Patent Number: 058833943
Section: description

In the various figures of the drawing, identical features will be indicated with the same reference numerals, and similar features in alternate embodiments or locations may be indicated with use of prime (') superscripts, without further mention thereof. DETAILED DESCRIPTION OP THE INVENTION Referring now to the drawing, FIG. 1 depicts, in a vertical position, a radiation shield 10 fabricated according to my design, affixed in place by steel bands 12 about a section of pipe 14. As illustrated, a first layer S.sub.1 of shield portions is provided; these are identified as shield portions S.sub.1 (1), S.sub.1 (2), and S.sub.1 (3). A second layer S.sub.2 of shield portions is provided; these shield portions are identified as shield portions S.sub.2 (1), S.sub.2 (2), and S.sub.2 (3). Thus, it can be seen that the radiation shield 10 can be fabricated using a sequence of radiation shield portions that are provided in one or more layers. When a plurality of layers S.sub.1, through S.sub.N are provided, N is a positive integral number corresponding to the number of layers provided. In each of the layers S.sub.1 through S.sub.N, one or more shield portions may be provided. In each such layer S.sub.N, shield portions may be described by a sequence of shield portions S.sub.N (1) through S.sub.N (X), where X is a positive integer representing the number of shield portions in that layer. As is intuitively obvious in view of the specific example set forth, and by use of the various figures of the drawing, the location of any one radiation shield layer S.sub.N may generally be described relative to other shield layers therebelow, such as S.sub.N-1 for the shielding layer immediately below layer S.sub.N, or relative to other layers thereabove, such as layer S.sub.N+1 for the layer immediately above layer S.sub.N. I prefer to fabricate each radiation shield 10 before attachment to pipe 14. As can be seen in FIG. 1A, when my radiation shields are used on a pipe 14, shield portions S.sub.1 (1), etc., must be fabricated so that the inner diameter D.sub.1 I substantially conforms to the outer diameter D.sub.P O of pipe 14. Then, the inner diameter D.sub.2 I of shield portions (e.g., S.sub.2 (1)) which are used in the second layer S.sub.2 must substantially conform to the outer diameter D.sub.1 O of the shield portions (e.g., S.sub.1 (1)) which are used in the first layer S.sub.1 of the shield portions. As is evident from FIG. 1A, each of the radiation shield portions is provided in the shape of a segment of an annulus. For convenience in fabrication, I have prepared a table which eliminates the need to calculate diameter dimensional data for commonly encountered pipe sizes. In Table I below, I have provided the size and weight encountered for a first layer S.sub.1, shield portion and for a second layer S.sub.2 shield portion, when the radiation shield making up each layer is fabricated from a sheet TABLE 1 ______________________________________ LEAD CUT SIZES FOR FABRICATION OF HALF-ROUND SHIELDS Pipe Width - W Width - W Pipe Outside for 1/4" for 1/2" Weight Weight size Diameter (inner piece) (outer piece-) 1/4" .times. 12" 1/2" .times. 12 (in.) D.sub.p O S.sub.1 layer) S.sub.2 layer) pounds pounds ______________________________________ 1 1.365 21/2 27/8 31/8 63/4 2 2.375 41/8 5 51/8+ 113/8+ 3 3.5 57/8 63/4 73/8 151/2 4 4.5 71/2 81/4 93/8 193/4 5 5.563 91/8 97/8 113/8 233/4 6 6.625 103/4 12 133/8 277/8 8 8.625 131/2 15 167/8 351/2 10 10.75 171/4 181/2 211/2+ 45 12 12.75 203/4 22 26 531/2 ______________________________________ NOTE: This table assumes 1/4 (0.25) inch lead sheet stock is used. of lead S of thickness T, and where the thickness T is selected at 1/4 (0.25) inches. As indicated in FIG. 1B, my preferred method of fabricating a half-round coated lead shield, such as any of the shield portions shown in FIG. 1, is to first determine the pipe size of pipe 14, and then cut a flat lead sheet S of 0.25 inches thickness T into the width W indicated according to Table 1, and in a desired length L. Then, using a pipe mold 14', the flat lead sheet is molded to fit the pipe 14 size. When a final radiation shield 10 is to be made in two 0.25 inch layers, the inner layer S.sub.1 is first made, and then the second layer S.sub.2 is preferably shaped over the piece for the first layer S.sub.1. For ease in fabrication, I prefer to leave an offset gap G of about one (1) inch, to offset, layerwise, the gap between adjacent shield portions (e.g., S.sub.1 (1) to S.sub.1 (2) and S.sub.2 (1) and S.sub.2 (2). Space 20 between adjacent shield portions should be minimized in order to avoid loss of shielding effectiveness. To assemble shield portions into a final radiation shield 10, for example when fabricating a final radiation shield 10 of 1/2 (0.5) inch thickness (using one quarter inch lead in each of layers S.sub.1 and S.sub.2, or TS.sub.1 +TS.sub.2 !=1/2 inch) I prefer to use 1" deck screws 22, as can be seen in FIG. 3. The shield portions (e.g., S.sub.1 (1) and S.sub.2 (1)) are fastened together by running the deck screws 22 from outside to the inside. Preferably, pre-drilled holes are avoided. Use of deck screws 22 is important since they do not require pre-drilled holes, and the threads do not load with lead and tear out as they are run into the lead. Also, the head 24 of deck screws 24 are of a counter sunk type and they will run in flush with the outside or upper surface 26 of the outer layer lead shield portion being assembled. Also, desirable deck screws are provided in hard, brittle materials, which make it easy to break off the threads that protrude through the lead, for example when using one (1) inch screws with a one-half (1/2) inch total shield thickness. Preferably, the protruding part can be broken off with a hammer or snipped off with pliers, and the lead around the stump 28 can be shaped to assure there are no protruding sharp edges. Likewise, corners C of the shaped lead sheet S are rounded, usually with a hammer, to assure that there are no sharp corners on the finished radiation shield 10. After the shield portions of the radiation shield 10 are joined, the shield 10 is coated to provide a final cured coating 30. A preferred coating material used to cover the lead and provide a coating 30 is a flexibilized Bisphenol A epoxy which is cross linked with a modified cycloaliphatic amine curing agent. Ideally, such a coatings is provided as a two component, medium viscosity (1250 cps at 77.degree. F.) epoxy, with 100 percent solids. I prefer a product with minimal color fade or degradation upon exposure to sunlight, and with the following performance properties: (1) Tensile strength, using method ASTM D-538: 1100 pounds per square inch PA1 (2) Percent elongation, using method ASTM D-638 60 percent (minimum) PA1 (3) Shore D Hardness, using method ASTM D-2230 37 hardness PA1 (4) Tensile Shear Strength, method ASTM D-1002 347 pounds per square inch. The coating can be applied by roller, paint-brush, or by spray. Particular attention must be paid to the corners C and edges E, to avoid any thin or shallow coated areas. If touch up coats are used or required, they should meet the same coating specifications as the original coating. Once completed, the radiation shield 10 can be placed directly on piping, such as pipe 14, or can also be used as shadow shielding, particularly if it is provided in flat sheet form (as shown as shield 40 in FIG. 4 below) rather than in the shaped shield form just described above. The installation method chosen will also depend upon whether the installation is to be temporary or permanent. For ease of installation, I prefer to use grommets 36 which have in inside wall 37 to define a through passageway 38 in the shield 40. When grommets 36 are used, it is preferable to coat the lead sheet S with coating 30 first, and then install grommet 36. I prefer to grommet shields 40 with grommets 36 on twelve (12) inch centers, starting about six (6) inches from an outer edge E and centered about one and one-half (1 1/2) inch from the top Z. Grommets are installed using a five-eighth (5/8) inch hole punch and ideally, five-eighths (5/8) inch brass grommets 36 are utilized. This size allows for some slack when the shield 40 is placed using one-half (1/2) inch bolts. After installing grommets, if the coating 30 has been damaged, it should be repaired, prior to using the shield 40. If sheets 40 of coated lead radiation shield are to be provided as temporary shadow shielding, then the sheets 40 can be supported by scaffold tube framing 42, with the coated lead shield sheets 40 hung on S-hooks 44, as indicated at the bottom of FIG. 8 below. As noted in FIG. 8A, I prefer to make S-hooks 44 from about a 5/16 inch round stock, with about a 2 1/8 inch diameter in each arm of the S-hook 44, and an extension arm 45 to each end of the S-hook 44 of about three quarters (3/4) of an inch. If the coated lead sheet 40 is used for temporary pipe shielding, then half-rounds can be supported from pipe 14 by wire ties, instead of bands 12 shown above in FIG. 1. However, if the installation is for permanent shadow shielding, then support will be analogous to that shown for a stainless steel encapsulated shield 50 as shown in FIG. 12 below. Specifically, a structural steel support 52 is used to hold an attachment structural steel member 54, to which the shield (such as 40 instead of 50) can be affixed via fastener such as bolt 56 and nut (not shown). Alternately, a shield 40 can be permanently affixed on scaffold tube support frame with wire ties approved for use in the service environment. I prefer to use a a lead sheet S sized 23.5 inches by 47.5 inches, for the normally encountered radiation shielding situations. Such size sheets S are also advantageous for manufacture of full size twenty four (24) inch by forty eight (48) inch radiation shields 50 which are encapsulated with stainless steel 60. By using the suggested lead sheet S size, space is allowed for covering the lead sheet S and riveting the stainless steel 60, so that the completed panel dimensions are not greater than twenty four (24) inches by forty eight (48) inches. Turning now to FIGS. 5, 6, and 7, one convenient method for manufacture of my stainless steel encapsulated lead shields is shown. Typically, I find that a 20 gauge stainless steel sheet 60 is adequate to provide the encapsulation that my radiation shields 50 require. First, an inner layer of at least one sheet S of solid radiation shielding material, preferably lead, is provided, cut to desired size as described herein. Then, a first, obverse stainless steel panel 62 is cut to a desired size. In FIG. 5, taken looking down at the left side flange 64 on the obverse side 65, shows how flange 64 preferably extends from the face 67 of obverse side 65 at at about a ninety (90) degree angle therefrom. A companion left side flange 66 extends also at preferably about a ninety (90) degree angle from the face 68 of the reverse side 69. This FIG. 5, in combination with FIG. 6, shows the method which is used for encasing the the right and left sides of a radiation shield 50 which has a stainless steel outer casing 60. Bottom 70 of the radiation shielding material S is at the left of FIG. 5. Left edge 72 the radiation shielding material S is at the top of FIG. 5. Preferably matching size apertures A defined by edge portions 80 are located in flanges 64 and 66 are provided for use in securing fasteners R thereto. Note that flanges 64 and 66 extend above edge 72 of the radiation shielding material by a distance I, to leave a void of width I, which void is filled with a suitable sealant 74. I prefer to use silicon caulking or adhesive, but in some applications, a polyvinylchloride type filler will also be acceptable. Preferably after filling the void with sealer 74, flanges 64 and 66 are joined with a mechanical fastener, typically pop type rivets R. I like to use rivets R on one inch centers along the edge of the radiation shield. In any event, sufficient space must be provided, i.e., width I, for the rivets R or other fastening device to be finally assembled without intruding into the at least one sheet S of solid radiation shielding material. Similar construction is typically used for both sides, and generally is also desirable along the bottom of shield, where an obverse bottom flange and a reverse bottom flange are joined in similar fashion. At the top, in order to provide an extra measure of protection against intrusion of water or steam, a U-shaped cap 80 is preferably provided. Just as with construction of the sides, a void of height K is provided to allow fasteners to join parts without intruding into the at least one sheet S of solid radiation shielding material. The obverse side 65 has a top flange 82, and the reverse side 69 has a top flange 84. Cap 80 in the shape of an elongate, a generally U-shaped channel having a reverse side leg 86 and an obverse side leg 88. The cap 80 is fitted downward over top flange 84 of the reverse side 69, and downward over the top flange 82 of the obverse side 65. The cap 80 is fitted in a manner where an inner portion 90 of the reverse side leg 86 is placed in an abutting relationship with the face 68 of the reverse side 69. Likewise, the cap 80 is fitted in a manner where an inner portion 92 of the obverse side leg 88 is placed in an abutting relationship with the face 67 of the obverse side 65. In this way, a first mechanical fastening device R.sub.1 is used to join the reverse side leg 86 of the cap 80 to said reverse side 69. A second mechanical fastening device R.sub.2 is used to join the obverse side leg 88 of the cap to the obverse side 65. It is important that the mechanical fastening devices R.sub.1 and R.sub.2 do not intrude into the at least one sheet S of radiation shielding material. Ideally, the flanges are formed in an integral, one-piece fashion with each of the obverse and reverse panels used to encapsulate the lead sheet used as a core. As further illustrated in FIG. 7, I prefer to provide a grommet 36' in my radiation shield 50. A plurality of grommets 36' defines through passageways in the radiation shield, so that the radiation shield 50 may be upheld by a supporting structure protruding through said grommet. An ideal supporting structure is provided by my hangers 100 and 110, as illustrated in FIGS. 9 and 10, respectively. As shown in FIG. 9, hanger 100 includes an elongate, flat bar portion 102, a backwardly curved hook portion 104, and a forwardly protruding stud 106. The stud 106 is attached to the elongate flat bar portion 102 at the upper reaches 108 thereof, and extends forwardly therefrom in a generally horizontal manner, so that the protruding stud 106 extends forward a distance to support, hanging vertically therefrom, a radiation shield 50. As shown in FIG. 10, an alternate hanger 110 is set forth. Hanger 110 is similar to the hanger 100 just described, but further includes a J-shaped hook 112 at the lower reaches 114 thereof. The J-shaped hook 112 is preferably formed as an integral part of the elongate flat bar portion 102, and is provided in sufficient width and shape to cradle therein a planar lower edge 116 of a shield 50 which may require support of stabilization. FIG. 10A shows a side view of the J-hook hanger. Radiation shields using my design can be custom manufactured to be installed around pipe, conduit, or other structures from which radiation is being emitted. The exact design of the shielding will be based on the radiation source(s), the dose rate both (i) contact and (ii) general area type, the project shielding requirements (whether job specific or area dose rate reduction driven), the area configuration, including environmental conditions, the duration (temporary or permanent), and various engineering requirements, such as structure loading and seismic requirements. In any event, it will thus be seen that the objects set forth above, including those made apparent from the proceeding description, are efficiently attained, and, since certain changes may be made in carrying out the construction of a radiation shielding apparatus to generally in the manner described, and while still achieving the objectives as set forth herein, it is to be understood that the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. For example, while I have set forth exemplary designs for a stainless steel encapsulated radiation shield design, many other embodiments are also feasible to attain the result of the principles of the apparatus and via use of the methods disclosed herein. Therefore, it will be understood that the foregoing description of representative embodiments of the invention have been presented only for purposes of illustration and for providing an understanding of the invention, and it is not intended to be exhaustive or restrictive, or to limit the invention to the precise forms disclosed. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as expressed in the appended claims. As such, the claims are intended to cover the structures and methods described therein, and not only the equivalents or structural equivalents thereof, but also equivalent structures or methods. Thus, the scope of the invention, as indicated by the appended claims, is intended to include variations from the embodiments provided which are nevertheless described by the broad meaning and range properly afforded to the language of the claims, or to the equivalents thereof.