Wireless Power Level and Power Distribution Monitoring and Control System for Subcritical Spent Fuel Assembly Arrays Using Removable SiC Neutron Detection Thimble Tubes

Abstract

A power sensor system for monitoring a subcritical neutron generator is provided. The power sensor system includes a self-powered sensor insert. The self-powered sensor insert includes an insert thimble and a detector assembly. The insert thimble includes an outer housing, a power generator configured to generate power based on incident radiation, and a first electrical interface electrically connected to the power generator. The detector assembly includes a solid-state radiation detector capable of providing a detector signal directly proportional to a neutron flux level, a transmitter configured to wirelessly output a transmitter signal based on the detector signal, and a second electrical interface configured to electrically couple to the first electrical interface. Also provided are a power monitoring system including the power sensor system and a control system, and a method for optimizing a subcritical neutron generator.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of and priority under 35 U.S.C. 120 of U.S. Patent Application Serial No. 17 / 813,156, filed July 18, 2023, entitled "Wireless Power Level And Power Distribution Monitoring And Control System For Subcritical Spent Fuel Assembly Array Using Removable Sic Neutron Detector Thimble Tube," the contents of which are incorporated herein by reference in their entirety. [Background technology]

[0002] Accurate and continuous monitoring of neutron flux levels within fuel assemblies contained within the spent fuel array of a subcritical neutron generator is essential to determine the maximum neutron flux and K eff This is necessary to ensure that the neutron flux in a subcritical neutron generator is not exceeded. The relatively low values of neutron flux in the spent fuel array make it difficult to use currently available neutron radiation measurement equipment and techniques employed in typical commercial power reactor and research reactor environments. Furthermore, the need to continuously and accurately monitor neutron flux in a subcritical neutron generator significantly limits the space available for incorporating neutron radiation measurement equipment. A need exists for developing monitoring systems and methods that optimize the neutron flux in a subcritical neutron generator without compromising safe operating conditions. Summary of the Invention

[0003] The following summary is provided to facilitate an understanding of some of the innovative features unique to the embodiments disclosed herein and is not intended to be a complete description. A complete understanding of the various embodiments disclosed herein can be obtained by taking the entire specification, claims, and abstract as a whole.

[0004] In various embodiments, a power sensor system for monitoring a subcritical neutron generator is disclosed. In some embodiments, the power sensor system includes a self-powered sensor insert for measuring neutron flux levels in a spent fuel assembly of the subcritical neutron generator. In some embodiments, the self-powered sensor insert includes an insert thimble and a detector assembly. In some embodiments, the insert thimble includes an outer housing including a closed end, a hollow tube disposed within the outer housing, a power generator disposed between the hollow tube and the outer housing, and a first electrical interface electrically connected to the power generator. In some embodiments, the outer housing is insertable into a guide thimble of the spent fuel assembly. In some embodiments, the power generator includes an electron emitter and an electron collector, the electron emitter comprising a first material and a second material, the electron emitter configured to respond to incident radiation generated by the spent fuel assembly, and the power generator configured to generate power based on the incident radiation. In some embodiments, the detector assembly includes a detector tube sized to fit into the hollow tube of the insert thimble, the detector tube including a solid-state radiation detector that provides a detection signal directly proportional to a neutron flux level; a transmitter portion including a transmitting circuit, the transmitter portion configured to wirelessly output a transmitter signal based on the detection signal; and a second electrical interface configured to electrically couple to the first electrical interface, the second electrical interface electrically connected to the transmitter circuit.

[0005] In various aspects, a power monitoring system for controlling a subcritical neutron generator is disclosed. In some aspects, the power monitoring system includes a power sensor system for monitoring the subcritical neutron generator and a control system. In some aspects, the power sensor system includes a self-powered sensor insert for measuring neutron flux levels in spent fuel assemblies of the subcritical neutron generator. In some aspects, the self-powered sensor insert includes an insert thimble and a detector assembly. In certain aspects, the insert thimble includes a housing, a first power generator for generating a first electrical power based on delta radiation, the first power generator comprising a material having a high neutron capture cross section, and a first electrical interface configured to output the first electrical power. In certain embodiments, the detector assembly includes a detector tube configured to be surrounded by a first power generator, at least one radiation detector including a silicon carbide-based Schottky diode, the at least one radiation detector encased within the detector tube, and the at least one radiation detector adapted to provide a first signal in response to incident neutron flux; a transmitter circuit including a transmitter for outputting a wireless signal based on the first signal; and a second electrical interface adapted to receive the first power and providing power to the transmitter circuit. In some embodiments, the control system includes an antenna for receiving the wireless signal, a signal interface, an input of the signal interface electrically connected to the antenna, the signal interface configured to output a third signal based on the wireless signal, and a controller including a processor. In certain embodiments, the processor is configured to receive the third signal and to control the neutron flux output by the electron neutron generator of the subcritical neutron generator based on the third signal.

[0006] In various aspects, a method of optimizing a subcritical neutron generator is disclosed. In some aspects, the method includes preparing a subcritical neutron generator and loading the subcritical neutron generator. In certain aspects, preparing the subcritical neutron generator includes opening a top of a containment vessel of the subcritical neutron generator and inserting a self-powered sensor insert of a power monitoring system into at least one spent fuel assembly. In certain aspects, loading the subcritical neutron generator includes individually inserting at least one spent fuel assembly into the open top of the containment vessel, continuously monitoring a signal generated by the self-powered sensor insert during loading to evaluate a neutron regeneration factor within the open containment vessel, and replacing the top of the containment vessel after loading the last of the at least one spent fuel assembly.

[0007] These and other objects, features, and characteristics of the present disclosure, as well as the method of operation and function of the associated elements of construction, and the combination of parts and economies of manufacture, will become more apparent from a study of the following description and the appended claims, taken in conjunction with the accompanying drawings, all of which constitute a part of this specification, and in which like reference numerals indicate corresponding parts in the different views. It is to be expressly understood, however, that the drawings are for the purposes of illustration and description only and are not intended as a definition of the limits of the embodiments disclosed herein. [Brief explanation of the drawings]

[0008] The various aspects described herein, together with their objects and advantages, may best be understood by referring to the following description taken in conjunction with the accompanying drawings, in which:

[0009] [Figure 1] 1 is a cross-sectional schematic diagram of a subcritical neutron generator according to at least one non-limiting embodiment of the present disclosure.

[0010] [Figure 2]1 is a cross-sectional schematic diagram of a power sensor system according to at least one non-limiting aspect of the present disclosure.

[0011] [Figure 3] 1 is a schematic diagram of an axial cross section of an exemplary self-powered sensor insert, according to at least one non-limiting embodiment of the present disclosure.

[0012] [Figure 4] 1 is a schematic diagram of an axial cross section of an insert thimble according to at least one non-limiting embodiment of the present disclosure.

[0013] [Figure 5] 1 is a schematic diagram of a cross section of a generator configured as a multi-layer wire, according to at least one non-limiting embodiment of the present disclosure.

[0014] [Figure 6] 1 is a schematic diagram of an axial cross section of a detector assembly according to at least one non-limiting embodiment of the present disclosure.

[0015] [Figure 7] 1 is a schematic block diagram of a transmitter circuit according to at least one non-limiting aspect of the present disclosure.

[0016] [Figure 8] 1 is a schematic diagram of a power monitoring system for a subcritical neutron generator, in accordance with at least one non-limiting embodiment of the present disclosure.

[0017] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set forth herein illustrate various aspects of the present disclosure in certain forms, and such exemplifications should not be construed as limiting the scope of any aspect disclosed herein. DETAILED DESCRIPTION OF THE INVENTION

[0018] Certain exemplary embodiments of the present disclosure will now be described to provide a general understanding of the principles of composition, function, manufacture, and use of the compositions and methods disclosed herein. Examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the compositions, articles, and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments, and that the scope of various embodiments of the present invention is defined only by the claims. Features shown or described in connection with one exemplary embodiment may be combined with features of other embodiments. Such modifications and variations are intended to be within the scope of the present invention.

[0019] Throughout this specification, references to "various embodiments," "some embodiments," "one embodiment," "an embodiment," etc., mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in the embodiment. Thus, the appearances of phrases such as "in various embodiments," "in some embodiments," "in one embodiment," "in an embodiment," etc. in various places throughout this specification do not necessarily all refer to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in embodiments. Thus, particular features, structures, or characteristics illustrated or described in connection with one embodiment may be combined, in whole or in part, with features, structures, or characteristics of another embodiment or other embodiments without limitation. Such modifications and variations are intended to be included within the scope of the present embodiments.

[0020] In the following description, like reference characters indicate like or corresponding parts throughout the several views of the drawings. It should also be understood that in the following description, terms such as "front," "rear," "left," "right," "top," "bottom," "upper," "lower," etc. are used for convenience and are not to be construed as limiting terms.

[0021] Synthetic radioisotopes are typically produced by enriching parent isotopes in a neutron-rich environment, such as within the fuel assemblies of an operating nuclear reactor or within a subcritical neutron generator. In an operating nuclear reactor, the fissile fuel in the fuel assemblies undergoes nuclear fission, producing fission products containing fast neutrons. In an operating power reactor, these fission products then initiate a self-sustaining chain reaction or critical reactor state. When the fissile fuel contained in a nuclear fuel assembly is depleted or otherwise spent, the spent fuel assembly is no longer capable of maintaining critical reactor state and is therefore no longer useful for commercial thermal power generation. However, the spent fuel assembly contains radioisotopes that continue to emit ionizing radiation, such as gamma rays.

[0022] Sufficient neutron flux is required to produce the desired radioisotopes in an irradiation target containing the parent isotope. Electronic neutron generators (hereinafter referred to as "ENGs") can generate a moderate neutron flux and are inherently safer to operate than commercial nuclear reactors, but ENGs cannot provide sufficient neutron flux to produce synthetic radioisotopes on a commercial scale. However, the neutron flux generated by an ENG can be used to induce subcritical fission of spent fuel, thereby producing gamma rays and sufficient subcritical neutron flux for commercial radioisotope production. For example, FIG. 1 illustrates a cross-sectional schematic diagram of a subcritical neutron generator 10 according to at least one non-limiting embodiment of the present disclosure. The subcritical neutron generator 10 can include a containment vessel 11 having an opening covered by a removable cover or lid, an array of ENGs 12, and a removable subcritical array of spent fuel assemblies 14. The subcritical neutron generator can direct neutron flux from the ENG toward the spent fuel assemblies, producing more neutrons than the ENG alone and sufficient neutron flux to commercially produce synthetic radioisotopes. Furthermore, the subcritical neutron generator 10 can be easily reloaded with a new array of spent fuel assemblies through an opening in the containment vessel 11, for example, by removing a cover / lid. In this manner, the subcritical neutron generator can be used to irradiate parent isotopes without the need for an operating reactor or its complex operating procedures. Additional details and applications related to sub-critical neutron generators are described in U.S. patent application Ser. No. 17 / 807,067, filed June 15, 2022, entitled "USE OF SUB-CRITICAL NEUTRON MULTIPLICATION DRIVEN BY ELECTRONIC NEUTRON GENERATORS TO PRODUCE RADIOISOTOPES," which is owned by the applicant of the present application and is incorporated herein by reference in its entirety.

[0023] As mentioned above, subcritical neutron generators can provide a significantly higher neutron flux than ENGs. However, the neutron flux provided by an ENG to spent fuel assemblies containing parent isotopes may require considerations specific to each fuel assembly. For example, the distribution and / or level of fission activity in an irradiated fuel assembly may depend on the level of source neutron flux provided by the ENG array and / or the location of the ENG array relative to the spent fuel assembly. Furthermore, the neutron regeneration factor K within the spent fuel assembly array may be eff In the unexpected event that increases beyond predicted values, the heat generated within the subcritical neutron generator may unexpectedly exceed maximum allowable values for a short period of time, thereby necessitating an emergency coolant injection response and / or ENG shutdown. Thus, methods of operating the subcritical neutron generator may be optimized with or otherwise benefit from a continuous source of information regarding the fission levels and / or neutron flux distribution present within the subcritical neutron generator.

[0024] In power-generating nuclear reactors, a bottom-accessible instrumentation thimble at the center of a fuel assembly is accessible through a penetration to the bottom of the reactor vessel. In-core detectors are typically inserted into the fuel assembly through the bottom penetration by a drive mechanism and positioned axially along the bottom-accessible thimble to provide fission level information at various axial locations along the core. However, these standard detection methods and devices are generally difficult to implement in a subcritical neutron generator 10 and cannot provide continuous and / or accurate measurements therein. For example, in-core detectors for detecting radiation in an operating power reactor may not be able to provide rapid and / or accurate measurements of the relatively low neutron flux and / or fission levels typically present in a subcritical neutron generator. Furthermore, the bottom-accessible thimble 14a of a spent fuel assembly 14 in a subcritical neutron generator 10 is typically reserved for an irradiation target insert 15, as shown in FIG. 1 . While the top-accessible guide thimble 14b could be free, the necessary associated penetrations for the drive mechanism to place the movable detector insert in the guide thimble 14b would require much more space than the subcritical neutron generator 10 provides, would impair the removability of the containment vessel 11 lid, and / or would require replacement of the containment vessel lid to perform measurements, thereby negating the safety and simplified operation benefits provided by the subcritical neutron generator. Furthermore, the extra time required to remove and replace a removable lid would significantly reduce process efficiency during the initial loading step, thereby negating the economic benefits of using a subcritical neutron generator. Accordingly, various aspects of the present disclosure provide various methods and apparatus for monitoring and / or controlling neutron population in a subcritical neutron generator without sacrificing measurement accuracy, operational safety, or process efficiency.

[0025] 2, a cross-sectional schematic diagram of a power sensor system 20 for monitoring neutron flux is provided, in accordance with at least one non-limiting embodiment of the present disclosure. In various embodiments, power sensor system 20 includes a self-powered sensor insert 22 for measuring neutron flux levels within a subcritical neutron generator. In some embodiments, power sensor system 20 can optionally include an auxiliary power system 24.

[0026] FIG. 3 illustrates a cross-sectional schematic view of a self-powered sensor insert 22 in accordance with at least one non-limiting embodiment of the present disclosure. In various embodiments, the self-powered sensor insert 22 includes an insert thimble 100 and a detector assembly 200. The self-powered sensor insert 22 can optionally include a coupler 300 axially disposed around the mating interface between the insert thimble 100 and the detector assembly 200. In one example, the coupler 300 includes an integral collar and at least one deformable O-ring seal coaxially disposed within the collar. In the collar configuration of the coupler 300, the size of the collar and / or O-ring can be configured to provide a fluid-tight seal and / or coupling force between the mating interface of the insert thimble 100 and the detector assembly 200. For example, the inner diameter of the collar can be configured with an inner diameter slightly larger than the outer cross-sectional shape of the insert thimble 100 and / or detector assembly 200, while the at least one deformable O-ring seal can be configured with an outer diameter substantially the same as or slightly larger than the inner diameter of the collar and an inner diameter slightly smaller than the outer cross-sectional shape of the insert thimble 100 and / or detector assembly 200 when nested inside the inner diameter of the collar. Other configurations are also contemplated by the present disclosure. For example, in some embodiments, the coupler 300 can be configured as a clamp-type coupler, a hinge-type coupler, a press-fit-type coupler, or a set-screw-type coupler.

[0027] 4 shows a schematic axial cross-sectional view of an insert thimble 100 according to at least one non-limiting embodiment of the present disclosure. In various embodiments, the insert thimble 100 includes an outer housing 102 having a closed end 104 and an open end 106, a hollow tube 108, a power generation device 110 disposed between the hollow tube 108 and the outer housing 102, and a first electrical interface 120 electrically connected to the power generation device 110. In some examples, the outer housing 102 can comprise a material with a low neutron cross-section. In particular examples, the outer housing 102 can comprise aluminum, titanium, or a combination thereof.

[0028] The outer housing 102 is configured to be insertable into a fuel assembly. For example, the outer housing 102 may be configured to have a cylindrical shape. When the outer housing 102 is cylindrical, the outer diameter of the outer housing 102 may be configured to be substantially the same as or slightly smaller than the inner diameter of the guide thimble of the fuel assembly. In one example, the outer diameter of the outer housing is configured to be approximately 10 millimeters. The length of the outer housing 102 may be substantially the same as or shorter than the length of the guide thimble of the fuel assembly. In one example, the length of the outer housing 102 is configured to be approximately 380 centimeters.

[0029] The hollow tube 108 is configured to be disposed within the outer housing 102. For example, the length of the hollow tube 108 is configured to be substantially the same as or slightly shorter than the length of the outer housing 102. In at least one example, the outer diameter of the hollow tube 108 is configured to be approximately 3 to 6 millimeters smaller than the inner diameter of the outer housing 102.

[0030] The generator 110 includes an electron emitter 112 and an electron collector 118. In various examples, the electron emitter 112 comprises a first material and a second material. In some examples, the generator 110 includes multiple layers. In examples including multiple layers, the electron collector 118 is configured as a layer surrounding the electron emitter 112.

[0031] The configuration of the power generation device 110 can be configured to respond to incident gamma rays. For example, the electron emitter 112 can comprise a metallic material having a high atomic number, such as greater than 40. In some examples, the electron emitter 112 comprises platinum. The metallic material of the electron emitter 112 can interact with the incident gamma rays to generate electrons in the form of high-energy electron or delta radiation emissions. Thus, an electron emitter incorporating this configuration can provide an electron source in response to nuclear fission events occurring within spent fuel assemblies.

[0032] The electron emitter 112 can also include a second material having a high neutron capture cross section. For example, the electron emitter 112 can include gadolinium-157, hafnium-177, or a combination thereof. In this configuration of the electron emitter 112, the second material can capture thermal neutrons and then rapidly generate gamma rays. In this manner, the electron emitter 112 incorporating this configuration can supplement the incident gamma rays received by the high atomic number metallic material, thereby supplementing the electron emission from the electron emitter 112.

[0033] The configuration of the electron collector 118 can be configured to absorb (sink) electron emissions. For example, the electron collector 118 can comprise a metallic material having a low atomic number, e.g., lower than 30. As an example, the electron collector 118 comprises aluminum. An electron collector 118 comprising aluminum can provide a sink for electron emissions. Thus, electrons emitted in response to incident neutron flux and / or gamma rays can generate a voltage between the electron emitter 112 and the electron collector 118.

[0034] The generator 110 can be configured to surround the hollow tube 108. For example, the generator 110 can be configured as a wire. In a wire configuration of the generator 110, the generator 110 can be tightly wrapped around the hollow tube 108, as shown in FIG. 3 . The outer diameter of the wire is sized to be substantially the same as or slightly smaller than the gap between the outer housing 102 and the hollow tube 108. In one example, the outer diameter of the wire is configured to be approximately 3 millimeters. The length of the wire can be sized to substantially completely cover the hollow tube 108 when wrapped around it. Furthermore, the outer housing 102 can be swaged or compressed when inserting the hollow tube 108 and generator 110 into the outer housing 102 to provide an optimal overall outer diameter for the insert thimble 100. Other configurations are also contemplated by the present disclosure. For example, in some embodiments, the generator 110 can be configured as a sleeve, rod, or plate.

[0035] 4 and 5, the wire configuration of the generator 110 can include multiple coaxial layers. For example, FIG. 5 shows a schematic cross-sectional view of the generator 110 configured as a multi-layer wire, according to at least one non-limiting embodiment of the present disclosure. In the multi-layer wire configuration of the generator 110, the electron emitter 112 can be configured as an emitter core including a first layer 112a surrounded by a second layer 112b, the electron collector 118 can be configured as an outer sheath, and an electrical insulation layer 116 can be disposed between the electron emitter 112 and the electron collector 118. The electrical insulation layer 116 can be configured to provide electrical insulation. For example, the electrical insulation layer 116 can comprise magnesium oxide, aluminum oxide, or a combination thereof. In some examples, the electron collector 118 can be compressed or swaged around the electrical insulation layer 116 to achieve a highly uniform density within the electrical insulation. In the particular example where the generator 110 is configured as a multi-layer wire, the multi-layer wire is wound in a very tight spiral around the hollow tube 108 to maximize the surface area of the electron emitter 112 per unit length of the hollow tube 108.

[0036] Returning now to FIG. 4 , the first electrical interface 120 can include a first electrical contact 122 and a second electrical contact 124. The first electrical contact 122 and / or the second electrical contact 124 can be configured as an electrical connector, an electrical lead, or a combination thereof. In some examples, the first electrical contact 122 and / or the second electrical contact 124 can be configured as a pin, a sleeve, a socket, a plug, a header, a terminal, an electrode, an integrated cable assembly, or a combination thereof. In certain examples, the first electrical contact 122 is surrounded by the second electrical contact 124. In one embodiment, the first electrical contact 122 and the second electrical contact 124 are coaxially arranged as a pin surrounded by a shorter sleeve such that the pin protrudes axially beyond the sleeve, as shown in FIG. 4 .

[0037] In examples where the generator 110 is configured as a multi-layer wire, the first electrical contact 122 can be electrically connected to the second layer 112b of the emitter core, and the second electrical contact 124 can be electrically connected to the electron collector 118. In some examples, the first electrical contact 122 is configured as a pin, and the second electrical contact 124 is configured as a sleeve. In one particular example, the first electrical contact 122 protrudes axially beyond the second electrical contact. In one embodiment, the first electrical contact 122 is configured as a tip, and the second electrical contact 124 is configured as a sleeve coaxially disposed around the tip. As described above, a voltage can be formed between the electron emitter 112 and the electron collector 118 based on incident neutron or gamma ray flux, and thus the generator 110 can supply current to a load connected to the first electrical contact 122 and the second electrical contact 124. As such, a first electrical interface 120 incorporating this configuration is adapted to output electrical power generated by the generator 110.

[0038] 6 shows a schematic axial cross-sectional view of a detector assembly 200 according to at least one non-limiting embodiment of the present disclosure. In various examples, the detector assembly 200 includes a sense tube 210, a second electrical interface 220, and a transmitter portion 240 including transmitter circuitry 250. The sense tube 210 is sized to be inserted into the hollow tube 108, and the second electrical interface 220 is positioned to abut the open end of the outer housing 102 when the sense tube 210 is fully inserted. In some examples, the sense tube 210 is hermetically attached to the transmitter portion 240.

[0039] The detector tube 210 is sized to fit within the hollow tube and includes at least one solid-state radiation detector 230. In some examples, the detector tube 210 can include several solid-state radiation detectors 230. While Figure 6 depicts three solid-state radiation detectors 230, any number and / or axial distribution of solid-state radiation detectors 230 necessary to accurately monitor the length of a fuel assembly within a subcritical neutron generator may be applied, limited only by the available space in the detector tube 210.

[0040] In various embodiments, the second electrical interface 220 includes a first electrical contact 222 and a second electrical contact 224, each of which is electrically connected to the transmitter circuit 250. The second electrical interface is configured to electrically couple to the first electrical interface 120. For example, the shapes of the first electrical contact 222 and the second electrical contact 224 can be configured to complement the shapes of the electrical contacts 122 and 124, respectively. In some examples, the first electrical contact 222 and / or the second electrical contact 224 can be configured as a pin, a sleeve, a socket, a plug, a header, a terminal, an electrode, an integrated cable assembly, or a combination thereof. In one example, as shown in FIG. 6 , the first electrical contact 222 is integrated into the inner axial surface of an annular power input ring socket, and the second electrical contact 224 is integrated into the sidewall of the annular power input ring socket. A second electrical interface 220 incorporating an annular power input ring configuration does not require specific rotational alignment to provide electrical connection, facilitating the mating of the detector assembly 200 with the insert thimble 100. As such, a second electrical interface incorporating this configuration can receive power from the first electrical interface 120 by simply inserting the detector assembly 200 axially into the insert thimble 100.

[0041] 2 , the second electrical interface 220 can be configured to receive power from multiple sources simultaneously. For example, the detector assembly 200 can optionally include a third electrical interface 260. The third electrical interface 260 can include a first electrical contact 262 and a second electrical contact 264, each of which can be configured similarly to the other electrical contacts described herein. The first electrical contact 262 and the second electrical contact 264 can be electrically connected to the first electrical contact 242 and the second electrical contact 244, respectively, by a cable 266. The cable 266 can be configured as a coaxial cable or a triaxial cable. In a triaxially configured cable 266, the cable 266 can include a mineral insulation layer separating a middle conductive layer from an outer conductive sheath.

[0042] Returning now to FIG. 6 , the solid-state radiation detector 230 is configured to output a detector signal that is directly proportional to the incident neutron flux level. For example, the solid-state radiation detector 230 may include a signal return lead 232 attached thereto. In various embodiments, the detection signal is an analog signal. In some embodiments, the solid-state radiation detector 230 may include a silicon carbide (hereinafter referred to as “SiC”)-based Schottky diode. The SiC-based Schottky diode can rapidly generate an electrical signal upon interaction with low levels of neutron flux and / or gamma rays. Furthermore, the SiC-based Schottky diode can be configured to be primarily sensitive to neutrons. For example, the SiC-based Schottky diode can include a highly neutron-sensitive material, such as boron, lithium, or a combination thereof. In this configuration, the highly neutron-sensitive material can generate relatively high-energy charged particle reaction products, which result in ionization in the SiC active volume. This makes the signal output from the SiC detector directly proportional to the neutron flux, providing a statistically meaningful measurement at very low neutron flux levels, such as those present in subcritical neutron generators.

[0043] SiC-based Schottky diodes can be manufactured in very small packages without compromising the accuracy and / or precision of the response. For example, SiC-based Schottky diodes can be devices with a diameter of approximately 4 mm. Thus, the detector tube 210 can be configured to fit into a very small diameter opening, such as a 4.1 mm diameter opening. Thus, the size of the hollow tube 108 can be configured to accommodate detector tubes 210 incorporating several SiC-based Schottky diodes without compromising the dimensions of the generator or the ability to accommodate the detector tube when wrapped around the outer housing 102.

[0044] 7 illustrates a schematic block diagram of transmitter circuitry 250 for transmitter section 240 in accordance with at least one non-limiting embodiment of the present disclosure. Transmitter circuitry 250 may include a neutron detector input signal buffer 250a, a bias voltage supply 250b, a voltage-controlled oscillator 250c, an amplifier 250d, and an output section 250e comprising a wireless transmitter and antenna. In various embodiments, the bias voltage supply of transmitter circuitry 250 is electrically connected to first and second electrical contacts 222 and 224 of second electrical interface 220. In some embodiments, neutron detector input signal buffer 250a of transmitter circuitry 250 is connected to a SiC-based Schottky diode via a pair of signal return leads 232. In a particular example, neutron detector input signal buffer 250a includes multiple inputs connected to multiple SiC-based Schottky diodes. In one embodiment, bias voltage supply 250b of transmitter circuit 250 can optionally be connected to a solid state radiation detector via a separate bias voltage lead 252, as shown in Figure 7. In this example, a negative bias voltage of up to 100 volts can be applied to provide a desired signal response in a particular radiation field.

[0045] The signal provided by the solid-state radiation detector 230 can be processed and wirelessly transmitted using hardware suitable for use in a nuclear reactor environment. For example, vacuum microelectronics (hereinafter referred to as "VME") transmitter technology can be used, as described in the article "Toward the implementation of self-powered, wireless, real-time reactor power sensing," published in Volume 139 of the journal "Annals of Nuclear Energy" on December 24, 2019, and incorporated herein by reference in its entirety. In some examples, the transmitter circuit 250 can transmit a continuous radio frequency signal representing the signal output by the solid-state radiation detector 230. In one particular example, the transmitter circuit 250 can transmit a signal having a frequency in the megahertz range. In one embodiment, the transmitter circuit 250 can include a multiplexer for simultaneously transmitting multiple signals from multiple radiation detectors.

[0046] Returning now to FIG. 2 , an auxiliary power system 24 may optionally be connected to the self-powered sensor insert 22. The auxiliary power system 24 includes an auxiliary insert thimble 400 and an auxiliary power cap 500. The auxiliary insert thimble 400 is similar in many respects to other insert thimbles disclosed elsewhere in this disclosure, but for the sake of brevity, will not be repeated at the same level of detail herein. In various embodiments, the auxiliary insert thimble 400 may include an outer housing, a power generator, and a first auxiliary electrical interface and may be configured similarly to the insert thimble 100 described above herein. Thus, the auxiliary insert thimble 400 may be insertable into a fuel assembly and configured to output electrical power via the first auxiliary electrical interface upon interaction with an incident neutron or gamma ray flux.

[0047] The auxiliary power cap 500 includes a second auxiliary electrical interface 510 and a third auxiliary electrical interface 520. The second auxiliary electrical interface 510 and the third auxiliary electrical interface 520 may be configured similarly to the second electrical interface 220 and the third electrical interface 260, respectively. Thus, the second auxiliary electrical interface 510 is configured to receive auxiliary power from the first auxiliary electrical interface of the auxiliary insert thimble 400, and the third auxiliary electrical interface 520 is configured as a peripheral electrical connector 522 electrically connected to a triaxial cable 524 and connected in parallel with the second auxiliary electrical interface 510. The peripheral electrical connector 522 may be configured as a plug, a socket, or a combination thereof. A peripheral electrical connector 522 incorporating both a plug and a socket may provide electrical connection between the second auxiliary electrical interface 510 and the third electrical interface 260, a separate peripheral electrical connector 700, and / or a termination cap 800, as depicted in FIG. 2 . Thus, auxiliary power cap 500 can be configured in combination with other auxiliary power inserts to supplement the power supplied to transmitter circuitry 250 from insert thimble 100. Power sensor system 20 can therefore maintain the power supplied to transmitter circuitry 250 in very low neutron flux conditions, providing the advantage of very low neutron flux measurements without the need for an external power source.

[0048] In a particular example, the auxiliary insert thimble 400 and the auxiliary power cap 500 may be coupled with a coupler 600, which may be configured similarly to coupler 300 described herein above. Accordingly, coupler 600 may be configured to provide a fluid-tight seal around the mating interface between the auxiliary insert thimble 400 and the auxiliary power cap 500.

[0049] Auxiliary power system 24 is not limited to providing power to self-powered sensor insert 22. For example, any device including an electrical interface configured similarly to second electrical interface 220 can be coupled to one or more auxiliary power systems 24 and, upon insertion into a spent fuel assembly, can be powered by one or more auxiliary power systems 24. Thus, one or more auxiliary power systems 24 can be incorporated into spent fuel assemblies in spent fuel pools or dry storage casks, with or without self-powered sensor inserts 22, to collect radiation and generate electrical power.

[0050] FIG. 8 illustrates a schematic diagram of a power monitoring system 1000 according to at least one non-limiting embodiment of the present disclosure. The power monitoring system includes at least one power sensor system 1100 and a control system 1200. Each of the at least one power sensor system 1100 includes a self-powered sensor insert 1110, which is similar in many respects to other power sensor systems disclosed elsewhere in this disclosure, but for brevity will not be repeated at the same level of detail herein. In various embodiments, the self-powered sensor insert 1110 includes an insert thimble and a detector assembly. The insert thimble includes a housing, a first power generator comprising a material having a high neutron capture cross section, and a first electrical interface, and may be configured similarly to other insert thimbles described elsewhere in this disclosure. Thus, the insert thimble may be configured to fit within a guide thimble of a spent fuel assembly, the first power generator may be configured to generate a first electrical power based on delta radiation, and the first electrical interface may be configured to output the first electrical power.

[0051] The detector assembly includes a detector tube, at least one radiation detector including a silicon carbide Schottky diode enclosed in the detector tube, a transmitter circuit including a transmitter, and a second electrical interface. In some examples, the detector assembly can include a third electrical interface. The detector assembly can be configured similarly to the other detector assemblies described herein. Thus, the detector tube can be configured to be surrounded by a first power generation device, the at least one radiation detector can be adapted to provide a first signal in response to incident neutron flux, the transmitter circuit can be configured to output a wireless signal based on the first signal from the at least one radiation detector, and the second electrical interface can be adapted to receive first power from the first electrical interface of the insert thimble and provide power for the transmitter circuit. In some examples, the third electrical interface can be configured to receive auxiliary power in parallel with the first power.

[0052] In some examples, each of the at least one power sensor system 1100 can include at least one auxiliary power system. Each of the at least one auxiliary power system can include an auxiliary insert thimble and an auxiliary power cap and can be configured similarly to the other auxiliary power systems described herein. Accordingly, each of the at least one auxiliary power system can be configured to provide at least a portion of auxiliary power through the third electrical interface to the second electrical interface.

[0053] The control system 1200 includes an antenna 1210 for receiving wireless signals, a signal interface 1220, and a controller 1230 with a processor. The antenna 1210 can be configured as a directional antenna or an omnidirectional antenna. In various embodiments, the antenna 1210 is electrically connected to the signal interface 1220 either directly or via a suitable shielded cable.

[0054] In various examples, the signal interface 1220 includes an input 1222 and an output 1224. The input 1222 can be configured to accept a wireless signal from the antenna 1210. For example, the input 1222 can be configured as a wireless receiver circuit. In one particular example, the input 1222 includes a demodulator for extracting information from a carrier wave. In one example, the input 1222 is a radio frequency signal demodulator. The output 1224 can be configured as a wireless transmitter or a wired output.

[0055] The signal interface 1220 may also include an analog-to-digital converter (hereinafter referred to as "ADC"). A signal interface 1220 incorporating an ADC can convert signals from the input 1222 into a digital representation proportional to the input signal. In some examples, the output 1224 is connected to the digital output of the ADC. Thus, a signal interface 1220 incorporating this configuration can convert analog signals into a digital representation and output a signal suitable for subsequent signal processing.

[0056] In various examples, the controller 1230 can include a controller input 1232 and a controller output 1234. The controller input 1232 can be configured to be electrically or wirelessly connected to the output 1224 of the signal interface 1220. For example, the controller input 1232 can include a digital input. In some examples, the controller input 1232 can include a wired port and / or a wireless receiver. Thus, the controller input 1232 can be configured to receive signals from the signal interface 1220.

[0057] In various examples, the processor includes an input in electrical communication with the controller input 1232 and an output in electrical communication with the controller output 1234. In some examples, the controller 1230 may include a level shifter electrically connected between the processor input and the controller input 1232 and / or between the processor output and the controller output 1234. In one particular example, the controller output 1234 may include a digital-to-analog converter (hereinafter referred to as a “DAC”).

[0058] The processor of the control unit 1230 can be configured as a general processor, microprocessor, microcontroller, embedded processor, digital signal processor, field programmable gate array, application-specific system processor, application-specific instruction set processor, application-specific integrated circuit, or combinations thereof. The processor can be configured to process the digital signals generated by the signal interface 1220. For example, a processor configured as a digital signal processor can analyze and manipulate data provided by the signal interface 1220 in real time. Thus, a processor incorporating this configuration can determine whether the incident light flux around the radiation detector of the self-powered sensor insert 1110 is within predetermined acceptable operating limits based on a real-time analysis of a digital representation of the signal provided by the radiation detector. The processor can then output commands or control signals based on the analyzed signals to control the neutron flux provided by the ENG. For example, the controller output 1234 may be connected to a controllable ENG power supply 1300 that supplies power to the ENG 12 via an ENG power cable 1310 within the subcritical neutron generator 10, providing control signals to continuously vary the power duty cycle and / or power level supplied to the ENG 12, thereby manipulating any fission events within the spent fuel assemblies that depend on the source neutron flux produced by the ENG. Thus, a controller 1230 incorporating this configuration can continuously and accurately monitor and control the neutron flux surrounding the self-powered sensor insert 1110 in real time.

[0059] 1 and 8, the power monitoring system 1000 can be incorporated into a subcritical neutron generator 10 adapted to accommodate the power monitoring system 1000. For example, the power sensor system 1100 can be located in a top-accessible guide thimble 14b of an array of spent fuel assemblies 14. In various embodiments, the removable lid 13 of the containment vessel 11 can be configured to have an opening substantially the same size as or slightly larger than the body of the antenna 1210, as shown in FIG. 8, to accommodate the antenna 1210, such that at least a portion of the antenna 1210 is disposed within the containment vessel 11 when the removable lid 13 is attached. In one example, the antenna 1210 can be inserted through the removable lid with an interference fit. A second end of the antenna 1210 can be connected, either directly or via a shielded cable, to an input of a signal interface 1220 located outside the containment vessel 11. An antenna 1210 incorporating this configuration can wirelessly receive a second signal provided by the radiation detector based on the first signal output by the transmitter of the self-powered sensor insert 1110, thereby avoiding interruption of flux measurements when the removable lid 13 is removed from the containment vessel 11. Thus, a spent fuel assembly 14 can be loaded into the containment vessel 11, and the radioactivity level K of the spent fuel assembly 14 based on the neutron population surrounding the spent fuel assembly can be determined. eff can be continuously monitored during the initial loading phase without repeatedly opening and closing the containment vessel.

[0060] As described herein, the power monitoring system 1000 can be incorporated into a method for optimizing a subcritical neutron generator 10 incorporating the power monitoring system 1000. For example, the method for optimizing a subcritical neutron generator 10 can include preparing the subcritical neutron generator 10 and loading the subcritical neutron generator 10. In various embodiments, preparing the subcritical neutron generator 10 includes opening a top of the subcritical neutron generator containment vessel and inserting a self-powered sensor insert of the power monitoring system into at least one spent fuel assembly. In various embodiments, loading the subcritical neutron generator can include individually inserting at least one spent fuel assembly into the open top of the containment vessel, continuously monitoring a signal generated by the self-powered sensor insert during loading to evaluate a neutron regeneration factor within the open containment vessel, and replacing the top of the containment vessel after loading the last of the at least one spent fuel assembly.

[0061] In some examples, a method for optimizing a subcritical neutron generator 10 can include irradiating at least one spent fuel assembly, the irradiating including monitoring a signal generated by a self-powered sensor insert with a control system of a power monitoring system to track a neutron population distribution within the at least one spent fuel assembly, and providing at least one source neutron flux with at least one electron neutron generator of the subcritical neutron generator. In one particular example, the providing irradiating step can include providing power to the at least one electron neutron generator of the subcritical neutron generator to generate at least one source neutron flux, which then irradiates the at least one spent fuel assembly to generate a subcritical neutron population within the at least one spent fuel assembly, and controlling the power source with a controller of the control system to optimize the distribution of the subcritical neutron population during irradiation, the controlling based in part on the monitored signal generated by the self-powered sensor insert.

[0062] When a subcritical neutron generator must be loaded or reloaded with spent fuel assemblies having different individual neutron regeneration factors, the overall neutron regeneration factor K of the array of spent fuel assemblies can be optimized after each insertion of an individual spent fuel assembly by using a power monitoring system in a method for optimizing the subcritical neutron generator as disclosed herein. eff The present invention can provide rapid and reliable verification of the containment vessel 11 closure, thereby avoiding the economical problems associated with repeatedly removing and replacing the lid during initial containment vessel loading. Furthermore, if the control unit determines that the neutron population distribution within the spent fuel assemblies is inappropriate for the production of medical radioisotopes, the power monitoring system can be used in the methods for optimizing a subcritical neutron generator disclosed herein to prompt the ENG power supply to increase its power output and / or duty cycle. Conversely, if the measurements exceed predetermined acceptable safety limits, the control system can prompt the shutdown of the ENG power supply and / or the emergency injection of borate-based fluid via the coolant circulation system attached to the containment vessel. In this manner, the methods for optimizing a subcritical neutron generator disclosed herein can rapidly and continuously optimize the radiation flux produced by the spent fuel assembly array and delivered to the irradiation target inserts located therein for predictable commercial-scale production of isotopes without sacrificing operational safety.

[0063] Various aspects of the invention according to the present disclosure include, but are not limited to, those listed in the following numbered paragraphs.

[0064] Item 1 - A power sensor system for monitoring a subcritical neutron generator, the power sensor system comprising a self-powered sensor insert for measuring neutron flux levels in a spent fuel assembly of the subcritical neutron generator. The self-powered sensor insert comprises an insert thimble and a detector assembly. The insert thimble further comprises: an outer housing having a closed end, the outer housing insertable into a guide thimble of a spent fuel assembly; a hollow tube disposed within the outer housing; a power generator disposed between the hollow tube and the outer housing, the power generator comprising an electron emitter and an electron collector, the electron emitter comprising a first material and a second material, the electron emitter configured to respond to incident radiation generated by the spent fuel assembly, the power generator configured to generate power based on the incident radiation; and a first electrical interface electrically connected to the power generator. The detector assembly further includes a detector tube sized to fit within the hollow tube of the insert thimble, a transmitter portion including a transmitter circuit, and a second electrical interface configured to electrically couple to the first electrical interface. The detector tube includes a solid-state radiation detector. The solid-state radiation detector provides a detector signal directly proportional to the neutron flux level. The transmitter portion is further configured to wirelessly output a transmitter signal based on the detector signal, and the second electrical interface is electrically connected to the transmitter circuit.

[0065] Clause 2 - The power sensor system of paragraph 1, wherein the power generator comprises a multilayer wire. The multilayer wire comprises an emitter core having a first layer and a second layer, an electrically insulating layer surrounding the emitter core, and a collector sheath surrounding the electrically insulating layer. The emitter core is configured to generate electron emissions in response to incident radiation, and the collector sheath is configured to absorb the electron emissions.

[0066] Item 3 - A power sensor system as described in item 2, wherein a first layer of the multilayer wire comprises a material having a high neutron capture cross section, and a second layer of the multilayer wire comprises a metallic material having a high atomic number.

[0067] Clause 4 - The power sensor system of clause 3, wherein the first layer of the multilayer wire comprises gadolinium-157, hafnium-177, or a combination thereof.

[0068] Clause 5 - A power sensor system as described in any one of clauses 2 to 4, wherein the collector sheath comprises a metallic material having a low atomic number.

[0069] Clause 6 - A power sensor system as described in any one of clauses 2 to 5, wherein the electrically insulating layer comprises magnesium oxide.

[0070] Clause 7 - A power sensor system as described in any one of clauses 2 to 6, wherein the multi-layer wire is spirally wrapped around a hollow tube.

[0071] Clause 8 - A power sensor system described in any one of clauses 2 to 7, wherein a first electrical contact of the first electrical interface is electrically connected to the emitter core and a second electrical contact of the first electrical interface is electrically connected to the collector sheath.

[0072] Clause 9 - A power sensor system as described in any one of clauses 1 to 8, wherein the solid-state radiation detector comprises a silicon carbide based Schottky diode.

[0073] Item 10 - The power sensor system of item 9, wherein the Schottky diode is configured to be primarily neutron sensitive.

[0074] Clause 11 - The power sensor system of any one of clauses 9 to 10, wherein the Schottky diode comprises boron, lithium, or a combination thereof.

[0075] Clause 12 - A power sensor system as described in any one of clauses 1 to 11, wherein the detection tube comprises a plurality of radiation detectors and the transmitter signal is based on a detection signal provided by each radiation detector.

[0076] Clause 13 - A power sensor system as described in any one of clauses 1 to 12, wherein the power sensor system comprises a coupler adapted to provide a watertight coupling between the insert thimble and the detector assembly.

[0077] Clause 14 - A power sensor system as described in any one of clauses 1 to 13, wherein the power sensor system comprises an auxiliary power system, the auxiliary power system comprising an auxiliary power insert and an auxiliary power output cap, the auxiliary power insert configured to generate auxiliary power based on incident radiation, the power output cap electrically connected to the auxiliary power insert and the second electrical interface, and the power output cap electrically connected in parallel with the power generation device.

[0078] Item 15 - A power monitoring system for controlling a subcritical neutron generator. The power monitoring system includes a power sensor system for monitoring the subcritical neutron generator and a control system. The power sensor system includes a self-powered sensor insert for measuring neutron flux levels within a spent fuel assembly of the subcritical neutron generator. The self-powered sensor insert includes an insert thimble and a detector assembly. The insert thimble includes a housing, a first power generator for generating a first power based on delta radiation, and a first electrical interface configured to output the first power. The first power generator includes a material having a high neutron capture cross section. The detector assembly includes a detector tube configured to be surrounded by the first power generator, at least one radiation detector including a silicon carbide-based Schottky diode, a transmitter circuit including a transmitter for outputting a wireless signal based on the first signal, and a second electrical interface adapted to receive the first power. The at least one radiation detector is contained within the detector tube and adapted to output a first signal in response to incident neutron flux. The second electrical interface provides power to the transmitter circuit. The control system includes an antenna for receiving the wireless signal, a signal interface, an input of the signal interface electrically connected to the antenna, the signal interface configured to output a third signal based on the wireless signal, and a controller including a processor. The controller is configured to receive the third signal and, based on the third signal, to control the neutron flux output by the electron neutron generator of the subcritical neutron generator.

[0079] Clause 16 - The power monitoring system of clause 15, wherein the detector assembly comprises a third electrical interface adapted to receive auxiliary power in parallel with the first power.

[0080] Clause 17 - The power monitoring system of clause 16, wherein the power monitoring system comprises at least one auxiliary thimble, the at least one auxiliary thimble comprising an auxiliary power generating device configured to generate at least a portion of the auxiliary power.

[0081] Paragraph 18 - A subcritical neutron generator comprising a power monitoring system as described in any one of paragraphs 15 to 17, wherein a removable lid of the subcritical neutron generator comprises an opening configured to hold a portion of an antenna of the control system, the portion of the antenna being positioned within a containment vessel of the subcritical neutron generator when the removable lid is attached to the containment vessel, and the signal interface is positioned outside the containment vessel.

[0082] Item 19 - A method for optimizing a subcritical neutron generator, the method including: preparing the subcritical neutron generator; and loading the subcritical neutron generator. Preparing the subcritical neutron generator comprises opening a top of a containment vessel of the subcritical neutron generator and inserting a self-powered sensor insert of a power monitoring system into at least one spent fuel assembly. Loading the subcritical neutron generator comprises individually inserting at least one spent fuel assembly into the open top of the containment vessel, continuously monitoring a signal generated by the self-powered sensor insert during loading to evaluate a neutron regeneration factor in the open containment vessel, and replacing the top of the containment vessel after loading the last of the at least one spent fuel assembly.

[0083] The method of any one of claims 20-19, further comprising irradiating at least one spent fuel assembly, wherein irradiating the at least one spent fuel assembly comprises monitoring a signal generated by a self-powered sensor insert with a control system of a power monitoring system to track a neutron population distribution within the at least one spent fuel assembly, and providing at least one source neutron flux with at least one electron neutron generator of the subcritical neutron generator. Providing at least one source neutron flux with at least one electron neutron generator of the subcritical neutron generator comprises providing power to the at least one electron neutron generator of the subcritical neutron generator to generate at least one source neutron flux, which then irradiates at least one spent fuel assembly to generate a subcritical neutron population within the at least one spent fuel assembly; and controlling the power source with a controller of a control system to optimize the distribution of the subcritical neutron population during irradiation, the control being based on a monitored signal generated by the self-powered sensor insert.

[0084] Various features and characteristics are described herein to provide an understanding of the organization, structure, manufacture, function, and / or operation of the inventions, including the disclosed methods and systems. It should be understood that the various features and characteristics of the inventions described herein may be combined in any suitable manner, whether or not such features and characteristics are expressly described in combination herein. The inventors and applicants expressly intend that such combinations of features and characteristics be included within the scope of the inventions described herein. Accordingly, the claims may be amended to recite any features and characteristics explicitly or inherently described or explicitly or inherently supported herein, in any combination. Furthermore, applicants reserve the right to amend the claims to affirmatively disclaim features and characteristics that may exist in the prior art, even if those features and characteristics are not expressly described herein. Accordingly, such amendments do not add new matter to the specification or claims, but rather comply with the requirements of description, fullness of description, and additional matter.

[0085] With respect to the appended claims, those skilled in the art will understand that the operations described therein may generally be performed in any order. Also, while various operational flows are shown in a certain order, it should be understood that the various operations may be performed in orders other than those shown, or may be performed simultaneously. Examples of such alternative orders include overlapping, interleaved, interrupted, reordered, incremental, preliminary, complementary, concurrent, reversed, or other variant orders, unless the context dictates otherwise. Furthermore, terms such as "responsive to," "related to," or other past tense adjectives are generally not intended to exclude such variants, unless the context dictates otherwise.

[0086] The inventions described herein can comprise, consist of, or consist essentially of various features and characteristics described herein. The terms "comprise" (and any form of comprise, such as "comprises" or "comprising"), "have" (and any form of have, such as "has" or "having"), "include" (and any form of include, such as "includes" or "including"), and "contain" (and any form of contain, such as "contains" or "containing") are open-ended linking verbs. Thus, a method or system that "comprises," "has," "includes," or "contains" the feature and / or characteristic has the feature and / or characteristic, but is not limited to having only the feature and / or characteristic. Similarly, an element of a composition, coating, or process that "comprises," "has," "includes," or "contains" a feature and / or characteristic possesses that feature and / or characteristic, but is not limited to possessing only the feature and / or characteristic, and may further possess additional features and / or characteristics.

[0087] As used herein, including the claims, the grammatical articles "a," "an," and "the" are intended to include "at least one" or "one or more," unless otherwise indicated. Accordingly, articles are used herein to refer to one or more than one (i.e., "at least one") of the grammatical object of the article. As an example, "a component" means one or more components, and thus, more than one component is contemplated and may be employed or used in the practice of the described compositions, coatings, and processes. Nevertheless, the use of the terms "at least one" or "one or more" in some instances but not in others is understood to not construe the absence of such terms as limiting the object of the grammatical articles "a," "an," and "the" to one. Furthermore, the use of a singular noun includes the plural, and the use of a plural noun includes the singular.

[0088] As used herein, unless otherwise indicated, all numerical parameters are understood to be prefaced and modified in all instances by the term "about." In this context, numerical parameters have inherent variability that is characteristic of the underlying measurement techniques used to determine the numerical value of the parameter. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter set forth herein should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0089] Numerical ranges recited herein include all subranges subsumed within the recited range. For example, a range of "1 to 10" includes all subranges between (and including) the minimum value of "1" and the maximum value of "10," i.e., having a minimum value of "1 or greater" and a maximum value of "10 or less." Also, all ranges recited herein include the endpoints of the recited range. For example, a range of "1 to 10" includes the endpoints 1 and 10. Every maximum numerical limitation recited herein is intended to include all lower numerical limitations subsumed therein, and every minimum numerical limitation recited herein is intended to include all higher numerical limitations subsumed therein. Accordingly, applicants reserve the right to amend this specification, including the claims, to explicitly recite any subranges subsumed within any explicitly recited range. All such ranges are inherently described herein.

[0090] As used herein, particularly in connection with layers, the terms "on," "onto," "over," and variations thereof (e.g., "coated on," "formed on," "deposited on," "provided on," "located on," etc.) mean coated, formed, deposited, provided, or otherwise located on the surface of a substrate, but not necessarily in contact with the surface of the substrate. For example, a layer "coated" on a substrate does not exclude the presence of another layer or other layer of the same or different composition located between the coated layer and the substrate. Similarly, a second layer "coated" on a first layer does not exclude the presence of another layer or other layer of the same or different composition located between the coated second layer and the coated first layer.

[0091] While particular embodiments of the present invention have been described above for purposes of illustration, it will be apparent to those skilled in the art that many changes in detail of the invention may be made without departing from the invention as defined in the appended claims.

Claims

1. 1. A power sensor system for monitoring a subcritical neutron generating device, comprising: a self-powered sensor insert for measuring neutron flux levels within spent fuel assemblies of the subcritical neutron generator, the self-powered sensor insert comprising: An insert thimble, a detector assembly; Equipped with The insert thimble is an outer housing having a closed end, the outer housing being insertable into a guide thimble of the spent fuel assembly; a hollow tube disposed within the outer housing; a power generating device disposed between the hollow tube and the outer housing, the power generating device comprising an electron emitter and an electron collector, the emitter comprising a first material and a second material, the electron emitter configured to respond to incident radiation produced by the spent fuel assembly, the power generating device configured to generate electrical power based on the incident radiation; a first electrical interface electrically connected to the power generation device; The detector assembly includes: a detector tube sized to fit within the hollow tube of the insert thimble, the detector tube comprising a solid state radiation detector, the solid state radiation detector providing a detection signal directly proportional to neutron flux level; a transmitter unit including a transmitter circuit, the transmitter unit configured to wirelessly output a transmitter signal based on the detection signal; a second electrical interface configured to electrically couple with the first electrical interface, the second electrical interface being electrically connected to the transmitter circuit; and A power sensor system comprising:

2. The generator includes a multi-layer wire, the multi-layer wire comprising: an emitter core comprising a first layer and a second layer, the emitter core configured to generate electron emissions in response to incident radiation; an electrically insulating layer surrounding the emitter core; a collector sheath surrounding the electrically insulating layer, the collector sheath configured to sink electron emissions; The power sensor system of claim 1 , comprising:

3. The power sensor system of claim 2 , wherein the first layer comprises a material having a high neutron capture cross section and the second layer comprises a metallic material having a high atomic number.

4. The power sensor system of claim 3 , wherein the first layer comprises gadolinium-157, hafnium-177, or a combination thereof.

5. The power sensor system of claim 2 , wherein the collector sheath comprises a metallic material having a low atomic number.

6. The power sensor system of claim 2 , wherein the electrically insulating layer comprises magnesium oxide.

7. The power sensor system of claim 2 , wherein the multi-layer wire is helically wrapped around the hollow tube.

8. The power sensor system of claim 2 , wherein a first electrical contact of the first electrical interface is electrically connected to the emitter core and a second electrical contact of the first electrical interface is electrically connected to the collector sheath.

9. The power sensor system of claim 1 , wherein the solid-state radiation detector comprises a silicon carbide based Schottky diode.

10. The power sensor system of claim 9 , wherein the Schottky diode is configured to be primarily neutron sensitive.

11. The power sensor system of claim 10 , wherein the Schottky diode comprises boron, lithium, or a combination thereof.

12. 2. The power sensor system of claim 1, wherein the detector tube comprises a plurality of radiation detectors, and the transmitter signal is based on a detection signal provided by each of the radiation detectors.

13. The power sensor system of claim 1 , wherein the power sensor system comprises a coupler adapted to provide a watertight coupling between the insert thimble and the detector assembly.

14. 2. The power sensor system of claim 1, wherein the power sensor system comprises an auxiliary power system, the auxiliary power system comprising an auxiliary power insert and an auxiliary power output cap, the auxiliary power insert configured to generate auxiliary power based on incident radiation, the power output cap electrically connected to the auxiliary power insert and the second electrical interface, and the power output cap electrically connected in parallel with the power generating device.

15. 1. A power monitoring system for controlling a subcritical neutron generator, the power monitoring system comprising: a power sensor system for monitoring the subcritical neutron generator; a control system; The power sensor system includes: a self-powered sensor insert for measuring neutron flux levels within spent fuel assemblies of the subcritical neutron generator, the self-powered sensor insert comprising: An insert thimble, a detector assembly; The insert thimble is Housing and a first power generator for generating a first electrical power based on delta radiation, the first power generator comprising a material having a high neutron capture cross section; a first electrical interface configured to output the first power; The detector assembly includes: a detection tube configured to be surrounded by the first power generation device; at least one radiation detector comprising a silicon carbide based Schottky diode, the at least one radiation detector being encased within the detector tube, the at least one radiation detector being adapted to provide a first signal in response to an incident neutron flux; a transmitter circuit including a transmitter for outputting a wireless signal based on the first signal; a second electrical interface adapted to receive the first power, the second electrical interface providing power to the transmitter circuitry; and Equipped with The control system includes: an antenna for receiving the radio signal; a signal interface, an input of the signal interface electrically connected to the antenna, the signal interface configured to output a third signal based on the wireless signal; a control unit including a processor, the processor being configured to receive the third signal and control a neutron flux output from an electron neutron generator of the subcritical neutron generator based on the third signal; A power monitoring system comprising:

16. The power monitoring system of claim 15 , wherein the detector assembly comprises a third electrical interface adapted to receive auxiliary power in parallel with the first power.

17. 17. The power monitoring system of claim 16, wherein the power monitoring system comprises at least one auxiliary thimble, the at least one auxiliary thimble comprising an auxiliary power generating unit configured to generate at least a portion of the auxiliary power.

18. 16. A subcritical neutron generator comprising the power monitoring system of claim 15, wherein a removable lid of the subcritical neutron generator comprises an opening configured to hold a portion of the antenna of the control system, the portion of the antenna being disposed within a containment vessel of the subcritical neutron generator when the removable lid is attached to the containment vessel, and the signal interface is disposed outside the containment vessel.

19. 1. A method of optimizing a subcritical neutron generator, the method comprising: providing a subcritical neutron generator; loading the subcritical neutron generator; The preparing step includes: opening the top of the containment vessel of the subcritical neutron generator; inserting a self-powered sensor insert of a power monitoring system into at least one spent fuel assembly; Equipped with The loading step comprises: individually inserting the at least one spent fuel assembly into the open top of the containment vessel; continuously monitoring the signal generated by the self-powered sensor insert to estimate a neutron regeneration factor within the containment vessel that is open during loading; replacing the top of the containment vessel after loading the last of the at least one spent fuel assembly; A method comprising:

20. The method includes irradiating the at least one spent fuel assembly, the irradiating comprising: monitoring the signal generated by the self-powered sensor insert with a control system of the power monitoring system to track a neutron population distribution within the at least one spent fuel assembly; providing at least one source neutron flux with at least one electron neutron generator of the subcritical neutron generator; Equipped with The providing comprises: providing power to at least one electron neutron generator of the subcritical neutron generator to generate the at least one source neutron flux, which then irradiates the at least one spent fuel assembly to generate a subcritical neutron population within the at least one spent fuel assembly; controlling the power supply using a controller of the control system to optimize the distribution of the subcritical neutron population during irradiation, the controlling being based on a monitored signal generated by the self-powered sensor insert; 20. The method of claim 19, comprising:

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