Radioactive monitoring apparatus, system, and method for radioactive isotopes

Abstract

A radioisotope activity monitoring system and method are disclosed. The system includes a fuel rod assembly having a plurality of nuclear fuel rods and a target assembly having an upper nozzle including an orifice plate and at least one target material rod fixedly coupled to the orifice plate. The at least one target material rod is slidably disposed within the fuel rod assembly. A sensing assembly defines an opening sized and configured to receive the target assembly therethrough. The sensing assembly includes a self-powered detector assembly for detecting the radioisotope activity of the target rod material. Also disclosed are methods for measuring the self-powered detector signal to calculate the radioisotope activity of the target assembly and for analyzing the total activity of the desired radioisotope.

Description

[Background technology]

[0001] Cross-reference of related applications This application claims the benefits of U.S. Nonprovisional Application No. 17 / 099,139, filed on November 16, 2020, entitled “RADIOISOTOPE ACTIVITY SURVEILLANCE APPARATUS, SYSTEM, AND METHOD,” the contents of which this nonprovisional application is incorporated herein by reference in their entirety.

[0002] This disclosure generally relates to radioactive isotope radioactivity monitoring devices, systems, and methods. More specifically, this disclosure generally relates to radioactive isotope radioactivity monitoring devices, systems, and methods for use in fuel assembly insertion targets. This disclosure also relates to techniques for measuring and analyzing signals received from monitoring tools and calculating the radioactivity of radioactive isotopes in the target assembly.

[0003] The generation of desired amounts of medical or industrial radioisotopes, such as cobalt-60 (Co-60), within commercial power reactors requires the target material to be placed inside the reactor and subjected to specific levels of neutron flux exposure for a minimum period of reactor operation. To determine whether the irradiated target is actually salvageable, the radioactivity levels of the desired radioisotopes within the target assembly must be measured. Therefore, apparatus, systems, and methods are needed to measure the radioactivity of the desired radioisotopes during reactor shutdowns for refueling, in order to determine whether or not to extract and process the irradiated target material. Furthermore, the progress of the generation of the desired radioisotopes must be determined during refueling shutdowns that occur prior to the expected extraction time. [Overview of the Initiative]

[0004] In one embodiment, the present disclosure provides a radioactive isotope radioactivity monitoring system comprising: a fuel rod assembly comprising a plurality of nuclear fuel rods; a target assembly comprising an upper nozzle comprising an orifice plate and at least one target material rod fixedly coupled to the orifice plate and slidably disposed within the fuel rod assembly; and a sensing assembly comprising a self-powered detector assembly for detecting the radioactivity of radioactive isotopes of the target rod material, which defines an opening of size and configuration that penetrates and receives the target assembly.

[0005] In another embodiment of a radioactive isotope radioactivity monitoring system, a self-powered detector assembly comprises a sensing unit having an emitter wire and a signal wire electrically coupled to the emitter wire, the emitter wire being made of a rapid-response gamma-ray sensitive material that generates an electric current when exposed to gamma rays, and the emitter wire and signal wire being enclosed in an outer sheath.

[0006] In another embodiment of a radioactive isotope monitoring system, the emitter wire contains platinum.

[0007] In another embodiment of a radioactive isotope monitoring system, the signal wires are made of steel.

[0008] In another embodiment of the radioactive isotope monitoring system, the outer sheath is made of steel. In another embodiment of the radioactive isotope monitoring system, the outer sheath is filled with an electrical insulating material. In another embodiment of the radioactive isotope monitoring system, the electrical insulating material is magnesium oxide (MgO).

[0009] In another embodiment of a radioactive isotope monitoring system, the sensing assembly comprises an inner case, an outer shield, and a defined space between the inner case and the outer shield for housing a helically wound sensing section of a self-powered detector assembly.

[0010] In another embodiment of a radioactive isotope monitoring system, the outer shielding consists of a material for shielding the sensing emitter wire from gamma rays originating from outside the sensing assembly. In yet another embodiment of a radioactive isotope monitoring system, the outer shielding consists of tungsten (W).

[0011] In another embodiment of a radioactive isotope monitoring system, the sensing assembly is connected to a handle. In yet another embodiment of a radioactive isotope monitoring system, the handle is configured to position the sensing assembly over a target assembly containing a target material rod that is inserted into and removed from a fuel rod assembly.

[0012] In one embodiment, the disclosure provides a method for measuring a self-powered detector signal to calculate the radioactivity of a radioisotope of a target assembly, the target assembly comprising an upper nozzle having an orifice plate, and at least one target material rod fixedly coupled to the orifice plate and slidably disposed within a fuel rod assembly. The method includes defining an opening of size and configuration to penetrate and receive the target assembly, positioning a sensing assembly, which includes a self-powered detector assembly for detecting the radioactivity of radioisotopes of the target rod material, on top of the fuel rod assembly; obtaining a first background gamma-ray signal measurement from an external gamma-ray source using the sensing assembly; recording the first background gamma-ray signal measurement using a recorder; passing the target assembly through the sensing assembly at a constant speed; recording the self-powered detector signal current (I) measured while the target assembly is passing through the sensing assembly as a function of time using the recorder; obtaining a second background gamma-ray signal measurement from an external gamma-ray source after the target assembly has completely passed through the sensing assembly; and recording the second background gamma-ray signal measurement using a recorder.

[0013] In another embodiment, the method includes determining the total radioactivity of the radioisotopes in the target assembly by integrating a function fitted to the relationship between the measured value of the self-powered detector signal current (I) and time over the active length of the target assembly.

[0014] In another embodiment, the method includes determining an integration region based on measurements of the insertion / extraction speed and the self-powered detector signal current (I) recorded when the active portion of the target assembly is inside an opening defined by the sensing assembly.

[0015] In another aspect of the method, first and second background gamma-ray signal measurements from an external gamma-ray source are obtained by measuring the current (I) through a self-powered detector signal cable.

[0016] In one embodiment, the present disclosure provides a method for analyzing the total radioactivity of a desired radioisotope. The method includes: recording a self-feeding detector signal as a function of time while a target assembly containing a target material rod used to create the desired radioisotope passes through a sensing assembly at a constant speed; creating a representation of a background-corrected self-feeding detector signal correction value as a function of position along the target assembly; creating a function that provides a fitted representation to the self-feeding detector signal measurement as a function of the target assembly position (L); integrating the function over the length of the target assembly containing the target material rod used to create the desired radioisotope; and converting the integral value to gamma-ray radioactivity based on gamma-ray sensitivity.

[0017] In another embodiment, the method includes determining whether or not to collect a desired radioisotope based on its gamma-ray radioactivity.

[0018] In another aspect of the method, the function is -y(L)=a0+a1(L)+a2(L) 2 +a3(L) 3 +...+a n (L) n It has the form of .

[0019] The foregoing summary is illustrative only and is not intended to be limiting in any way. In addition to the exemplary aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description of the invention.

Brief Description of the Drawings

[0020] The various features of the embodiments described herein, together with their advantages, can be understood in accordance with the following description taken in conjunction with the accompanying drawings below.

[0021] [Figure 1] A radioactivity monitoring system for radioactive isotopes for use in a fuel rod assembly insertion target, according to at least one aspect of the present disclosure, is shown. [Figure 2] A self-powered detector (SPD) assembly, according to at least one aspect of the present disclosure, is shown. [Figure 3] A top view of a sensing assembly, according to at least one aspect of the present disclosure. [Figure 4] A cross-sectional view of the sensing assembly taken along section line 4-4, according to at least one aspect of the present disclosure. [Figure 5] A method for measuring an SPD signal to calculate the radioactivity of a radioactive isotope of a target assembly 102, according to at least one aspect of the present disclosure, is shown. [Figure 6] A method for analyzing the total radioactivity of a desired radioactive isotope, according to at least one aspect of the present disclosure, is shown.

[0022] Corresponding reference characters indicate corresponding parts throughout the several views. The examples described herein illustrate various embodiments of the invention in one form, and such examples should not be construed as limiting the scope of the invention in any way.

Detailed Description of the Invention

[0023] In one embodiment, the Disclosure provides a radioactive isotope monitoring device, system, and method for measuring the radioactivity of a desired radioisotope during a reactor refueling shutdown to determine whether or not to extract and process an irradiation target material. In another embodiment, the Disclosure provides a radioactive isotope monitoring device, system, and method for determining the progress of production of a desired radioisotope during a refueling shutdown that occurs prior to an expected extraction time.

[0024] In one embodiment, the disclosure provides an apparatus, system, and method for verifying a design prediction of the production rate of a desired radioisotope and determining whether the radioactivity of the desired radioisotope is sufficiently high to initiate extraction operations. The apparatus has no moving parts and is less susceptible to changes in operating characteristics due to radiation exposure.

[0025] In one embodiment, the apparatus, system, and method of the present disclosure enable the generation of radioisotopes, such as cobalt-60, above a certain minimum required radioactivity level without cutting the rodlet of the target assembly. The application of the apparatus, system, and method of the present disclosure can reduce certain commercial risks associated with the generation of radioisotopes.

[0026] Referring here to the figures, Figure 1 shows a radioactive isotope monitoring system 100 for use in a fuel rod assembly insertion target according to at least one aspect of the present disclosure. The radioactive isotope monitoring system 100 comprises a target assembly 102 slidably positioned within a fuel rod assembly 104 of a reactor, and a sensing assembly 106 configured to receive the target assembly 102 as indicated by arrow A. The target assembly 102 comprises a target material rod 108 fixedly coupled to an orifice plate 122 of an upper nozzle 110 which is slidably inserted within the fuel rod assembly 104. The target material rod 108 is fabricated from a metallic structure such as steel. The target material rod 108 is subjected to a specific neutron flux exposure level for a minimum amount of reactor operating time. The radioactive isotope monitoring system 100 is used to measure the radioactivity of the radioactive isotopes of the target material rod 108. The orifice plate 122 is sized and configured to receive the target material rod 108, and the upper nozzle 110 allows the target material rod 108 to be withdrawn from or inserted into the fuel rod assembly 104. The upper nozzle 110 is withdrawn or inserted through the sensing assembly 106.

[0027] To generate a desired amount of medical or industrial radioisotope, such as cobalt-60, in a commercial power reactor, a target material rod 108 must be inserted into the fuel rod assembly 104 in the reactor and subjected to a specific level of neutron flux exposure for a minimum amount of reactor operating time. To determine whether the irradiated target material rod 108 is salvageable, the radioactivity level of the desired radioisotope within the target assembly 102 must be measured. By using the radioisotope radioactivity monitoring system 100 during a reactor refueling shutdown to measure the radioactivity of the desired radioisotope, it is possible to determine whether or not to withdraw and process the irradiated target material rod 108. When the radioisotope radioactivity monitoring system 100 is used, it becomes possible to determine the progress of the generation of the desired radioisotope during a refueling shutdown that occurs before the expected time of extraction.

[0028] The fuel rod assembly 104 comprises a plurality of fuel rods 118. The grid spacers 120 hold the fuel rod bundles 118 in place, maintain appropriate rod-to-rod clearance, and enhance the critical heat flux. The target material rod 108 is slidably positioned between the fuel rods 118.

[0029] The sensing assembly 106 defines an opening 112 large enough to receive the target assembly 102. In the embodiment shown in Figure 1, the sensing assembly 106 defines a rectangular opening 112 for accommodating a rectangular orifice plate 122 that lifts the target material rod 108. However, in various embodiments, the shape of the opening 112 may be hexagonal for use with a hexagonal fuel assembly design, or it may define any suitable shape for accommodating a fuel assembly design, square, circular, elliptical, or any other suitable configuration. The sensing assembly 106 is connected to a handle 114. The sensing assembly 106 is electrically coupled to a platinum self-powered detector (SPD) signal cable 116 located within the handle 114. To measure the radioactivity of the radioisotopes of the target material rod 108, the target assembly 102 passes through the opening 112 of the sensing assembly 106 at a constant speed while the fuel rod assembly 104 remains stationary below the opening 112. The gamma rays detected by the sensing assembly 106 generate a current (I) through the SPD signal cable 116, which is recorded by the voltage and current data logger or recorder 124.

[0030] Figure 2 shows a self-powered detector (SPD) assembly 200 according to at least one aspect of the present disclosure. Referring also to Figure 1, the sensing assembly 106 includes the self-powered detector assembly 200. The SPD assembly 200 comprises a sensing unit 202 using, for example, an emitter wire 204 made of platinum, or other rapid-response gamma-ray sensitive material. The emitter wire 204 is electrically connected to, for example, a steel signal wire 206. The emitter wire 204 and the steel signal wire 206 are enclosed in an outer sheath 208, which may be made of, for example, steel. An electrical insulating material 210, such as magnesium oxide (MgO), fills the space defined in the outer sheath 208. The electrical insulating material 210 is used as an insulating core surrounding the emitter wire 204 and functions as a guide insulator for guiding the signal wire 206. In one aspect, the outer diameter "d" of the outer sheath 208 may be about 0.08 inches. In various embodiments, the outer diameter "d" of the outer sheath 208 can be selected, for example, within the range of 0.05 inches to 0.15 inches. The emitter wire 204 may have a length "L1" of, for example, about 10 feet, and the signal wire 206 may have a length "L2" of, for example, about 60 feet.

[0031] In various embodiments, the emitter wire 204 of the SPD assembly 200 includes an emitter core made of at least one material selected from nickel, iron, titanium, and alloys based on these metals, and an emitter jacket around the core having a thickness in the range of about 0.03 mm to about 0.062 mm and being at least one material selected from platinum, tantalum, osmium, molybdenum, and cerium. This structure increases the neutron-to-gamma ray sensitivity ratio and therefore the rapid response rate while keeping the burnup at an acceptable low by increasing the emitter diameter beyond what is optimal for a solid platinum emitter. The large-diameter emitter of this structure has response characteristics that closely match the characteristics required for fuel power detectors, such as those in heavy water-moderated natural uranium power reactors. The emitter core is preferably Inconel®, and the emitter jacket is preferably platinum.

[0032] Figure 3 is a top view 300 of a sensing assembly 106 according to at least one aspect of the present disclosure. Figure 4 is a cross-sectional view of a sensing assembly taken along cutting line 4-4 according to at least one aspect of the present disclosure. Referring here to Figures 1 to 4, the sensing assembly 106 includes an inner case 302, an outer shield 304, and a space 306 defined between them, which houses the helically wound sensing unit 202 of the self-powered detector assembly 200 shown in Figure 2. The inner case 302 is a shell that functions as the inner surface of the sensing assembly 106. The inner case 302 has an inner surface 308 and an outer surface 310. The outer surface 310 faces the opening 112. The sensing unit 202 of the SPD assembly 200 is a coil 312 helically wound around the outer surface 308 of the inner case 302. The length "L1" of the sensing portion 202 of the SPD emitter wire 204 and the tightness of the coil 312 are determined using the measured SPD gamma-ray sensitivity and the expected gamma-ray radioactivity of the desired radioisotope per unit length of the target being measured. The length "L1" of the coil 312 bend and the tightness may be selected to maximize the SPD current per unit length output and minimize the height of the SPD cable coil, thereby minimizing the time required to obtain a measurement with the minimum measurement error.

[0033] The outer shielding 304 of the sensing assembly 106 may be made of a material such as tungsten (W) to shield the sensing portion 202 of the SPD emitter wire 204 from gamma rays originating from outside the sensing assembly 106. The inner case 302 of the sensing assembly 106 is made of a material such as steel to minimize the attenuation of gamma rays used to determine the radioactivity of the target material on the target material rod 108, for example. The sensing assembly 106 is sealed to prevent water from entering during use.

[0034] The sensing assembly 106 is connected to a handle 114, which serves as a means for positioning the sensing assembly 106 on top of a target assembly 102 containing a target material rod 108 that is withdrawn from or inserted into the fuel rod assembly 104. The length of the handle 114 is sufficient to facilitate access from the bridge of the refueling pool or casking pool. The handle 114 also serves as a conduit for the portion of the SPD signal wire 116 of the SPD assembly 200. The total length of the SPD signal wire 116 is sufficient to allow the SPD signal to be measured at a desired location within the target sampling area. The height "H" of the sensing assembly 106 may be selected to be about 10 inches, but this disclosure should not be limited in this context.

[0035] In some embodiments, the radioactivity measurement system 100 shown in Figure 1, and its components shown in detail in Figures 2 to 4, may be used to measure the SPD signal and calculate the radioactivity of the target assembly 102. Figure 5 shows a method 400 for measuring the SPD signal to calculate the radioactivity of radioisotopes in the target assembly 102, according to at least one embodiment of the present disclosure. Referring again to Figures 1 to 4, according to method 400, a sensing assembly 106 is positioned on top of a suitable fuel rod assembly 104 (402) so that the tools necessary for removing or installing the target assembly 102 can be used. This can be done by manipulating the sensing assembly 106 on the fuel rod assembly 104. The position of the device handle 114 is fixed so as not to shift during insertion or removal of the target assembly 102 through the opening 112 defined by the sensing assembly 106.

[0036] After positioning the sensing assembly 106 to the desired position (402), a first background gamma-ray signal measurement from an external gamma-ray source is obtained by measuring the current (I) through the SPD signal cable 116 with the desired measurement accuracy (404), and then the target assembly 102 is passed through (inserted / removed) the sensing assembly 106. Next, the measurement of the current (I) representing the background gamma rays is recorded by the recorder 124 (406).

[0037] After recording the background gamma-ray signal current (I) (406), the target assembly 102 passes through the sensing assembly 106 at a constant speed (is withdrawn or inserted) (408). The speed should be controlled so as to control the measurement accuracy of the measured SPD signal current (I). While the target assembly 102 passes through the sensing assembly 106 (408), the measured SPD signal current (I) as a function of time is recorded by the recorder 124 (410). After the target assembly 102 has completely passed through the sensing assembly (408), a second background gamma-ray signal measurement from an external gamma-ray source is acquired (412), and the measured SPD signal current (I) is recorded by the recorder 124 (414). Method 400 is repeated as necessary to measure gamma-ray signals for all desired target assemblies 102.

[0038] The total radioactivity of the desired radioisotope in the target assembly 102 is determined by integrating a function fitted to the relationship between the self-feeding detector signal current (I) measurement and time over the active length of the target assembly 102. The integration region is determined using insertion / extraction (408) speed and self-feeding detector signal current (I) measurement data when the active portion of the target assembly 102 is inside the opening 112 defined by the sensing assembly 106. An example of the analysis method used in one approach is illustrated by process 500, which is shown in Figure 6.

[0039] Figure 6 shows a method 500 for analyzing the total radioactivity of a desired radioisotope according to at least one aspect of the present disclosure. Referring again to Figures 1-4, according to method 500, an SPD signal is recorded as a function of time as a target assembly 102 passes through a sensing assembly 106 at a constant speed (502). The target assembly 102 includes a target material rod 108 used to create the desired radioisotope. A background-corrected representation of the SPD signal measurement is created as a function of position along the target assembly 102 (504). A function providing a fitted representation to the SPD signal measurement as a function of position (L) of the target assembly 102 (e.g., -y(L) = a0 + a1(L) + a2(L)) 2 +a3(L) 3 +...+a n (L) n A function is created (506). After the function has been created (506), the function is integrated over the length (i.e., -0-L) of the target assembly 102 containing the target material rod 108 used to create the desired radioisotope (508). The integrated value is converted to gamma-ray radioactivity using either the gamma-ray sensitivity measured or provided by the manufacturer (510), and spatial adjustments can be readily determined by those skilled in the art. The results of this method 500 may be used to determine whether to proceed with the extraction or production of the desired radioisotope (512). [Examples]

[0040] Various aspects of the subject matter described herein are illustrated in the following examples.

[0041] Example 1. A radioactive isotope radioactivity monitoring system comprising: a fuel rod assembly comprising a plurality of nuclear fuel rods; a target assembly comprising an upper nozzle comprising an orifice plate and at least one target material rod fixedly coupled to the orifice plate and slidably disposed within the fuel rod assembly; and a sensing assembly defining an opening of size and configuration that penetrates and receives the target assembly, the sensing assembly comprising a self-powered detector assembly for detecting the radioactivity of radioactive isotopes of the target rod material.

[0042] Example 2. A radioactive isotope radioactivity monitoring system according to Example 1, wherein the self-powered detector assembly comprises a sensing unit having an emitter wire and a signal wire electrically coupled to the emitter wire, the emitter wire being made of a rapid-response gamma-ray sensitive material that generates an electric current when exposed to gamma rays, and the emitter wire and signal wire being sealed in an outer sheath.

[0043] Example 3. A radioactive isotope monitoring system according to Example 1 or 2, wherein the emitter wire contains platinum.

[0044] Example 4. A radioactive isotope monitoring system according to one or more of Examples 1 to 3, wherein the signal wire is made of steel.

[0045] Example 5. A radioactive isotope monitoring system according to one or more of Examples 1 to 4, wherein the outer sheath is made of steel.

[0046] Example 6. A radioactivity monitoring system for radioisotopes according to one or more of Examples 1 to 5, wherein the outer sheath is filled with an electrical insulating material.

[0047] Example 7. A radioactivity monitoring system for radioisotopes according to one or more of Examples 1 to 6, wherein the electrical insulating material is magnesium oxide (MgO).

[0048] Example 8. A radioactive isotope monitoring system according to any one or more of Examples 1 to 7, wherein the sensing assembly comprises an inner case, an outer shield, and a defined space between the inner case and the outer shield for housing a helically wound sensing section of a self-powered detector assembly.

[0049] Example 9. A radioactive isotope monitoring system according to one or more of Examples 1 to 8, wherein the outer shielding consists of a material for shielding the sensing portion of the emitter wire from gamma rays originating from outside the sensing assembly.

[0050] Example 10. A radioactivity monitoring system for radioisotopes according to one or more of Examples 1 to 9, wherein the outer shielding is made of tungsten (W).

[0051] Example 11. A radioactivity monitoring system for radioisotopes according to one or more of Examples 1 to 10, wherein the sensing assembly is connected to a handle.

[0052] Example 12. A radioactive isotope monitoring system according to one or more of Examples 1 to 11, wherein a handle is configured to position a sensing assembly over a target assembly containing a target material rod that is inserted into and removed from a fuel rod assembly.

[0053] Example 13. A method for measuring a self-powered detector signal to calculate the radioactivity of radioisotopes in a target assembly, wherein the target assembly comprises an upper nozzle having an orifice plate, and at least one target material rod fixedly coupled to the orifice plate and slidably positioned within a fuel rod assembly, the method comprising defining an opening of size and configuration to penetrate and receive the target assembly, positioning a sensing assembly including a self-powered detector assembly for detecting the radioactivity of radioisotopes in the target rod material, and using the sensing assembly to detect external gamma rays A method comprising: acquiring a first background gamma-ray signal measurement from a source; recording the first background gamma-ray signal measurement by a recorder; passing a target assembly through a sensing assembly at a constant speed; recording a self-powered detector signal current (I) measured while the target assembly passes through the sensing assembly as a function of time by a recorder; acquiring a second background gamma-ray signal measurement from an external gamma-ray source after the target assembly has completely passed through the sensing assembly; and recording the second background gamma-ray signal measurement by a recorder.

[0054] Example 14. The method according to Example 13, comprising determining the total radioactivity of radioisotopes in a target assembly by integrating a function fitted to the relationship between the measured value of the self-powered detector signal current (I) and time over the active length of the target assembly.

[0055] Example 15. The method according to Example 13 or 14, comprising determining the integration region based on measurements of insertion / extraction speed and self-powered detector signal current (I) recorded when the active portion of the target assembly is inside an opening defined by the sensing assembly.

[0056] Example 16. The method according to any one or more of Examples 13 to 15, wherein measured values of first and second background gamma-ray signals from an external gamma-ray source are obtained by measuring a current (I) through a self-powered detector signal cable.

[0057] Example 17. A method for analyzing the total radioactivity of a desired radioisotope, the method comprising recording a self-powered detector signal as a function of time while a target assembly including a target substance rod used for creating the desired radioisotope passes through a sensing assembly at a constant speed; creating a representation of the background-corrected self-powered detector signal measurement as a function of position along the target assembly; creating a function that provides a fitting representation to the self-powered detector signal measurement as a function of the target assembly position (L); integrating the function over the length of the target assembly including the target substance rod used for creating the desired radioisotope; and converting the integrated value to gamma-ray radioactivity based on gamma-ray sensitivity.

[0058] Example 18. The method according to Example 17, comprising determining whether to collect a desired radioisotope based on gamma-ray radioactivity.

[0059] Example 19. The method according to Example 17 or 18, wherein the function has the form of -y(L)=a0+a1(L)+a2(L) 2 +a3(L) 3 +...+a n (L) n

[0060] While specific embodiments of the present invention have been described in detail, various modifications and alternatives to those details may be developed in light of the overall teachings of this disclosure, and it will be understood by those skilled in the art that one or more selected elements from the exemplary embodiments may be combined with one or more elements from other embodiments without deviating from the scope of the disclosed concept. Accordingly, the specific embodiments disclosed are for illustrative purposes only and do not limit the scope of the present invention to the entirety of the appended claims and any or all of their equivalents.

[0061] Those skilled in the art will generally recognize that the terms used herein, and in particular in the appended claims (e.g., the body of the appended claims), are generally intended to be “open” terms (for example, the term “includes” should be interpreted as “includes but not limited,” the term “has” should be interpreted as “at least has,” and the term “includes” should be interpreted as “includes but not limited,” etc.). If a particular number of claims to be introduced is intended, such intention will be explicitly enumerated in the claims, and if there is no such enumeration, such intention will not exist, as will be understood by those skilled in the art. For example, to aid understanding, the following appended claims may contain the use of the introductory phrases “at least one” and “one or more” to introduce an enumeration of claims. However, the use of such phrases should not be interpreted as implying that the introduction of a claim enumeration by the indefinite article “a” or “an” limits any particular claim containing such introduced claim enumeration to only one such claim, even when the same claim contains the introductory phrase “one or more” or “at least one” and an indefinite article such as “a” or “an” (for example, “a” and / or “an” should typically be interpreted as meaning “at least one” or “one or more”), and the same applies to the use of specific articles used to introduce a claim enumeration.

[0062] In addition, even if a particular number of claims enumerated is explicitly listed, a person skilled in the art will understand that such enumeration should typically be interpreted as meaning at least the number listed (for example, the literal enumeration of “two enumerations” without other modifiers means at least two enumerations, or two or more enumerations). Furthermore, in such cases where a convention similar to “at least one of A, B, and C, etc.” is used, such construction is generally intended to mean that a person skilled in the art will understand the convention (for example, “a system having at least one of A, B, and C” would not be limited to systems having A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or systems having A, B, and C together, etc.). In cases where a convention similar to "at least one of A, B, or C" is used, such construction is generally intended to mean that a person skilled in the art will understand the convention (for example, "a system having at least one of A, B, or C" would not be limited to, but would include, systems having A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or systems having A, B, and C together). A person skilled in the art will further understand that typical disjunctive words and / or phrases presenting two or more alternative terms in any description, claims, or drawings should be understood to intend the possibility of including one of the terms, either of the terms, or both, unless the context otherwise indicates. For example, the phrase "A or B" would typically be understood to include the possibilities of "A" or "B" or "A and B".

[0063] With respect to the attached claims, those skilled in the art will understand that the operations listed therein may generally be performed in any order. Furthermore, while various operation flowcharts are presented in sequence, it should be understood that various operations may be performed in other orders than those exemplified, or simultaneously. Examples of such alternative orderings include, unless otherwise indicated by the context, overlap, alternating, interruption, reordering, incremental, substituting, supplementing, simultaneous, reverse, or various other orderings. Moreover, unless otherwise indicated by the context, terms such as “responding,” “related,” or other past tense adjectives are generally not intended to exclude such variations.

[0064] Any reference to “one aspect,” “one aspect,” “one example,” or “one example” should be noted as meaning that a particular feature, structure, or characteristic described in relation to an aspect is included in at least one aspect. Therefore, throughout this specification, the occurrences of the phrases “in one aspect,” “in one aspect,” “one example,” and “one example” in various places do not necessarily all refer to the same aspect. Furthermore, a particular feature, structure, or characteristic may be combined in any preferred manner in one or more aspects.

[0065] Any patent application, patent, non-patent publication, or other disclosure material referenced herein and / or enumerated in any application data sheet is incorporated herein by reference and, to that extent, is not inconsistent with the material incorporated herein. Accordingly, the disclosures contained herein supersede, to the extent necessary, any inconsistent material incorporated herein by reference. Any material, or any part thereof, that is inconsistent with existing definitions, descriptions, or other disclosure materials contained herein but is referred to as being incorporated herein by reference will be incorporated only to the extent that there is no inconsistency between the incorporated material and the existing disclosure material.

[0066] The terms “to have” (and any form of “comprise,” such as “comprises” and “comprising”), “to possess” (and any form of “have,” such as “has” and “having”), “to include” (and any form of “include,” such as “includes” and “including”), and “to contain” (and any form of “contains” and “containing”) are open-ended linking verbs. As a result, a system that “has,” “possesses,” “possesses,” or “contains” one or more elements possesses, but is not limited to possessing only, those one or more elements. Similarly, an element of a system, device, or apparatus that “possesses,” “possesses,” or “contains” one or more features possesses, but is not limited to possessing only, those one or more features.

[0067] In summary, numerous benefits resulting from adopting the concepts described herein are described. The above descriptions of one or more forms are presented for illustrative and explanatory purposes only. They are not intended to exhaust or limit the exact forms disclosed. Modifications or variations are possible in light of the above teachings. One or more forms are selected and described to illustrate the principle and practical application, thereby enabling those skilled in the art to utilize various forms and various modifications suitable for the particular use to be envisioned. The claims submitted herein are intended to define the overall scope of this disclosure.

Claims

1. A radioactive isotope radioactivity monitoring system, A fuel rod assembly comprising multiple nuclear fuel rods, A target assembly, An upper nozzle equipped with an orifice plate, A target assembly comprising: at least one target material rod fixedly coupled to the orifice plate and slidably disposed within the fuel rod assembly; A radioactive isotope monitoring system comprising: a sensing assembly that defines an opening of size and configuration for penetrating and receiving the target assembly, the sensing assembly including a self-powered detector assembly for detecting the radioactivity of radioactive isotopes of the target material rod.

2. The self-powered detector assembly, A sensing unit equipped with an emitter wire, The emitter wire is electrically coupled to a signal wire, The emitter wire is made from a fast-response gamma-ray sensitive material and generates an electric current when exposed to gamma rays. The radioactivity monitoring system for radioisotopes according to claim 1, wherein the emitter wire and the signal wire are enclosed within an outer sheath.

3. The radioactivity monitoring system for a radioisotope according to claim 2, wherein the emitter wire contains platinum.

4. The radioactivity monitoring system for radioisotopes according to claim 2, wherein the signal wire is made of steel.

5. The radioactivity monitoring system for radioisotopes according to claim 2, wherein the outer sheath is made of steel.

6. The radioactivity monitoring system for radioisotopes according to claim 2, wherein the outer sheath is filled with an electrical insulating material.

7. The radioactivity monitoring system for radioisotopes according to claim 6, wherein the electrical insulating material is magnesium oxide (MgO).

8. The sensing assembly, The inner case and External shielding, A radioactive isotope radioactivity monitoring system according to claim 1, comprising: a space defined between the inner case and the outer shield for housing the helically wound sensing portion of the self-powered detector assembly.

9. The radioactivity monitoring system for radioisotopes according to claim 8, wherein the outer shielding is made of a material for shielding the sensing part from gamma rays originating from outside the sensing assembly.

10. The radioactivity monitoring system for radioactive isotopes according to claim 9, wherein the outer shielding is made of tungsten (W).

11. The radioactivity monitoring system for radioisotopes according to claim 1, wherein the sensing assembly is connected to a handle.

12. The radioactivity monitoring system for radioisotopes according to claim 11, wherein the handle is configured to position the sensing assembly on the target assembly, which includes the target material rods that are inserted into and removed from the fuel rod assembly.

13. A method for measuring a self-powered detector signal to calculate the radioactivity of radioisotopes in a target assembly, wherein the target assembly comprises an upper nozzle having an orifice plate, and at least one target material rod fixedly coupled to the orifice plate and slidably disposed within a fuel rod assembly, and the method is Positioning a sensing assembly on the fuel rod assembly, which includes a self-powered detector assembly for detecting the radioactivity of at least one target material rod's radioisotope, defining an opening of size and configuration to penetrate and receive the target assembly, The sensing assembly acquires a first background gamma-ray signal measurement from an external gamma-ray source, The recorder records the first background gamma-ray signal measurement value, Passing the target assembly through the sensing assembly at a constant speed, The recorder records the self-powered detector signal current (I) measured while the target assembly passes through the sensing assembly as a function of time, After the target assembly has completely passed through the sensing assembly, a second background gamma-ray signal measurement from an external gamma-ray source is obtained. A method comprising recording the second background gamma-ray signal measurement using the recorder.

14. The method according to claim 13, comprising determining the total radioactivity of the radioisotopes in the target assembly by integrating a function fitted to the relationship between the measured value of the self-powered detector signal current (I) and time over the active length of the target assembly.

15. The method according to claim 14, comprising determining an integration region based on measurements of the insertion / removal speed and the self-powered detector signal current (I) recorded when the active portion of the target assembly is inside the opening defined by the sensing assembly.

16. The method according to claim 13, wherein the first and second background gamma-ray signal measurements from an external gamma-ray source are obtained by measuring a current (I) through the self-powered detector signal cable of the sensing assembly.

17. A method for analyzing the total radioactivity of a desired radioisotope, wherein the method is The self-powered detector signal is recorded as a function of time while the target assembly, which includes a target material rod used to create the desired radioisotope, passes through the sensing assembly at a constant speed. To create a representation of the background-corrected self-powered detector signal as a function of the position (L) along the target assembly, To create a function that provides a fitted representation to the self-powered detector signal as a function of the position (L) along the target assembly, The integral value is obtained by integrating the function over the length of the target assembly, which includes the target material rod used to create the desired radioactive isotope, A method comprising converting the integral value into gamma-ray radioactivity based on gamma-ray sensitivity.

18. The method according to claim 17, comprising determining whether or not to collect the desired radioisotope based on the gamma-ray radioactivity.

19. The aforementioned function is, -y(L) = a ０ +a １ (L) + a ２ (L) ２ +a ３ (L) ３ +. . . +a ｎ (L) ｎ The method according to claim 17, having the form of the above.

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