专利摘要:
Example embodiments are directed to methods of producing desired isotopes in commercial nuclear reactors using instrumentation tubes conventionally found in nuclear reactor vessels to expose irradiation targets to neutron flux found in the operating nuclear reactor. Example embodiments include assemblies for retention and producing radioisotopes in nuclear reactors and instrumentation tubes thereof. Example embodiments include one or more retention assemblies that contain one or more irradiation targets and are useable with example delivery systems that permit delivery of irradiation targets. Example embodiments may be sized, shaped, fabricated, and otherwise configured to successfully move through example delivery systems and conventional instrumentation tubes while containing irradiation targets and desired isotopes produced therefrom.
公开号:SE1050865A1
申请号:SE1050865
申请日:2010-08-24
公开日:2011-02-26
发明作者:Melissa Allen;Nicholas R Gilman;Heather Hatton;William Earl Russell
申请人:Ge Hitachi Nucl Energy America;
IPC主号:
专利说明:

IRRADIATION TARGET RETENTION ASSEMBLIES FOR ISOTOPEDELIVERY SYSTEMS BACKGROUND m Example embodiments generally relate to isotopes and apparatuses and methods forproduction thereof in nuclear reactors.
Description of Related Art Radioisotopes have a variety of medical and industrial applications stemming fromtheir ability to emit discreet amounts and types of ionizing radiation and forrn usefuldaughter products. For example, radioisotopes are useful in cancer-related therapy,medical imaging and labeling technology, cancer and other disease diagnosis, andmedical sterilization.
Radioisotopes having half-lives on the order of days are conventionally produced bybombarding stable parent isotopes in accelerators or low-power research reactors Withneutrons on-site at medical or industrial facilities or at nearby production facilities.These radioisotopes are quickly transported due to the relatively quick decay time andthe exact amounts of radioisotopes needed in particular applications. Further, on-siteproduction of radioisotopes generally requires cumbersome and expensive irradiationand extraction equipment, Which may be cost-, space-, and/or safety-prohibitive atend-use facilities.
Because of difficulties With production and the lifespan of short-terrn radioisotopes,demand for such radioisotopes may far outWeigh supply, particularly for thoseradioisotopes having significant medical and industrial applications in persistent demand areas, such as cancer treatment.
SIJh4h4fRÄ{ Example embodiments are directed to methods of producing desired isotopes incommercial nuclear reactors and associated apparatuses. Example methods mayutilize instrumentation tubes conventionally found in nuclear reactor vessels to exposeirradiation targets to neutron flux found in the operating nuclear reactor. Short-terrnradioisotopes may be produced in the irradiation targets due to the flux. These short-terrn radioisotopes may then be relatively quickly and simply harvested by removingthe irradiation targets from the instrumentation tube and reactor containment, Withoutshutting down the reactor or requiring chemical extraction processes. The short-terrnradioisotopes may then be immediately transported to end-use facilities.
Example embodiments may include assemblies for retention and producingradioisotopes in nuclear reactors and instrumentation tubes thereof. Exampleembodiments may include one or more retention assemblies that contain one or moreirradiation targets. Example embodiments may be useable With example deliverysystems that perrnit delivery of irradiation targets. Example embodiments may besized, shaped, fabricated, and otherwise configured to successfully move throughexample delivery systems and conventional instrumentation tubes While containingirradiation targets and desired isotopes produced therefrom.
BRIEF DESCRIPTIONS OF THE DRAWINGS Example embodiments Will become more apparent by describing, in detail, theattached draWings, Wherein like elements are represented by like reference numerals,Which are given by Way of illustration only and thus do not limit the exampleembodiments herein.
FIG. l is an illustration of a conventional nuclear reactor having an instrumentation tube.
FIG. 2 is an illustration of an example embodiment system for delivering exampleembodiments into an instrumentation tube of a nuclear reactor.
FIG. 3 is a detail view of the example embodiment system of FIG. 2.
FIG. 4 is a detail view of the example embodiment system of FIG. 3.
FIG. 5 is an illustration of a conventional nuclear reactor TIP system.
FIG. 6 is an illustration of a further example embodiment system for deliveringexample embodiments into an instrumentation tube of a nuclear reactor.
FIG. 7 is an illustration of a first example embodiment irradiation target retentionassembly.
FIG. 8 is an illustration of several example embodiment irradiation target retentionassemblies Within an example embodiment delivery system.
FIG. 9 is an illustration of a second example embodiment irradiation target retentionassembly.
DETAILED DESCRIPTION Detailed illustrative embodiments of example embodiments are disclosed herein.
HoWever, specific structural and functional details disclosed herein are merelyrepresentative for purposes of describing example embodiments. The exampleembodiments may, however, be embodied in many altemate forms and should not beconstrued as limited to only example embodiments set forth herein.
It Will be understood that, although the terms first, second, etc. may be used herein todescribe various elements, these elements should not be limited by these terms. Theseterms are only used to distinguish one element from another. For example, a firstelement could be terrned a second element, and, similarly, a second element could be terrned a first element, Without departing from the scope of example embodiments.
As used herein, the terrn "and/or" includes any and all combinations of one or more ofthe associated listed items.
It will be understood that when an element is referred to as being "connected,""coupled," “mated,” “attached,” or “f1xed” to another element, it can be directlyconnected or coupled to the other element or intervening elements may be present. Incontrast, when an element is referred to as being "directly connected" or "directlycoupled" to another element, there are no intervening elements present. Other wordsused to describe the relationship between elements should be interpreted in a likefashion (e.g., "between" versus "directly between", "adjacent" Versus "directlyadjacent", etc.).
The terrninology used herein is for the purpose of describing particular embodimentsonly and is not intended to be limiting of example embodiments. As used herein, thesingular forms "a", "an" and "the" are intended to include the plural forms as well,unless the language explicitly indicates otherwise. It will be further understood thatthe terms "comprises", "comprising,", "includes" and/or "including", when usedherein, specify the presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of one or more otherfeatures, integers, steps, operations, elements, components, and/or groups thereof It should also be noted that in some altemative implementations, the functions/actsnoted may occur out of the order noted in the figures. For example, two figuresshown in succession may in fact be executed substantially and concurrently or maysometimes be executed in the reverse order, depending upon the functionality/actsinvolved.
FIG. 1 is an illustration of a conventional reactor pressure vessel 10 usable with example embodiments and example methods. Reactor pressure vessel 10 may be used in at least a 100 MWe commercial light Water nuclear reactor conventionallyused for electricity generation throughout the world. Reactor pressure vessel 10 maybe positioned within a containment structure 411 that serves to contain radioactivity inthe case of an accident and prevent access to reactor pressure vessel 10 duringoperation of the reactor pressure vessel 10. A cavity below the reactor pressure vessel10, known as a drywell 20, serves to house equipment servicing the vessel such aspumps, drains, instrumentation tubes, and/or control rod drives. As shown in FIG. 1,at least one instrumentation tube 50 extends vertically into the vessel 10 and well intoor through core 15 containing nuclear fuel and relatively high amounts of neutron fluxduring operation of the core 15. Instrumentation tubes 50 may be generallycylindrical and widen with height of the vessel 10; however, other instrumentationtube geometries are commonly encountered in the industry. An instrumentation tube50 may have an inner diameter and/or clearance of about 0.3 inch, for example.
The instrumentation tubes 50 may terrninate below the reactor pressure vessel 10 inthe drywell 20. Conventionally, instrumentation tubes 50 may perrnit neutrondetectors, and other types of detectors, to be inserted therein through an opening at alower end in the drywell 20. These detectors may extend up through instrumentationtubes 50 to monitor conditions in the core 15. Examples of conventional monitortypes include wide range detectors (WRNM), source range monitors (SRM),interrnediate range monitors (IRM), and/or Local Power Range Monitors (LPRM).Although vessel 10 is illustrated with components commonly found in a commercialBoiling Water Reactor, example embodiments and methods may be useable withseveral different types of reactors having instrumentation tubes 50 or other accesstubes 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 instrumentationtubes at several different positions from those shown in FIG. l may be useable withexample embodiments and methods. As such, instrumentation tubes useable inexample methods may be any protruding feature at any geometry about the core thatallows enclosed access to the flux of the nuclear core of various types of reactors.Applicants have recognized that instrumentation tubes may be useable to quickly andconstantly generate desired isotopes on a large-scale basis without the need forchemical or isotopic separation and/or waiting for reactor shutdown of commercialreactors. Example methods may include inserting irradiation targets intoinstrumentation tubes and exposing the irradiation targets to the core while operating,thereby exposing the irradiation targets to the neutron flux commonly encountered inthe operating core. The core flux may convert a substantial portion of the irradiationtargets to a useful radioisotope, including short-term radioisotopes useable in medicalapplications. Irradiation targets may then be withdrawn from the instrumentationtubes, even during ongoing operation of the core, and removed for medical and/orindustrial use.
Example deliverv svstems Example delivery systems are discussed below in conjunction with exampleembodiment irradiation target retention assemblies and irradiation targets useabletherewith, which are described in detail later. It is understood that exampleembodiment irradiation target retention assemblies may be useable with other types ofdelivery systems than those described below.
FIGS. 2-6 are illustrations of related systems for delivering example embodimentirradiation target retention assemblies and irradiation targets into a nuclear reactor, described in co-pending application XX/XXX,XXX, filed on the same date herewith, entitled “CABLE DRIVEN ISOTOPE DELIVERY SYSTEM,” the contents of whichare herein incorporated by reference in their entirety. Example embodimentirradiation target retention assemblies are useable with the related systems describedin FIGS. 2-6; however, it is understood that other delivery systems may be used withexample embodiment irradiation target retention assemblies.
FIG. 2 illustrates a related cable-driven isotope delivery system 1000 that may use theinstrumentation tubes 50 to deliver example embodiment irradiation target retentionassemblies into a reactor pressure vessel l0 (FIG. l). Cable driven isotope deliverysystem l000 may be capable of transferring an irradiation target retention assemblyfrom a loading/unloading area 2000, to an instrumentation tube 50 of reactor pressurevessel l0 and/or from instrumentation tube 50 of the reactor pressure vessel l0 to theloading/unloading area 2000. As shown in FIG. 2, cable driven isotope deliverysystem l000 may include a cable l00, tubing 200a, 200b, 200c, and 200d, a drivemechanism 300, a first guide 400, and/or a second guide 500. The tubing 200a, 200b,200c, and 200d may be sized and configured to allow the cable l00 to slide therein.Accordingly, the tubing 200a, 200b, 200c, and 200d may act to guide the cable fromone point in the cable driven isotope delivery system l000 to another point in thecable driven isotope delivery system l000. For example, tubing 200a, 200b, 200c,and 200d may guide cable l00 from a point outside of containment structure 4ll(FIG. l) to a point at instrumentation tube 50 inside containment structure 4l l.
An example cable l00 is illustrated in FIGS. 3 and 4. Example cable l00 may have atleast two portions: l) a relatively long driving portion ll0; and 2) a target portionl20. Driving portion ll0 of cable l00 may be fabricated of a material having a lownuclear cross-section, such as aluminum, silicon, and/or stainless steel. Driving portion ll0 of cable l00 may be braided in order to increase the flexibility and/or strength of cable 100 so that cable 100 may be more easily bendable and capable ofbeing Wrapped around a reel, for example. Although cable 100 may be easilybendable, cable 100 may additionally be sufficiently stiff in an axial direction so thatcable 100 may be pushed through tubing 200a, 200b, 200c, and/or 200d Withoutbuckling.
As shown in FIG. 4, target portion 120 of example cable 100 may include a pluralityof example embodiment irradiation target retention assemblies 122. Target portion120 may be attached to a first end 114 of the driving portion 110. The length of thetarget portion 120 may vary depending on a number of factors, including theirradiation target material, the size of the example embodiment irradiation targetretention assemblies, the amount of radiation the target is expected to be exposed to,and/or the geometry of the instrumentation tubes 50. As an example, the targetportion 120 may be about 12 feet long.
Referring to FIGS. 3 - 4, target portion 120 may include a first end cap 126 at a firstend 127 of target portion 120 and a second end cap 128 at a second end 129 of targetportion 120. First end cap 126 may be configured to attach to a first end 114 ofdriving portion 110. First end cap 126 and first end 114 of driving portion 110 mayform a quick connect/disconnect connection. For example, first end cap 126 mayinclude a holloW portion having intemal threads 126a. First end 114 of drivingportion 110 may include a connector 113 having extemal threads that may beconfigured to mesh With the intemal threads 126a of the first end cap 126. Althoughthe example connection illustrated in FIGS. 3 and 4 is described as a threadedconnection, one skilled in the art Would recognize various other methods of connecting target portion 120 of the cable 100 to driving portion 110 of cable 100.
An operator may conf1gure first guide 400 and second guide 500 so that cable 100may be advanced to a desired destination. For example, between loading/unloadingarea 2000 and instrumentation tube 50.
After configuring first and second guides 400 and 500, an operator may operatedriving mechanism 300 to advance cable l00 through tubing 200a, first guide 400,and second tubing 200b to place first end ll4 of driving portion ll0 of cable l00 intothe loading/unloading area 2000. An operator may advance cable l00 by controllinga worrn gear in driving mechanism 300 that meshes with cable l00. The location offirst end ll4 of driving portion ll0 of cable l00 may be tracked via markings ll6 oncable l00. Altematively, position of first end ll4 of driving portion ll0 of cable l00may be known from information collected from a transducer that may be connected todrive mechanism 300.
After the cable l00 has been positioned in the loading/unloading area 2000 exampleembodiment retention assemblies l22 may then be connected to cable l00 asdescribed below with reference to example embodiment retention assemblies. Anoperator may operate driving mechanism 300 to pull the cable from theloading/unloading area 2000 through tubing 200b and through first guide 400. Theoperator may then reconfigure first guide 400 to send cable l00 and exampleembodiment assemblies l22 to reactor pressure vessel l0. After first guide 400 isreconfigured, the operator may advance cable l00 through third tubing 200c, secondguide 500, fourth tubing 200d, and into a desired instrumentation tube 50. Locationof first end ll4 of the driving portion ll0 of cable l00 may be tracked via markingsll6 on cable l00. In the altemative, position of first end ll4 of driving portion ll0of cable l00 may be known from information collected from a transducer that may be connected to drive mechanism 300.
After cable 100 bearing example embodiment retention assemblies 122 has beenadvanced to the appropriate location within instrumentation tube 50, the operator maystop cable 100 in the instrumentation tube 50. At this point, irradiation targets withinexample embodiment irradiation target retention assemblies may be irradiated for theproper time in the nuclear reactor. After irradiation, the operator may operate drivingmechanism 300 to pull cable 100 out of instrumentation tube 50, fourth tubing 200d,second guide 500, third tubing 200c, and/or first guide 400.
An operator may operate driving mechanism 300 to advance cable 100 through f1rstguide 400, and second tubing 200b to place first end 114 of driving portion 110 of thecable 100 and example embodiment irradiation target retention assemblies 122 intothe loading/unloading area 2000. Example assemblies 122 may be removed fromcable 100 and stored in a transfer cask or another desired location. An exampletransfer cask may be made of lead, tungsten, and/or depleted uranium in order toadequately shield the irradiated targets. Attachment and detachment of exampleembodiment retention assemblies 122 may be facilitated by the use of cameras whichmay be placed in the loading/unloading area 2000 to allow an operator to visuallyinspect the equipment during operation.
An altemate delivery system includes use of a conventional Transverse In-core Probe(TIP) system 3000. A conventional TIP system 3000 is illustrated in FIG. 5. Asshown in FIG. 5, TIP system 3000 may include a drive mechanism 3300 for driving acable 3100, tubing 3200a between driving system 3300 and a chamber shield 3400,tubing 3200b between chamber shield 3400 and a valve 3600, tubing 3200c betweenvalve 3600 and a guide 3500, and tubing 3200d between guide 3500 and aninstrumentation tube 50. Cable 3100 may be similar to the cable 100 described with reference to FIGS. 2-4. Guide 3500 of conventional TIP system 3000 may guide a TIP sensor to a desired instrumentation tube 50. Chamber shield 3400 may resemblea barrel filled with lead pellets. The chamber shield 3400 may store the TIP sensorwhen not utilized in the reactor pressure vessel l0. Valves 3600 are a safety featureutilized with TIP system 3000.
Because TIP system 3000 includes a tubing system 3200a, 3200b, 3200c, and 3200dand/or a guide 3500 for guiding a cable 3l00 into an instrumentation tube 50, thesesystems may be used as an example delivery mechanism for example embodimentirradiation target retention assemblies and irradiation targets stored therein.
FIG. 6 illustrates an example delivery system including a modified TIP system 4000.As shown in FIG. 6, modified TIP system 4000 is similar to conventional TIP system3000 illustrated in FIG. 5, with a guide 4l00 introduced between chamber shield wall3400 and valves 3600 of conventional TIP system 3000. Guide 4l00 may serve as anaccess point for introducing a cable, for example, cable l00, into modified TIP system4000. As shown in FIG. 6, drive system 300 (FIG. 2) may be placed in parallel withdrive system 3300 of modified TIP system 4000. Drive system 300 may includecable storage reel 320 on which cable l00 may be wrapped. Tube 200a may extendfrom the drive system 3300 to first guide 400 which may direct cable l00 to a desiredlocation. For example, an operator may configure first guide 400 to direct cable l00to a loading/unloading area 2000 via tubing 200b by controlling a rotary cylinder offirst guide 400 to align a second end of tubing 200b with an appropriate exit point.Rather than having an exit point that may direct cable l00 to second guide 500 (FIG.2), first guide 400 in modified TIP system 4000 may be configured to direct cable l00to guide 4l00 instead. In this way, first guide 400 may guide cable l00 into the TIP system tubing 3200a,b,c,d via guide 4l00. ll Cable 100 should be sized to function With existing tubing in example deliverysystems and perrnit passage of example embodiment irradiation target retentionassemblies. For example, the inner diameter of tubing 3200a, 3200b, etc. may beapproximately 0.27 inches. Accordingly, cable 100 may be sized so that dimensions transverse to the cable 100 do not exceed 0.27 inches.
Example Embodiment Irradiation Target Retention Assemblies Example delivery systems being described, example embodiment irradiation targetretention assemblies useable therewith are now described. It is understood thatexample retention assemblies may be configured/sized/shaped/etc. to interact With theexample delivery systems discussed above, but example retention assemblies mayalso be used in other delivery systems and methods in order to be irradiated Within anuclear reactor.
FIG. 7 is an illustration of a first example embodiment irradiation target retentionassembly 122a. As shown in FIG. 7, irradiation target retention assembly 122a hasdimensions that enable it to be inserted into instrumentation tubes 50 (FIG. 1) used inconventional nuclear reactors and/or through any tubing used in delivery systems.For example, irradiation target retention assembly 122a may have a maximum outerdiameter 137 of an inch or less. Although irradiation target retention assembly 122ais shown as cylindrical, a variety of properly-dimensioned shapes, includinghexahedrons, cones, and/or prismatic shapes may be used for irradiation targetretention assembly 122a.
Example embodiment irradiation target retention assembly 122a may include one ormore bores 135 that extend partially into assembly 122a in an axial direction from a top end / face 138. Altematively, bores 135 may extend into assembly 122a 12 circumferentially or from other positions. Bores 135 may be arranged in any patternand number, so long as the structural integrity of example embodiment irradiationtarget retention assemblies is preserved. Bores 135 themselves may have a variety ofdimensions and shapes. For example, bores 135 may taper With distance from topface 138 and/or may have rounded bottoms and edges, etc. Example assembly 122amay be fabricated of a material that is configured to retain its structural integrity Whenexposed to flux encountered in an operating nuclear reactor. For example, exampleassembly 122a may be fabricated of zirconium alloy, stainless steel, aluminum, nickelalloy, silicon, graphite, and/or Inconel, etc.
Irradiation targets 130 may be inserted into one or more bores 135 in any desirednumber and/or pattem. Irradiation targets 130 may be in a variety of shapes andphysical forms. For example, irradiation targets 130 may be small filings, roundedpellets, Wires, liquids, and/or gasses. Irradiation targets 130 may be dimensioned tofit Within bores 135, and/or bores 135 are shaped and dimensioned to containirradiation targets 130. Additionally, example embodiment irradiation target retentionassembly 122a may be fabricated from and/or intemally contain irradiation targetmaterial, so as to become irradiation targets themselves. Irradiation targets 130 mayfurther be sealed containers of a material designed to substantially maintain physicaland neutronic properties When exposed to neutron flux Within an operating reactor.The containers may contain a solid, liquid, and/or gaseous irradiation target and/orproduced radioisotope so as to provide a third layer of containment for irradiationtargets 130 Within example embodiment retention assembly 122a.
A cap 131 may attach to top end / face 138 and seal irradiation targets 130 into bores135. Cap 131 may attach to top end 138 in several known Ways. For example, cap 131 may be directly Welded to top face 138. Or, for example, cap 131 may screw 13 onto top end 138 Via threads on example retention assembly 122a and/or withinindividual bores 135. Although cap 131 is shown sized to cover a single bore 135, itis understood that cap may cover several or all bores 135, so as to seal irradiationtargets 130 in multiple bores 135. For example, cap 131 may be annular and seal allbores 135 radially positioned in example retention assembly 122a but leave a middlebore 135 or hole 136 unsealed. In any of these attachments, cap 131 may retainirradiation targets 130 within a bore 135 and allow easy removal of cap 131 forcontainment and harvesting of desired solid, liquid, or gaseous radioisotopes anddaughter products from irradiation targets 130.
As shown in FIG. 7, first example embodiment irradiation target retention assembly122a may further include a hole 136 extending through assembly 122a. Hole 136may be sized to capture a wire 124 (FIG. 4) and perrnit example retention assembly122a to slide on wire 124. Similarly, hole 136 may be threaded or have other intemalconf1gurations that perrnit assembly 122a to join to and/or be moved along cable 100(FIG. 2). In this way, one or more retention assemblies 122a may be placed in adelivery system, such as the ones illustrated in FIGS. 2-6, and successfully deliveredin an instrumentation tube 50 in order to be irradiated.
FIG. 8 is an illustration of multiple example embodiment irradiation target retentionassemblies 122a that may be used in combination. As shown in FIG. 8, severalassemblies 122a may be serially placed on a wire 124 or other attaching mechanism toa delivery system. Example assemblies 122a may be tightly stacked with otherexample assemblies 122a on wire 124. A flexible adhesive tape 139 may furtherflexibly hold example assemblies 122a together. The flexible adhesive tape 139 mayperrnit some relative movement of example retention assemblies 122a for bends in tubing 200a, b, c, d. Further, example retention assemblies 122a may have a length 14 that perrnits passage through bends in tubing 200a, b, c, d, without becomingfrictionally stuck in the tubing.
If a stack of example embodiment assemblies 122a are substantially flush against oneanother on cable 124, because bores 135 may not pass entirely through exampleassemblies 122a, the bottom surface of each assembly may be largely flat so as tofacilitate a containing seal against another example assembly 122a stackedimmediately below. In this way, irradiation targets 130 may be contained withinbores 135 with or without an additional cap 131.
FIG. 9 is an illustration of a second example embodiment irradiation retentionassembly 122b. As shown in FIG. 9, example embodiment irradiation targetassembly 122b may be a generally hollow, sealed tube containing one or moreirradiation targets 130. Irradiation targets 130 may additionally be sealed in acontainment device within example assembly 122b so as to provide an additionallevel of containment and/or separate different types of targets and produced daughterproduces. Irradiation targets 130 may be attached to a sidewall 133 of exampleassembly 122b in order to hold irradiation target 130 in place. Any type of knownfastening/joining device may be used to join irradiation target 130 to sidewall 133.Example embodiment irradiation target retention assembly 122b has dimensions thatenable it to be inserted into instrumentation tubes 50 (FIG. 1) used in conventionalnuclear reactors and/or through any tubing 200a,b,c,d used in delivery systems. Forexample, irradiation target retention assembly 122b may have a maximum outerdiameter of an inch or less. Although irradiation target retention assembly 122b isshown as cylindrical, a variety of properly-dimensioned shapes, includinghexahedrons, cones, and/or prismatic shapes may be used for irradiation target retention assembly 122b. Similarly, irradiation target retention assembly 122b may have a length that perrnits it to pass through any bends in tubing 200a,b,c,d, Withoutbecoming stuck.
Example embodiment irradiation target retention assembly 122b may be fabricated ofa material that is configured to retain its structural integrity When exposed to fluxencountered in an operating nuclear reactor. For example, example assembly 122bmay be fabricated of aluminum, silicon, stainless steel, etc. Altemately, exampleembodiment irradiation target retention assembly 122b may be fabricated from aflexible material that perrnits some bending/deforrnation through bends in tubing200a,b,c,d, including, for example, a high-temperature plastic. Still altemately,example embodiment irradiation target retention assembly 122b may be fabricatedfrom an irradiation target material itself Example embodiment irradiation target retention assembly 122b may further include afirst endcap 126 configured to join the assembly 122b to driving portion 110 of cable100 (FIG. 3). For example, first endcap 126 may be threaded With intemal threads126a to join to an opposing-threaded end connector 113 of cable 100. In this Way,example embodiment irradiation target retention assembly 122b may join to theexample delivery system described in FIG. 3 and be delivered into an instrumentationtube 50 for irradiation in an operating nuclear reactor.
Example embodiments of irradiation target retention assemblies 122 may perrnitseveral different types and phases of irradiation targets 130 to be placed in eachassembly 122. Because several example assemblies 122a,b may be placed at preciseaxial levels Within an instrumentation tube 50, it may be possible to provide a moreexact amount/type of irradiation target 130 at a particular axial level Withininstrumentation tube 50. Because the axial flux profile may be known in the operating reactor, this may provide for more precise generation and measurement of 16 useful radioisotopes in irradiation targets 130 placed within example embodimentirradiation target retention assemblies. Example embodiment irradiation targetretention assembly being described, example irradiation targets useable therein are described below.
Example irradiation targets An irradiation target is a target that is irradiated for the purpose of generatingradioisotopes. Accordingly, sensors, which may be irradiated by a nuclear reactor andwhich may generate radioisotopes, do not fall within the scope of term target as usedherein since their purpose is to detect the state of the reactor rather than to generateradioisotopes.
Several different radioisotopes may be generated in example embodiments andexample methods. Example embodiments and example methods may have aparticular advantage in that they perrnit generation and harvesting of short-terrnradioisotopes in a relatively fast timescale compared to the half-lives of the producedradioisotopes, without shutting down a commercial reactor, a potentially costlyprocess, and without hazardous and lengthy isotopic and/or chemical extractionprocesses. Although short-terrn radioisotopes having diagnostic and/or therapeuticapplications are producible with example assemblies and methods, radioisotopeshaving industrial applications and/or long-lived half-lives may also be generated.Further, irradiation targets 130 may be chosen based on their relatively smallerneutron cross-section, so as to not interfere substantially with the nuclear chainreaction occurring in an operating commercial nuclear reactor core.
For example, it is known that Molybdenum-98 may be converted into Molybdenum- 99, having a half-life of approximately 2.7 days when exposed to a particular amount l7 of a neutron flux. In turn, Molybdenum-99 decays to Technetium-99m having a half-life of approximately 6 hours. Technetium-99m has several specialized medical uses,including medical imaging and cancer diagnosis, and a short-terrn half-life. Usingirradiation targets 130 fabricated from Molybdnenum-98 and exposed to a neutronflux in an operating reactor based on the size of irradiation target 130, Molybdenum-99 and/or Technetium-99m may be generated and harvested in example embodimentassemblies and methods by deterrnining the mass of the irradiation target containingMo-98, the axial position of the target in the operational nuclear core, the axial profileof the operational nuclear core, and the amount of time of exposure of the irradiationtarget.
Table 1 beloW lists several short-terrn radioisotopes that may be generated in examplemethods using an appropriate irradiation target 130. The longest half-life of the listedshort-terrn radioisotopes may be approximately 75 days. Given that reactor shutdoWnand spent fuel extraction may occur as infrequently as tWo years, With radioisotopeextraction and harvesting from fuel requiring significant process and cool-doWntimes, the radioisotopes listed below may not be viably produced and harvested from conventional spent nuclear fuel. 18 Table l - List of potential radioisotopes produced Parent Material Radioisotope Half-Life Potential UseProduced a rox Molybdenum-98 Molybdenum-99 2.7 days Imaging of cancer &poorly perrneated organs Chromium-50 Chromium-5l 28 days Label blood cells andgastro-intestinaldisorders Copper-63 Copper-64 l3 hours Study of Wilson°s &Menke°s diseases Dysprosium- l 64 Dysprosium- l 65 2 hours Synovectomy treatmentof arthritis Erbium- l 68 Erbium- l 69 9.4 days Relief of arthritis pain Holmium- l 65 Holmium- l 66 27 hours Hepatic cancer andtumor treatment Iodide- l 30 Iodine- l 3 l 8 days Thyroid cancer and usein beta therapy Iridium- l 9 l Iridium- l 92 74 days Intemal radiotherapycancer treatment Iron-58 Iron-59 46 days Study of ironmetabolism and splenaicdisorders Lutetium- l 76 Lutetium- l 77 6.7 days Imagine and treatment ofendocrine tumors Palladium- l 02 Palladium- l 03 l 7 days Brachytherapy forprostate cancer Phosphorus-3l Phosphorous-32 l4 days Polycythemia veratreatment Potassium-4l Potassium-42 l2 hours Study of coronary bloodfloW Rhenium- l 85 Rhenium- l 86 3.7 days Bone cancer therapy Samarium- l 52 Samarium- l 53 46 hours Pain relief for secondarycancers Selenium-74 Selenium-75 l20 days Study of digestiveenzymes Sodium-23 Sodium-24 l5 hours Study of electrolytes Strontium-88 Strontium-89 5l days Pain relief for prostateand bone cancer Ytterbium- l 68 Ytterbium- l 69 32 days Study of cerebrospinalfluid Ytterbium- l 76 Ytterbium- l 77 l .9 hours Used to produce Lu- l 77 Yttrium-89 Yttrium-90 64 hours Cancer brachytherapy Table l is not a complete list of radioisotopes that may be produced in example embodiments and example methods but rather is illustrative of some radioisotopes l9 useable With medical therapies including cancer treatment. With proper targetselection, almost any radioisotope may be produced and harvested for use throughexample embodiments and methods.
Example embodiments thus being described, it Will be appreciated by one skilled inthe art that example embodiments may be Varied through routine experimentation andWithout further inVentiVe activity. Variations are not to be regarded as departure fromthe spirit and scope of the exemplary embodiments, and all such modifications asWould be obvious to one skilled in the art are intended to be included Within the scope of the following claims.
权利要求:
Claims (10)
[1] 1. What is claimed is:1. An irradiation target retention system comprising:at least one irradiation target retention assembly (122), dimensioned to fit Within a nuclear reactor instrumentation tube (50) and to fit Within a tubing (200) of a delivery system (1000), and configured to join to the delivery system (1000) so as to be movable into the nuclear reactor instrumentation tube (5 0); and at least one irradiation target (130) contained Within the at least one irradiation targetretention assembly (122), the irradiation target (130) conf1gured to substantiallyconvert to a radioisotope When exposed to a neutron flux in an operating nuclear reactor.
[2] 2. The system of claim 1, Wherein the irradiation target retention assembly (122)is fabricated of a material configured to substantially maintain its physical andneutronic properties When exposed to the neutron flux in the operating nuclear reactor.
[3] 3. The system of claim 1, Wherein the at least one irradiation target retention assembly (122) is fabricated of the at least one irradiation target.
[4] 4. The system of claim 1, Wherein the irradiation target (122) is at least one ofMolybdenum-98, Chromium-50, Copper-63, Dysprosium-164, Erbium-168,Holmium-165, Iron-58, Lutetium-176, Palladium-102, Phosphurus-31, Potassium-41,Rhenium-185, Samarium-152, Selenium-74, Sodium-23, Strontium-88, Ytterbium- 168 , Ytterbium-176, Ytterium-89, Iridium-191, and Cobalt-5 9.
[5] 5. The system of claim 1, Wherein the at least one irradiation target retentionassembly (122) def1nes at least one hole (136) passing through the irradiation targetretention assembly (122), the hole (136) having a diameter configured to secure the atleast one irradiation target retention assembly (122) to a Wire (124) of the delivery system (1000). 21
[6] 6. The system of claim 1, Wherein the at least one irradiation target retentionassembly (122) is fabricated from at least one of a zirconium alloy, stainless steel, aluminum, nickel alloy, silicon, graphite, and Inconel.
[7] 7. An isotope delivery system (1000), comprising:a cable (200); at least one irradiation target retention assembly (122) joined to the cable (100), the atleast one irradiation target retention assembly (122) configured to contain at least oneirradiation target (130) that substantially converts to a radioisotope When exposed to a neutron flux in an operating nuclear reactor; a drive system (300) configured to move the cable (100) and the at least oneirradiation target retention assembly (122) into an instrumentation tube (50) of the nuclear reactor; and a guide (400/500) configured to guide the cable (100) and the at least oneirradiation target retention assembly (122) to and from the instrumentation tube (50) of the nuclear reactor.
[8] 8. The system of claim 7, Wherein the cable (100) includes a driving portion (110)and a target portion (120), the target portion (120) being directly joined to the at least one irradiation target retention assembly (122).
[9] 9. A method of producing isotopes in a nuclear reactor With an irradiation target retention system, the method comprising: inserting at least one irradiation target (130) into an irradiation target retentionassembly (122), the irradiation target (130) configured to substantially convert to a radioisotope When exposed to a neutron flux in the operating nuclear reactor; inserting the irradiation target retention assembly (122) into an instrumentation tube (50) of a nuclear reactor; irradiating the at least one irradiation target (130); 22 removing the irradiation target retention assembly (122) from the nuclear reactor; and harVesting a produced isotope from the irradiation target retention assembly (122), the produced isotope being produced from the irradiated at least one irradiation target (130).
[10] 10. The method of claim 9, Wherein the inserting the irradiation target retentionassembly (120) into the instrumentation tube (50) includes attaching the irradiationtarget retention assembly (122) to a cable (100), pushing the cable (100) through afirst guide (400) and into the instrumentation tube (50) using a drive system. 23
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法律状态:
优先权:
申请号 | 申请日 | 专利标题
US12/547,210|US8488733B2|2009-08-25|2009-08-25|Irradiation target retention assemblies for isotope delivery systems|
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