Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F1/00—Shielding characterised by the composition of the materials
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F3/00—Shielding characterised by its physical form, e.g. granules, or shape of the material

Definitions

• the present invention relates to improvements in and relating to X-ray barriers, and in particular to a system including a wallboard and complimentary wallboard jointing compound which provides a required level of X-ray transmission resistance.
• X-rays are defined as the spectrum of electromagnetic radiation with a wavelength shorter than that of visible light and which exhibit a high level of penetration and are suitable of use in internal imaging of humans.
• X-ray machines or CAT scan machines of various types are required to be operated and in situations where during operation the human operators, or observers or occupants of adjacent rooms, have a risk of exposure to the X-rays.
• the X-ray machines or the like will be situated in a room dedicated for this purpose and it is well recognised that the walls, ceilings and floors in such rooms need to be resistant to the transmission of X-rays in order to ensure that the occupants of adjacent rooms or spaces are not subjected to unacceptable levels/doses of the X-rays.
• barium sulphate has been identified as a preferred X-ray transmission resistant substance or compound and it will be referred to later in this context.
• other substances or compounds having an equivalent or better blocking effect may be available, or become available, and such are intended to be included within this specification as alternatives to barium sulphate as appropriate.
• Appropriate barium sulphate equivalents may include other heavy metal salts, such as lead or uranium, or the actual metal particles. From a health and safety point of view barium sulphate, the material used in barium meals, is the safest and most cost effective.
• barium sulphate is the only cost effective heavy metal salt, but this may change in the future. If cost effective, lead particles could also be used.
• Drywall This consists of a vertical framing of steel or timber studs. Sheets of paper faced gypsum plasterboard manufactured worldwide on special high speed machines, are fixed to these studs with screws or nails and adhesive. The board has a recess [or taper] on the two long edges.
• the recess When assembled, the recess is filled with three coats of a gypsum setting compound or a calcium carbonate based air drying compound or a combination of the two types of jointing compound.
• a paper or fibre glass mesh tape is commonly inserted in the recess [ embedded in the jointing compound] to reinforce the joint.
• the recess is overfilled with jointing compound and flushed out to a width of 150mm or more on either side of the joint.
• the compound when dry is lightly sanded to provide a smooth surface which after decoration with paint or a paper or vinyl lining, presents a continuous surface with no signs of the joints.
• plasterboard The sheets of plasterboard currently used produce a readily assembled system that may also provide, fire, sound and moisture protection. However, plasterboard as currently manufactured and assembled provides virtually no x-ray protection. The benefits of the current system are that plasterboard is manufactured and jointed in the normal fashion, but also provides X-ray resistance.
• a feature of the sealant is that it is able to elastically deform while still providing a required radiation shielding performance.
• One problem with such a substance is that it may be unsuitable for use as a jointing compound for use between adjacent sheets of X-ray transmission resistant wallboard.
• the flexible nature of the compound may mean that it is not easily trowelled or sanded, meaning that it is difficult to provide the smooth monolithic surface normally achieved with gypsum based wallboard systems.
• the putty uses barium in the form of a metal soap as a thickener rather than to provide an X-ray shielding effect.
• An inorganic binder with a density of not less than 5 is used to provide the radiation shielding.
• This putty may also be difficult to sand or trowel and so may not be suitable for use as a wallboard jointing compound.
• the material is suitable for shielding against neutrons and gamma rays but not X- rays.
• a wall or ceiling lining system having a required level of X-ray transmission resistance, the system including a plurality of X-ray transmission resistant wallboards wherein at least one joint or gap between an adjacent two or more of said X-ray transmission resistant wallboards is provided with a wallboard jointing material including at least 30 per cent by weight of barium sulphate or an equivalent.
• the X-ray transmission resistant wallboard may be paper faced gypsum wallboard.
• the X-ray transmission resistant wallboard may be formed by a continuous process.
• the wallboard jointing material may be provided as a ready to use paste air-drying compound holding the barium sulphate in a homogenous mixture.
• the wallboard jointing material may be provided as a dry powder premixed with spray dried synthetic binders
• the wallboard jointing material may include between 30 per cent and 80 per cent by weight barium sulphate or equivalent in the ready to use paste.
• the wallboard jointing material may include between 50 per cent and 75 per cent by weight barium sulphate in the ready to use paste.
• a method of lining a wall or ceiling with a wall or ceiling lining system having a required resistance to the transmission of X-rays including lining said ceiling or wall with a plurality of sheets of X-ray ray resistant wallboard such that there is at least one joint or gap between an adjacent two or more of said wallboards, the method further including filling said at least one joint or gap with a jointing material including at least 30 per cent by weight of barium sulphate or an equivalent.
• the method may include providing the wallboard jointing material as a ready to use paste air-drying compound holding the barium sulphate or equivalent in a homogenous mixture.
• the method may include providing the wallboard jointing material with between 30 per cent and 80 per cent by weight barium sulphate or equivalent in the ready to use paste.
• the method may include providing the wallboard jointing material with between 50 per cent and 75 per cent by weight barium sulphate in the ready to use paste.
• a wall or ceiling lining system having a required resistance to the transmission of X-rays is substantially as herein described with reference to any one of Figure 2, Figure 4, Figure 5a, 5b or 5c or Figure 6a, 6b or 6c.
• Figure 1 Shows a wall lining fastened to a wooden stud prior to the application of a wallboard jointing compound.
• Figure 2 Shows the wall lining of Figure 1 provided with a jointing compound according to a preferred embodiment of the present invention.
• Figure 3 Shows a similar wall lining system to Figure 1 mounted to a metal stud.
• Figure 4 Shows the wall lining of Figure 3 provided with a jointing compound according to a preferred embodiment of the present invention.
• Figures 5a-c and 6a-c Show very diagrammatically plan cross-sectional views of rooms featuring joint and gap material according to one possible embodiment of the invention.
• any joint or gaps in the wall or ceiling lining system provide an avenue for the penetration through the wall system of the X-rays and into adjoining rooms or spaces.
• joint or jointing compounds will be typically used to fill any gaps in order to provide a ⁇ seamless wall for the purpose of providing an attractive decorative finish.
• Paper or fibreglass reinforcing tape is typically embedded in the jointing compounds in order to reduce the likelihood of the joint cracking with any movements of the underlying structure.
• the joint compounds used for embedding of the reinforcing tapes will be of a setting type based on gypsum plaster (which is mixed with water prior to use) or an air drying type joint compound (either as a premixed ready to use paste or a premixed powder which is mixed with water prior to use) utilising a calcium carbonate filler together with a synthetic polymeric type binder.
• Setting type compounds are typically utilised for first and second coats of compound in the jointing process (not for the finishing or top coats) whereas air drying joint compounds may be formulated as either taping compounds and/or finishing or topping compounds.
• air drying joint compounds may include:
• An inert filler usually a finely ground calcium carbonate such as calcite or limestone, but which may include portions of fillers such as perlite and/or mica to impart additional properties such as light weight and crack resistance.
• a binder which may include but is not limited to styrene-butadiene copolymers, polyvinyl acetates and polymers. based on acrylic monomers as either an emulsion or a dry powder and may include polymeric materials of natural origin such as a starch or casein.
• Fungicides which may be designed to protect the joint compound from fungal and bacterial attack both before and after use. 5. Water in order to achieve a desired viscosity.
• an air drying ready mix joint compound may contain between 60 and 80 percent by weight of calcium carbonate or other similar inert fillers and between 15 and 25 percent by weight of water.
• the system of the present invention includes a wallboard joint compound which has been formulated to provide an air drying ready mixed formulation including between 30 and 80 percent by weight of a barium sulphate (or an equivalent as herein defined), and preferably between 50 and 75 percent of that material.
• a barium sulphate or an equivalent as herein defined
• the barium sulphate may be dispersed homogeneously throughout the compound in order to ensure that the level of resistance to X-ray transmission is consistent.
• the air dried joint compound of the present invention may be provided as a dry powder premixed with spray dried synthetic binders and between 30 and 95 percent by weight of barium sulphate, and preferably between 50 and 93 percent of that material, to which water is added and mixed prior to application to the joint, gap or fastener head.
• the present invention may provide between 25 and 75 percent by weight of barium sulphate and preferably between 50 and 70 percent with hydraulic binders including but not confined to gypsum plaster.
• Gypsum wallboard is conventionally manufactured by enclosing a core containing an aqueous slurry of calcined gypsum (stucco or calcium sulphate hemihydrate) between two sheets of paper under high speed continuous conditions. Typically the longitudinal edges of the face paper are wrapped to contain the slurry. A recess or taper is typically incorporated on the face side of each of the longitudinal edges of the gypsum wallboard to facilitate the wallboard jointing operation.
• Gypsum wallboard with X-ray transmission resistance is manufactured in a conventional manner with the addition of sufficient barium sulphate to provide the required X-ray resistance.
• the ratio of barium sulphate to stucco may be easily varied to provide a wide range of X-ray transmission resistant performance.
• X-ray transmission resistant gypsum wallboards typically have a stucco to barium sulphate ratio of between 0.3 and 0.7.
• the effectiveness of these X-ray transmission resistant gypsum wallboards as a component in an X-ray barrier system is expressed as equivalent to a specific thickness of lead sheeting when measured at a specific X-ray intensity.
• a typical X-ray intensity for these tests would be 100 kVp.
• Table 1 shows the results of the Applicant's tests regarding the relationship of lead equivalent and mass of barium sulphate per unit area of 13mm thick wallboard at an X-ray intensity of 100kVp.
• the equivalent lead thickness will increase proportionally with increased barium sulphate weight per square metre, which can be increased by increasing board thickness, or increasing number of layers of board.
• the jointing compound may contain 72.8% barium sulphate by weight in the readymix compound.
• a joint compound with a high level of barium sulphate, such as 72%.8 by weight in the wet or ready to use compound, may, when dried, contain 1.8kg per square metre of barium sulphate per millimetre of dried thickness in the joint.
• a 13mm wallboard might have just 0.75 kg of barium sulphate per square metre per mm of board thickness.
• jointing compound of the present invention provides a relatively greater X-ray transmission resistance than the wallboard.
• flow of joint compound into the gap between adjacent boards may result in some jointing compound flowing behind the board and further increasing the X-ray transmission resistance.
• a further embodiment would be to generate machine made edges on the X-ray transmission resistant wallboards with a rounded profile to enhance penetration of the X-ray transmission resistant jointing compound into the joint.
• the machine made edge of the X-ray transmission resistant wallboard may be 'lightly buttered' with the joint compound prior to fastening to the framing.
• Figure 1 shows very diagrammatically a cross section through part of a wall system of a room which is required to provide a specified resistance to X-ray transmission.
• the wall system 1 is shown including a pair of abutting X-ray transmission resistant gypsum wallboards 2, 3 which although butted tightly edge to edge is still likely to create a gap along the adjacent edges indicated by arrow 4.
• the wallboards 2, 3 which will provide X-ray resistance to the required level, are shown secured to a vertical wooden stud 5 behind which is the wallboard 6 of an adjacent room or space.
• a joint is shown provided between the boards 2, 3 and utilising a jointing compound 8.
• a jointing compound 8 may preferably contain between 30 and 80 percent of barium sulphate or an equivalent, although the percentage may be lower or higher.
• the boards 2, 3 will also provide X-ray transmission resistance of a suitable level but unlike the jointing compound 8 will be typically composed of a gypsum to barium sulphate ratio of between 0.3 and 0.7.
• FIGS 1 and 2 where appropriate. However, in this embodiment wooden stud 5 is shown replaced by a metal stud 7.
• FIGS 5a-c and 6 a-c again with the alternative use of metal or wooden studs 7, 5, diagrammatic cross sectional views across a wall system for a room are shown.
• the jointing compound is shown provided in joints along the wall faces and joints 8A in the wall corners.
• Figures 5a, 5b, 6a and 6b show the overlapping joints preferred when two or more layers of X-ray transmission resistant wallboard 2, 9 are used.
• Any fasteners in the field of face of the X-ray transmission resistant gypsum wallboard will require application of a coat of X-ray transmission resistant jointing compound.
• the present invention provides a wall or ceiling lining system which may be provide most or all of the benefits of a standard gypsum wallboard interior cladding (or drywall) while also providing a required level of resistance to transmission of X-rays.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Building Environments (AREA)
• Finishing Walls (AREA)

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Citations (8)

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• 2002
  • 2002-02-21 NZ NZ517385A patent/NZ517385A/en not_active IP Right Cessation
• 2003
  • 2003-02-21 WO PCT/NZ2003/000033 patent/WO2003071556A1/en not_active Application Discontinuation
  • 2003-02-21 EP EP03705560A patent/EP1512153A4/de not_active Withdrawn
  • 2003-02-21 AU AU2003206481A patent/AU2003206481B2/en not_active Expired

Patent Citations (8)

Non-Patent Citations (1)

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