Abstract:
Mobile apparatuses move within contaminated fluid to create fluid flows against structures that remove and prevent contaminant deposition on structure surfaces immersed in the fluid. Unsettling flows in water may exceed approximately 2 m/s for radionuclide particles and solutes found in nuclear power plants. Mobile apparatuses include pressurized liquid from a pump or pressurized source that can be chemically and thermally treated to maximize deposition removal. When spraying the pressurized liquid to create the deposition-removing flow, mobile apparatuses may be self-propelled within the fluid about an entire surface to be cleaned. Mobile apparatuses include filters keyed to remove the contaminants moved into the coolant by the flow, and by taking in ambient fluid, enable such filtering of the ambient fluid along with a larger flow volume and propulsion. Propulsion and the pressurized liquid in turn enhance intake of ambient fluid.

Description:
BACKGROUND 
       [0001]    As shown in  FIG. 1 , a nuclear power station conventionally includes a reactor pressure vessel  10  sealed within a containment structure  50  that houses several power-producing systems and equipment. Reactor  10  may include various configurations of fuel and reactor internals for producing nuclear power. For example, vessel  10  may include several fuel assemblies positioned within a general cylindrical core. Fluid coolant and/or moderator may flow through reactor  10 ; for example, in US light water reactors, the fluid may be purified water, in natural uranium reactors, the fluid may be purified heavy water, and in gas-cooled reactors, the fluid coolant may be a gas such as helium, with moderation provided by other structures. 
         [0002]    Vessel  10  may be sealed and opened through upper head  95  at flange  90 . As shown in  FIG. 1 , during plant fabrication and at regular service and/or refueling outages, upper head  95  may be removed and operators and/or equipment can access internals of vessel  10  inside of containment structure  50  for various purposes. For example, with access to the reactor internals, some of fuel bundle assemblies may be replaced and/or moved between within the core and a fuel staging or spent fuel pool area(s), and maintenance/installation on other reactor structures in containment  50  may be performed. 
         [0003]    During such maintenance, a refueling cavity  20  above flange  90  and surrounding reactor  10  may be filled, or flooded, with fluid coolant. The fluid coolant may both remove heat and block radiation from escaping to operators around cavity  20 , such as workers performing maintenance on operations floor  25  above cavity  20 . With such shielding, refueling cavity  20  may be used for storage of radioactive structures and a staging area for fuel handling, as well as a general interface for access into reactor  10 . 
         [0004]    Refueling bridge  1  with mast  3  and grapple  4  are useable during outages with access to reactor vessel  10  to perform fuel offloading, reloading, shuffling, and/or maintenance. Refueling bridge  1  may be positioned on operations floor  25  above or about flange  90  when reactor vessel  10  is opened. Bridge  1  may include a trolley  2  capable of rotating and/or laterally moving to any horizontal or vertical position. Trolley  2  may include a refueling mast  3  with hoist box and grapple  4  that descend into reactor  10  and perform fuel and other structure movements throughout cavity  20  during outages. 
         [0005]    At other outage periods and during operations, cavity  20  may be drained completely or partially (such as down to flange  90 ). Because cavity  20  may have previously been flooded with fluid coolant before such draining, residues from and particulates in the fluid coolant may adhere to cavity surfaces, including cavity walls  21 . These remnants from the fluid may be undesirable—such as radioactive or chemically corrosive—for operating conditions within cavity  20 , on operations floor  25 , and/or anywhere throughout containment building  50 . As such, operators sometimes take measures to reduce particulates and impurities in any fluid that fills cavity  20 . For example, plant operators may add solvents or otherwise change coolant chemistry to reduce deposition on surfaces drained of coolant and/or may use submersible, stationary filters on a floor of cavity  20 . For example, underwater filters from Tri Nuclear Corporation may sit on a bottom of cavity  20  and filter or demineralize fluid in cavity  20 . 
       SUMMARY 
       [0006]    Example embodiments and methods reduce settling of unwanted materials out of a fluid onto structures by causing a flow around the structures. Example embodiments use a fluid source and discharge the fluid from the source against the structure in the fluid. The discharged fluid flow and ambient fluid surrounding the structure may be the same or different. For example, both fluids may be water, but the ambient fluid may have unwanted particulate or dissolved contaminates in it, whereas the sprayed fluid might be filtered and/or chemically treated to help remove the unwanted materials from the structures. Example embodiments and methods may use a flow rate of approximately 2 meters per second or more, which is effective in several types of water to prevent deposition out of the water onto surfaces. The flow rate may be created by a pressurized fluid source and/or a local pump, and the jetted fluid may come from the same volume surrounding the structure, but with optional filtering, temperature adjustment, and/or chemical treatment, for all or a portion of the fluid jet. 
         [0007]    Example embodiments may be wholly submerged in the fluid and still operate, using the flow discharge to move in the fluid to spray different desired surfaces, as well as other movement methods like changing buoyancy. Example embodiment systems may also work with portions in the fluid and other portions outside the fluid. For example, a multi-stage filter may be fitted inside a mobile assembly and submerged in coolant water in a flooded cavity, where the water is passed through the filter and dispersed to create the 2 m/s rate by an induction pump. Alternatively or additionally, another filter and pump may suck the water coolant from the cavity and feed it through a base outside the cavity where the water is treated chemically and thermally and delivered back into the cavity to be sprayed at deposition surfaces. With proper buoyancy, sizing, and spray discharge, any submerged mobile assembly may move between or to desired surfaces to be cleaned. 
         [0008]    Multi-stage filters useable with example embodiments may remove a variety of contaminants, including metallic conjugates specifically liberated by the water chemistry of the flow. Example embodiment filters may include coarse reservoirs, fibrous filters, charged particles, sintered metallics, resins, etc. in several different stages that are independently removable and disposable. 
     
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         [0009]    Example embodiments will become more apparent by describing, in detail, the attached drawings, wherein like elements are represented by like reference numerals, which are given by way of illustration only and thus do not limit the terms which they depict. 
           [0010]      FIG. 1  is an illustration of a related art nuclear reactor containment structure interior with refueling cavity. 
           [0011]      FIG. 2  is an illustration of an example embodiment flow inducer system. 
           [0012]      FIG. 3  is an illustration of an example embodiment mobile assembly. 
           [0013]      FIG. 4  is an illustration of an example embodiment base. 
           [0014]      FIG. 5  is an illustration of an example embodiment filter. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    This is a patent document, and general broad rules of construction should be applied when reading and understanding it. Everything described and shown in this document is an example of subject matter falling within the scope of the appended claims. Any specific structural and functional details disclosed herein are merely for purposes of describing how to make and use example embodiments or methods. Several different embodiments not specifically disclosed herein fall within the claim scope; as such, the claims may be embodied in many alternate forms and should not be construed as limited to only example embodiments set forth herein. 
         [0016]    It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
         [0017]    It will be understood that when an element is referred to as being “connected,” “coupled,” “mated,” “attached,” or “fixed” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.). Similarly, a term such as “communicatively connected” includes all variations of information exchange routes between two devices, including intermediary devices, networks, etc., connected wirelessly or not. 
         [0018]    As used herein, the singular forms “a”, “an” and “the” are intended to include both the singular and plural forms, unless the language explicitly indicates otherwise with words like “only,” “single,” and/or “one.” It will be further understood that the terms “comprises”, “comprising,”, “includes” and/or “including”, when used herein, specify the presence of stated features, steps, operations, elements, ideas, and/or components, but do not themselves preclude the presence or addition of one or more other features, steps, operations, elements, components, ideas, and/or groups thereof. 
         [0019]    It should also be noted that the structures and operations discussed below may occur out of the order described and/or noted in the figures. For example, two operations and/or figures shown in succession may in fact be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Similarly, individual operations within example methods described below may be executed repetitively, individually or sequentially, so as to provide looping or other series of operations aside from the single operations described below. It should be presumed that any embodiment having features and functionality described below, in any workable combination, falls within the scope of example embodiments. 
         [0020]    The inventors have recognized that existing coolant cleanup in nuclear power facilities, focusing on ion removal from reactor coolant with stationary scrubbers in a flooded cavity and/or through existing coolant clean-up filters, resins, and deionizers in combination with adjusting coolant chemical properties to decrease particulate deposition, does not fully remove complexed metal ions present as particulates in reactor coolant. This is especially problematic with metallic radioisotopes like Cobalt, Cesium (particularly in the case of a fuel rod leak), and Zinc, which readily complex with Iron to form particulates that deposit on flooded surfaces and cannot be effectively removed with conventional mechanical and chemical remediation measures. These radioisotopes deposited on flooded surfaces generally remain over time and can become airborne upon dry-out, presenting a significant radiation dose contribution to personnel and equipment in the areas during and after flooding, as well as serving as a reservoir for future coolant contamination when disturbed from the surfaces by re-flooding. 
         [0021]    The inventors have recognized that radioactive, complexed metallic particulates that have deposited on plant surfaces during contact with coolant may be removed through fluid-mechanical action. On deposition surfaces, particulates are generally not exposed to higher fluid flows because of the nature of the boundary layer adjacent to a stationary surface formed in a reactor coolant like water. However, by causing fluid flows of sufficient velocity, the metallic particulates can be removed from the surface and prevented from re-depositing on the surface. Thus, by moving coolant at a sufficient transport velocity at deposition surfaces, metallic particulates may be kept in the coolant where they can be removed through conventional scrubbing and/or additional filtering, preventing them from depositing and increasing radiation exposure. 
         [0022]    In order to discover the necessary transport velocity to avoid the newly-recognized fluid-dynamic solution to radioisotope deposition, the inventors looked to Poirier, “Minimum Velocity Required to Transport Solid Particles from the 2H-Evaporator to the Tank Farm” US DoE Technical Report WSRC-TR-2000-00263, Sep. 27, 2000, incorporated by reference herein in its entirety, as a reference for particulate transport velocities in closed systems. Repurposing the transport and settling velocity calculations from the Poirier report for open systems with the density characteristics of Cobalt particulates and using typical diameters of such particulates to derive Reynolds numbers in the solutions, the inventors discovered that a flow rate of about 2 meters per second inhibited deposition of particulates up to 5 millimeters in diameter. This rate is well below the expected necessary rate for particulate transport speed, especially in light of its use in an open system and compared to the velocities in the Poirier report. 
         [0023]    The inventors further recognized that movement of fluid at speeds well below 2 m/s at deposition surfaces results in high levels of settling of radioactive particulates. The below disclosure uniquely overcomes these and other problems, by leveraging systems and methods that move particulate-bearing fluid at calculated speeds near or above 2 m/s, sufficient to prevent settling of radioactive contaminants on these surfaces. 
         [0024]    The present invention is systems and methods of reducing and/or preventing unwanted depositions on surfaces by creating fluid flows on those surfaces above a settling velocity of the unwanted substances. In contrast to the present invention, the few example embodiments and example methods discussed below illustrate just a subset of the variety of different configurations that can be used as and/or in connection with the present invention. 
         [0025]      FIG. 2  is an illustration of an example embodiment flow inducer system  100  usable to prevent particulate settling on surfaces in fluid coolant, including preventive radioactive particle deposition on structures immersed in fluids bearing the same. As shown in  FIG. 2 , system  100  may include a base  120  positioned about or above a reactor  10 . For example, inducer system  100  may be positioned about flange  90  of reactor  10  during a maintenance outage in which an upper head of reactor  10  is removed for access to the fuel core and reactor internals. Example embodiment system  100  includes a mobile assembly  150  that can extend down into reactor  10  and into coolant therein, via a connection  101 . In this way, example embodiment flow inducer system  100  may include components and/or operations interfaces in base  120 , such as electrical power connections, user interfaces, purified coolant sources, external movement structures, etc., that function best outside of coolant, while mobile assembly  150  induces flow in coolant in which it is immersed and remote from base  120 . Alternatively, it is understood that base  120  may be combined into mobile assembly  150  to provide a unitary structure for inducing flow and preventing particulate deposition on surfaces exposed to coolant or other particulate contaminant-bearing fluids. 
         [0026]    Mobile assembly  150  causes coolant flow of approximately 2 meters per second or more to be directed to desired surfaces. Mobile assembly  150  is moveable within the coolant along surfaces and in spaces containing the same to prevent deposition at several positions. For example, as shown in  FIG. 2 , mobile assembly  150  may move vertically along connection  101  to reach several different axial positions of a wall of reactor  10 . Similarly, mobile assembly  150  may move radially or angularly with proper forces to any other surface at which an induced flow may be desired to reduce deposition. A track  190  or other movement path, such as one provided via crane or other locomotive structures, may be provided about flange  90  to permit angular movement of base  120  as well. Similarly, track  190  could be positioned on an operations floor  25  or other area to provide desired movement and/or positioning of example embodiment flow inducer system  100 . 
         [0027]    Although example embodiment flow inducer system  100  is shown in  FIG. 2  about a reactor  10  at flange  90 , it is understood that inducer  100  may be installed at other locations. For example, a base  120  could be positioned on a containment operations floor  25  ( FIG. 1 ), with mobile assembly  150  extending into and moving within a cavity  20  ( FIG. 1 ). Or, for example, system  100  may be used in a spent fuel pool or new fuel staging area within a nuclear power plant. Still further, example embodiment flow inducer system  100  may be used in any system with fluid contamination removable through fluid flow. 
         [0028]      FIGS. 3 and 4  are illustrations of portions of example embodiment flow inducer systems, with  FIG. 3  illustrating in detail an example embodiment mobile assembly and  FIG. 4  illustrating in detail an example embodiment base. As such, the components of  FIG. 3  could be useable as or with mobile assembly  150  of  FIG. 2 , and components of  FIG. 4  could be useable as or with base  120  of  FIG. 2 . Or example embodiments of  FIGS. 3 and 4  may be used separately or with different systems or combined into a single mobile system, for example. 
         [0029]    As shown in  FIG. 3 , an example embodiment mobile assembly  300  may include a variety of components to create a deposition-reducing coolant flow against several different surfaces in a volume of coolant fluid. Assembly  300  may be connected to a guide or movement arm for positioning. For example, a wire, pole, or removably fixed rod  301  may span an axial depth of a refueling cavity  20  or other space, and example embodiment assembly  300  may connect to rod  301  through a movable connector  302  like a keyhole, loop, or grommet that permits only axial movement of assembly  300  along fixed rod  301 . Rod  301  may connect to other components outside of cavity  20 , such as a base  120  including coolant supply  354 , electrical supply  358 , etc., or rod  301  may be used in isolation. 
         [0030]    Coolant supply  354  may be coupled with pole  301  or otherwise supplied to mobile assembly  300 . Coolant supply  354  may provide additional volume of coolant or other compatible fluid for creating induced flow for removing particulates. For example, if coolant is deionized or borated light water, coolant supply  354  may supply matching water. Coolant supply  354  may also provide relatively cleaner fluid as well as chemically-treated and temperature-moderated fluid for optimal contaminate clean-up. For example, coolant supply  354  may provide relatively colder water treated with a weak acid and/or oxidizer to enhance particulate solubility and removability by filters. Coolant supply  354  may also provide coolant for inducing fluid flow at a higher or operating pressure for example embodiment mobile assembly  300 . Coolant supply  354  may feed directly into assembly  300  or connect via a coolant supply connection  355 , which may be tubing or an injector, for example. 
         [0031]    Example embodiment mobile assembly  300  may also include a pump  344  or other hydrodynamic flow-inducing structure. For example, pump  344  may be an inductive jet pump, a centrifugal pump, a hydraulic pump, etc. Pump  344  may be locally powered through batteries or may be connected to an external, remote power source, such as electrical supply  358  via rod  301 . Although pump  344  may be omitted with sufficient pressure and flow shaping from coolant supply  354  to create desired coolant flows, pump  344  may be used with a pressurized coolant supply  354  or without coolant supply  354 . 
         [0032]    Example embodiment mobile assembly  300  may use fluid provided from coolant supply  354  and/or coolant from cavity  20  to create a flow directed at desired surfaces, such as cavity wall  21 . In the example of  FIG. 3 , assembly  300  uses both provided and ambient coolant fluid in creating a flow  352 . For example, lower-temperature coolant from coolant supply  354  may enter an upper manifold  356  and flow down through a series of tubes and/or baffles in a heat exchanger  357 . The coolant may flow into a lower collection manifold  358  from the tubes and into a final section of coolant supply connection  355 , which may be a flexible tube or injection device. Pump  344  then pressurizes and accelerates the coolant, potentially through a nozzle and/or diffuser, into an induced flow  352  against surfaces  21 . 
         [0033]    Additionally, ambient coolant from cavity  20  may be taken in through a top inlet  353  and passed through an internal filter  350  around heat exchanger  357 . Internal filter  350  may filter out impurities and dislodged/dissolved radionuclide depositions from ambient coolant taken from cavity  20 , permitting relatively cleaner induced fluid flows. An example embodiment filter useable as filter  350  is discussed in connection with  FIG. 5 . If coolant from coolant supply  354  is colder than coolant in cavity  20 , natural convection from the lower-temperature coolant in heat exchanger  357  may aid in driving ambient coolant from cavity  20  into inlet  353  and internal filter  350 . Ambient coolant, after being filtered through internal filter  350 , may connect to pump  344  through an ambient coolant connector  345 . 
         [0034]    Pump  344  may entrain ambient coolant from ambient coolant connector  345  with any accelerated coolant provided from coolant supply  354  via coolant supply connection  355 . With the use of a proper flow path, potentially including a diffuser, accelerated coolant from pump  344  may provide a suction to ambient coolant connector  345 , drawing additional ambient coolant into inlet  353  and through filter  350 . For example, with proper pump power and flow path, coolant may be drawn from ambient coolant at a 2-to-1 ratio of coolant from coolant supply  354 . 
         [0035]    Although example embodiment mobile assembly  300  uses both provided coolant and ambient coolant to create a coolant flow with a pump, it is understood that other combinations are useable in example embodiments. For example, only a pressurized coolant source and nozzle may be used to generate a desired coolant flow without a pump or filter. Or, for example, only a locally-powered pump and ambient coolant may be used to create coolant flows without need for external sources. Or, as shown in  FIG. 3 , all systems may be used together. 
         [0036]    Induced coolant flow  352  is ejected or discharged under the force of pump  344  and potentially a nozzle or diffuser at any desired velocity. For example, with proper pump power and/or flow path narrowing, coolant flow  352  may be  2  m/s or greater, resulting in desired deposition preventing and removing discussed above. Coolant flow  352  may be directed at various surfaces desired to be keep free from radionuclide deposition while immersed in coolant, such as cavity wall  21 . 
         [0037]    Example embodiment mobile assembly  300  may also be moveable, axially or otherwise, due to coolant flow  352 . For example, if the coolant is light water in a flow  352  into a flooded cavity  20  of the same, sufficient force may be generated by flow  352  on assembly  300  to move assembly  300  upward along pole  301 , even with flow  352  at only a slight downward angle. Flow  352  may be redirected and/or changed in intensity to create desired upward or downward movement of mobile assembly  300  along pole  301 , potentially reaching an entire axial length of a surface positioned nearby under only the forces generated by coolant flow  352 . Similarly, gravity and buoyancy may be used to selectively move example embodiment mobile assembly  300  in a sufficiently dense coolant like water, alone or in combination with forces from flow  352 , as well as other movement structures and forces. Sufficient upward movement axially may also enhance ambient coolant flow into inlet  353  for filtering, if used. 
         [0038]    As shown in  FIG. 4 , an example embodiment base  400  may include a variety of components to treat and provide fluid coolant to, and potentially move and control, a mobile assembly for creating flow. Example embodiment base  400  may be positioned near or above a coolant-filled space to be jetted or exposed to deposition-removing flows by mobile assembly  150 , such as refueling cavity  20  for example. Or base  400  may be more distantly located, potentially spread among several different facilities, or a component within mobile assembly  150 . 
         [0039]    Coolant may be provided to base  400  from any source, including a flooded cavity  20 , coolant reserve, plant feedwater, local taps, etc. For example, a suction filter  410  may be immersed in coolant in cavity  20 , and coolant may be drawn into base piping  411  through filter  410  by a pump  413 . Filter  410  may effectively remove radionuclides in solution or as particulates in coolant. For example, filter  410  may be similar to example embodiment filter  500  discussed in connection with  FIG. 5  useable in an example embodiment mobile assembly  300 . Piping  411  may be any transport path capable of carrying fluid coolant, including plastic tubing and metal pipes. Pump  413  may be any type of fluid-motive device, including those designs useable as pump  344  ( FIG. 3 ) in an example embodiment mobile device as well as larger or non-submergible pumps that work outside of a coolant. 
         [0040]    Example embodiment base  400  may include several components for creating optimal coolant to supply to mobile assembly  150 , including optimal cleanliness, optimal temperature, and/or optimal chemistry. For example, a heat exchanger  412  may be placed along piping  411  at any point to substantially reduce a temperature of coolant, such that coolant provided to mobile assembly  150  is lower than ambient coolant temperature and can be used for natural convective movement and/or reduce deposition potential with lower temperature. And, for example a chemical injector system  420  may be installed along piping  411  to provide desired pH, buffering, oxidation, oxygenation, boration, surfactant, clarity, salinity, replacement cations, and/or resin concentration, etc. to coolant. 
         [0041]    As shown in  FIG. 4 , an example of a chemical injector system  420  may include a venturi  421  installed along piping  411 . The low-pressure pinch point of venturi  421  may provide a suction for chemicals to be injected into the coolant at that point when a stop valve  422  is opened. Similarly, an injector or flow mixer may be used for venturi  421  to provide desired additions to coolant. Beyond stop valve  422  may be several different additive tanks with their own stop valves to control specific types of additives. For example, a pre-oxidizer, such as hydrogen peroxide, may be held in tank  424  by valve  423 , and a dilute acid, such as a relatively weaker nitric acid, may be held in tank  426  by valve  425 . 
         [0042]    By mixing the components of tanks  424  and  426  in desired proportions and total amounts through valves  423 ,  425 , and  422 , water used as coolant may include a dilute acid that catalyzes or accelerates oxidation reactions within surfaces exposed to induced flows including the acid. Local water coolant pH in the range of 5-6 can be maintained near such surfaces to in this way, facilitating metallic deposition removal and dissolution. Metal-enriched oxides on the surfaces can further be oxidized by hydrogen peroxide in the water coolant to a soluble ion, such as oxidizing chromium-based oxides to soluble chromates, under these conditions. Radionuclides in the oxides may thus be more readily removed through filters in example embodiment systems as well as in existing coolant cleanup systems. Of course, other desired chemicals may be injected through any number of different tanks to achieve desired coolant flow chemistry. 
         [0043]    Example embodiment base  400  may connect to a mobile assembly  150  through connection  101 , providing treated coolant at a desired pressure for use in creating a flow to prevent particulate settling. Similarly, electrical power, operator instructions, and/or relocation/locomotion may be provided through connection  101  from base  400 . 
         [0044]      FIG. 5  is an illustration of an example embodiment filter  500  useable as filter  350  in example embodiment mobile assembly  300  ( FIG. 3 ) and/or base filter  410  ( FIG. 4 ). As shown in  FIG. 5 , filter  500  may include several different layers configured to filter out unwanted coolant impurities, including radionuclides in a metallic complexes dissolved in the coolant, potentially after being removed from a surface deposition in the coolant by example embodiment systems. The layers may be discreetly staged or progressive to filter finer and finer contaminants. 
         [0045]    For example, just below inlet  353  ( FIG. 3 ), may be a coarse reservoir  534  with wide-pitch filters to stop macro objects like filings, paint chips, fasteners, rags, etc. that often fall into coolant spaces during maintenance. A fibrous filter  533  may be next with denser mesh or fibrous layers that catch large particulates in the coolant. Below may be a charged bed  532  of a material with an electrostatic potential, like a sand or fine gravel with varying surface ions or charged polymer chains, that attracts and holds smaller corrosion particles out of the coolant passing therethrough. A metallic filtering bed  531  may be placed next with sintered or finely-porous corrugated metallic sheets. 
         [0046]    Finally a resin bed  530  may be captured between two screens  529  and  528 . Resin bed  530  may be a non-soluble ionized resin, like those used in conventional nuclear power coolant polishing and cleanup systems. These resins may include known products like Amberlyte, cross-linked polystyrenes, and Amberjet. Resin bed  530  may be specifically matched to capture known metallic complexes released into coolant following exposure of a contaminated surface to a flow rate of a transport velocity. Screens  529  and  528  may be sufficiently fine to prevent resin from migrating out of filter  500  while allowing clean coolant to freely pass. A backup screen  527  may be below screen  528  to prevent escape of resin  530  in the case of failure of screen  528 . 
         [0047]    Coolant may flow through each filter stage  534 ,  533 ,  532 ,  531 , and  530  progressively, into collector  526 , which may drain into an outlet, like coolant supply line  345  ( FIG. 3 ) or piping  411  ( FIG. 4 ), for example. In the instance of coolant supply line  345  in an example embodiment filter  300  of  FIG. 3 , suction from an induction pump may be sufficiently large to overcome pressure drop across each layer, driving and filtering coolant through filter  500  in sufficient volumes to create a larger, combined and clean induced flow of at least 2 m/s. In this way an induced flow may not only reduce radionuclide particulate depositions on surfaces immersed in coolant, but it may also propel a mobile assembly cleaning the same and filter coolant through the mobile assembly near an area likely to have much coolant contaminate to be intercepted through example embodiment filters. 
         [0048]    Example embodiment filter  500  may be constructed in a manner that permits easy assembly/disassembly and minimizes additional handling of potentially radioactive components post-use. For example, each stage  534 ,  533 ,  532 ,  531 , and  530  may be contained in a resilient filter segment with exterior flanges  501  around a perimeter of each segment end. Each flange  501  may seal against an adjacent flange between adjacent segments with a quick release  502  like a buckle or fastener that allows individual segments to be easily removed for cleaning and/or disposal at flanges  501 . Flanges  501  and releases  502  may be compatible with high integrity disposal systems in shape and joining structure to permit direct disposal of used, dirty filter elements from a filter segment. Further, flanges  501  may accommodate additional shielding and/or flotation rings to be added to filter  500 . For example, a dense shielding ring, such as one made out of tungsten, may be added to surround filter  500  and sit against flanges  501  to minimize exposure during handling. Similarly, a buoyant floatation ring may pass around a segment of filter  500  under a flange  501  and change buoyancy of filter  500  and example embodiment mobile assembly  300  ( FIG. 3 ) to allow desired buoyancy and movement in coolant. 
         [0049]    Example embodiment system  100 , including a base  120  and/or mobile assembly  150  and their example embodiment components  300 ,  400 ,  500 , may be configured to operate in a nuclear reactor environment. For example, all structural components in example embodiment base  400  and example embodiment mobile assembly  300  may be fabricated of materials designed to substantially maintain their physical characteristics when exposed to radiation, variable temperatures, and caustic environments encountered in nuclear reactors. Similarly, materials used in example embodiments may be of a reliable quality for failure avoidance in probabilistic risk assessment determinations and may be designed to minimize radionuclide particulate or solute entrainment or adsorption to minimize radioactive contamination and cleanup requirements post-use. 
         [0050]    Example embodiments can be used in a variety of ways to prevent particulate deposition on surfaces immersed in a fluid. For example, in a nuclear power plant, like a BWR, ESBWR, PWR, CANDU, or ABWR, areas, like a refueling cavity or chimney, may be flooded with water coolant during operations and/or maintenance, and example embodiment systems may be installed in such areas to induce coolant water flow of about 2 meters per second against surfaces in the coolant. This may be achieved with an example embodiment mobile assembly creating the flow while immersed in the coolant. Operators may configure and direct example embodiments to specifically position flows about surfaces for deposition removal in the coolant. Example embodiments may also provide active filtering of coolant water in the direct vicinity of the flow that dislodges particulate deposition from the surfaces. Example embodiments may further provide water chemistry with deposition-removing and -dissolving pH, oxidation, replacement cations, etc. By keeping depositions from coolant off of surfaces, radionuclides may not easily remain on submerged surfaces or later become airborne when the surfaces are dried during other operations. 
         [0051]    Example embodiments and methods thus being described, it will be appreciated by one skilled in the art that example embodiments may be varied and substituted through routine experimentation while still falling within the scope of the following claims. For example, a fluid like light water reactor coolant may be used to create a flow against surfaces in some embodiments, but other fluids, like heavy water, are equally useable in example embodiments. Although example embodiments are shown in parts of a base, mobile assembly, and filter, it is understood that these parts may be combined in a unitary submersible and/or further divided or omitted entirely depending on desired functionality. A variety of different reactor and reactor designs and radwaste management structures are compatible with example embodiments and methods simply through proper dimensioning. All such changes fall within the scope of the following claims, and such variations are not to be regarded as departure from the scope of the following claims.