GB2358415A

GB2358415A - Protective screen block

Info

Publication number: GB2358415A
Application number: GB0020385A
Authority: GB
Inventors: John Sims; Malcolm Thomson
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-01-18
Filing date: 2000-08-21
Publication date: 2001-07-25
Anticipated expiration: 2020-08-21
Also published as: GB0000990D0; GB0020385D0; GB2358415B

Abstract

A protective screen block for inhibiting transmission of radiation through a wall built of these has two main faces 11,12, upper and lower sides 14,22 and a pair of vertical sides 18,20, one side of each pair having a male formation 16,18 extending therealong, and the other side of each pair having a corresponding female formation 20,22, the block having a hollow interior into which a fluid may be introduced.. The block may have a port 28, with stopper 27, for the introduction of e.g. water, sand, lead shot, or concrete. Corner and half blocks may be produced: the blocks may have hand-holds 23, or may have recesses for the receipt of auxiliary fasteners.

Description

2358415 PROTECTIVE SCREEN BLOCK This invention relates to screens for

protection of persons against radiation, in particular for the radiological protection of operators of nuclear equipment.

Protective screens at nuclear sites may be produced by building walls of concrete or concrete blocks. Conventionally, shielding walls are built using traditional wooden formwork, reinforcing bars and poured concrete which requires many days to harden sufficiently to be able to remove the formwork. All of this work is achieved with the engineers working on the nuclear site and even being at risk of absorbing radiation during the process. The wall must eventually be destroyed when no longer required. Concrete blocks cast off site are costly to produce since their production is labour intensive and a week is required before the casting can be removed from the mould which is required to secure the close tolerances required so that the blocks interlock. These blocks are prone to damage which reduces their effectiveness as a radiation screen, and are very heavy, which is a disadvantage during transportation and screen construction.

It is an object of the present invention to provide a range of hollow blocks for the production of a protective screen which are light to transport, can be filled with a variety of dense materials on site and can be recovered for re-use if required. These blocks may be hard wearing and re-usable over many different applications.

The invention provides a protective screen block of cuboid form for inhibiting radiation transmission through a screen built from the blocks, the block having a pair of main faces, upper and lower sides and a pair of generally vertically disposed sides forming end faces of the block, one side of each pair having a male formation extending therealong and the other side of each pair having a corresponding R formation extending therealong, the block having a hollow interior into which a: I i( material can be introduced.

Each male fon-nation may comprise a tongue and each female formaiii( groove.

At least the grooves may have substantially parallel sidewalls anq C tongues and/or the grooves may be substantially circular in cross-section betweeh C sidewalls.

Preferably the male and female formations on the top and bottom sides h e the same dimensions in cross-section as those on the end sides.

The block may be of a moulded plastics material, and may have an (i er skin of a hot forming plastics material and a foamed lastics material within and W d p to the outer skin. The block may be hollow and have a filler hole for receiving a. PI Rd material into the interior of the block. A plug may be provided for sealing the filler e. The filler hole may be provided in one of the faces or in one of said formations.1; te i block may be filled with a pourable substance such as water, sand, lead or iron I t' concrete or similar dense material. Preferably the faces of the block are substant-, y planar and free from protrusions, but the faces may be provided with indentation,$ r facilitating lifting of the block.

The block may typically be about I m in length between the end s Id S, about 0.75 m in height between the top and bottom sides and about 0.5 m in thick4c s between the faces.

The invention will now be further described by way of example with reference to the accompanying drawing in which:

Fig. 1 is a perspective front view of one embodiment; Fig. 2 is a partly cut away front view of the embodiment of Fig. 1; Fig 3 is a plan view of two blocks of Fig. I in juxtaposition, Fig. 4 is a plan view of a comer turning block; Fig. 5 is a section through an embodiment with a service arrangement; Figure 6 is a perspective view of a radiological protection screen assembled from blocks in accordance with the invention; Figures 7 and 8 are respectively front and plan elevations of a modified form of block; Figure 9 is a sectional view along line A-A in Figure 7 or Figure 9; Fgures 10 and 11 are similar views to those of Figures 7 and 8 but showing a comer block; Figure 12 is a view of one side of a screen in accordance with the invention; and Figures 13 to 15 are enlarged, perspective views of various fittings fir S( with the blocks of Figures 7 to 12.

Referring now to Figs. I and 2, there is shown a protective screen blo I C of cuboid form for use in the construction of a radiological protection screep 01 inhibiting radiation through the block 10 between opposed main faces 11, 12. Cenir, ly disposed on the top side 13 is a tongue 14 which extends parallel with the faces 1. 2. The tongue 14 has relatively small substantially vertical side walls 15 and a part cir W main transverse section 16 thereabove. The tongue 14 is bordered by flat shoulders.' I A which maybe substantially coplanar with each other.

Similarly, one end side 17, in this case the right-hand end as shown i, e Figures, has a corresponding tongue 18 of similar dimensions in crosssection tl' e tongue 14 and is bordered by substantially coplanar shoulders 17A. The left-handil s e 19 has a centrally disposed groove 20 extending parallel with the faces 11, 1211 d bordered by shoulders 19A. The shape and dimensions in cross-section of the growle 0 correspond with those of the tongue 18 so that two identical blocks 10 may be 11 d end-toend in an interlocking manner as shown in Fig. 3 with shoulders 17A in abut In t with shoulders 19A. Similarly the bottom surface 21 has a groove 22 therein W h corresponds in shape and dimensions with the tongue 14 and is bordered by should rs, 21A so that two blocks 10 may be placed one on top of the other also in an interloc 9 manner with shoulders ZIA seating, in load transmitting relation, on shoulders 1311V The faces 11, 12 are free from protrusions so that two blocks 10 mav e placed face to face to double the thickness of the screen if the radiation level warria ts ! I such screen protection. Recesses 23 in the opposed faces 11, 12 facilitate lifting of e block 10 by hand or by means of lifting equipment. The block 10 is 1 m in le between the end sides 17, 19, 0.75 in in height between the top and bottom sides 13, 21 and 0. 5 in in thickness between the faces 11, 12.

The blocks 10 are produced by a rotational moulding technique using a steel moulding tool. This ensures that all of the blocks are identical in dimension and construction. The construction is shown in Fig. 2, and this Figure shows the outer skin 24 of a hot forming plastics material which is stiffened by a foamed hot forming plastics material layer 25 within the outer skin 24. The block 10 is hollow, and a filling hole 26, shown in Fig. I together with a cap 27, provides access to the interior 28 so that the block 10 may be filled with any suitable flowable material to give the appropriate radiation transmission prevention dependent on the particular application. The blocks 10 may be filled with water, sand, lead or iron shot or concrete as desired. In the case of water, sand or shot, the blocks may be emptied for transportation to another site, thereby providing that the blocks 10 are particularly suited to temporary installation of radiation screens. For more permanent installations, the blocks 10 may be filled with concrete.

Fig. 4 shows a block 29 for use at a comer of a wall construction. The block 29 has tongues 14 and 18, and grooves 20 and 22 of identical shape and dimensions as block 10 so that blocks 10 can be interlocked with blocks 29 at the comers of a wall construction. In Figure 4, the comer block is illustrated with one section C2 projecting from the other Cl. However, in a modification, the extent of projection C2 may be reduced to zero so that, effectively the end -face 17 is coplanar with the main face 11.

Figure 5 illustrates a block 10 which is provided with a service duct arrangement 51 comprising stepped, plastics material tubes 52, 53 welded into the block 10 with a filling 54, for example of cement, with a helically-disposed tube 5 5 for taking service lines such as electricity, water or other coolant.

Figure 6 illustrates a radiological protection screen assembled from cl< s in accordance with the present invention, e.g. blocks as described above in relai 1611 W Figures I to 5 or blocks which are described below in relation to Figures 7 to 111 1 As -613 shown, the screen is formed as an enclosure comprising walls 60, 62, 64 and 66A, IS I each comprising 4 courses of blocks, although it will be appreciated that in practic Mew may be more or less courses than this, e.g. 6 to 8 courses. Some of the blocks, as dmi ate i by reference numeral 68, are full length stretcher blocks of the type shown in Fig- pi es to 3, some are half length stretcher blocks 70, some are comer blocks 72 as desqdbe I with reference to Figure 4 and some are ducted blocks 74 as shown in Figure 5 V lic I may provide remote access for services and/or for handling, e.g. manual hand-1 n E,, i i which case appropriate gloved protection facilities will be associated with such 1) c C U In addition, one or more blocks 76 may have radiologically protected viewing wir d w; built into them to allow inspection of the screened zone. As shown in Figure 6, t N I of the walls 66A and 66B are extend in parallel spaced relation so as to afford a scP-Ale access corridor or labyrinthe entry to the enclosed zone. If desired, instead of the labyrinthe entry, one of the walls may be built with an opening and a sliding ship ded door may be provided for closing the opening.

Referring now to Figures 7 to 9 showing a fall length stretcher blocl 00, the block is of generally similar configuration to that of Figures I to 3. The b](4 A hollow and is fabricated as described above in relation to Figures I to 3 as a pl?d ic, moulding by 4 rotational moulding technique with an outer skin 24 of a hot fol 11 k inj plastics material stiffened by a foamed plastics material layer 25 within and fused x the outer skin. The block has a pair of main faces 102, 104 which are free of protnAd ns, upper and lower sides 106, 108 and vertical sides 110 and 112. The upper side IC6 i a central tongue 114 which extends from a point inboard of one end to a point outA ard of the other end, the tongue 114 being bordered on each side thereof by shoulders 106A which are coplanar with each other and typically occupy at least about 20%, preferably at least 25%, of the total width of the block.

The tongue 114 comprises inwardly sloping side walls 116 and a main transverse bridging wall 118, the gradient of which varies across the width of the block to ensure that there is no significant rectilinear pathway along which radiation could travel. Although the bridging wall 118 may comprise a number of successive rectilinear portions extending across the block width, it is shown as being curvilinear with an external radius R1.

The lower side 108 is formed with a groove 120 which is substantially coterminous with the tongue 114 and is bordered by shoulders 108A, the arrangement being such that when block is assembled with its groove 120 receiving the tongue of a second block, the shoulders 106A seat on the shoulders 108A and transmit load thereto. The groove 120 has an internal configuration which is generally complementary with that of the tongue 114. In particular, it comprises side walls 122 which are either vertical or slope to a lesser extent than the side walls 116 to ensure that the tongue 114 and groove 120 fit snugly together without binding. The sides walls 122 are joined by bridging portion 124 which, like bridging portion 118, has a varying gradient across the width of the block. It may for instance be curvilinear with an external radius of curvature R2 where R2 is slightly greater than RI so that, when one block is assembled above another, there is a small.gap between the external surfaces of the tongue 114 and groove 120. This ensures that the shoulders 108A and 106A seat together in firm abutting relation and are not held off each other as a result of engagement between the external surfaces of bridging portions 118 and 124. In practice, the small gap which would otherwise constitute a potential partial shine-through pathway is taken up by a small degree of deformation of the bridging portion 118, e.g. through resilient deformation thereof, whenthe block is filled with water, sand or other shielding material.

The vertical sides 110 and 112 are likewise provided with a groo. e an tongue arrangement, namely groove 128 and tongue 130 which are substaitailly coterminous and may be of identical configuration in crosssection to their counle aris 120 and 114 on the lower and upper sides of the block. Again there may be a srna 11 ga) between external surfaces of the the bridging portions 132, 134 of groove 128 and toi tgu-. 130 which, in practice, may be taken up by some degree of deformation of the side lalls 136 of the groove when the block is filled with shielding material. The vertical sides 1 iav Icoplanar sets of shoulders 11 OA and 1 12A which mate with each other when one: lb ock is fitted alongside a second block.

It will be noted that the tongues 114 and 13 0 merge into each other, it on corner of the block, i.e. so that there is effectively a continuous tongue running a - lm two contiguous sides of the block. Likewise the grooves merge into one another a th opposite corner of the block resulting in a continuous groove running around thel c (her two contiguous sides of the block.

The hollow block in this embodiment is filled through its uppermost st ii Uct and, for this purpose, the upper extremity of the tongue 114 is provided with a 1111 ing :1 hole 140 (with an appropriate closure which may be screwthreadedly and seaAgly engaged with the hole 140) so that substantially the entire interior of the block c a 1 b, -, filled with a shielding material appropriate to the screening application that the t lg)ck are to be used for. If desired, each block may be provided with more than one filling ol and associated closure. The block is also provided with a number of blind holes 14 2 th centres of which are equidistantly spaced inwardly of the edges of the 106A, 108A, 1 W and 1 12A. These blind holes have a dual purpose. During assembly of the blocks, a 1 ew t some of them may may be used as anchorage points for reception of lifting gear. A fte r assembly, t. hey may be used to tie the blocks together and to supporting uprig. er stanchions as described further below.

Referring to Figures 10 and 11, these show one form of comer block 150 which may be fabricated as a plastics moulding by rotational moulding as described above. The block has a front face comprising sections 152A and 152B at right angles to each other, a rear face 154, angularly related upper and lower sides 156A, 156B, 158A, 158B and vertical sides 160, 162, the vertical sides also being at right angles to each other. In this embodiment, the vertical side 162 is coplanar with the rear face 154 although, as will be understood from the embodiment of Figure 4, this need not necessarily be the case. The counterpart 164A, B of the tongue 114 extends along the upper sides 156A, B while the counterpart 166A, 166B of the groove 120 extends along the lower sides 158A, B. The vertical side 160 has a groove 168 corresponding to the groove 128 of Figures 7 to 9 while the vertical side 162 has a corresponding tongue 170. The tongues and grooves of the comer block have substantially the same configurations in cross-section as in the embodiment of Figures 7 to 9 and are flanked on each side by shoulders in the same way except that the shoulder flanking the inside edge of the tongue 170 is coplanar with the rear face 154. The comer block is also provided with a topmost filling hole 176 and closure member and blind holes 178 which are likewise equidistantly spaced inwardly of the edges of the front and rear faces.

The blocks of Figures 7 to 11 may be assembled in the manner illustrated in Figure 6 and may be adapted to incorporate viewing facilities and afford access for remote handling and/or services. Although described with reference to full length stretcher and comer blocks, it will be understood that the block sizes may be adapted according to needs. For example, some blocks may be sized as half or quarter length or as half height stretcher or comer blocks, the features of the blocks otherwise being the same as described above so that such smaller size blocks can be used in the construction of the screen while eliminating shine-through pathways.

Figures 12 to 15 illustrate how the blocks of Figures 7 to I I n i! b assembled in the production of a screen as shown in Figure 6. The lowermost "0' 0 blocks 100, including a half length comer block 150A, is first assembled at groun 0 I level F. At least some of these blocks may, if required, be anchored to the floor by floor bs, Th' of angle section floor plates 200 which are coupled to a pair of contiguous blocks 1. b means of fasteners passing through apertures 202 in the plates and engaging in the n holes 140 of contiguous blocks. Such engagement may be effected in any sult I manner, e.g. by Rawlbolts inserted into the blind holes or by screw threaded i -is t which may be screwthreadedly engaged within the blind holes and which re v fasteners in the form of bolts engaging the plates 200. Before or after laying the s course, the blocks may be filled with water or other shielding material and then selp d.

After the first course has been laid, th next course is then assembled. in the blocks may be prefilled or they may be filled after placement in the course u. er construction. Adjacent blocks and courses are tied together, if required, by means ie plates 204 with apertures 206 arranged on a triangular pitch in such a way that one ir of apertures 204 can be registered with the blind holes of two contiguous blocks i, e course and the remaining aperture 204 can be registered with a centrally located I d hole in a block above or below that course. Suitable fasteners may then be used to se e the tie plates to the blocks, thereby rendering the structure more stable especially N n the screen is intended to be used in regions which may be subject to seismic acti Further stabilit, may be obtained by coupling the blocks to uprights or stanchions 8.Y secured to the floor through bottom plate 210. The stanchions may be coupled to I e blocks by modified tie plates 212 which attach to the blocks in the same way as tie pl S 204 but also include a lug 214 with apertures 216 whereby the lugs can be affixed tol t e stanchions 208 by suitable fasteners.

By means of the invention a block is provided which is designed to interlock with identical blocks to form a wall for the radiological protection of, for example, operators of nuclear equipment or whilst decommissioning nuclear plant, temporary protection around mobile waste treatment plants and storage facilities for nuclear waste. The tongue and groove construction provides that there is no straight path for radiation leakage or shine-through. The blocks produced by rotational moulding can be produced to close tolerances and identical dimensions thereby ensuring good interlocking of the blocks and ease of interchangeability if required. The outer skin of hot forming plastics material provides protection against surface damage. Unlike conventional concrete blocks, no steel reinforcing is required. A block can be produced in this wkv every 2 hours, compared with every 5 or more days for conventional blocks, The blocks may be filled with an appropriate filler dependent on the radiation protection required, and dependent on the filler material are suitable for temporary installations. The screen may be constructed with the blocks empty, thereby easing the construction process, and the filler material if required inserted after construction is completed. The interlocking form of the blocks allows for rapid construction and dismantling of a radiation screen and the blocks may be used many times.

Alternative embodiments of block in accordance with the invention will be readily apparent to persons skilled in the art. For example the dimensions and shape of the tongues and grooves may differ from those shown in the Figures. The shape and/or the dimensions of the tongue and groove on the end sides may differ from the shape and/or the dimensions of the tongue and groove on the top and bottom sides. Each side may have two or more mutually parallel tongues or grooves, or each side may have both a tongue and a groove thereon.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance, it should be understood that the Applicant claims protection in respect of any patentable featlr I combination of features disclosed herein and/or shown in the drawings whether ('r particular emphasis has been placed on such feature or features.

Claims

1. A protective screen block of cuboid form for inhibiting radiation transmission through a screen built from the blocks, the block having a pair of main faces, upper and lower sides and a pair of generally vertically disposed sides forming end faces of the block, one side of each pair having a male formation extending therealong and the other side of each pair having a corresponding female formation extending therealong, the block having a hollow interior into which a fluid material can be introduced.

2. A protective screen block according to claim 1, wherein each male formation comprises a tongue and each female formation a groove.

3. A protective screen block according to claim 2, wherein the tongues and grooves have substantially parallel sidewalls.

4. A protective screen according to claim 2, wherein the grooves have substantially parallel side walls while the tongues have sloping side walls.

5. A protective screen block according to any one of claims 2 to 4, wherein the tongues and/or grooves each have a main transverse surface which extends between side walls of the tongues and/or grooves and varies in slope across the width thereof

6. A protective screen block according to claim 5 in which said main surface is of curvilinear configuration in cross-section.

7. A protective screen block according to claim 5 in which the main ac e :v includes at least two, and preferably at least threec, rectilinear sections across th(-. dt i thereof

8. A protective screen according to claim 6 or 7 in which, when fitted to+ ei, there is a gap between the main groove surface and the associated main tongue s;lr - cC of at least the upper and lower sides of the block, which gap is reduced or eliminLtl 1 by deformation of the block in those regions when filled with dense material.

9., A protective screen block according to any one of claims 1 to 8, wheren h( male and female formations on the top and bottom sides have the substantially c dimensions in cross-section as those on the end sides.

10. A protective screen block according to any one of claims 1 to 9, wherei c block is of a moulded plastics material.

11. A protective screen block according to claim 10, wherein the block hs n outer skin of a hot forming plastics material and a foamed plastics material withi e outer skin.

12. A protective screen block according to any one of claims 1 to 11 in h the block has g filler hole via which a fluid material can be introduced into the int r of the block.

13. A protective screen block according to claim 8, wherein a plug is provId d for sealing the filler hole.

14. A protective screen block according to claim 12 or claim 13, wherein the filler hole is provided in one of the faces.

15. A protective screen block according to claim 12 or 13, wherein the filler hole is provided in one of said formations.

16. A protective screen block according to any one of the preceding claims in which the male formations are of hollow construction.

17. A protective screen block according to any one of the preceding claims, filled with water, sand, lead shot, iron shot or concrete.

18. A protective screen block according to any one of claims 1 to 17, wherein the faces of the block are substantially planar and free from protrusions.

19. A protective screen block according to claim 18, wherein the faces are provided with indentations for facilitating lifting of the block and/or serving as anchorage points for the attachment of fittings to the block.

20. A protective screen block according to claim 19 in which at least some of the indentations are spaced inwardly by a predetermined amount from the edges of the face in which they are provided.

21. A protective screen block according to any one of the preceding claims, wherein the block is a comer block.

22. A protective screen block according to any one of claims I to 2 1, pro1v e, I with a service duct arrangement.

23. A protective screen block according to claim 22, in which the servic c t arrangement comprises outer tubes with a filling holding therein a helically disj( e( tube for taking service lines.

24. A protective screen block according to claim 23, in which the outer beE are stepped.

25. A protective screen block according to claim 23 or claim 24 in whi ck I he outer tubes are welded into the block.

26. A protective screen block according to any one of claims 23 to 25 in 4t h the outer tubes are of plastic.

27. A protective screen block according to claim 1, wherein the blo I is substantially I in in length between the end sides, 0.75 m in height between the to d bottom sides and 0.5 m in thickness between the faces.

28. A protective screen block substantially as hereinbefore described h reference to, and as illustrated in, Figures I and 2, or Figure 4 of the accompan g drawings.

29. A radiological protection screen comprising a plurality of interfitted bl.clc. the blocks each being as claimed in any one of the preceding claims.

30. A radiological protection screen according to claim 29 in which the screen includes at least two wall portions disposed at an angle to each other.

31. A radiological protection screen according to claim 29 or 30 comprising a plurality of courses of said blocks.

32. A radiological protection screen according to any one of claims 29 to 31 including one or more stanchions.

33.. A radiological protection screen according to any one of claims 29 to 32 in which at least one block is connected to at least one neighboring block by a tie plate.

34. A radiological protection screen acdording to claim 33 in which the tie plates interconnect contiguous blocks in one course with a block above or below such contiguous blocks.

35. A radiological protection screen according to claim 33 or 34 in which the connection between each tie plate and said blocks is efected via fasteners arranged on a triangular pitch, the fasteners being received in blind holes formed in the blocks.

36. A radiological protection screen as claimed in any one of claims 33 to 35 when dependeqt on claim 32 in which the blocks are coupled to the stanchions through the tie plates.

37. A radiological protection screen substantially as hereinbefore described with reference to, and as shown in, Figure 6 or Figure 12 of the accompanying drawings.