High temperature gas-cooled reactor core

Abstract

The disclosure relates to a high temperature gas-cooled reactor core including a plurality of elongate fuel elements arranged in the form of a multi-lobed prism. Each prismatic fuel element includes an elongate prismatic body and a plurality of elongate fuel channels located within the prismatic body, wherein the cross-sectional area of each prismatic fuel element in a plane parallel to the bases of the prismatic fuel element is no more than 800 cm.sup.2 and wherein a ratio of the height of the prismatic body to its greatest width is greater than or equal to 3.0.

Claims

1. A high temperature gas-cooled reactor core comprising a plurality of elongate prismatic fuel elements, each fuel element having a hexagonal cross-section in a plane parallel to bases of each respective prismatic fuel element, the plurality of fuel elements being formed in a contiguous arrangement of lobes to define an annulus of fuel elements which share a common contiguous border with one another, wherein each lobe is defined by multiple fuel elements and each lobe forms a projection which projects radially beyond an adjacent recessed region of the contiguous border, with one recessed region separating adjacent projections, and wherein each prismatic fuel element comprises an elongate prismatic body and a plurality of elongate fuel channels located within each prismatic body together with a plurality of cooling channels interspersed among the fuel channels, wherein a cross-sectional area of each prismatic fuel element in the plane parallel to the bases of the respective prismatic fuel element is no more than 800 cm.sup.2, and wherein a ratio of a height of each prismatic body to its greatest across-the-flats width is greater than or equal to 3.0, and wherein the annulus of fuel elements surrounds a central trunk of moderator material comprising a plurality of columns of moderator material.

2. The high temperature gas-cooled reactor core according to claim 1, wherein the ratio of the respective prismatic body's height to its greatest across-the-flats width is greater than or equal to 3.2.

3. The high temperature gas-cooled reactor core according to claim 1, wherein the plurality of elongate fuel elements are arranged in an annulus having three lobes.

4. The high temperature gas-cooled reactor core according to claim 1, wherein the plurality of columns of moderator material are arranged together to form a solid prismatic body.

5. The high temperature gas-cooled reactor core according to claim 1, wherein the cross-sectional area of each prismatic fuel element in the plane parallel to the bases of the respective prismatic fuel element is between 500 cm.sup.2 and 800 cm.sup.2.

6. The high temperature gas-cooled reactor core according to claim 5, wherein the cross-sectional area of each prismatic fuel element in the plane parallel to the bases of the respective prismatic fuel element is between 600 cm.sup.2 and 700 cm.sup.2.

7. The high temperature gas-cooled reactor core according to claim 6, wherein the cross-sectional area of each prismatic fuel element in the plane parallel to the bases of the respective prismatic fuel element is between 650 cm.sup.2 and 675 cm.sup.2.

8. The high temperature gas-cooled reactor core according to claim 1, wherein a total cross-sectional area of the fuel channels in the plane parallel to the bases of the respective prismatic fuel element is no more than 24% of the cross-sectional area of the respective prismatic fuel element in the plane parallel to the bases of the respective prismatic fuel element.

9. The high temperature gas-cooled reactor core according to claim 8, wherein the total cross-sectional area of the fuel channels in the plane parallel to the bases of the respective prismatic fuel element is between 22% and 24% of the cross-sectional area of the respective prismatic fuel element in the plane parallel to the bases of the respective prismatic fuel element.

10. The high temperature gas-cooled reactor core according to claim 8, wherein the total cross-sectional area of the fuel channels in the plane parallel to the bases of the respective prismatic fuel element is approximately 23% of the cross-sectional area of the respective prismatic fuel element in the plane parallel to the bases of the respective prismatic fuel element.

11. The high temperature gas-cooled reactor core according to claim 1, further comprising a plurality of elongate cooling channels located in each prismatic body.

12. An elongate prismatic fuel element for a high temperature gas-cooled reactor as claimed in claim 1, the prismatic fuel element comprising an elongate prismatic body and a plurality of elongate fuel channels located within the prismatic body, wherein a ratio of the prismatic body's height to its greatest across-the-flats width is greater than or equal to 3.0, and wherein a cross-sectional area of each prismatic fuel element in a plane parallel to bases of the prismatic fuel element is no more than 800 cm.sup.2.

13. The elongate prismatic fuel element according to claim 12, wherein the ratio of the prismatic body's height to its greatest across-the-flats width is greater than or equal to 3.2.

14. The high temperature gas-cooled reactor core according to claim 1, wherein some of the plurality of fuel elements in the annulus of fuel elements are located radially outward of others of the plurality of fuel elements in the annulus of fuel elements.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present disclosure will now be described by way of non-limiting examples with reference to the following figures, in which:

(2) FIG. 1A shows a schematic plan view of a prior art fuel element;

(3) FIG. 1B shows a schematic isometric view of a prior art fuel element;

(4) FIG. 2 shows a schematic plan view of a prior art HTGR core;

(5) FIG. 3A shows a schematic plan view of a fuel element according to the present disclosure;

(6) FIG. 3B shows a schematic isometric view of a fuel element according to the present disclosure; and

(7) FIG. 4 shows a schematic plan view of a HTGR core according to the present disclosure.

DETAILED DESCRIPTION

(8) FIGS. 3A and 3B show a new design of fuel element 30. The fuel element 30 includes an elongate prismatic body 40 having opposing parallel bases 41 at either end of the prismatic body 40 and six sidewalls 42 extending between the bases 41. The cross-section of the prismatic body 40 in a plane parallel to the bases 41 is a regular hexagon. In one embodiment, the hexagonal cross-section of the prismatic body has an across-the-flats dimension of about 25.9 cm such that the surface area of the cross-section is about 581 cm.sup.2, but this is only an example. Typically, in embodiments of the disclosure, the cross-sectional area of the prismatic fuel element in a plane parallel to the bases of the prismatic fuel element may be within the range of between 500 cm.sup.2 and 800 cm.sup.2, and is no more than 675 cm.sup.2.

(9) The elongate prismatic body 40 has a length (distance between the bases 41) of about 80 cm such that it is taller than it is wide. With a height of about 80 cm and an across-the-flats width of 25.9 cm, the ratio of the prismatic body's height to its greatest across-the-flats width is approximately 3.09. Typically, for example, embodiments of the disclosure include a prismatic body with a ratio of the height of the prismatic body 40 to its greatest width (across-the-flats) of at least 3.0.

(10) Notably, the cross-section of the fuel element 30 of the disclosure is just over half the size (around 52%) of the cross-section of the prior art fuel element 10, and so is much more compact.

(11) The prismatic body 40 includes a graphite material within which are located a plurality of fuel channels 43. The fuel channels 43 each house a column, or stack, of fuel compacts. In this example, the fuel element 30 includes 102 fuel channels 43.

(12) A plurality of cooling channels 44, 45 are also located within the prismatic body 40 interspersed among the fuel channels 43 in a regular pattern. In this example, the fuel element 30 has 54 cooling channels 44, 45 including 48 large diameter cooling channels 44, and 6 small diameter cooling channels 45. The small diameter cooling channels 45 are located in an approximate annular arrangement around a central portion 46 of the fuel element 30. As in the prior art example of FIG. 1A, the central portion 46 includes no fuel channels 43 or cooling channels 44, 45 and is recessed below the top surface 41 of the fuel element 30 to provide an engagement point for a fuel handling machine.

(13) In this example, the fuel element 30 also includes 6 burnable poison channels 47, each of which is located within the prismatic body 40 at each apex of the hexagonal cross-section of the prismatic body 40.

(14) The fuel channels 43 have a diameter of about 1.3 cm and the cross-sectional area of each fuel channel 43 is therefore about 1.33 cm.sup.2. The total cross-sectional area of all 102 fuel channels 43 together is therefore about 135 cm.sup.2 so that the fuel channels 43 occupy approximately 23% (about 23.2%) of the total cross-sectional area (around 580 cm.sup.2) of the fuel element 30. In other embodiments, the total cross-sectional area of all the fuel channels may be slightly larger, but is typically no more than 24% of the total cross-sectional area of the fuel element 30.

(15) FIG. 4 shows a schematic plan view of a new HTGR core arrangement 60. The core 60 includes twelve columns 61 of fuel elements 30 (two of which are identified) arranged in a multi-lobed configuration to form a multi-lobed prismatic body 66. The multi-lobed prismatic body 66 is a contiguous arrangement of lobes (i.e. projections, relative to a central axis, of curved form) which arranged to define an annulus. The shape resembles that of a three-leaf clover, or may be considered to be a “serpentine” arrangement. In the example of FIG. 4, the arrangement has three lobes (two of which are identified generally, at 68) which are arranged to define a contiguous and broadly annular configuration. Each lobe defines a projection, of curved form, and each lobe projects radially beyond an adjacent recessed region 70 of the contiguous border. One recessed region 70 separates adjacent lobes 68.

(16) Each column 61 of fuel elements 30 includes a plurality of fuel elements 30 stacked one on-top of another. By virtue of the smaller size of the fuel elements 30, as discussed above with reference to FIGS. 3A and 3B, it is possible to arrange the elements in such a multi-lobed configuration. Using fuel elements of larger size, as in the prior art, is not compatible with this type of beneficial multi-lobed configuration which in the disclosure permits an increased proportion of graphite moderator material to be used. This is especially important in HTGRs where the use of moderator material is critical to the functioning of the reactor.

(17) The prismatic body 66 surrounds a central trunk 62 of graphite moderator material. The central trunk 62 of moderator material itself includes four graphite moderator material columns 64 (only two of which are identified with reference numbers) arranged together to form a solid prismatic body. The moderator material columns 64 each include stacks of identically sized graphite blocks of hexagonal cross-section. The graphite moderator material columns 64 and the annulus of fuel elements 30 are surrounded by a solid graphite frame 65 which also acts as a moderator in use.

(18) It will be appreciated that the aforementioned dimensions are given by way of example only and other dimensions are possible without departing from the scope of the disclosure as defined by the features of the accompanying claim set.