generator tubes 36. Each sinuous pipe 52 has a plurality of longitudinally spaced apertures 54 and each aperture 54 is angled towards the tube-sheet 32 and/or a U-shaped steam generator tube 36. The apertures 54 in the tube-sheet 32 are arranged in rows and columns. The rows and columns are arranged perpendicularly. The blowdown apparatus 50B works in substantially the same way as the blowdown apparatus in figures 2 to 6.

The at least one, or each, sinuous pipe 52 may be oval or ellipsoidal in cross-5 section. The major dimension of the at least one, or each, sinuous pipe 52 may be arranged perpendicularly to the tube-sheet. The annular pipe 58 may be oval or ellipsoidal in cross-section. The major dimension of the annular pipe 58 may be arranged perpendicularly to the tube-sheet 32. The apertures 54 in the sinuous pipe 52 may have different diameters or different cross-sectional areas. 10 The at least one, or each, sinuous pipe 52 may be manufactured by additive layer manufacturing. The at least one, or each, sinuous pipe 52 may be manufactured by powder bed laser deposition, direct laser deposition, selective laser sintering etc. The blowdown apparatus 50, 50A or 50B according to the present disclosure has the advantage that the flow reaches the entire tube-sheet 32 through the sinuous pipes 52. The blowdown apparatus 50 according to the present disclosure reduces the number of dead spots or eliminates dead spots and hence reduces or eliminates the associated build-up of crud or sediments on the tube-sheet 32. The blowdown apparatus 50 may be additively manufactured to ensure good coverage and the cross-sectional area and/or the number of apertures 54 at different regions of the sinuous pipes 52 may be selected to ensure optimal flow across the entire tube-sheet 32.

In all of the embodiments of the present disclosure the at least one, or each, sinuous pipe 52 may be a serpentine pipe or a sinusoidal pipe. The at least one, or each, sinuous pipe 52 may be a pipe with many curves arranged along its length. The at least one, or each, sinuous pipe 52 may be a pipe in which the curves are in opposite directions along its length, e.g. the pipe curves alternately in opposite directions. The curves of the at least one, or each, sinuous pipe 52 may be arranged in a plane parallel to the plane of the tube-sheet 32.

The present disclosure is also applicable to other types of steam generators which have a horizontal tube-sheet in which one end of each steam generator tube is located.

The steam generator may comprise a plurality of straight steam generator tubes. Each straight steam generator tube has a first end located in one of the apertures in the tube-sheet and has a second end located in a respective one of a plurality of apertures in a further tube-sheet. The further tube sheet is arranged above the tube-sheet. The blowdown apparatus again comprises at least one sinuous pipe, each sinuous pipe is arranged to pass between a plurality of adjacent straight steam generator tubes and each sinuous pipe extends around a portion of the perimeter of a plurality of straight steam generator tubes. Each sinuous pipe has a plurality of longitudinally spaced apertures and each aperture is angled towards the tube-sheet and/or a straight steam generator tube. The tube-sheet is generally arranged horizontally and each straight steam generator tube extends vertically upwardly to the further tube-sheet. This type of steam generator is also known as a once through steam generator. In this type of steam generator the secondary fluid, water, flows around and over the steam generator tubes in counter-flow to the flow of primary fluid within the steam generator tubes.

A once through steam generator 26A, as shown more clearly in figure 9, comprises an outer shell, or vessel wall, 30A, a lower tube-sheet 32A having a plurality of apertures 34C, an upper tube-sheet 32B having a plurality of apertures 34D and a plurality of steam generator tubes 36A. The outer shell 30A is generally cylindrical with domed ends. The upper tube-sheet 32B is arranged at an upper region of the outer shell 30A and is spaced from the top of the outer shell 30A to define a first chamber 40A. The lower tube-sheet 32A is arranged at a bottom region of the outer shell 30A and is spaced from the bottom of the outer shell 30A to define a second chamber 42A. The first chamber 40A is fluidly connected to the pipe 25A to receive primary fluid from the nuclear reactor 12 and the second chamber 42A is fluidly connected to the pipe 25B to supply primary fluid back to the nuclear reactor 12. Each steam generator tube 36A has a first end located in one of the apertures 34C in the lower tube-sheet 32A and a second end located in one of the apertures 34D in the upper tube-sheet 32B. The apertures 34C and 34D in the tube-sheets 32A and 32B are arranged in rows and columns. The rows and columns are arranged perpendicularly. The apertures 34D in the upper tube-sheet 32B are fluidly connected to the first chamber 40 and the apertures 34C in the lower tube-sheet 32A are fluidly connected to the second chamber 42A to allow the primary fluid to flow from the first chamber 40 through each of the steam generator tubes 36A and to the second chamber 42 to define a portion of the primary circuit 25 within the steam generator 26A. The steam generator tubes 36A are located above the tube-sheet 32. A wrapper, a cylindrical wall, 44A is arranged concentrically within the outer vessel 30A and is arranged around and spaced from the steam generator tubes 36A. The wrapper 44A is also spaced from the outer shell 30A to define an annular passage, a downcomer passage, 46A and the bottom of the wrapper 44A is spaced longitudinally, or axially, from the lower tube-sheet 32A. A feed water manifold 48A is arranged in the outer vessel 30A and is fluidly connected to a pipe 27C supplying secondary fluid, water, to the feed water manifold 48A. The lower and upper tube-sheets 32A and 32B are generally arranged horizontally and each steam generator tube 36A extends vertically between the lower tube-sheet 32A and the upper tube-sheet 32B. A blowdown apparatus 50 is shown, which is substantially the same as that shown in figures 3 to 6. However, the blowdown apparatus 50A as shown in figure 7 or the blowdown apparatus as shown in figure 8 may be used with the steam generator 26A.

The steam generator may comprise a plurality of helical steam generator tubes. Each helical steam generator tube has a first end located in one of the apertures in the tube-sheet and a second end located in a respective one of a plurality of apertures in a further tube-sheet. The further tube sheet is arranged above the tube-sheet. The blowdown apparatus again comprises at least one sinuous pipe, each sinuous pipe is arranged to pass between a plurality of adjacent helical steam generator tubes and each sinuous pipe extends around a portion of the perimeter of a plurality of helical steam generator tubes. Each sinuous pipe has a plurality of longitudinally spaced apertures and each aperture is angled towards the tube-sheet and/or a helical steam generator tube. The tube-sheet is generally arranged horizontally and each helical steam generator tube extends vertically upwardly to the further tube-sheet. This type of steam generator is a once through steam generator but with helical steam generator tubes. In this type of steam generator the secondary fluid, water, flows around and over the steam generator tubes in counter-flow to the flow of primary fluid within the steam generator tubes.

It may be possible to simply have at least one sinuous pipe fluidly connected to a pipe fluidly connected to a filter. The pipe may have a pump to supply water there-through from the sinuous pipe to the filter. The filter may be arranged to supply filtered water to a water supply. The water supply may supply water as the secondary fluid to the secondary circuit of the steam generator.

It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.

Claims (15)

1. Claims 1. A steam generator comprising a tube-sheet having a plurality of apertures, a plurality of steam generator tubes, each steam generator tube 5 having a first end located in one of the apertures in the tube-sheet and a blowdown apparatus, the blowdown apparatus being arranged adjacent to but spaced from the tube-sheet, the blowdown apparatus comprising at least one sinuous pipe, each sinuous pipe being arranged to pass between a plurality of adjacent steam generator tubes and each sinuous pipe extending around a 10 portion of the perimeter of a plurality of steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each aperture being angled towards the tube-sheet and/or a steam generator tube.
2. 2. The steam generator as claimed in claim 1, comprising a plurality of U-shaped steam generator tubes, each U-shaped steam generator tube having a first end located in one of the apertures in the tube-sheet and a second end located in a further one of the apertures in the tube-sheet, the blowdown apparatus comprising at least one sinuous pipe, each sinuous pipe being arranged to pass between a plurality of adjacent U-shaped steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of U-shaped steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each aperture being angled towards the tube-sheet and/or a U-shaped steam generator tube.
3. 3. The steam generator as claimed in claim 1, comprising a plurality of straight steam generator tubes, each straight steam generator tube having a first end located in one of the apertures in the tube-sheet and a second end located in a respective one of a plurality of apertures in a further tube-sheet, the further tube sheet being arranged above the tube-sheet, the blowdown apparatus comprising at least one sinuous pipe, each sinuous pipe being arranged to pass between a plurality of adjacent straight steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of straight steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each aperture being angled towards the tube-sheet and/or a straight steam generator tube.
4. 4. The steam generator as claimed in claim 1, comprising a plurality of 5 helical steam generator tubes, each helical steam generator tube having a first end located in one of the apertures in the tube-sheet and a second end located in a respective one of a plurality of apertures in a further tube-sheet, the further tube sheet being arranged above the tube-sheet, the blowdown apparatus comprising at least one sinuous pipe, each sinuous pipe being arranged to pass 10 between a plurality of adjacent helical steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of helical steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each aperture being angled towards the tube-sheet and/or a helical steam generator tube.
5. 5. The steam generator as claimed in claim 1, claim 2, claim 3 or claim 4, wherein each sinuous pipe is spaced from the tube-sheet and each sinuous pipe is spaced from the steam generator tubes.
6. 6. The steam generator as claimed in any of claims 1 to 5, wherein the blowdown apparatus comprises a cruciform pipe, an annular pipe and a plurality of sinuous pipes, the annular pipe is connected to the cruciform pipe, each sinuous pipe is connected at one end to the cruciform pipe and is connected at an opposite end to the annular pipe, each sinuous pipe being arranged to pass between a plurality of adjacent steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each apertures being angled towards the tube-sheet and/or a steam generator tube.
7. 7. The steam generator as claimed in any of claims 1 to 5, wherein the blowdown apparatus comprises a cruciform pipe and a plurality of sinuous pipes, each sinuous pipe is connected at one end to a first limb of the cruciform pipe and is connected at an opposite end to a second limb of the cruciform pipe, the second limb of the cruciform pipe is arranged perpendicularly to the first limb of the cruciform pipe, each sinuous pipe being arranged to pass between a plurality of adjacent steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each apertures being angled towards the tube-sheet and/or a steam generator tube.
8. 8. The steam generator as claimed in any of claims 1 to 5, wherein the blowdown apparatus comprises an annular pipe and a plurality of sinuous pipes, each sinuous pipe is connected at one end to the annular pipe and is connected at an opposite end to the annular pipe, each sinuous pipe being arranged to pass between a plurality of adjacent steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each apertures being angled towards the tube-sheet and/or a steam generator tube.
9. 9. The steam generator as claimed in any of claims 1 to 8, wherein the apertures in the tube-sheet are arranged in rows and columns.
10. 10. The steam generator as claimed in any of claims 1 to 9, wherein the at least one sinuous pipe is oval or ellipsoidal in cross-section.
11. 11. The steam generator as claimed in any of claims 1 to 10, wherein the apertures in the sinuous pipe have different diameters or different cross-sectional areas.
12. 12. The steam generator as claimed in any of claims 1 to 11, wherein the at least one, or each, sinuous pipe is manufactured by additive layer 30 manufacturing.
13. 13. The steam generator as claimed in any of claims 1 to 12, wherein the at least one, or each, sinuous pipe is a serpentine pipe or a sinusoidal pipe.
14. 14. A nuclear reactor arrangement comprising a nuclear reactor and a steam generator comprising a tube-sheet having a plurality of apertures, a plurality of steam generator tubes, each steam generator tube having a first end located in one of the apertures in the tube-sheet and a blowdown apparatus, the blowdown 5 apparatus being arranged adjacent to but spaced from the tube-sheet, the blowdown apparatus comprising at least one sinuous pipe, each sinuous pipe being arranged to pass between a plurality of adjacent steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of steam generator tubes, each sinuous pipe having a plurality of longitudinally 10 spaced apertures, each aperture being angled towards the tube-sheet and/or a steam generator tube.
15. 15. The nuclear reactor arrangement as claimed in claim 14 comprising a plurality of U-shaped steam generator tubes, each U-shaped steam generator tube having a first end located in one of the apertures in the tube-sheet and a second end located in a further one of the apertures in the tube-sheet, the blowdown apparatus comprising at least one sinuous pipe, each sinuous pipe being arranged to pass between a plurality of adjacent U-shaped steam generator tubes and each sinuous pipe extending around a portion of the perimeter of a plurality of U-shaped steam generator tubes, each sinuous pipe having a plurality of longitudinally spaced apertures, each aperture being angled towards the tube-sheet and/or a U-shaped steam generator tube.