Abstract:
A water sampling device and method for use with a radiation probe. The device includes a base, filtrate reservoir, filter media support disc, and sample reservoir. The sample reservoir may be interchanged with a radiation probe adaptor. The device and method provide a simple and convenient means to separate particulate solids from a water sample prior to measuring radioactivity without the need for a heat source or electrical power to evaporate the water. The device and method can be used with a variety of commercially available radiation probes and is suitable for field applications.

Description:
GOVERNMENTAL INTEREST 
     The invention described herein may be manufactured, used and licensed by or for the U.S. Government. 
    
    
     TECHNICAL FIELD 
     This invention relates to the field of radioactivity measurements of water samples. 
     BACKGROUND 
     The detection of alpha and beta radiation in water samples is complicated by the fact that these forms of radiation are attenuated by water. Current procedures require evaporation of the water in a given sample in order to separate the particulate solids found in the water sample from the water prior to measuring radioactivity. Such practices are described in the International Organization for Standardization (ISO) method 9696 and U.S. Environmental Protection Agency (EPA) method 900.0. The evaporation step, as required in these methods, requires a heat source and electrical power. The additional time needed to perform the evaporation step, along with the requirement for a heat source and electrical power, are generally undesirable for field applications where time, weight, volume, and power requirements pose logistical problems. The present invention overcomes these problems by providing a water sampling device for use with a radiation probe which utilizes a filter means to separate the solids from the water, thereby eliminating the evaporation step. In addition, the device and method of the present invention allow larger volumes of water to be sampled in shorter periods of time, thus enabling short test cycles producing high concentrations of radioactive material collected onto the filter media, if such radioactive material is present in the sample. The device of the present invention can be used with a variety of commercially available radiation probes and is compact, light, and portable. As such, it is well suited for field applications. 
     SUMMARY 
     The present invention provides a simple and convenient means to separate particulate solids from a water sample prior to measuring radioactivity without the need for a heat source or electrical power. The device and method of the present invention can be used with a variety of commercially available radiation probes and is suitable for field applications. Aspects of the invention may include one or more of the following: a base for supporting the device so that it is self-standing, a filtrate reservoir for holding a water sample after it has passed through a filter media to collect solids within the water sample, a filter media support disc for holding the filter media and connecting parts, and interchangeable sample reservoir and radiation probe adaptor. The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is an exploded view of one embodiment of a water sampling device for use with a radiation probe according to the teachings of the present invention. 
         FIG. 2  is a perspective view showing the embodiment of  FIG. 1  in its assembled state. 
         FIG. 3  is an exploded view illustrating the interaction of the present invention with a radiation probe. 
         FIG. 4  is a perspective view showing the embodiment of  FIG. 3  in its assembled state. 
         FIG. 5  is an exploded view illustrating the filter media support disc and the filter media containment means of the present invention. 
     
    
    
     Like reference symbols in the drawings indicate like elements. 
     DETAILED DESCRIPTION 
     One embodiment of the present invention is illustrated in the exploded view of  FIG. 1 . Device  10  includes a base  12 , filtrate reservoir  14 , filter media support disc  16 , filter media  18 , and sample reservoir  20 . Base  12  may include a base stabilization member  24  to prevent device  10  from tipping over when in use with a radiation probe as will be illustrated below in  FIGS. 3-4 . Base  12  also includes a circular lip  26  for engaging filtrate reservoir  14  in a compression or friction fitting. The terms “compression fitting” and “friction fitting” are used interchangeably herein to describe the following type of attachment or mounting means. Circular lip  26  has an inner diameter slightly less than the outer diameter of filtrate reservoir  14 , both of which are made of material with some elasticity to allow a degree of flexibility. Accordingly, filtrate reservoir  14  fits snuggly into circular lip  26  with the bottom end of filtrate reservoir  14  effectively capped by the circular portion of base  12 . The friction between connecting members, which is caused by the force from compression of one of the members, or the expansion of another member, serves to hold the two parts together. 
     Filtrate reservoir  14 , in the embodiment illustrated, is a hollow cylinder for receiving the sample water after it has drained through filter media  18  and filter media support disc  16 . A vacuum port  22  may be provided in filtrate reservoir  14  to aid in the passage of the water sample through filter media  18 . That is, by connecting a vacuum source (not shown) to vacuum port  22 , the resulting suction force on filter media support disc  16  and filter media  18  will cause an increase in flow across these elements, thus speeding up the sampling process if so desired. Conversely, the liquid sample can be eluted through the filtration media via gravitational force or by other means of applying positive and/or negative pressure. Positive pressure, for example, may be required if an ultra filtration media is selected. 
     Filter media support disc  16  is a circular disc with a disc recess  26  for receiving filter media  18 . Filter media support disc  16  also includes upper rim  30 , lower rim  32  (See  FIG. 5 ), and disc lip  28  for supporting disc  16  when placed on top of filtrate reservoir  14 . The structure of filter media support disc  16  in this embodiment provides a compression fitting between it and sample reservoir  20  on one side, and between it and filtrate reservoir  14  on the other side. 
     Disc recess  26  includes a plurality of apertures or holes, which may be round in cross-section, or any other shape, to allow the sample water to pass through filter media support disc  16  while still providing support to filter media  18  so that filter media  18  is held in place and does not fall or drop into filtrate reservoir  14  even when water is flowing through filter media  18 . 
     Filter media  18  is a made of a suitable filtration material that allows water to pass through, but prevents any solids in the water above a certain particulate size from passing through it. That is, the filtration material is preferably of a size exclusion type. Size exclusion filtration is required to orient the analyte of interest on the upper surface of the filtration media so as not to have the radioactive component shielded by the filtration media itself. Additionally, the material of the filtration media must be hydrophobic and non-hydroscopic in nature as the presence of water on the surface of and within the filtration media could shield the alpha and beta radiation emissions from the detection probe. The desired porosity of filter media  18  may be varied in the use of device  10  depending on the nature of the water sample collected. For example, in water samples containing ultra and very fine solid particulate matter, an ultra and very fine filter material is needed for filter media  18 . One suitable material for use as filter media  18  is sold under the trademark TEFLON, and other filter materials are well know in the art to which the invention pertains. 
     The shape of filter media  18  is such that it fits within disc recess  26  of filter media support disc  16 , covering all of the apertures in disc recess  26  such that the water sample must pass through filter media  18  as the water flows from sample reservoir  20  into filtrate reservoir  14 . 
     Sample reservoir  20  is a substantially hollow cylindrical shape with walls of suitable height and openings on both ends to provide a reservoir or basin for the water sample to be held in contact with filter media  18  so that it may flow through filter media  18  and into filtrate reservoir  14 , thus causing particulate solids that were in the water to be deposited on or within filter media  18 . The walls of sample reservoir  20  may be angled outward in the upward direction as shown in  FIGS. 1-2  for ease of filling with the water sample. 
     Turning to  FIG. 2 , the embodiment illustrated in the exploded view of  FIG. 1  is shown in its assembled condition. Base  12  includes base stabilization member  24  and lip  26 . Filter reservoir  14  rests atop base  12  with lip  26  forming a compression fitting with the bottom end of filtrate reservoir  14 . 
     Filter media support disc  16  is held between sample reservoir  20  and filtrate reservoir  14  by a compression fitting formed between it and sample reservoir  20  on one end, and it and filtrate reservoir  14  on the other end. The majority of the top surface of filter media support disc  16  is exposed through the opening of the bottom end of sample reservoir  20  such that filter media  18  (not shown) can be placed atop filter media support disc  16  covering the apertures within filter media support disc  16  with the filter material. Sample reservoir  20 , as illustrated, provides ample volume for holding a water sample in contact with filter media  18  (not shown) so that the water can flow through the filter media and into filtrate reservoir  14 . 
     Turning to  FIG. 3 , device  10  is shown with radiation probe adapter  34  for use with a conventional radiation probe  38  having a probe handle  40 . The bottom end of radiation probe adaptor  34  is sized to fit with the upper surface of filter media support disc  16  with sample reservoir  20  (not shown) removed. That is, in operation, sample reservoir  20  is removed and radiation probed adaptor  34  is put in its place. Alternatively, sample reservoir  20  may include features of radiation probe adapter  34  as described below such that the former serves as both a sample reservoir and radiation probe adapter. 
     Radiation probe adapter  34  may include notch  36  to accommodate probe handle  40 . Protruding rim  35  is provided to hold radiation probe  38  at a set distance above filter media  18 . This prevents physical contact between radiation probe  38  and any solid particulates that may be on the face of filter media  18 , as well as between radiation probe  38  and the filter media  18 . By providing a repeatable and consistent separation distance and orientation between radiation probe  38  and the solid particulates collected from the water sample on the face of filter media  18 , the measurements taken with radiation probe  38  are more accurate and precise than without this feature of the present invention. 
     Turning to  FIG. 4 , the embodiment illustrated in the exploded view of  FIG. 3  is shown in its assembled condition. Radiation probe  38  is held within device  10  by radiation probe adaptor  34 . Notch  36  accommodates probe handle  40 . The bottom of radiation probe adaptor  34  rests atop filter media support disk  16  and is held secure by a compression fitting between radiation probe adaptor  34  and filter media support disk  16 . As illustrated here, stabilization member  24  of base  12  is placed so that it is orientated in substantially the same direction as probe handle  40  in order to offset the overturning force or moment created by the weight of probe handle  40 . In a preferred embodiment, radiation probe adaptor  34  and filter media support disk  16  may accommodate an interlocking feature as provided by a male-female hole and plug. This would allow radiation probe adaptor  34  to sit with only one orientation such that probe handle  40  is oriented in the same direction as stabilization member  24 . 
     As illustrated and described, device  10  is thus self-standing and stable when resting on any flat surface even with an overturning force resulting from the weight of a probe handle. As apparent to those with ordinary skill in the art to which the invention pertains, radiation probe adaptor  34  may be made in a variety of shapes and sizes to accommodate different radiation probes. For example, the radiation probe may have a surface area larger than the diameter of filtrate reservoir  14  and filter media support disc  16 . In this case, the diameter of the upper portion of radiation probe adaptor  34  would be larger than illustrated here. As another example, in the situation where the particular radiation probe used with device  10  does not have a handle, or the handle is removed and there are no wires or other objects protruding from the side of the probe, notch  36  is not necessary. In addition, stabilization member  24  is not needed if there is no overturning moment to destabilize the device. 
     Turning to  FIG. 5 , a larger view of filter media support disc  16  is provided to further describe its features. Filter media support disc  16  includes disc recess  26  having a plurality of apertures, lip  28 , upper rim  30 , and lower rim  32 . Disc recess  26  is sized to accommodate filter media  18 . When filter media  18  is placed in disc recess  26 , the top surface of filter media  18  rests at an elevation below the top face of upper rim  30  and the material of filter media  18  covers all of the apertures within disc recess  26 . Lower rim  32  and disc lip  28  form a first compression fitting in this embodiment, which is used to connect filter media support disc  16  to filtrate reservoir  14 . Similarly, upper rim  30  and disc lip  28  form a second compression fitting in this embodiment, which is used to connect filter media support disc  16  to sample reservoir  20  or radiation probe adapter  34 , interchangeably and without the need for tools. 
     Having fully described the structural features and elements of the present invention, attention is now turned to a description of its operation. There are many ways in which the present invention may be used as a water sampling device with a radiation probe for measuring the radioactivity of particulate solids found in water samples. The following description is provided by way of one example. 
     Device  10 , with sample reservoir  20  inserted, is placed on a work surface which is relatively horizontal, flat, and stable. Such work surface may be a field-portable bench or table, or even the hood or bumper of a parked vehicle. Device  10  may also be used in a facility such as a laboratory where it can be placed on a laboratory bench or table. An aliquot of water is sampled and transferred into sample reservoir  20 . This can be done manually or by an automated system of tubing and control valves. 
     Once the water sample has been added to the sample reservoir  20 , gravity will cause the water to drain through filter media  18  and into filtrate reservoir  14 . The solid particulates in the water sample that cannot pass through filter media  18  because of size restriction will deposit on or within filter media  18 . Vacuum port  22  may be provided and utilized if a faster flow rate and shorter sample time are desired, or to overcome the filter bubble-point pressure. In such case, a vacuum source is attached to vacuum port  22  and the corresponding suction force increases the flow rate of water through filter media  18 . Once the water sample has drained out of sample reservoir  20  and through filter media  18 , one or more additional water samples may be added to sample reservoir  20 , or the sample reservoir may be removed to proceed to the next step. 
     With sample reservoir  20  removed, radiation probe adaptor  34  is placed on top of filter media support disk  16  where it is fits snuggly by way of the compression fitting described above. Radiation probe  38  is then placed inside of radiation probe adaptor  34  where it is held at a set distance and orientation from filter media  18  by protruding rim  35 . The orientation is such that the detection surface of radiation probe  38  is substantially parallel with and directly over filter media  18 , thus providing for a consistent, optimal application of radiation probe  38 . 
     After completing the radiation measurement, filter media  18  can be encapsulated by placing sample cap  46  over filtration media  18  and securing sample cap  46  to filter media support disc  16  by means of a compression fitting. A second sample cap may be provided to attach to the other side of filter media support disc  16 , also by means of a compression fitting, thus sealing access that the air would otherwise have to filter media  18  through the apertures within filter media support disc  16 . In this condition, the sample is preserved and may be transported or stored as desired. 
     While specific embodiments of the invention have been described, it will be understood that additional embodiments and various modifications may be made without departing from the spirit and scope of the invention. For example, the attachment means described in the preferred embodiment are compression fittings, but could be accomplished with threaded fittings or other coupling means. The parts of device  10 , aside from filter media  18 , can be made of a wide variety of impermeable or substantially impermeable materials, ranging from plastics and other polymers to metals and ceramics. Filter media  18  may be made of TEFLON or other filter media that are substantially inert, hydrophobic and non-hydroscopic, available in the desired shape, and allow water to pass freely while trapping solid particles on the surface of the filtration media. The suction means, which may be provided in some embodiments of the present invention, may be accomplished using a syringe, aspirator, or any type of mechanical vacuum pump. A pressurization means, which may be provided in some embodiments of the present invention, may be accomplished using various commercially available pumps, such as a positive displacement or plunger pump. The sample reservoir  20  may be of various shapes and sizes to accommodate the desired volume of sample. Similarly, the radiation probe adaptor  34  may be of different shapes and sizes to accommodate different radiation probes. Accordingly, these and other embodiments of the invention fall within the scope of the following claims.