NL2023142B1 - Portable temporary radioactive screening device - Google Patents

Abstract

The invention aims to provide for solving this object by means of a radiation screen container, for containing radiation screening liquid, comprising one or more flexible sheets, configured to form a closed panel shaped container that is capable of containing gas and/or radiation screening liquids. The radiation screening liquid container may be capable of forming a temporary radiation screen including at least one radiation screening liquid container. A valve is configured as a pressure relief valve or a separate pressure relief valve is provided. The sheets are provided With an internal array of elastomer strands according to a drop stitch construction that shape the container into a predetermined shape When pressurised.

Description

P121933NL00 Title: Portable temporary radioactive screening device

DESCRIPTION

BACKGROUND OF THE INVENTION The present invention relates to the reduction of absorbed dosages of radiation in areas known or suspected to be exposed to radioactivity. The device and method is particularly suitable for reducing absorbed dosages of humans performing situational work in radioactive environments. Prolonged exposure to absorbed dosages are known to be, amongst other stochastic effects, carcinogenic and can lead to mortality.

Existing devices and methods are known as radiation screens or barriers and include lead sheeting, concrete bricks and water tanks. The known devices involve much effort to deploy in the desired areas, due to the inherent weight and bulk of the devices and lead to increased absorbed dosages for persons performing the required work. Typically devices are more suited to permanent or prolonged installation the more they weigh as a result of the increased installation times which then counter productively increases absorption dosages.

In European Patent FR2528615 a water container is proposed for radiation screening. Such a container is quite cumbersome in handling, especially when used as building blocks for a protective screen since a considerable amount of water is necessary to provide for sufficient screening.

SUMMARY OF THE INVENTION The object to be solved is to provide a radiation screening liquid container that is less cumbersome and more practical in use. The radiation screening liquid container should be easily constructed in screening arrangements, particularly in nuclear power stations where maintenance and repair work is often required in radioactive areas. The radiation screening liquid container should reduce radiation exposure dosages of persons working temporarily in areas exposed to radiation as well as persons performing safe making work . The invention aims to provide a solution to this object with a radiation screen liquid container, for containing radiation screening liquid, comprising one or more flexible sheets, configured to form a closed panel shaped container that is capable of containing gases and/or radiation screening liquids. The radiation screening Liquid container may be positioned to construct a radiation screen, e.g. in a vertically upright, horizontally flat, angled or other orientations. The radiation screen comprises at least one radiation screening liquid container. The container is filled with a radiation screening liquid preferably water or heavy water. When the container is filled with liquids an amount of gas inside the container should be left to prevent the container from rupturing when an incompressible liquid inside experiences pressure shocks. At least one first valve is fitted to the container, which is configurable to allow ingress, storing under pressure or expelling of screening liquids and at least one second valve fitted to the said container of which is configurable to allow ingress, storing under pressure or expelling of gas. The second valve may be configured as a pressure relief valve or a separate pressure relief valve is provided.

The sheets are provided with an internal array of elastomer strands that shape the container into a predetermined shape when pressurised.

In this way, the containers can be provided as lightweight panels, e.g. necessary for providing sufficient and well defined screening thickness.

In another aspect it is aimed to provide a method for constructing a temporary radiation screen by inflating at least one container by allowing gas to ingress through a valve until inflated and sufficiently rigid to shape the container when pressurised; positioning said inflated container, in a planar array between the source of the radiation and the space to be screened from the radiation; filling the said inflated container with radiation screening liquid by forcing said liquid through the first valve and partially displacing the gas in said container through a pressure relief valve. For example, areas in a nuclear power station which are radioactive can be screened off from the source of the radiation with minimal absorption exposure to persons constructing the screens and persons working in the screened areas, and the internal array of elastomer strands provide a high structural integrity and strength allow the panels to have a well defined shape.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is further described with reference to the drawings wherein: figure 1 shows radiation screening liquid container; figure 2 shows cross sectional element of drop stitch elastomer strand array and container sheets with coating; figure 3 shows a radiation screen constructed from multiple radiation screening containers; figure 4 shows a planar array radiation screen [3] constructed between a radiation source and a person; figure 5 shows a weft yarn used as a drop stitch.

DETAILED DESCRIPTION The present invention provides for the rapid installation of a collapsible container 1 that is to contain a radiation screening liquid 1.5. The container is constructed from one or more flexible sheets 2.2 & 2.4. The sheets are configured to form the container 1 and to give it the capability of containing gas 1.4 and/or radiation screening liquids 1.5 in Figure 1. The container 1 is then first filled and pressurised with gas 1.4 through one of the container’s valves known as the first valve 1.1 and a gas supply hose 1.8.

The first valve is fitted to the container and is configurable to allow the ingress, storing under pressure or expelling of the gas.

The pressurised container 1 is then filled with radiation screening Liquid 1.5, preferably water or heavy water, through a liquid supply hose and at least one other valve 1.6 know as the second valve. The second valve is fitted to the container 1 and is configurable to allow ingress, storing under pressure or expelling of screening liquids 1.5 and a liquid supply hose 1.7. As the liquid 1.5 fills the container it displaces the gas 1.4 contained in the container 1 through the first valve 1.1 or a separate pressure relief valve until the majority of gas has been displaced. When the tank is filled with liquids a small amount of gas should remain in the tank to provide a controllable pressure and to protect the tank from rupturing. The first valve

1.1 is also configured to be a pressure relief valve and/or a separate pressure relief valve may be provided.

Both or either the first valve 1.1 or if present a separate pressure relief valve, should be set or configured to provide a minimum threshold pressure inside the container. Should the pressure rise above the threshold pressure then the pressure in the container is reduced by automatically opening either or both of the valves and venting the pressure. The threshold pressure is the pressure at which the container has the correct rigidity and may typically be at pressures higher than 1,2 or even higher than 1,5 or 2,5 kPa.

The container is constructed from flexible sheeting 2.2 & 2.4 and the flexible sheeting 2.2 &2.4 1s constructed with an internal array of elastomer strands 2.3 that shape the container into a shape when pressurised.

Figure 2 shows an embodiment with an internal array of elastomer strands 2.3, that shape the container into a shape when pressurised. The internal array of elastomer strands e.g. with a density of at least 1 strand/cm2 may be provided by a drop stitch construction 2, e.g. as used in flotation devices such as a SUP (standing up paddling) board.

Drop stitch fabric materials are typically created by weaving yarns between two or more fabric sheet layers that are a distance apart but can also be glued, welded, vulcanized or similarly be created. 5 The internal array of strands distributes the mechanical stress evenly over the container’s 1 internal surfaces 2.6 which has the advantage of creating a container 1 that has a uniform thickness 2.7. The uniform thickness 2.7 of the container 1 ensures uniform radiation screening through the containerl.

The container can have a thickness of 10 mm or more but a container with a thickness of 100mm or less requires supporting means similar to figure 3 to support the container from folding under its own weight.

In another aspect of the invention, the external sheet surface 2.8 of the container 1 is provided with securing fixtures 1.3 which provided the means for securing the container 1 in any position but may include upstanding, laid down, hanging or oblique positions.

The securing means 1.3 may be provided by straps 1.3 that are attachable to the container 1 to form a loop but other securing fixtures may be used.

In another aspect of the invention a radiation screen 3 e.g. shown in figure 3, is constructed by containers 1 being positioned in a planar array 4 e.g. shown in figure 4, between the source of the radiation 4.1 and the space to be screened from the radiation 4.2. The screen 4 can also be constructed by positioning the containers 1 in a layout other than a planar layout 4, like radially or overlapping, but a planar layout 4 is common.

A planar array or other layout may be orientated in an upstanding position, hanging, laid down or angled position.

In a laid down position the screens may support a portion of their own weight and could be used to construct an overhead screen amongst others with sufficient support.

A planar array may also be suspended by hanging the radiation screening containers from an overhead support structure using straps similar to figure 3.

Figure 3 shows a temporary radiation screen 3 that is constructed by inflating multiple containers 1, and allows gas to ingress through valves

1.6 until the containers are inflated and sufficiently rigid to shape the containers 1 into panel shapes when pressurised. To construct the temporary radiation screen the containers 1 are positioned in a planar array between the source of the radiation 4.1 and the space to be screened 4.2 from the radiation, as shown in figure 4, by placing consecutive inflated containers 1 tangentially. The containers 1 are constrained to remain in their positioned locations with fastening belts 3.2 and anchoring 3.3 of the belts. The containers may be capable of maintaining an upstanding orientation without fastening means even when the containers have a nominal thickness of 50 to 100mm.

By connecting more than one container and orientating them relative to each other, the containers may provide support for each other.

The containers 1 may be placed in a guiding groove 3.4. The guiding groove 3.4 helps to position and secure the containers 1 quickly when constructing the temporary radiation screen 4 but may include other ways to guide and secure the containers 1. After the containers 1 are positioned and their locations fixed the containers 1 are filled with radiation screening liquid 1.5. To fill the containers 1 with the radiation Liquid 1.5, the radiation liquid 1.5 is forced through each containers 1 second valve 1.6 and partially displaces the gas 1.4 in the containers 1 through a pressure relief valve 1.1.

In a further aspect of the invention a portable temporary radiation screen 3 can be deconstructed by draining the radiation screening liquid 1.5 from the containers 1 through the second valve 1.6. The radiation screening liquid 1.5 can be forced and displaced out through the liquid valve 1.6 by pumping gas 1.4 through the first valve 1.1 with a gas supply hose 1.8 or other means. The containers 1 may be removed from the securing straps 3.1 and deflated through a valve, preferably the first valve 1.1 once the valve

1.1 has been configured in an open position or by any other valve that is suitable.

Thus the container 1 can be extremely light and exceptionally easy to maneuver and place. The fasting straps 1.3 can also act as gripping handles to facilitate constructing and deconstructing the radiation screen 3. By being rigid the container 1 minimizes radiation dosages and prevents accidental leakage from disturbances to the container 1. The rigidity of the container 1 causes the container 1 to recover its original dimensions rapidly in contrast to European Patent FR2528615. In FR2529615 a water envelope 1s proposed for radiation screening. Such an envelope is cumbersome in handling, especially when used as building blocks for a protective screen. The envelope is cumbersome due to it lacking sufficient rigidity. This rigidity may also result in unnoticed deformation to the envelope due to external disturbances which could leave areas intended to be screened exposed to radiation.

By letting out the radiation liquid 1.5 from the containers with a water supply hose 1.7 the radiation screening liquid can be removed away from persons in the vicinity. Using a water supply hose 1.7 to let the radiation screening liquid out of the container decreases the possible absorbed dosages of persons in the vicinity of the containers 1.

The container 1 is resistant to radioactive damage and reusable and has economical and safety benefits.

Further description of embodiments An alternative embodiment further detailed in figure 5 refers to a multilayered three dimensional fabric 5 which is continuously woven. For double layered drop stich fabrics 5 the different layers 5.4 & 5.5 of the three dimensional fabric are connected to each other by taking a weft yarn 5.3 from the first layer 5.4 of fabric and weaving it into the second layer 5.5 before weaving it back into the first layer 5.4 and repeating the process until the correct amount of drop stitched strands 5.3 are present. It may be possible to use yarn, strands or fibers for weaving a drop stitched fabric but yarns are the preferred material. The dropped yarns 2.3 are capable of creating a dense connecting structure 2 for example of 20 - 80 strands per cm2, between the layers 5.4 & 5.5 of fabric. The fabric sheets maybe spaced apart equal to the length of the dropped yarn 5.3 and determines the fabric’s thickness 2.7. The dropped yarn 5.3 is called a “dropped stitch” even though it is actually woven. The length of the dropped yarn 5.3 is limited by the constraints of the loom used to weave the fabric 5 but can typically range from 5cm to 75 cm. The sheets 5.4 & 5.5 of the drop stitched fabric 5 are woven with a consistent wave pattern 5 where one such pattern is called a plain weave pattern 5 and is the preferred pattern because it offers high stability but other patterns may also be used. A plain weave pattern 5 is a weave pattern where every warp yarn 5.1 passes under or over every subsequent weft yarn 5.2. In the plain weave example the undulations of adjacent warp yarns 5.1 are a hundred and eighty degrees out of phase relative to one another and no two adjacent pairs of warp yarns 5.1 pass the same way over an adjacent weft yarn 5.1. The fabric 5 may be woven from yarn such as polyester yarn or nylon yarn and the dropped stich yarn may be Dacron, Vectran or Nylon yarn but other yarns could also be used in either case. The dropped stitch yarns 5.3 can either be woven normal to the fabric surfaces or at slight angles to create a V-shaped structure. The dropped stitched fabric 5 can then be shaped and joined on the peripheral edges of the fabric to produce a container 1 with a desired shape. Joining of the material could be done by welding, gluing or vulcanizing but may include other joining methods. To seal the sheets of fabric a coating 2.1 &

2.5 1s applied, preferably Chlorosulfonated Polyethylene but other coating materials may also be acceptable, to enable the container to retain pressurised liquids 1.5 and/or gases 1.4.

An alternative embodiment of the container’s 1 valve 1.1 has instead of a combined air filling/deflation and pressure relief valve has an air filling/deflation valve and a third pressure relief valve.

Another alternative embodiment of the said container uses channeling or routing of the contained gas 1.4 or liquid 1.5 to enable one valve to fill and drain the container 1.

Another alternative embodiment of the containers 1 is fitted with detachable fixtures. The fixtures may make connections between the containers 1 surfaces of neighbouring containers to facilitate the construction of the radiation screen 3 and reduce inter container leakage.

An alternative embodiment of container 1 is a container 1 that has, instead of gripping straps 1.3, any gripping arrangement understood by the person skilled in the art as suitable for gripping the container 1.

Claims (9)

Conclusions A collapsible radiation shielding container, for containing radiation shielding fluid, comprising: one or more flexible layers configured to form a container that can contain gas and / or radiation shielding liquids; at least one first valve attached to the container that is configurable to allow access, pressurized storage, or expel gas; at least one second valve attached to the container, which is configurable to allow access, storage under pressure, or expelling shielding fluids; wherein said first valve is configured as a pressure relief valve or a separate pressure relief valve is configured, and wherein the layers are provided with an internal pattern of elastomer strands that form the container in a panel shape when pressurized. A container according to claim 1, wherein the arrangement of elastomer strands is provided by a drop stitch construction. A container according to claim 1 or 2, wherein the external layer of the container comprises fastening means for fastening said container in an upright position. A container according to any one of the preceding claims, wherein said fastening means is provided by straps that can be attached to the container. A container according to any of the preceding claims, wherein said pressure relief valve is capable of withstanding a pressure of at least 1.2 kPa. A container according to any of the preceding claims, wherein the panel shape has a thickness between 50mm and 300mm. A method of constructing a temporary radiation shield according to the following steps: a. Inflating at least one container according to claims 1 and 2 by allowing gas to pass through the first valve until it is inflated and has enough rigidity to container into a panel shape when pressurized. b. positioning said inflated container, in a planar array between the source of the radiation and the space to be shielded from the radiation. c. filling said inflated container with radiation shielding liquid by forcing said liquid through the second valve and expelling the gas through a pressure relief valve except for a residual portion of gas that controls the set pressure of at least 1.2 kPa. A method according to claim 7, wherein the array of panels is located within a planar array by placing the container in a control groove. A method, according to claim 7, of decommissioning a portable temporary radiation shield according to the following steps: a. Draining radiation shielding fluid from a container, according to any one of claims 1-6, by forcing gas through the first valve to moving shielding fluid through the second valve. b. removing the fasteners and deflating said container through the first valve configured to allow the gas to pass through said valve.