Patent Description:
A number of operating reactors employ a Moveable In-core Detector System (MIDS), such as the one described in <CIT>, to periodically measure the axial and radial power distribution within the core. The moveable detector system generally comprises four, five or six detector/drive assemblies, depending upon the size of the plant (two, three or four loops), which are interconnected in such a fashion that they can assess various combinations of in-core flux thimbles. In some instances, approximately <NUM>/<NUM> of the fuel assemblies in the reactor core host the flux thimbles used to support the core power distribution measurements.

To obtain the thimble interconnection capability, each detector has associated with it a five-path and ten-path rotary mechanical transfer device. A core map is made by selecting, by way of the transfer devices, particular thimbles through which the detectors are driven. To minimize mapping time, each detector is capable of being run at high speed (such as <NUM> feet per minute (<NUM> metres per second)) from its withdrawn position to a point just below the reactor core. At this point, the detector speed is reduced to a low speed (such as <NUM> feet per minutes (<NUM> metres per second)) and the detector is traversed to the top of the core, the direction is reversed, and then the detector is traversed to the bottom of the core. The detector speed is then increased to a high speed (such as <NUM> feet per minute (<NUM> metres per second)) and the detector is moved to its withdrawn position. A new flux thimble is selected for mapping by rotating the transfer devices and the above procedure repeated.

<FIG> shows the basic system for the insertion of the movable miniature detectors using an in core moveable detector arrangement. Retractable thimbles <NUM>, into which miniature detectors <NUM> are driven, take the routes approximately as shown. The thimbles <NUM> are inserted into the reactor core <NUM> through conduits <NUM> extending from the bottom of the reactor vessel <NUM> through the concrete shield area <NUM> and then up to a thimble seal table <NUM>. Since the movable detector thimbles <NUM> are closed at the leading (reactor) end, they are dry inside. The thimbles <NUM>, thus, serve as a pressure barrier between the reactor water pressure (<NUM> psig design) and the atmosphere. Mechanical seals between the retractable thimbles <NUM> and the conduits <NUM> are provided at the seal table <NUM>. The conduits <NUM> are essentially extensions of the reactor vessel <NUM>, with the thimbles <NUM> allowing the insertion of the in-core instrumentation movable miniature detectors. During operation, the thimbles <NUM> are stationary and will be retracted only under depressurized conditions during refueling or maintenance operations. Withdrawal of a thimble <NUM> to the bottom of the reactor vessel <NUM> is also possible if work is required on the vessel <NUM> internals.

The drive system for insertion of the miniature detectors <NUM> includes drive units <NUM>, safety switches <NUM>, limit switch assemblies <NUM>, <NUM>-path rotary transfer devices <NUM>, <NUM>-path rotary transfer devices <NUM>, and isolation valves <NUM>, as shown in <FIG>. Each drive unit <NUM> drives a hollow helical wrap drive cable into the core with a miniature detector <NUM> attached to the leading end of the cable and a small diameter coaxial cable, which communicates the detector <NUM> output, threaded through the hollow center back to the trailing end of the drive cable.

Commercial power reactors have an abundance of neutrons that do not significantly contribute to the heat output from the reactor used to generate electrical power. As a result, the use of the MIDS flux thimbles <NUM> allows for the production of irradiation desired neutron activation and transmutation products, such as Co-<NUM>, W-<NUM>, Ni-<NUM>, Bi-<NUM> and Ac-<NUM>, or other isotopes used in medical procedures. The valuable radioisotopes that are produced via neutron transmutation require multiple neutron induced transmutation reactions to occur in order to produce the desired radioisotope product, which results in a core residence time of a fuel cycle or more.

In order to precisely monitor the neutron exposure received by the target radioisotope to ensure the amount of activation or transmutation product being produced is adequate, it is necessary to allow an indication of neutron flux in the vicinity of the target material to be continuously measured. Co-owned <CIT>, entitled "IRRADIATION TARGET HANDLING DEVICE", now <CIT>, describes an isotope production cable assembly satisfies this consideration. <CIT> discloses an apparatus for continuously inserting, removing, and storing irradiation targets to be converted to useable radioisotopes or other desired materials at several different origin and termination points accessible outside an access barrier. <CIT> discloses an isotope delivery system with a cable including at least one target for irradiation, a drive system configured to move the cable, and a guide configured to guide the cable for insertion and extraction from a nuclear reactor.

Currently, the success of the production of a desired minimum amount of a particular radioisotope is not known until the reactor is shut down at the end of the operating cycle and the activity of the desired radioisotope produced is measured after the target material is removed from the reactor core. At this point, there is little that can be done to remedy or compensate for a production activity shortfall. Accordingly, a system and method for periodically measuring activity of the desired radioisotope in the target material prior to the end of the operating cycle is desired. Creation of a methodology and associated equipment that can be used to measure the isotopic activity while the reactor is in operation would provide the flexibility to adjust the reactor operating conditions needed to improve the production of the desired radioisotope, or at least prepare other measures that may be required to achieve satisfactory commercial production results.

In various embodiments, a system for measuring radiation activity of a target radioisotope being produced in a reactor core is disclosed. The system includes a cable assembly and a radiation detector. The cable assembly includes a housing, a target cable configured to position the housing, and a drive cable couplable and decouplable with the target cable. The target radioisotope is positioned within the housing. The drive cable is configured to drive the target cable. The radiation detector configured to periodically measure the radiation activity of the target radioisotope while being produced.

In various embodiments, a method for measuring radiation activity of a target radioisotope being produced in a reactor core using a radiation detector and a cable assembly is disclosed. The cable assembly includes a housing, a target cable configured to position the housing, and a drive cable configured to drive the target cable. The target radioisotope is positioned in the housing. The method includes coupling the drive cable with the target cable, withdrawing the target radioisotope from the reactor core via the drive cable, and periodically measuring the radiation activity of the target radioisotope while being produced with the radiation detector.

In various embodiments, the housing comprises an enclosure, the drive cable is configured to drive the target cable between the inserted position and the retracted position, and the radiation detector comprises a radiation sensor configured to sense the radiation activity of the target radioisotope while being produced.

Various features of the embodiments described herein, together with advantages thereof, may be understood in accordance with the following description taken in conjunction with the accompanying drawings as follows:.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate various embodiments of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

Numerous specific details are set forth to provide a thorough understanding of the overall structure, function, manufacture, and use of the embodiments as described in the specification and illustrated in the accompanying drawings. Well-known operations, components, and elements have not been described in detail so as not to obscure the embodiments described in the specification. The reader will understand that the embodiments described and illustrated herein are non-limiting examples, and thus it can be appreciated that the specific structural and functional details disclosed herein may be representative and illustrative. Variations and changes thereto may be made without departing from the scope of the claims.

<FIG> illustrates a system <NUM> for measuring radiation activity of a target radioisotope being produced in a reactor core, according to at least one aspect of the present disclosure.

The system <NUM> can include a cable assembly that includes a drive cable <NUM> and a target cable <NUM>. The drive cable <NUM> and the target cable <NUM> can be selectively couplable and decouplable at a coupling interface <NUM>. In one embodiment, the coupling interface <NUM> can be located just below the <NUM>-path transfer of the MIDS drive. In another embodiment, the coupling interface <NUM> can be located above the <NUM>-path transfer and below the <NUM>-path transfer. In another embodiment, the coupling interface <NUM> can be located anywhere above the <NUM>-path transfer. In another embodiment, the coupling interface <NUM> can be located anywhere below the <NUM>-path transfer and above the seal table <NUM>.

The system <NUM> can further include a housing, capsule, or enclosure <NUM>. The housing <NUM> can be any suitable container that has a size and shape that can house a target radioisotope <NUM> therein. In various embodiments, the housing <NUM> can be similar to the target material holder described in <CIT>, the isotope target capsule described in <CIT>, or the specimen holder described in <CIT>.

In one aspect, the housing <NUM> can be coupled to the target cable <NUM> such that movement of the target cable <NUM> within the thimble <NUM> moves and positions the housing <NUM>. In one example embodiment, the target cable <NUM> can be moveable between an inserted position and a retracted position. In one embodiment, the inserted position can correspond to the housing <NUM> and the target radioisotope <NUM> being positioned at a location within in the reactor core <NUM> and the retracted position can correspond to the housing <NUM> and the target radioisotope <NUM> being positioned at a location outside of the reactor core <NUM>.

The target cable <NUM> can position the housing <NUM> and the target radioisotope <NUM> at any location within the reactor core <NUM> in order provide a suitable amount of neutron flux to the target radioisotope <NUM>. In one embodiment, the inserted position can correspond to the housing <NUM> and the target radioisotope <NUM> being inserted <NUM>% of the way up the reactor core <NUM>. In another embodiment, the inserted position can correspond to the housing <NUM> and the target radioisotope <NUM> being inserted <NUM>% of the way up the reactor core <NUM>. In another example embodiment, the inserted position can correspond to the housing <NUM> and the target radioisotope <NUM> being inserted <NUM>% of the way up the reactor core <NUM>. In another embodiment, the inserted position can correspond to the housing <NUM> and the target radioisotope <NUM> being <NUM>% of the way up the reactor core <NUM>.

In addition, the target cable <NUM> can position the housing <NUM> and the target radioisotope <NUM> at a location outside of the reactor core <NUM> within the thimble <NUM> such that a radiation detector <NUM>, described in more detail below, can sense or detect the radiation activity of the target radioisotope <NUM> within the housing <NUM>. In one embodiment, the retracted position can correspond to the housing <NUM> and the target radioisotope <NUM> being positioned just below the seal table <NUM>. In one embodiment, the retracted position can correspond to the housing <NUM> and the target radioisotope <NUM> being positioned just below the reactor core <NUM>. In one embodiment, the retracted position can correspond to the housing <NUM> and the target radioisotope <NUM> being positioned at any location along the thimble <NUM> between the bottom of the reactor core <NUM> and below the seal table <NUM>. In one embodiment, the retracted position can correspond to the housing <NUM> and the target radioisotope <NUM> being positioned at a location next to, or substantially next to, the radiation detector <NUM>.

In one aspect, the target cable <NUM> can have a length that is defined by the distance from the coupling interface <NUM> to a desired location corresponding to the target radioisotope <NUM> being in the inserted position into the reactor core <NUM>. In one example embodiment, the target cable <NUM> can have a length that is defined by the distance from the coupling interface <NUM> to a location corresponding to the target radioisotope <NUM> being inserted <NUM>%, <NUM>%, or <NUM>% of the way up the reactor core.

As described above, the drive cable <NUM> and the target cable <NUM> can be selectively couplable and decouplable at the coupling interface <NUM>. In one embodiment, the drive cable <NUM> and the target cable <NUM> can be manually coupled and decoupled at the coupling interface <NUM>. In one embodiment, the drive cable <NUM> and the target cable <NUM> can be selectively coupled and decoupled at the coupling interface <NUM> by an external machine in response to a user input. In one embodiment, the drive cable <NUM> and the target cable <NUM> can be automatically coupled and decoupled at the coupling interface <NUM> by an external machine once the coupling interface <NUM> has reached a predetermined location, such as a location corresponding to the target cable <NUM> being in the inserted position.

The drive cable <NUM> can have a length that is defined by the output of the drive unit <NUM> to the location of the coupling interface <NUM>. When the drive cable <NUM> is coupled to the target cable <NUM> at the coupling interface <NUM>, the drive cable <NUM> can drive the target cable <NUM> between the inserted position and the retracted position, described above. The drive cable <NUM> can be coupled to the drive unit <NUM> through the <NUM>-path transfer device and the <NUM>-path transfer device such that the drive unit <NUM> can selectively drive the drive cable <NUM>, and as a result, the target cable <NUM> and target radioisotope <NUM>, between the inserted position and the retracted position.

A limit switch, such as limit switches <NUM>, can be utilized to limit the distances that the drive unit <NUM> and drive cable <NUM> can drive the target cable <NUM>. In one example embodiment, the limit switch can automatically halt the drive unit <NUM> when the target cable <NUM> has reached the inserted position or the retracted position. In another example embodiment, the limit switch can automatically halt the drive unit <NUM> when the target housing <NUM> and the target radioisotope <NUM> are positioned near the radiation detector <NUM>. In another example embodiment, the limit switch can automatically halt the drive unit <NUM> when the coupling interface <NUM> has reached a predefined location, such as just below the <NUM>-path transfer device.

As described above, a radiation detector <NUM> can sense or detect the radiation activity of the target radioisotope <NUM> within the housing <NUM>. As shown in <FIG>, the radiation detector <NUM> can be positioned at a location outside of the reactor core <NUM>, just below the seal table <NUM>. Other example embodiments are contemplated where the radiation detector <NUM> is positioned at other suitable locations along the thimble <NUM> between the reactor core <NUM> and the seal table <NUM>, such as just below the reactor <NUM> or a location intermediate the reactor <NUM> and the seal table <NUM>. As shown in <FIG>, the radiation detector <NUM> can be located on one side of the seal table <NUM>, such as just below the seal table <NUM>, while the coupling interface <NUM> is located on another side of the seal table <NUM>, such as just above the seal table <NUM> and isolation valves <NUM>.

The radiation detector <NUM> allows for periodic measurement of the radiation activity of the target radioisotope <NUM> while being produced. As discussed above, the success of the production of a desired minimum amount of a particular radioisotope is currently not known until the reactor is shut down at the end of an operating cycle and the target radioisotope <NUM> is removed from the reactor core <NUM>. The radiation detector <NUM> allows for the radiation activity of the target radioisotope <NUM> to be measured during a reactor operating cycle. In one embodiment, the radiation detector <NUM> can measure the radiation activity of the target radioisotope <NUM> halfway through the operating cycle. In one embodiment, the radiation detector <NUM> can measure the radiation activity of the target radioisotope <NUM> a quarter of the way through the operating cycle. In one embodiment, the radiation detector <NUM> can measure the radiation activity of the target radioisotope <NUM> at any time in which a reading is desired during an operating cycle.

In one example embodiment, the radiation detector can comprise a Platinum Self-powered Detector (SPD) wrapped in a tight spiral around a selected position on an exterior of the guide thimble <NUM>. In other embodiments, other types of solid-state gamma detectors that would allow the use of gamma spectroscopy methods to more accurately measure the specific gamma intensities associated with the desired product radioisotope can be utilized, such as those described in co-owned <CIT>.

As described above, the radiation detector <NUM> allows for the radiation activity of the target radioisotope <NUM> to be measured periodically during a reactor operating cycle while the target radioisotope <NUM> is being produced. The measured radiation activity can be compared to a radiation activity threshold to determine if a desired amount of radiation activity is being achieved. In addition, the measurement can allow the production rate of the desired radioisotope to be compared with an expected result so that appropriate compensation activities can be determined and implemented during the operating cycle of the reactor.

Based on the measured radiation activity, an appropriate compensation activity can include adjusting an operational parameter of the reactor core <NUM>, such as temperature, pressure, or a number or amount of control rods inserted therein, as examples, to improve the production of the target radioisotope <NUM>. In one example embodiment, a control system can automatically adjust an operational parameter of the reactor core based on the measured radiation activity. In another example embodiment, the control system can provide an alert or a readout indicative of the amount of radiation activity measured or sensed by the radiation detector <NUM>. An operator can analyze the readout and make any necessary adjustments to the operation parameter of the reactor core based on the measured radiation activity. In addition, the radiation detector <NUM> allows an operator to determine if, after a reactor operator cycle, the target radioisotope <NUM> has reached a sufficient radiation activity threshold and can be removed from the reactor <NUM>, or if the target radioisotope <NUM> needs to remain in the reactor core for another reactor cycle.

As described above, the drive cable <NUM> and the target cable <NUM> can be selectively couplable and decouplable at the coupling interface <NUM>. The ability to decouple the drive cable <NUM> from the target cable <NUM> allows for selective coupling when a measurement of the radiation activity of the target radioisotope <NUM> is desired. When a measurement of the radiation activity of the target radioisotope is not desired, the drive cable <NUM> can be decoupled from the target cable <NUM> at the coupling interface <NUM>. When decoupled, the associated <NUM>-path transfer device and <NUM>-path transfer device are free to rotate, allowing the other core locations associated with the <NUM>-path transfer device to be accessed by using other drives operating in Emergency or Common mode. In one embodiment, decoupling the drive cable <NUM> from the target cable <NUM> allows the drive cable <NUM> to be used for other activities, such as controlling and driving a miniature detector <NUM> into the reactor core <NUM> to determine radiation activity therein. In addition, the drive cable <NUM> can be coupled to another, separate and distinct, target cable <NUM> such that one drive cable <NUM> can be used to withdraw a different target radioisotope <NUM> to be measured by a radiation detector <NUM>. This gives the drive cable <NUM> the ability to control more than one target cable <NUM> if desired. When a reading of the radiation activity of the target radioisotope <NUM> is desired, the drive cable <NUM> can be connected to the target cable <NUM> at the coupling interface <NUM>. Once coupled, the drive cable <NUM> can drive the target cable <NUM> and the associated housing <NUM> and target radioisotope <NUM> between the inserted and withdrawn positions.

In one embodiment, the drive cable <NUM> can couple and decouple with the target cable <NUM> at the coupling interface <NUM> when the target cable <NUM> is in the inserted position. In another example embodiment, the drive cable <NUM> can couple and decouple with the target cable <NUM> at the coupling interface <NUM> when the target cable <NUM> and is in a position intermediate the inserted position and the retracted position, such as when the target radioisotope <NUM> is located outside of the reactor core <NUM>, such as just below the reactor core <NUM> or just below the seal table <NUM>, as examples. In one embodiment, the radiation detector <NUM> can measure the radiation activity of the target radioisotope <NUM> when the target cable <NUM> is in the retracted position. In another example embodiment, the radiation detector <NUM> can measure the radiation activity of the target radioisotope <NUM> at a location intermediate the inserted position and retracted position, such as just below the reactor core <NUM>, as an example.

Referring now to <FIG>, a method <NUM> for measuring radiation activity of a target radioisotope being produced in a reactor core using a radiation detector and a cable assembly is disclosed, according to at least one aspect of the present disclosure. The cable assembly can comprise a housing, a target cable configured to position the housing, and a drive cable configured to drive the target cable. A target radioisotope is positionable in the housing. The method <NUM> includes coupling <NUM> the drive cable with the target cable, withdrawing <NUM> the target radioisotope from the reactor core via the drive cable, and measuring <NUM> the radiation activity of the target radioisotope while being produced with the radiation detector.

The method <NUM> can optionally include decoupling <NUM> the drive cable from the target cable after inserting the target radioisotope into the reactor core. The method <NUM> can also optionally include repeating <NUM> the method <NUM> at another time during the reactor operating cycle. The method <NUM> can optionally also include adjusting <NUM> an operational parameter of the reactor core based on the measured radiation activity. While shown in <FIG> as being completed after the measuring <NUM> the radiation activity, the adjustment <NUM> can occur at any other time during the method, such as after inserting <NUM> the target radioisotope into the reactor core <NUM> or decoupling <NUM> the drive cable from the target cable, as an example.

The above described systems and methods can be implemented in any suitable manner in a nuclear reactor plant. For example, while the above-described systems and methods were described as being utilized with the MIDS in Pressure Water Reactors (PWR), the systems and methods can also be implemented utilizing a Traversing Incore Probe System (TIPS) used in Boiling Water Reactors (BWR). The ability to modify an existing system, such as the MIDS or TIPS, with the above described systems and methods provides the advantages described herein above, such as the ability to periodically measure radiation activity of a target radioisotope during a reactor operating cycle, as opposed to after the operating cycle has ended and the target radioisotope has been removed from the reactor core. The above described systems and methods further allow for the ability to adjust operational parameters of the reactor core to compensate for measurements below expectations, which can decrease the number of operating cycles a target radioisotope needs to remain in the reactor core.

Unless specifically stated otherwise as apparent from the foregoing disclosure, it is appreciated that, throughout the foregoing disclosure, discussions using terms such as "processing," "computing," "calculating," "determining," "displaying," or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.

One or more components may be referred to herein as "configured to," "configurable to," "operable/operative to," "adapted/adaptable," "able to," "conformable/conformed to," etc. Those skilled in the art will recognize that "configured to" can generally encompass active-state components and/or inactive-state components and/or standby-state components, unless context requires otherwise.

Those skilled in the art will recognize that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to claims containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations.

In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that typically a disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms unless context dictates otherwise. For example, the phrase "A or B" will be typically understood to include the possibilities of "A" or "B" or "A and B.

With respect to the appended claims, those skilled in the art will appreciate that recited operations therein may generally be performed in any order. Also, although various operational flow diagrams are presented in a sequence(s), it should be understood that the various operations may be performed in other orders than those which are illustrated, or may be performed concurrently. Examples of such alternate orderings may include overlapping, interleaved, interrupted, reordered, incremental, preparatory, supplemental, simultaneous, reverse, or other variant orderings, unless context dictates otherwise. Furthermore, terms like "responsive to," "related to," or other past-tense adjectives are generally not intended to exclude such variants, unless context dictates otherwise.

It is worthy to note that any reference to "one aspect," "an aspect," "an exemplification," "one exemplification," and the like means that a particular feature, structure, or characteristic described in connection with the aspect is included in at least one aspect. Thus, appearances of the phrases "in one aspect," "in an aspect," "in an exemplification," and "in one exemplification" in various places throughout the specification are not necessarily all referring to the same aspect. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner in one or more aspects.

The terms "comprise" (and any form of comprise, such as "comprises" and "comprising"), "have" (and any form of have, such as "has" and "having"), "include" (and any form of include, such as "includes" and "including") and "contain" (and any form of contain, such as "contains" and "containing") are open-ended linking verbs. As a result, a system that "comprises," "has," "includes" or "contains" one or more elements possesses those one or more elements, but is not limited to possessing only those one or more elements. Likewise, an element of a system, device, or apparatus that "comprises," "has," "includes" or "contains" one or more features possesses those one or more features, but is not limited to possessing only those one or more features.

The term "substantially", "about", or "approximately" as used in the present disclosure, unless otherwise specified, means an acceptable error for a particular value as determined by one of ordinary skill in the art, which depends in part on how the value is measured or determined. In certain embodiments, the term "substantially", "about", or "approximately" means within <NUM>, <NUM>, <NUM>, or <NUM> standard deviations. In certain embodiments, the term "substantially", "about", or "approximately" means within <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>% of a given value or range.

Claim 1:
A system for measuring radiation activity of a target radioisotope being produced in a reactor core, the system comprising:
a cable assembly; and
a radiation detector (<NUM>);
characterized in that
the cable assembly comprises:
a housing (<NUM>), wherein the target radioisotope (<NUM>) is positioned within the housing (<NUM>);
a target cable (<NUM>) configured to position the housing (<NUM>); and
a drive cable (<NUM>) couplable and decouplable with the target cable (<NUM>), wherein the drive cable (<NUM>) is configured to drive the target cable (<NUM>); and
the radiation detector (<NUM>) is configured to periodically measure the radiation activity of the target radioisotope (<NUM>) while being produced.