Abstract:
Systems and methods permit discriminate access to nuclear reactors. Systems provide penetration pathways to irradiation target loading and offloading systems, instrumentation systems, and other external systems at desired times, while limiting such access during undesired times. Systems use selection mechanisms that can be strategically positioned for space sharing to connect only desired systems to a reactor. Selection mechanisms include distinct paths, forks, diverters, turntables, and other types of selectors. Management methods with such systems permits use of the nuclear reactor and penetration pathways between different systems and functions, simultaneously and at only distinct desired times. Existing TIP drives and other known instrumentation and plant systems are useable with access management systems and methods, which can be used in any nuclear plant with access restrictions.

Description:
PRIORITY STATEMENT 
     This application is a continuation-in-part of, and claims priority under 35 U.S.C. §120 to, co-pending application Ser. No. 13/477,244 filed May 22, 2012, the contents of said application being incorporated by reference herein in their entirety. 
    
    
     GOVERNMENT SUPPORT 
     This invention was made with Government support under contract number DE-FC52-09NA29626, awarded by the U.S. Department of Energy. The Government has certain rights in the invention. 
    
    
     BACKGROUND 
     Elements, and specific isotopes thereof, may be formed by bombarding parent materials with appropriate radiation to cause a conversion to desired daughter isotopes. For example, precious metals and/or radioisotopes may be formed through such bombardment. Conventionally, particle accelerators or specially-designed, non-commercial test reactors are used to achieve such bombardment and produce desired isotopes in relatively small amounts. 
     Radioisotopes have a variety of medical and industrial applications stemming from their ability to emit discreet amounts and types of ionizing radiation and form useful daughter products. For example, radioisotopes are useful in cancer-related therapy, medical imaging and labeling technology, cancer and other disease diagnosis, and medical sterilization. 
     Radioisotopes having half-lives on the order of days or hours are conventionally produced by bombarding stable parent isotopes in accelerators or low-power, non-electricity-generating reactors. These accelerators or reactors are on-site at medical or industrial facilities or at nearby production facilities. Especially short-lived radioisotopes must be quickly transported due to the relatively quick decay time and the exact amounts of radioisotopes needed in particular applications. Further, on-site production of radioisotopes generally requires cumbersome and expensive irradiation and extraction equipment, which may be cost-, space-, and/or safety-prohibitive at end-use facilities. 
     SUMMARY 
     Example embodiments include systems and methods for allowing access to nuclear reactor internals between multiple systems, such as irradiation target loading/offloading systems, instrumentation systems, and other external systems that may need access to the reactor during operations or times of general inaccessibility. Example systems provide penetration pathways to the reactor from exterior, accessible points. Example systems further permit users and operators to selectively allow/disallow such access among several systems. For example, an example embodiment system can use any type of selection mechanism to connect only desired systems into a penetration pathway accessing the reactor, while blocking other systems from the same access. Such selective management of access may permit multiple, simultaneous use of the nuclear reactor and penetration pathways between different systems and functions. For example, instrumentation delivery and measurement in instrumentation tubes may be performed simultaneously with irradiation target irradiation in a core of the reactor, when such targets are separately deliverable and harvestable through a selection mechanism. Such management may reduce or prevent interference between multiple systems and uses, while ensuring that accidental or harmful access to a nuclear reactor during access-limited times is reduced or prevented. 
    
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
       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. 
         FIG. 1  is an illustration of a conventional commercial nuclear reactor. 
         FIG. 2  is an illustration of an example embodiment irradiation target system with a system selector in a target loading configuration. 
         FIG. 3  is an illustration of an example embodiment system selector. 
         FIGS. 4   a  &amp;  4   b  are illustrations of an example embodiment system selector in various configurations. 
         FIG. 5  is an illustration of an example embodiment system selector. 
     
    
    
     DETAILED DESCRIPTION 
     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. Several different embodiments not specifically disclosed herein fall within the scope of the appended claims; 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. 
     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. 
     It will be understood that when an element is referred to in a spatial or physical relationship, 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, for example, 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. 
     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 terms like “have,” “having,” “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. 
     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. 
       FIG. 1  is an illustration of a conventional nuclear reactor pressure vessel  10  usable with example embodiments and example methods. Reactor pressure vessel  10  may be, for example, a 100+ MWe commercial light water nuclear reactor conventionally used for electricity generation throughout the world. Reactor pressure vessel  10  is conventionally contained within an access barrier  411  that serves to contain radioactivity in the case of an accident and prevent access to reactor  10  during operation of the reactor  10 . As defined herein, an access barrier is any structure that prevents human access to an area during operation of the nuclear reactor due to safety or operational hazards such as radiation. As such, access barrier  411  may be a containment building sealed and inaccessible during reactor operation, a drywell wall surrounding an area around the reactor, a reactor shield wall, a human movement barrier preventing access to instrumentation tube  50 , etc. 
     A cavity below the reactor vessel  10 , known as a drywell  20 , serves to house equipment servicing the vessel such as pumps, drains, instrumentation tubes, and/or control rod drives. As shown in  FIG. 1  and as defined herein, at least one instrumentation tube  50  extends into the vessel  10  and near, into, or through core  15  containing nuclear fuel and relatively high levels of neutron flux and other radiation during operation of the core  15 . As existing in conventional nuclear power reactors and as defined herein, instrumentation tubes  50  are enclosed within vessel  10  and open outside of vessel  10 , permitting spatial access to positions proximate to core  15  from outside vessel  10  while still being physically separated from innards of the reactor and core by instrumentation tube  50 . Instrumentation tubes  50  may be generally cylindrical and may widen with height of the vessel  10 ; however, other instrumentation tube geometries may be encountered in the industry. An instrumentation tube  50  may have an inner diameter of about 1-0.5 inch, for example. 
     Instrumentation tubes  50  may terminate below the reactor vessel  10  in the drywell  20 . Conventionally, instrumentation tubes  50  may permit neutron detectors, and other types of detectors, to be inserted therein through an opening at a lower end in the drywell  20 . These detectors may extend up through instrumentation tubes  50  to monitor conditions in the core  15 . Examples of conventional monitor types include wide range detectors (WRNM), source range monitors (SRM), intermediate range monitors (IRM), and traversing Incore probes (TIP). Access to the instrumentation tubes  50  and any monitoring devices inserted therein is conventionally restricted to operational outages due to containment and radiation hazards. 
     Although vessel  10  is illustrated with components commonly found in a commercial Boiling Water Reactor, example embodiments and methods are useable with several different types of reactors having instrumentation tubes  50  or other access tubes that extend into the reactor. For example, Pressurized Water Reactors, Heavy-Water Reactors, Graphite-Moderated Reactors, etc. having a power rating from below 100 Megawatts-electric to several Gigawatts-electric and having instrumentation tubes at several different positions from those shown in  FIG. 1  may be useable with example embodiments and methods. As such, instrumentation tubes useable in example methods may be at any geometry about the core that allows enclosed access to the flux of the nuclear core of various types of reactors. 
     Applicants have recognized that instrumentation tubes  50  may be useable to relatively quickly and constantly generate short-term radioisotopes on a large-scale basis without interfering with an operating or refueling core  15 . Applicants have further recognized a need to generate short-term radioisotopes and remove them from within access barrier  411  quickly, without having to shut down an operating nuclear reactor to access an area within access barrier  411 . Example methods include inserting irradiation targets into instrumentation tubes  50  and exposing the irradiation targets to the core  15  while operating or producing radiation, thereby exposing the irradiation targets to the neutron flux and other radiation commonly encountered in the operating core  15 . The core flux over time converts a substantial portion of the irradiation targets to a useful mass of radioisotope, including short-term radioisotopes useable in medical applications. Irradiation targets may then be withdrawn from the instrumentation tubes  50 , even during ongoing operation of the core  15 , and removed for medical and/or industrial use. 
     Applicants have further recognized a need for a maximized amount of radioisotope production within instrumentation tubes  50 , but also identified that such need is limited by relatively few and sensitive pathways through access barrier  411  during operation. Such pathways through access barrier  411  may require compatibility with existing instrumentation, including TIP probes that are inserted into instrumentation tubes  50  during TIP runs. Example embodiments and methods address this problem by permitting irradiation targets  250  to be inserted into and removed from instrumentation tubes  50  from a first access point, while reliably permitting TIP tubes to be inserted and removed at other instances from the instrumentation tubes  50  from a second access point. In this way, multiple operations and use of instrumentation tubes  50  can be safely achieved in an access-sensitive environment such as a nuclear power plant. 
       FIG. 2  is a schematic drawing of an example embodiment irradiation target delivery and retrieval system  1000  having a penetration pathway, a loading/offloading system, and a drive system.  FIG. 2  illustrates various components of example system  1000  in a loading configuration, parts of which are also described in US Patent Publication 2013/0170927, titled “Systems and Methods for Processing Irradiation Targets Through a Nuclear Reactor,” filed Dec. 28, 2011, said application incorporated by reference herein in its entirety. As shown in  FIG. 2 , example embodiment irradiation target delivery and retrieval system  1000  may include or use one or more elements to facilitate irradiation target loading, irradiation, and harvesting in a timely, automatic, and/or consumption-enhancing manner. System  1000  includes a penetration pathway that provides a path from outside access barrier  411  to instrumentation tube  50  for one or more irradiation targets, a loading/offloading system that permits new irradiation targets to be inserted and irradiated targets to be harvested outside access barrier  411 , and a drive system that moves irradiation targets between instrumentation tube  50  and loading/offloading in example embodiment system  1000 . 
     A penetration pathway in example embodiment system  1000  provides a reliable path of travel for irradiation targets  250  between an accessible location, such as an offloading or loading area outside access barrier  411  into one or more instrumentation tubes  50 , so irradiation targets  250  can move within the pathway to a position in or near an operating nuclear core  15  for irradiation. Example pathways can include many delivery mechanisms used alone or in combination, including tubing, frames, wires, chains, conveyors, etc. in example embodiment system  1000  to provide a transit path for an irradiation target between an accessible location and an operating nuclear core. As a specific example shown in  FIG. 2 , a penetration pathway may include penetration tubing  1100 , including  1100   a  and  1100   b , running between, either in portions or continuously, a loading junction  1200  and instrumentation tube  50  in a nuclear reactor. 
     Penetration tubing  1100  may be flexible or rigid and sized to appropriately permit irradiation targets  250  to enter into and/or through penetration tubing  1100  and navigate various structures and penetrations in and within access barrier  411 . Penetration tubing  1100  may be continuously sealed or include openings, such as at connecting junctions. Penetration tubing  1100  may junction with other tubes and/or structures and/or include interruptions. One possible advantage of penetration tubing  1100  being sealed and securely mating at junctures and/or with any terminal/originating points is that penetration tubing  1100  better maintains pneumatic pressure that can be used for target withdrawal, and also may provide additional containment for irradiation targets  250  and any products (gas, fluid, solid, particulate, etc.) formed as irradiation products in example embodiment system  1000 . 
     Penetration tubing  1100  may be fabricated of a material that maintains its physical characteristics in an operating nuclear reactor environment and does not significantly react with or entrain materials from irradiation targets  250  coming into contact therewith, including, for example, aluminum, stainless steel, carbon steel, nickel alloys, PVC, PFA, rubber, etc. Penetration tubing  1100  may be cylindrical or any other shape that permits irradiation targets  250  to enter into and/or pass through penetration tubing  1100 . For example, penetration tubing  1100  may have a generally circular cross section with a 0.5-inch diameter and smooth interior surface that permits spherical irradiation target  250  to roll within penetration tubing  1100 . One potential advantage of using such an example penetration tubing  1100  may be roughly matching diameters and geometries with instrumentation tubes  50  for consistent irradiation target movement therein; however, alternate geometries, shapes, and sizes for penetration tubing  1100 , or any other penetration pathway used in example embodiments, including those that limit movement, may be desirable, advantageous, and used. 
     Penetration tubing  1100  used in example embodiment system  1000  provides a route from an origin at loading junction  1200 , where irradiation targets may enter/exit penetration tubing  1100  outside of access barrier  411 . As shown in  FIG. 2 , for example, penetration tubing  1100  leads irradiation targets  250  from loading junction  1200  to access barrier  411 , which may be, for example, a steel-lined reinforced concrete containment wall or drywell wall or any other access restriction in conventional nuclear power stations. 
     Penetration pathways usable in example embodiment system  1000  provide a route through access barrier  411  and to reactor vessel  10  where irradiation targets  250  may enter an instrumentation tube  50 . For example, as shown in  FIG. 2 , penetration tubing  1100  penetrates access barrier  411  and extends to instrumentation tubes  50 . Penetration tubing  1100  may pass through an existing penetration in access barrier  411 , such as an existing TIP tube penetration, or may use a new penetration created for penetration tubing  1100 . Penetration tubing  1100  negotiates or passes through any other objects inside of access barrier  411  before reaching instrumentation tube  50 . 
     An annular reactor pedestal  412  may be present in a drywell  20  beneath reactor  10 , and penetration tubing  1100  is shown in  FIG. 2  passing through a penetration in pedestal  412 . It is understood that penetration pathways may follow any number of different courses and negotiate different obstacles in different reactor designs aside from the specific example path shown with penetration tubing  1100  in  FIG. 2 . Similarly, penetration pathways need not be consistent or uniform; for example, penetration tubing  1100  may terminate on either side of, and be connected to, a penetration in pedestal  412  to permit irradiation targets  250  to pass through the penetration between penetration tubing  1100 . 
     Penetration pathways useable in example embodiment system  1000  may terminate at or within an instrumentation tube  50 . As shown in  FIG. 2 , penetration tubing  1100  terminates at a flange  1110  at a base of instrumentation tube  50 , permitting irradiation targets  250  to pass from penetration tubing  1100  into instrumentation tube  50 . Similarly, penetration tubing  1100  may join with an indexer that provides access to several instrumentation tubes  50  from a single penetration through reactor wall  411  and/or pedestal  412 . Such a system is described in US Patent Publication 2013/0315361, titled “Systems and Methods for Processing Irradiation Targets Through Multiple Instrumentation Tubes in a Nuclear Reactor,” filed May 22, 2012, said application incorporated herein by reference in its entirety. 
     Penetration pathways useable in example embodiments may be pre-existing in part or in whole and/or installed during access to containment areas and/or restricted access areas in a nuclear power plant, such as during a pre-planned outage. For example, penetration tubing  1100  may be installed in access barrier  411  during an outage, with penetration tubing  1100  being passed through penetrations in access barrier  411  and pedestal  412 , moved and secured in an area within access barrier  411  and a drywell space  20  under reactor  10 , and secured to flange  1110 . Portions of penetration tubing  1100  extending outside access barrier  411  may be installed at loading junction  1200  at any time. Penetration tubing  1100  may be secured at various points inside access barrier  411  and/or divert around existing equipment to minimize congestion or clutter in a drywell  20  or other space bounded by access barrier  411  while preserving a traversable path for irradiation targets  250  to and from instrumentation tube  50 . Again, other penetration pathways, including wire guides, meshes, compartments, bored tunnels, etc. are useable in example embodiments to provide a path from outside an access-restricted area such as containment to an instrumentation tube of an operating nuclear reactor. 
     System  1000  may be dual purpose throughout and equally used with a TIP drive or other instrumentation and reactor components. Or system  100  may be exclusively dedicated to isotope production and harvesting with its own driving mechanism, pathways, reservoirs, etc. and excluding use with other instrumentation or a TIP drive. Or system  1000  may be exclusive in some part and shared in others. For example, outside of pedestal  412  and/or drywell  20 , example embodiment system  1000  may be dedicated to irradiation target production and harvesting. Within pedestal  412  and drywell  20 , space may be at a premium and installation of new dedicated components and/or movement of other components may be undesirable, such that example system  1000  may use and share pathways with conventional TIP drives and instrumentation. 
     Dual shared functionality can be achieved in several ways. For example, as shown in  FIG. 2 , within pedestal  412 , penetration pathway  1100  may be a shared penetration pathway  1100   b  useable to transport both irradiation targets  250  and other conventional devices including TIP runs. Outside of pedestal  412 , penetration pathway may be an exclusive pathway  1100   a  used only for irradiation target  250  transport and harvesting. A system selector  630  is capable of selectively providing access to at least shared penetration pathway  1100   b  inside pedestal  412  between several systems. For example, existing TIP tubing  300  and exclusive pathway  1100   a  may be selectively connected to shared pathway  1100   b  via system selector  630 . Of course, more than one system selector  630  may be useable in example system  1000 , and/or system selector  630  may be used at other points besides outside of pedestal  412  to provide access to shared pathways for multiple existing and/or new systems. 
     System selector  630  may selectively provide access to shared pathway  1100   b  at any desired time. For example, exclusive pathway  1100   a  can be given access during times of irradiation target insertion and/or withdrawal, while TIP tubing  300  can be given access during standard TIP runs while irradiation targets  250  are not using shared pathway  1000   b , such as when all irradiation targets  250  are harvested or being held within particular instrumentation tubes  50 . In this way, simultaneous irradiation of irradiation targets and TIP runs to multiple instrumentation tubes may be performed. System selector  630  may be operated manually, remotely, and/or automatically, based on time frames and/or detected plant conditions, for example. Similarly, system selector  630  may be useable with retention mechanisms and other systems in US Patent Publication 2013/0177126 titled, “Systems and Methods for Retaining and Removing Irradiation Targets in a Nuclear Reactor,” by Runkle et al., filed Dec. 10, 2012, said application being incorporated by reference in its entirety herein. System selector  630  may further be useable in the systems described in incorporated application Ser. No. 13/477,244 at flange  1110  to replace and/or be used with various mechanisms described therein for selecting systems. 
       FIG. 3  is an illustration of a cross-section of an example embodiment system selector  630 . As shown in  FIG. 3 , example embodiment system selector  630  includes a selection block  633  coupled to at least one motor  634 . Selection block  633  provides several different pathways, depending on its position. For example, selection block  633  may include two distinct paths  631  and  632  with openings vertically spaced from one another. A higher distinct path  632  may connect to an exclusive pathway  1100   a  that services components of an irradiation target loading and harvesting system, while a lower distinct path  631  may connect to a TIP tube  300  servicing conventional TIP drives and sensors or other instrumentation. Based on the vertical positioning of selection block  633 , only one of paths  631  and  632  may align with, and open into, shared pathway  1100   b  headed toward an instrumentation tube  50  ( FIG. 2 ). For example, as shown in  FIG. 3 , only lower distinct path  631  joins to shared pathway  1100   b , such that only TIP Tube  300  and instrumentation therein can access shared pathway  1100   b  and an instrumentation tube, while exclusive pathway  1100   a  and instrumentation targets moving therethrough are blocked from shared pathway  1100   b . Vertical movement of selection block  633  may reverse this functionality. 
     Selection block  633  can be fabricated out of a variety of materials that are compatible with an operating nuclear reactor environment and transport of radioisotopes and instrumentation. For example, aluminum or stainless steel alloys may be useable for selection block  633 , as may be high-grade plastics or ceramics. Distinct paths  632  and  631  may be formed of or from the same materials and have relatively smooth and continuous inner surfaces and a shape that matches anticipated instrumentation and irradiation targets  250 , so as to provide smooth passage through the paths  631  and  632  without significant material entrainment or snagging. Although irradiation targets  250  are shows as spheres in some example embodiment systems, it is understood that paths  632  and/or  631  can be shaped and sized to accommodate a variety of shapes and configurations of both irradiation targets and instrumentation, including prismatic shapes, obloids, wires, chains, etc. 
     Example embodiment system selector  630  may join selector block  633  to motors  634  through a sealed piston  635  and crankshaft  638  that may include groves that mate with a gear of motor  634 , or through any other powered arrangement. For example, motor  634  may be sized and keyed to crankshaft  638  such that an exact half-rotation of motor  634  moves selector block  633  the required distance to alternate between pathways  632  and  631 , improving reliability and predictability of position of selector block  633 . Example embodiment system selector  630  may further include one or more electrical switches and actuator  636  to provide appropriate control to motor  634 . For example, switches and actuator  636  may be set to provide exact rotation of motor  634  for reliable movement of selection block  633 , and/or actuator  636  may be programmed to appropriately time movement of selection block  633  at desired instances. In this way, example embodiment system selector  630  may be a self-contained operational unit with self-provided fail-safe and standard operating characteristics. Of course, remote communications from a control room or other outside operator may also be provided to example embodiment system selector  630  through any communicative connection such that a remote user can dictate actuation and movement direction of selection block  633  through appropriate signaling, and/or so that system selector  630  may provide feedback to users as to status, position, errors, etc. 
       FIGS. 4   a  and  4   b  are side views of example embodiment system selector  630  showing two different configurations of selection block  633 . In  FIG. 4   a , piston  635  and selection block  633  have been lowered such that only upper distinct path  632  connects to shared penetration pathway  1100   b  and has access to in instrumentation tube connected thereto. In this configuration, a complete penetration pathway  1100  may be formed between  1100   a  and  1100   b  and provide loading and/or harvesting of irradiation targets from/to instrumentation tubes and loading/harvesting systems. In this configuration, lower distinct path  631  does not connect to shared penetration pathway  1100   b  and may be blocked in this configuration. Alternately, TIP tube  300  may not connect to lower distinct path  631  in the configuration of  FIG. 4   a , to further prevent and/or block any TIP instrumentation from even entering selection block  633 . In  FIG. 4   b , piston  635  and selection block  633  have been raised such that only lower distinct path  631  connects to shared penetration pathway  1100   b  and has access to in instrumentation tube connected thereto. In this configuration, a complete penetration pathway may be formed between TIP tube  300  and shared penetration pathway  1100   b  and provide access of TIP or other instrumentation from/to instrumentation tubes without interaction with irradiation targets and harvesting/loading systems for the same. In this configuration, upper distinct path  632  does not connect to shared penetration pathway  1100   b  and may be blocked in this configuration. Alternately, irradiation target penetration pathway  1100   a  may not connect to upper distinct path  632  in the configuration of  FIG. 4   a , to further prevent and/or block any irradiation targets from even entering selection block  633 . 
       FIG. 5  is an illustration of example embodiment system selector  630  including an outside frame  639  that may receive and align the various entries and exits  1100   a ,  1100   b ,  300  with specific positions of selection block  633  ( FIG. 3 ) and distinct pathways  631  and  632  therein ( FIG. 3 ). Outside frame  639  may also serve to terminally block pathways that are not selectively aligned by example embodiment system selector  630 . In this way, only a single system may have ultimate access to shared penetration pathway  1100   b  and instrumentation tube(s)  50  ( FIG. 2 ) connected thereto. Non-aligned systems may further be prevented from accessing, or blocking or causing malfunction in, example embodiment system selector  630  due to the blocking nature of outside frame  639 . It is further understood that various entrances and exits between systems interacting with example embodiment system selector  630  may have any position or orientation; for example, in  FIG. 5 , TIP Tube  300  and exclusive penetration pathway  1100   a  are in opposite vertical positioning from the example of  FIGS. 3-5 . 
     Although example embodiment system selector  630  is shown with a vertical discrimination function in selection block  633 , it is understood that horizontal or other angled movement, driving, and positioning of selection block  633 , with respect to penetration pathways or driving motors, are useable in example embodiments. For example, motors  634  may drive crankshaft  638 , piston  635 , and selection block  633  horizontally to select between two or more distinct paths  631 / 632  that may be side-by-side in selection block  633 . Furthermore, it is understood that more than two distinct paths can be provided by a single selection block  633 , potentially creating three or more distinct access paths into a single shared penetration pathway  1100   a  to accommodate several distinct activities and access needs to instrumentation tubes  50  ( FIG. 2 ), while blocking several other inactive paths. 
     Even further, it is understood that other configurations for system selector  630  are useable as example embodiments in system  1000 . For example, a rotatable Y-tube can be used to differentiate between various systems requiring access to instrumentation tubes at different times. Or, for example, system selector  630  may use a turntable that rotates instead of using vertical or horizontal displacement. Even further, system selector  630  can use a variety of known diverters, selectors, gating arrangements, and routers useable in nuclear reactor environments to discriminate between multiple systems for shared access. 
     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, the types and locations of system selectors that gate various penetration pathways are not limited to the specific systems shown and described in the figures—other specific devices and systems for reliably selecting one path for equipment access into an access-restricted area of a nuclear power station and instrumentation tube are equally useable as example embodiments and fall within the scope of the claims. Furthermore, it is understood that example systems and methods are useable in any type of nuclear plant with access barriers that prevent unlimited access to the reactor, including known light water reactor designs, graphite-moderated reactors, and/or molten salt reactors, as well as any other nuclear plant design. Such variations are not to be regarded as departure from the scope of the following claims.