DE1811631A1 - Process for the construction of a nuclear reactor and nuclear reactor which is produced according to the process - Google Patents

Description

Description of the patent application

of Atomic Power Constructions Limited ₃ Vigilant House, 6/14 Sutton Court Road ;, Sutton, Surrey / ENGLAND

concerning:

"Procedure for building a nuclear reactor and nuclear reactor, which is produced by the process.

The invention relates to a nuclear reactor, in particular to a method for the construction and construction of nuclear reactors in which the core of the reactor with the side shield is housed within a metallic pressure bell which is located in the pressure vessel. The side shield consists of a ring-shaped group of columns made of an iföutronen-I "Oderiermaterial j z.3. Calcium hydroxide, which extend over the entire height of the core and are arranged in such a way that there is no straight radiation path through the side shield does not lead through the "loutron" oration material.

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OBiGSMAL

1811831

_ ο -

In the case of reactors with a pressure bell (see, for example, the British patent 1 123 972) it is very convenient to use the bell as a boundary for a "clean area" to be used during the construction of the reactor core that is built inside the bell jar. However, it has been shown Difficulties arise in building the side shield because of the length of the pillars that make up the side shield is built up and because of the very little space available within the pressure bell. It would be conceivable that Columns through an access opening in the dome-shaped roof of the bell jar but it has been found that such an access opening is provided in such a part of the roof would have to be where the curvature is greatest, and this leads to serious tensile loads on the roof in the vicinity of the Access opening.

In accordance with the present invention, a method of building a nuclear reactor includes the step of: erecting the side shield of the reactor, by means of an in the dom- ' shaped roof of a pressure bell located access opening in an area., from that part of the roof where the Curvature of the same is greatest. Tubes made from neutron moderating material are introduced whose length and cross-sectional dimensions allow them through the access opening are introduced and brought into the operating position within the pressure bell.

A nuclear reactor according to the invention comprises a bell jar with an access opening so in the dome-shaped Roof of the bell jar is arranged so that it is away from that part of the roof where the curvature of the same is at largest is and a side shield. consisting of tubes made of neutron absorbing material, which are so arranged are that there is no straight radiation path that does not run through some material, polygamy pipes one such

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Have a size that they can be introduced through the access opening and brought into the operating position can inside the pressure bell.

The tubes may comprise steel shielding tubes containing the neutron absorbing material, e.g. B. Compressed calcium hydroxide. Each tube can have a cross-sectional shape ₃ perpendicular to its length, which is round, rectangular, triangular or hexagonal. Pipes with a round cross-sectional shape are less satisfactory because of the inevitable gaps between adjacent pipes, which, however, can also be advantageous, as will be explained later.

The tubes can be arranged in a series of concentric circles around the core, with each circle having pillars includes different layers of tubes stacked one on top of the other. The connection points are more appropriate to the pipes Layers in different rows can be offset from one another to avoid any possibility of a straight line Radiation path that does not lead through neutron absorbing material. Additionally or alternatively you can the abutting ends of the tubes may be beveled or otherwise shaped to avoid any possibility of such exclude straight radiation path.

At least some of the 'innermost row' tubes may have spacers to keep them in the Keep a distance from the holding cylinder of the reactor. Other adjacent rows can also be spaced apart so that a coolant can circulate.

The lower ends of the tubes in the lowest layer of tubes have positioning devices _to

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To be able to correct the position of the pipes. ■

The invention will be explained in more detail below with reference to the accompanying drawings.

Fig. 1 is a vertical section through part of a reactor according to the invention,

Figures 2a-2d are side views of portions of various arrangements of pillars in one Side shield,

Fig. 3 is a horizontal section through part of the reactor,

Fig. 4 is a section along line IV-IV in Fig. Fig. 5 is a section along line V-V in Fig. G. 11th

Fig. 6 is a vertical section through a single one. Side shield component,

7, 8 and 9 show details, partly in section, at points in FIG. H are indicated,

Figure Io is a top view of the side shield according to Fig. 11, and

11 schematically shows a plan view of a Part of the side shield.

Fig. 1 shows part of a pressure bell 1, which is located in the space 2 within a concrete pressure vessel, part of which can be seen at 3. The dome-shaped roof of the pressure vessel has an access opening 5, the ze ^ mllch

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is far from part 6 of the roof, where the curvature of the same is greatest. The access opening 5 is about elliptically shaped, with parallel longer sides and semicircular short sides. in plan view, wherein the shorter axis extends along a chord of a circular arc that is struck around the vertical axis of the pressure vessel 3 is to be thought.

Inside the bell jar 1 there is a reactor core 7 / surrounded by a core holding cylinder 8, outside of which the side shield 9 is located. The shield 9 consists of a plurality of tubes Io, the so are arranged to ensure that there is no straight radiation path that does not go through at least part of the shield leads.

The tubes Io each consist of stahlümhüllteni compressed ^ ien calcium hydroxide. and have a square cross-sectional shape in the plan perpendicular to the axis. As can be seen from Fig. 1, there are several rows of tubes arranged in concentric circles around the vertical axis of the core, and each row has columns of different layers of tubes arranged one on top of the other. The joints between adjacent layers in the various rows are offset from one another, as in Pig. 1 indicated, and in addition, the tubes in a row, with respect to the tubes in the next row, are offset from one another. In this way a "flow" of neutrons is prevented, because there is no straight path _; which does not lead through some neuter moderation material.

The lower ends of the tubes of the bottom tier of tubes in each row are tapped for positioning to enable in the supporting structure of the side shield

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union, which is indicated generally by 11. Between - Positioning of the tubes stacked on top of each other in the rows is achieved by means of plug and socket connections (not shown) causes. The distances between the layers of pipes in the rows immediately near the holding cylinder 8 and the latter, is effected by metallic spacers, which are welded to the tubes of these layers, but are not shown in the drawing.

The tubes are enclosed on the outside by a steel side shield, which is indicated at 12 in FIG. 3.

In addition, support plates 13 are arranged above the annular space between the holding cylinder 8 and the shield 12.

The support plates 13 are attached during the construction of the pipe layers in which they are arranged, and can with the holding cylinder and with the shield 12 by welding, riveting, screwing or other conventional techniques get connected.

The support plates 13 prevent., The falling Tubes laterally in the circumferential direction due to thermal effects and vibration.

To accommodate the different expansion of the holding cylinder and the shield 12, a (not shown) resilient packing between the outermost row of tubes and the shield or resilient blocks can be connected to the tubes of the innermost row.

Such an arrangement also facilitates the inclusion of the pipe enlargement due to corrosion in the radial direction; it may be necessary to circumferentially spaced the tubes

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- 7 to be ordered to accommodate such an increase.

Preferably, each pipe is provided with a pneumatic test point to ensure that the pipe is not leaking before it is installed to consider.

The multiple row construction of the side shield, described above makes it easier to insert Usual neutron flux detectors in the side shield, and additional steel shielding can be provided need to compensate for the presence of such detectors.

The reactor described above can advantageously can be constructed as follows.

Before erecting the side shield, the following work on a workshop is close to the actual one The reactor site has been completed: the construction of the core frame and the core holding cylinder. The pressure bell is have been erected around the core frame, and the holding cylinder and the bottom and side membranes are at the reactor site installed »qjwrden. The assembly that makes up the core shoring includes, the holding cylinder and the pressure bell, is then moved into the correct position on the reactor floor. A ^ Pressure equalization of the pressure vessel can take place before or after the assembly including the pressure bell has been brought into its end position.

The moderator himself is then put together, namely inside the bell jar, with the components through the Access opening are guided. In this way the bell can be used as a boundary for a "clean area".

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It is now possible to build up the side shield. Dles-takes place in stages. As shown in Fig. 4, there are four rows of tubes, each comprising a plurality of sheets stacked one on top of the other. The lowermost part is DER "shield 12 errichteti ¹ surrounding ^ hichten the lowest S. Pipes for the formation of the lowermost Schichtferr in batches, then durchIdle access opening are guided 5- and in their position in the annular space between, the Haltezyl-incMr The next layer of pipes of all rows is then built up after more pipes have been passed through access opening 5 and after another layer of shielding has been erected 12. This process is repeated until the side shielding and the shield is fully assembled.

It is understood that the length of the tubes that make up the side shielding is less than that of the full length tubing used for rare shielding so that the pipes can be passed through the access opening and maneuvered into place. the The size of the access opening is kept to a minimum, accordingly the size of the components »which have to be guided through and according to the necessity »these components in their operational position to maneuver.

In addition to the above-mentioned spacers, integrally attached extensions of the steel sheaths are used and / or radial extensions of the end caps with which the steel sheaths can be provided.

If necessary, spacers can be inserted between every other row to allow circulation of the coolant between the rows is possible.

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In the described embodiment, the neutron flow by offsetting the location of each junction between the tubes of stacked layers prevented. The same result can be achieved by chamfering the butting rows of pipes as shown in Figures 2a-d. Relocation of the connection points can also be provided at the bevel as an additional precaution.

Figures 4-11 show one with greater accuracy another side shield construction using cylindrical casings containing compressed calcium hydroxide contain. Although it was noted above that the use of cylindrical envelopes automatically leads to loss of space between leads adjacent casings, this loss of space can also bring benefits, and it is also possible to use cylindrical Coverings can be produced more economically than coverings with the other cross-sectional shapes mentioned above.

A typical complete tube is in vertical section shown in fig. The tube comprises a cylindrical steel casing 1Λ, which at the top or bottom with a Top plug 15 or bottom plug 16 is welded. Both plugs are similar and each have a centric one Bore 17, of which that of the cover plug 15 is closed by a connector 18, which the pneumatic Checkpoint that was mentioned above. The hole the bottom plug is by a tenon assembly 19 inclusive a hexagonal socket locked at 2o. "

The soite shielding is described in the above Way assembled between the holding cylinder 21 and an outer steel shield 22 and comprises five concentric Rows of pillars in a band of 3 and a band

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are arranged from 2 rows.

The columns of the innermost row 23 are positioned by port sets 2k extending outwardly from the support cylinder 2i and by strips 25 which couple the tops of the tubes in each layer in the row 23 together in groups of four. This arrangement determines the position of the columns in the innermost row, and this determines the spacing of the columns in the other rows. The distance is chosen so that adjacent pipes are just so far apart that there is enough space for the corrosion to increase. The innermost row 23 is arranged behind the neutron shield, which is denoted by 26 in FIGS. 4 and 5 , and thus prevents the columns of the innermost row from tilting vertically.

Outside the row 23 there is a second row 27, the columns of which are opposite the very narrow ones Columns between adjacent columns of row 23 are located. The distances are determined by interposed steel bars 28 which form the gaps between adjacent columns fill and also take on part of the shielding function. A vertical displacement of the columns of row 27 is prevented by port sets 29 on the tubes of the uppermost tube layer this series, which is under port sets 3o of the corresponding Grab the pipes in the top layer of row 23.

As can be seen from Figures H and 5, the lower ends of the lowermost layer of tubes of rows 23 and 27 are positioned by means of their tenon assemblies on a step 31 which forms part of the moderator support-

scaffolding forms. -

All around row 27 is a third row 33, which from the columns of row 27 by further steel

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Rods 28 is separated as well as by a surrounding "fence" consisting of steel shielding rods 34 that are spaced apart are held by means of pairs of steel plates 35 · The plate 35 are flexible, .that they move in the event of a radial increase can bend. The rods 34 rest on the supporting framework 32 and extend practically to the top of the shield, as shown in FIG. 4 and 7 recognizes.

The shape and arrangement of the rods 34 allows the columns to be reoriented into a row 36 surrounding the row 33, as shown in FIG. To recognize Io. The columns of the rows 36 are positioned in line with the columns of the row 27 and thus exactly in the line of the dummy paths between the adjacent columns of the rows 23, 27 and 33, ViOmIt the "opacity ^{11 of} the shielding for neutrons for a given thickness is increased The "dummy line" is a straight path that leads between adjacent columns in rows 23, 27 and 33, which are arranged at a short distance from each other.

Outside row 33 is the last row 37, the columns of which are radially in line with the distances lie between the adjacent "columns of row 36. The columns of row 37 also lie on the dummy line; the mentioned above.

The positioning of the columns of the rows 33 and 37 is effected by further rods 28 and by positioning plates 38 which form part of side brackets 39 which are screwed to the outer steel shield 22, as in FIG Figjuren Io and 7 can be seen. The bars 4ο are free and form additional shielding material. After assembling the side shield, the screws 41 are tightened to to keep all the pillars in their correct position.

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A vertical evasion of the columns of rows J> 6 and is prevented by extensions 42 on the tubes of the uppermost layer of row 37, which grip under positioning plates 38, and by port sets 43 on the tubes of the top layer of row 36, which under further port sets 44 at the top layer of pipes in row 37. Further port sets 45 on the top layer of the row 36 prevent any upward movement of the rods 34.

stacked tubes in the same tube column in rows 23 and 37 are held from each other ^ 'Ab stood by means of spacers 46, which can be seen in FIG are, while between the tubes of the lowest and second lowest layer of columns of the row 37 lateral retaining screws 47 are provided, the puncture of which consists of exert an inward compression force similar to that of; exerted by the lateral retaining screws 41 which have been mentioned above. A more even compression of the side shield is accordingly achieved.

As shown in FIG. 9, the outermost three rows 33 *> 36 and 37 are positioned by means of pin arrangements of the tubes of the lowest layer of these rows in positioning holes in a level plate 48 which is built up on the support frame 32.

5 and 11 also show the positioning of the neutron flux measuring channels 49, which extend through the dome 5o the bell jar 51 in the high curved area of the strike the latter. A number of such channels are provided, which in the circumferential direction at a distance from one another in the Side shield are arranged; two are shown in Fig. 11, along with the surrounding graphite blocks 52 in which such channels are normally arranged. Appropriate

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Gaps are of course in rows 23, 27, 33,36 and 37 left to hold the graphite blocks. The presence of the channels 49 also helps guide against a circumferential displacement of the columns in the side shield.

One can use the openings in the cathedral for the implementation Do not use the channels 49 because special fits must be welded to the dome in order to prevent the weakening through the holes to compensate, and the shape of these Fits prevent these holes from being used as access openings. Furthermore, if the side shield once has been completed, channels 49 are up connected to the fits, and this prevents the subsequent ones Holes for the passage of the graphite blocks for the construction of the core after the assembly of the Side shielding has been completed.

It goes without saying that the inevitable gaps present because of the use of tubes with round Cross-section creates space for and for the increase in corrosion the flow of coolant through the side shield. This current is quite high but does not create any lifting of the pipes as a result of the precautionary measures for the stopping the vertical movement described above.

It has been explained above with reference to FIG. 1 how the individual tubes pass through the access opening 5 are introduced, then rotated and then brought into their "position between the holding cylinder and the pressure bell will. The movement can be simplified by making a vertical slot in the holding cylinder corresponding to it Dimensions is attached. Each tube can be vertical

χ exploitation

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be lowered down through the access opening and then moved laterally through the Sc & litz into the correct position in the side shield. The shorter length of the tubes reduces the length of the gap, which in the Holding cylinder is required.

It goes without saying that instead of Kaiζiumhydroxyd other materials can also be used as a neutron moderator, for example organic compounds such as Anthracin and certain plastics, or inorganic compounds such as hydrides and HydroxydejZ.B. Barium and Iron hydroxide and zirconium hydroxide.

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Claims (1)

Claims 1. A process for building a nuclear reactor, characterized by the process step that the side shield of the reactor is built by a bell jar of the through an access opening in the dome-shaped roof Reactor in an area remote from that part of the roof with the greatest curvature Neutron absorbing material introduced xierden, their The length and cross-section allow them to pass through the access opening and into their operative position within the Bell can be brought. 2. The method according to claim 1, characterized in that an assembly ^ comprising the pressure-relieved pressure bell, which comprises the core frame and the main cylinder of the reactor their end position is shifted to the bottom of the reactor. 3 «Method according to claim 2, characterized in that that the moderator structure is assembled within the pressure bell. k. Nuclear reactor constructed according to the method according to one of the preceding claims, characterized by a pressure vessel containing a pressure bell in which the reactor core is housed, through an access opening _/ which is arranged in the dome-shaped roof of the pressure bell so that it is removed from that part of the roof, the curvature of which is greatest, and by a side screen, consisting of tubes made of neutron-absorbing material, which are arranged in such a way that no straight - 16 9 09 829/1107 There is a long radiation path from the core that does not pass through some of the material, which tubes are sized to pass through the access opening and maneuver into their operative position within the pressure vessel. ', - 5. Nuclear reactor according to claim 4, characterized in that that each tube has a cross-sectional shape perpendicular to its axis that is rectangular, triangular, round, or hexagonal is. 6. Nuclear reactor according to claim 4 or 5, characterized in that that the tubes are arranged in rows that lie on concentric circles around the vertical axis of the core, and that each circle comprises columns of a plurality of tubes arranged one above the other. 7. Nuclear reactor according to claim 6, characterized in that the connection points between the tubes in adjacent Layers in a row are offset from one another, relative to the corresponding joints in the sewing adjacent row. 8. Nuclear reactor according to Claim 7, characterized in that that the columns of one row are offset from one another with respect to the columns of the next adjacent row. 9. Nuclear reactor according to one of claims 6 ^ 7 or 8, characterized in that spacers are provided for defining the distances between the tubes of the innermost row and the holding cylinder of the reactor core. Io. Nuclear reactor according to one of claims 6, 7, 8 or 9, characterized in that spacers are provided for defining the distance between adjacent ones Rows and. To allow coolant circulation. 90 9 829/1107 11. Nuclear reactor according to one of claims 6 to Io, characterized in that pipes of the lowest layers are provided with positioning devices around these pipes to be able to position correctly. 909829/1107