GB2282011A

GB2282011A - A helical annular linear induction pump

Info

Publication number: GB2282011A
Application number: GB9319461A
Authority: GB
Inventors: Thomas Andre Lennox
Original assignee: NNC Ltd
Current assignee: NNC Ltd
Priority date: 1993-09-21
Filing date: 1993-09-21
Publication date: 1995-03-22
Also published as: JPH07113729A; GB9319461D0

Abstract

A helical annular linear pump (HALIP) has a central magnetic core 3 and at least one surrounding annular winding (5) separated by a annular space (7) through which a sample of fluid material can pass. A further annular sheath about the winding may define a further flow passage. Guide vanes 19 and a barrier 9 are formed on the core 3. A failed fuel detection apparatus including a source selecting valve (for use in a nuclear reactor) using the pump is disclosed. <IMAGE>

Description

PUMP This invention relates to a pump and to apparatus incorporating such pump and arranged to detect failed fuel in a nuclear reactor which is cooled by liquid metal.

The fuel for nuclear reactors of the liquid metal cooled kind is usually contained in closed sheaths, the fuel pins thus formed being disposed side-by-side in an open-ended wrapper to form a fuel sub-assembly which, together with a multiplicity of other subassemblies, form the core of the nuclear reactors Liquid metal is caused to flow upwardly through the sub-assembly to remove fission-generated heat from the fuel pins by heat exchange.

It is necessary to be able to detect any failure of the sheaths of the fuel pins of a particular sub-assembly so that that sub-assembly can be removed and replaced at the earliest opportunity, to avoid contaminating the coolant and prejudicing the safety of the reactors Failed fuel detection apparatus for such nuclear reactors generally employs one coolant sampling pipe for each fuel sub-assembly of the core. The pipes are terminated at respective ports of a multi-port selector valve, by means of which sequential samples are taken, each sample being monitored to detect the presence of fission products, which would indicate one or more fuel sheathing failures in the particular fuel sub-assembly associated with the selected port.

It is necessary to employ a pump to circulate each sample of liquid metal from the relevant sub-assembly to the selector valve, from there to the monitoring equipment, and thence back to the liquid metal pool of the nuclear reactor.

The kind of pump which has been found particularly effective for this purpose is a helical annular linear induction pump, or HALIP and and is described for example, in an article entitled 'Sodium Electro Technology at Risley Nuclear Power Developments' by Davidson Duncombe and Thatcher in Nuclear Energy 198 Vol. 20 Feb No.1 Page 79-90 and particularly Pages 88 and 89.

Our European Patent Specification No. 0172622 describes such sample monitoring apparatus including a HALIP, in which samples are conducted through the pump via respective tubes which extend through the magnetic circuit of the pump.

It is an object of the present invention to provide an improved HALIP which is more compact than that described above.

According to the invention there is provided a helical annular linear induction pump comprising a magnetic core structure; an elongate annular winding structure encircling the core structure with an annular space between the winding structure and the core structure for conducting at least one sample of fluid material.

The pump may also comprise an elongate tubular member encircling the winding structure with an annular space between tubular member and the winding structure for conducting at least one further sample of fluid material.

The or each annular space may be provided with guide fins located in the space and extending longitudinally of the space to form a plurality of conduits there between for conducting respective samples of material.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which Figure 1 is a schematic vertical cross-sectional view of a configuration of pump in accordance with the invention; Figure 2 shows a cross section taken on a line II-II of Figure 1; Figure 3 is a schematic vertical cross-sectional view of an alternative configuration of pump in accordance with the invention; Figure 4 shows a cross section taken on a line IV-IV of Figure 3; Figure 5 is a schematic cross-sectional view of a failed fuel detection and location (FFDL) unit incorporating either of the pumps of Figures 1 and 2 or Figures 3 and 4; and Figure 6 is a schematic cross-sectional view of a sample selector valve for use in the vL unit of Figure 5.

Referring to Figures 1 and 2 of the drawings, a HALIP 1 comprises a central elongate magnetic core structure 3 and an annular winding structure 5 concentric with the core structure and forming an annular space 7 therebetween. A vertical barrier is formed by elongate flow guides 11, 13 which extend from the outer surface of the core structure 3 to the inner surface of the winding structure 5. The barrier 9 divides the space 7 into two conduits 15, 17 which can each conduct a respective sample. Further vertical flow guides 19, 21 are provided within the conduits. The top and the bottom of the HALIP are sealed to flanges 23, 25, so that a chamber is formed around the HALIP. Sample inlets 27 and 29 are provided at the bottom of the conduits 15 and 17, respectively, and sample outlets 31 and 33 are provided at the top of the conduits. This configuration allows two samples to be pumped independently by the HALIP 1.

If desired, one of the two conduits 15, 17 may extend over only part of the length of the HALIP, thereby providing two samples with different flow rates. Further radial barriers could be provided to divide the space 7 into a larger number of conduits.

Figures 3 and 4 illustrate an alternative pump configuration in accordance with the invention. In this case, a HALIP 35 comprises a central magnetic core structure 37 and a winding structure 39 encircling it, with an annular space 41 therebetween. Two orthogonal pairs of elongate longitudinal flow guides 43 are provided in the space 41. An annular member 45 encircles the winding structure 39, with an annular space 47 therebetween. Two orthogonal pairs of elongate longitudinal flow guides 49 are provided in the space 47. An inlet port 51 is provided at the lower end of the space 47 and an outlet port 53 at its upper end.

In operation of the pump, one sample enters the bottom of the space 41 and is pumped out of the top of the space, and a second sample enters the space 47 via the port 51 and is pumped out of the port 53. The samples are pumped with different flow rates.

Figure 5 illustrates, schematically, a failed fuel detection and location unit 55 incorporating one or other of the above described HALIPs 1 or 35. An array of sample pipes 57 feed individual samples to a selector valve 59 from the fuel sub-assemblies, while a sample pipe 61 feeds a mixed (or bulk) sample directly to one conduit of the HALIP. The selected individual sample is fed to the other conduit of the HALIP. The HALIP pumps the samples round respective coils 63, 65, the coil 65 is the mixed sample coil. The samples therein are monitored for fission products in the sodium inside the coils by detectors 67 and 69, respectively. The samples then return to the sodium pool. The selector valve 59 is rotated by a stepping moter 71 via a drive unit 73 and a shaft 75, and is also indexed up and down by the drive unit.

Figure 6 shows, schematically, the construction of the selector valve 59. The individual samples are fed via the sample pipes 57 into the bottom of rings of respective bores 72. A rotary valve 79 selects the bores in turn in a ring at one level and is then indexed up to select the bores of the next level in turn. The selected individual liquid sodium sample is fed to the HALIP via a pipe 81, and the mixed sample is fed via a pipe 83.

Claims

1. A helical annular linear induction pump comprising a magnetic core structure; an elongate annular winding structure encircling the core structure with an annular space between the winding structure and the core structure for conducting at least one sample of fluid material.

2. A pump as claimed in Claim 1, comprising an elongate tubular member encircling the winding structure with an annular space between the tubular member and the winding structure for conducting at least one further sample of fluid material.

3. A pump as claimed in Claim 1 or Claim 2, wherein the or each annular space is provided with guide fins located in the space and extending longitudinally of the space to form a plurality of conduits therebetween for conducting respective sample of material.

4. A helical annular linear induction pump substantially as hereinbefore described with reference to Figures 1 and 2 or Figures 3 and 4 of the accompanying drawings.

5. A failed fuel detection and location unit incorporating a pump as claimed in any preceding claim.