WO2022204680A1

WO2022204680A1 - Production of high energy gamma radiation using an electronic neutron generator for food and medical device sterilization

Info

Publication number: WO2022204680A1
Application number: PCT/US2022/071260
Authority: WO
Inventors: Michael D. Heibel
Original assignee: Westinghouse Electric Company Llc
Priority date: 2021-03-26
Filing date: 2022-03-22
Publication date: 2022-09-29
Also published as: TWI821958B; TW202243692A

Abstract

Devices, systems, and methods for producing gamma radiation using a neutron generator are disclosed herein. In some aspects, a device for producing gamma radiation includes a neutron generator configured to generate a neutron flux field and a neutron capture reservoir including a neutron capture material. The neutron capture material can be configured to emit gamma radiation in response to exposure to the neutron flux field. In one aspect, the emitted gamma radiation can be used to sterilize a food product. In another aspect, the emitted gamma radiation can be used to sterilize a medical device.

Description

TITLE PRODUCTION OF HIGH ENERGY GAMMA RADIATION USING AN ELECTRONIC NEUTRON GENERATOR FOR FOOD AND MEDICAL DEVICE STERILIZATION CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims the benefit of and priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No.63/166,718, titled PRODUCTION OF HIGH ENERGY GAMMA RADIATION USING AN ELECTRONIC NEUTRON GENERATOR FOR FOOD AND MEDICAL DEVICE STERILIZATION, filed March 26, 2021, the disclosure of which is hereby incorporated by reference in its entirety. FIELD [0002] The present disclosure is generally related to devices, systems, and methods for producing gamma radiation. In some aspects, the devices, systems, and methods described herein can produce high energy gamma radiation using an electronic neutron generator. In some aspects, the devices, systems and methods described herein can be used for sterilization of food products, sterilization of medical equipment, and/or for other applications where gamma radiation may be used to irradiate or otherwise treat materials and products. SUMMARY [0003] The following summary is provided to facilitate an understanding of some of the innovative features unique to the aspects disclosed herein, and is not intended to be a full description. A full appreciation of the various aspects disclosed herein can be gained by taking the entire specification, claims, and abstract as a whole. [0004] In various aspects, a device for producing gamma radiation is disclosed. In some aspects, the device includes a neutron generator configured to generate a neutron flux field and a neutron capture reservoir including a neutron capture material. In one aspect, the neutron capture material can be configured to emit gamma radiation in response to exposure to the neutron flux field. In another aspect, the neutron capture reservoir can be configured to be positioned between the neutron generator and an irradiation target to irradiate the irradiation target with the emitted gamma radiation. [0005] In various aspects, a system for producing gamma radiation is disclosed. In some aspects, the system includes a plurality of devices. Each of the plurality of devices can include a neutron generator configured to generate a neutron flux field and a neutron capture reservoir including a neutron capture material. In one aspect, the neutron capture material can be configured to emit gamma radiation in response to exposure to the neutron flux field. In another aspect, for each device, the neutron capture reservoir can positioned proximate to an end of the neutron generator that generates the neutron flux field. In yet another aspect, each of the plurality of devices can be positioned to irradiated a common irradiation target with the emitted gamma radiation [0006] In various aspects, a method for producing gamma radiation is disclosed. In some aspects, the method includes generating, by a neutron generator, a neutron flux field; exposing a neutron capture reservoir including a neutron capture material to the neutron flux field; emitting, by the neutron capture material, gamma radiation; positioning the neutron capture reservoir between the neutron generator and an irradiation target; and irradiating the irradiation target with the emitted gamma radiation. [0007] These and other objects, features, and characteristics of the present disclosure, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of any of the aspects disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS [0008] The various aspects described herein, together with objects and advantages thereof, may best be understood by reference to the following description, taken in conjunction with the accompanying drawings as follows. [0009] FIG.1 illustrates a perspective view of a device configured to produce gamma radiation using a neutron generator and a neutron capture reservoir, in accordance with at least one non-limiting aspect of the present disclosure; [0010] FIG.2 is cross-sectional schematic representation of the device of FIG.1, in accordance with at least one non-limiting aspect of the present disclosure; [0011] FIG. 3 is a cross-sectional schematic representation of a system of devices configured to produce gamma radiation, each device using a neutron generator and a neutron capture reservoir, in accordance with at least one non-limiting aspect of the present disclosure; and [0012] FIG. 4 is a cross-sectional schematic representation of a system of neutron generators configured to produce gamma radiation using a common neutron capture reservoir, in accordance with at least one non-limiting aspect of the present disclosure. [0013] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate various aspects of the present disclosure, in one form, and such exemplifications are not to be construed as limiting the scope of any of the aspects disclosed herein. DETAILED DESCRIPTION [0014] Numerous specific details are set forth to provide a thorough understanding of the overall structure, function, manufacture, and use of the aspects as described in the disclosure and illustrated in the accompanying drawings. Well-known operations, components, and elements have not been described in detail so as not to obscure the aspects described in the specification. The reader will understand that the aspects described and illustrated herein are non-limiting examples, and thus it can be appreciated that the specific structural and functional details disclosed herein may be representative and illustrative. Variations and changes thereto may be made without departing from the scope of the claims. [0015] In the following description, like reference characters designate like or corresponding parts throughout the several views of the drawings. Also in the following description, it is to be understood that such terms as “forward,” “rearward,” “left,” “right,” “above,” “below,” “upwardly,” “downwardly,” and the like are words of convenience and are not to be construed as limiting terms. [0016] Gamma irradiation is used in a wide variety of applications related to the treatment and sterilization of food products. For example, meat, vegetables, spices, and other food products can be irradiated with gamma radiation to kill bacterial and other pathogens without altering taste or nutrition levels. Gamma radiation treatments can also help delay ripening, inhibit sprouting, and otherwise extend the shelf life of certain foods. Moreover, gamma irradiation can be used as an alternative to chemical phytosanitary food treatment methods, which are increasingly regulated and potentially dangerous. [0017] Gamma irradiation is also used in a wide variety of applications related to the medical industry. For example, medical instruments and implantable medical devices (e.g., stents, heart valves, etc.) can be sterilized with gamma radiation. Moreover, gamma irradiation can be more efficient and/or more effective than other sterilization methods because, for example, gamma radiation can penetrate dense materials and can be used to sterilize devices after they have been sealed within packaging. Additionally, gamma radiation can be used to sterilize tissue-based devices such as bone grafts and tendons to increase patient safety. [0018] Existing gamma irradiation methods typically involve the use of irradiators employing radioisotopes such as cobalt-60 (sometimes referred to herein as “Co-60”) to emit high energy gamma radiation. These irradiators can initially exhibit enough high energy gamma radiation activity to efficiently irradiate a target object (e.g., food product, medical device) in a reasonable amount of time. However, as the radioisotopes of the irradiator decay, the exposure time needed to deliver the required dose of gamma radiation increases. Eventually the irradiator is depleted to a point where it is no longer cost effective to use. As a result, the depleted irradiator needs to be replaced and disposed of. [0019] The disposal of depleted irradiators can be extremely costly. This is because depleted irradiators generally exhibit residual gamma radiation activity. Thus, expensive containment measures may be required to ensure that the depleted irradiator is safely disposed of or otherwise stored. In some cases, the disposal cost may ultimately outweigh the commercial benefits of producing and/or using radioisotope-based irradiators such as cobalt-60 irradiators. Moreover, facilities that produce radioisotope-based irradiators and/or facilities that perform irradiation using these irradiators typically require a heavily shielded and secured infrastructure to ensure that facility personnel are not inadvertently exposed to gamma radiation and to ensure that the radioisotope material is not improperly used. Accordingly, there is a need for devices, systems, and methods that are able to produce gamma radiation for irradiating objects and without using residually decaying irradiator sources such as cobalt-60. [0020] The present disclosure provides devices, systems and methods for producing gamma radiation using a neutron generator. The neutron generator can be used to produce thermal neutrons that are captured by a neutron capture reservoir. The thermal neutrons can react with a neutron capture material of the neutron capture reservoir to cause the immediate generation of gamma radiation (i.e. prompt neutron capture gamma radiation). In some aspects, after the neutron generator is deactivated, no residual neutron flux and/or gamma radiation is released. Thus, costly disposal measures related to the use of residually decaying irradiator sources may be alleviated or eliminated. The devices, systems, and methods provided herein can be used for the sterilization of food products, the sterilization of medical equipment, and/or for other applications where gamma radiation may be used to irradiate or otherwise treat materials and products. [0021] FIGs.1 and 2 illustrate a device 100 configured to produce gamma radiation 105 using a neutron generator 102, in accordance with several non-limiting aspects of the present disclosure. FIG.1 illustrates a perspective view of the device 100 and FIG. 2 illustrates an axial cross-sectional schematic of the device 100. [0022] Referring primarily to FIG. 2, and also to FIG. 1, the device 100 includes a neutron generator 102 configured to generate thermal neutrons. In some aspects, the neutron 102 generator can be a commercially available, tubular-shaped electronic neutron generator. The thermal neutrons generated by the neutron generator 102 create a neutron flux field 107. [0023] The device 100 further includes a neutron capture reservoir 104 including a neutron capture material configured to react with incident neutrons to produce gamma radiation. The neutron capture reservoir 104 can be positioned proximate to an end of the neutron generator 102 configured to generate the neutron flux field 107 (i.e., a fusion reaction source end of the neutron generator 102). Thus, the thermal neutrons (i.e., neutron flux field 107) generated by the neutron generator 102 may be directed towards the neutron capture reservoir 104. In response to incident thermal neutrons from the neutron generator 102, the neutron capture reservoir 104 can emit gamma radiation 105 (i.e., prompt neutron capture gamma radiation). Further, the device 100 can be configured such that the emitted gamma radiation 105 is directed towards an irradiation target 200 (e.g., a food product 200, a medical device 200, etc.). As a result, the irradiation target 200 is irradiated with gamma radiation 105. [0024] In some aspects, the gamma radiation 105 emitted from the neutron capture reservoir 104 is high energy gamma radiation. As used herein, “high energy gamma radiation” can refer to gamma radiation that has an energy of no less than 1.2 MeV, such as no less than 2 MeV, no less than 3 MeV, no less than 4 MeV, no less than 5 MeV, no less than 6 MeV, no less than 7 MeV, or about 7 MeV. [0025] In some aspects, the neutron capture reservoir 104 and/or the neutron capture material included in the neutron capture reservoir 104 can be replicable. In one aspect, the neutron capture material can include a gadolinium material. The gadolinium material may be enriched in gadolinium-157 (sometimes referred to herein as Gd-157). In another aspect, the neutron capture material can include a hafnium material. The hafnium material may be enriched in hafnium-174 (sometimes referred to herein as Hf-174). In yet another aspect, the neutron capture material can have a high thermal neutron cross section. As used herein, a “high thermal neutron cross section” can mean a thermal neutron cross section greater that of hafnium-174. In yet other aspect, the irradiation target material can have a thermal neutron cross section of about 257,000 barns and/or greater than about 257,000 barns. [0026] The neutron capture reservoir 104 can be configured to produce gamma radiation 105 when exposed to the neutron flux field 107 generated by the neutron generator 102. Further, the neutron capture reservoir 104 can be configured to stop producing gamma radiation 105 when the neutron flux field 107 is removed. In other words, the device 100 can be configured such that, when the neutron generator 102 is deactivated, no residual gamma radiation 105 and/or neutron flux 107 is emitted from the device 100. For example, the gadolinium material can include Gd₂O₃ that is enriched in Gd-157. As the Gd-157 captures thermal neutrons emitted from the neutron generator 102, a Gd-157m isotope can form. Upon formation, the Gd-157m isotope immediately emits one or more gamma photos that can have a total energy of about 7 MeV. The one or more emitted gamma photons can irradiate the irradiation target 200. Further, because the Gd-157m isotope immediately emits the one or more gamma photons, no residual gamma radiation 105 is emitted by the device after the neutron generator 102 is deactivated. [0027] The device 100 can allow for significant cost savings and increased safety when used for food and medical-related irradiation purposes compared to other methods. This cost savings and increased safety can result from the device 100 not emitting residual radiation after the neutron generator 102 is deactivated. For example, the device 100 can be employed as an alternative to various irradiators that use residually decaying radioisotopes, such as cobalt-60, to avoid the potentially costly disposal requirements and the heavily shielded and secured infrastructure that are often associated with using such irradiators. [0028] Still referring primarily to FIG. 2, and also to FIG. 1, in some aspects, the device 100 can include a neutron moderator 108 configured to control and/or optimize a level of neutron flux 107 at the neutron capture reservoir 104. The neutron moderator 108 can be positioned between the neutron generator 102 and the neutron capture reservoir 104. The neutron moderator 108 includes a neutron moderator material and a neutron moderator thickness. In some aspects, the neutron moderator material includes graphite, water, or a combination thereof. In some aspects, the neutron moderator thickness may be adjustable. In yet other aspects, a position of the neutron moderator 108 relative to the neutron generator 102 and/or the neutron capture reservoir 104, the neutron moderator material, and/or the neutron moderator thickness 108 can be optimized to control the level of thermal neutron flux 107 at the neutron capture reservoir 104. This optimization may be performed using various software tools, such as Monte Carlo N-Particle Transport Code (MCNP). In some aspects, the device 100 may include an access door and/or opening to allow for the placement of the neutron moderator 120 and/or other components of device 100. [0029] Still referring primarily to FIG.2, and also to FIG.1, the device 100 can include shielding 106 that surrounds at least a portion of the device 100 and/or the components thereof. For example, the shielding 106 may be configured to surround an end of an elongated portion of the neutron generator 102 and extend past the end of the elongated portion, surrounding the neutron moderator 108, as shown in FIG.2. In some aspects, the shielding 106 may continue to extend past the end of the elongated portion of the neutron generator 102 and at least partially encompass the neutron capture reservoir 104. For example, the shielding 106 can be configured to surrounding the sides of the neutron moderator 104 have and have an opening proximate to the target 200. The shielding 106 includes a shielding material. In some aspects, the shielding material can include lead or another similar shielding material suitable for minimizing and/or preventing gamma radiation 106 from escaping the device 100 in an unwanted direction. For example, the shielding 116 may be configured to minimize the amount of gamma radiation 106 that escapes the device 100 from the neutron capture reservoir 104 in a direction away from the irradiation target 200. In some aspects, the shielding material can include lead or another similar shielding material suitable for helping to contain the neutron flux field 107 within the device 100. For example, the shielding 106 may be configured to minimize the amount of thermal neutrons (neutron flux field 107) that escape the device 100 from the neutron generator 102 in a direction away from the neutron capture reservoir 104. In some aspects, the shielding 106 may be adjustable. Further, the shielding 106 may be configured to fit around a portion of the outer surface of the neutron generator 102 to minimize neutron 107 and/or gamma radiation 105 exposure to equipment that may be surrounding the device. The shielding 106, neutron moderator 108, and/or neutron capture reservoir 104 may be configured to be used with traditional tubular-shaped electronic neutron generator designs. [0030] Still referring primarily to FIG.2, and also to FIG.1, an intensity of the gamma radiation 105 field at the irradiation target 200 can be controlled based on operating parameters such as the characteristics of the neutron flux field 107 at the neutron capture reservoir 104, the characteristics of the neutron capture material (e.g., the amount of Gd-157 in the neutron capture reservoir 104), and the distance of neutron capture reservoir 104 from the irradiation target 200. Further, the equivalent dose of gamma radiation 105 delivered to the irradiation target 200 can be determined based on the above parameters (e.g. based on the intensity of the gamma radiation 105 field and the Gd-157m decay scheme). This determination of the equivalent dose of gamma radiation 105 delivered to the irradiation target 200 may be performed using commercially available software packages, such as MCNP. Accordingly, the device 100 can be configured to deliver a desired dose of gamma radiation 105 to the irradiation target 200. [0031] In some aspects, multiple devices 100 can be employed together to produce a gamma radiation field that has an intensity equivalent to the sum of the gamma radiation field intensity produced by an individual device 100. Moreover, multiple devices 100 can be configured in various arrangements to produce a gamma radiation field that is larger and/or has a more uniform intensity compared to an individual device 100. For example, FIG. 3 illustrates cross-sectional schematic representation of a system 300 of devices 100 configured to produce a gamma radiation 105 field. According to the non-limiting aspect of FIG.3, five (5) devices 100 are shown arranged around the irradiation target 200. In other aspects, any number of devices 100 (e.g., two (2) devices 100, three (3) devices 100, four (4) devices 100, five (5) devices 100, more than five (5) devices 100) and any arrangement of devices 100 (e.g., a linear array, two-dimensional array, a three-dimensional array, a circular array, a semi- spherical array, etc.) can be implemented to create a system 300 of devices 100 to produce a gamma radiation 105 field with a desired uniformity, intensity, and/or size. Moreover, in some aspects, an individual device 100 or a system 300 of devices 100 can be configured to irradiate multiple target objects 200 at the same time. [0032] In some aspects, multiple neutron generators 102 can be employed together to generate multiple (e.g., overlapping) neutron flux fields 107 that are used to produce prompt neutron capture gamma radiation from a common neutron capture reservoir 104. Similar to the system 300 of devices 100, the use of multiple neutron generators 102 with a common neutron capture reservoir 104 can be used to produce a larger, more uniform, and/or more intense gamma radiation 105 field compared to an individual device 100. For example, FIG. 4 illustrates schematic representation of a system 400 of neutron generators 102 configured to produce gamma radiation using a common neutron capture reservoir 104. According to the non-limiting aspect of FIG. 4, three (3) neutron generators 102 are shown arranged in parallel and adjacent to each other to generate overlapping neutron flux fields 107. In other aspects, any number of neutron generators 102 (e.g., two (2) neutron generators 102, three (3) neutron generators 102, four (4) neutron generators 102, five (5) neutron generators 102, more than five (5) neutron generators 102) and any arrangement of neutron generators 102 (e.g., a linear array, two-dimensional array, a three-dimensional array, a circular array, a semi-spherical array, etc.) can be implemented to create a system 400 of neutron generators 102 that produce a gamma radiation 105 field with a desired uniformity, intensity, and/or size using a common neutron capture reservoir 104. [0033] Still referring to FIG. 4, the system 400 can include shielding 106. The shielding can be configured to help prevent thermal neutrons (i.e., the neutron flux fields 107) and/or gamma radiation 105 from escaping the system 400 in an undesired direction. For example, according to the non-limiting aspect of FIG.4, the system 400 is shown with shielding 106 forming an outer perimeter surrounding the neutron generation portions of the array of neutron generators 108. The shielding 106 is also shown in various gaps between adjacent neutron generators 108. [0034] Still referring to FIG.4, the system 400 can include a neutron moderator 108. The neutron moderator 108 of the system 400 may be configured based on the various parameters described above with respect to FIGs.1 and 2 to optimize characteristics of the neutron flux field(s) 107 at the neutron capture reservoir 104. Moreover, similar to the individual device 100 and system 300 of devices 100, the system 400 of neutron generators 102 can be configured to irradiate multiple target objects 200 at the same time. [0035] As discussed in more detail below with respect to Example 1, the device 100 can be configured to deliver a dose of gamma radiation sufficient to sterilize a target object 200 in a short period of time (e.g., less than 1.5 hours, less than 1 minute, etc. depending on the operating parameters of the device 100). Moreover, the use of multiple devices 100 (e.g., system 300) and/or multiple neutron generators 102 (e.g., system 400) can be used to sterilize multiple target objects 200 in a short period of time (e.g., less than 1.5 hours, less than 1 minute, etc.). [0036] The devices 100 and systems 300, 400 disclosed herein can also sterilized target objects 200 quicker (i.e., at a higher dose rate) than other irradiation methods having equivalent activity levels. For example, the neutron capture reservoir 104 can include Gd-157. Prompt neutron gamma radiation emitted by Gd-157m has an energy of about 7 MeV. Comparatively, Co-60 emits gamma ration having an energy of about 1.2 MeV. Thus, a device 100 using a neutron capture material including Gd-157 can deliver a required sterilization dose in less time compared to an irradiator source having an equivalent activity level resulting from Co-60 decay. Moreover, as discussed above, unlike Co-60 irradiators, the devices 100 and systems 300, 400 do not rely on the use of residually decaying radioisotopes that become depleted over time and need to be disposed of. [0037] Furthermore, the devices 100 and systems 300, 400 disclosed herein can require less radiation shielding and security-related infrastructure compared irradiators such as Co-60. Thus, the devices 100 and systems 300, 400 may be implemented by food packaging facilities and/or medical device manufacturing facilities thereby reducing or eliminating the need for dedicated irradiator facilities. This may reduce the cost of treating food and/or medical devices and streamline supply chains. [0038] Exemplary capabilities of various devices, systems, and methods described herein are provided in the example below: Example 1 [0039] A neutron capture reservoir including Gd₂O₃ enriched to comprise about 87 wt.% Gd-157 and having a mass of about 100 mg was prepared. The neutron capture reservoir was exposed to a thermal neutron flux of about 6x10⁶ neutrons/cm²/s. The resulting gamma radiation dose rate produced at the irradiation target surface was about 625 R/second or 2.25x10⁶ R/hour. This converts to about 22.5 kGy/hr. [0040] Standard NIST (National Institute of Standards and Technology) guidelines specify that a delivered gamma radiation dose of 25 kGy is needed to achieve the commercial required SAL (sterility assurance level) of 10^-6 (i.e. a 10^-6 probability of a microorganism being present after sterilization). Thus, the neutron flux field and neutron capture reservoir described in this Example 1 can deliver the required gamma dose of 25 kGy in just over 1 hour. If the neutron flux is increased by a factor of 10 and the mass of Gd₂O₃ is also increased by a factor of 10, the time required to generate the 25 kGy would decrease by a factor of 100. [0041] Modern electronic neutron generators are capable of thousands of hours of operation without replacement. Moreover, thermal neutron fluxes of the order of 10⁷ can be generated and the mass and enrichment of the Gd₂O₃ can be controlled. Thus, the thermal neutron flux and neutron capture reservoir of this Example 1 can be adjusted to control the irradiation time required for sterilization. Furthermore, multiple neutron generators can be implemented with a neutron capture reservoir having a large mass and surface area (e.g., similar to system 400). Thus, multi-neutron generator systems can be configured to sterilize materials and objects in a time comparable to that of current methods which rely on radioisotopes like Co-60. Yet further, unlike methods relying on residually decaying radioisotopes, the devices 100 and systems 300, 400 do not require disposal of radioactive waste or infrastructure to address security concerns associated with the improper use of the irradiator. [0042] Various aspects of the devices, systems, and methods described herein are set out in the following clauses. [0043] Clause 1: A device for producing gamma radiation, the device comprising: a neutron generator configured to generate a neutron flux field; and a neutron capture reservoir comprising a neutron capture material, the neutron capture material configured to emit gamma radiation in response to exposure to the neutron flux field; wherein the neutron capture reservoir is configured to be positioned between the neutron generator and an irradiation target to irradiate the irradiation target with the emitted gamma radiation. [0044] Clause 2: The device of clause 1, wherein the neutron capture material comprises a gadolinium material. [0045] Clause 3: The device of any of clauses 1-2, wherein the gadolinium material is enriched in gadolinium-157. [0046] Clause 4: The device of any of clauses 1-3, wherein the neutron capture reservoir is configured to allow the replacement of the neutron capture material. [0047] Clause 5: The device of any of clauses 1-4, wherein the gamma radiation emitted by the neutron capture material is no less than 2 MeV. [0048] Clause 6: The device of any of clauses 1-5, further comprising a neutron moderator positioned between an end of the neutron generator and the neutron capture reservoir, wherein the neutron moderator is configured to optimize the exposure of the neutron capture material to the neutron flux field. [0049] Clause 7: The device of any of clauses 1-6, wherein the neutron moderator comprises a neutron moderator material, and wherein the neutron moderator material comprises graphite, water, or a combination thereof. [0050] Clause 8: The device of any of clauses 1-9, further comprising shielding surrounding at least a portion of the neutron generator; wherein the shielding is configured to maximize the containment of the neutron flux field within the device; and wherein the shielding is configured to minimize an amount of gamma radiation that escapes the device from the neutron capture reservoir in a direction away from the irradiator target. [0051] Clause 9: A system for producing gamma radiation, the system comprising: a plurality of devices, each of the plurality of devices comprising: a neutron generator configured to generate a neutron flux field; and a neutron capture reservoir comprising a neutron capture material, the neutron capture material configured to emit gamma radiation in response to exposure to the neutron flux field; wherein the neutron capture reservoir is positioned proximate to an end of the neutron generator that generates the neutron flux field; and wherein each of the plurality of devices is positioned to irradiate a common irradiation target with the emitted gamma radiation [0052] Clause 10: The system of clause 9, wherein the neutron capture material comprises a gadolinium material. [0053] Clause 11: The system of any of clauses 9-10, wherein the gadolinium material is enriched in gadolinium-157. [0054] Clause 12: The system of any of clauses 9-11, wherein gamma radiation emitted by the neutron capture material is no less than 2 MeV. [0055] Clause 13: The system of any of clauses 9-12, wherein each of the plurality of devices further comprises a neutron moderator positioned between an end of the neutron generator and the neutron capture reservoir, wherein the neutron moderator is configured to optimize the exposure of the neutron capture material to the neutron flux field. [0056] Clause 14: A method for producing gamma radiation, the method comprising: generating, by a neutron generator, a neutron flux field; exposing a neutron capture reservoir comprising a neutron capture material to the neutron flux field; emitting, by the neutron capture material, gamma radiation; positioning the neutron capture reservoir between the neutron generator and an irradiation target; and irradiating the irradiation target with the emitted gamma radiation. [0057] Clause 15: The method of clause 14, wherein the neutron capture material comprises enriched in gadolinium-157. [0058] Clause 16: The method of any of clauses 14-15, further comprising replacing the neutron capture material. [0059] Clause 17: The method of any of clauses 14-16, wherein emitting gamma radiation by the neutron capture material comprises emitting gamma radiation having an energy of no less than 2 MeV. [0060] Clause 18: The method of any of clauses 14-17, wherein irradiating the irradiation target with the emitted gamma radiation comprises sterilizing a food product or sterilizing a medical device. [0061] Clause 19: The method of any of clauses 14-18, wherein irradiating the irradiation target with the emitted gamma radiation comprises delivering a gamma radiation dose of no less than 25 kGy to the irradiation target in less than 1.5 hours. [0062] Clause 20: The method of any of clauses 14-19, wherein irradiating the irradiation target with the emitted gamma radiation comprises delivering a gamma radiation dose of no less than 25 kGy to the irradiation target in less than 1 minute. [0063] Those skilled in the art will recognize that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to claims containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. [0064] In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that typically a disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms unless context dictates otherwise. For example, the phrase “A or B” will be typically understood to include the possibilities of “A” or “B” or “A and B.” [0065] It is worthy to note that any reference to “one aspect,” “an aspect,” “an exemplification,” “one exemplification,” and the like means that a particular feature, structure, or characteristic described in connection with the aspect is included in at least one aspect. Thus, appearances of the phrases “in one aspect,” “in an aspect,” “in an exemplification,” and “in one exemplification” in various places throughout the specification are not necessarily all referring to the same aspect. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner in one or more aspects. [0066] Any patent application, patent, non-patent publication, or other disclosure material referred to in this specification and/or listed in any Application Data Sheet is incorporated by reference herein, to the extent that the incorporated materials is not inconsistent herewith. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material. [0067] The terms "comprise" (and any form of comprise, such as "comprises" and "comprising"), "have" (and any form of have, such as "has" and "having"), "include" (and any form of include, such as "includes" and "including") and "contain" (and any form of contain, such as "contains" and "containing") are open-ended linking verbs. As a result, a system that "comprises," "has," "includes" or "contains" one or more elements possesses those one or more elements, but is not limited to possessing only those one or more elements. Likewise, an element of a system, device, or apparatus that "comprises," "has," "includes" or "contains" one or more features possesses those one or more features, but is not limited to possessing only those one or more features. [0068] The term “substantially”, “about”, or “approximately” as used in the present disclosure, unless otherwise specified, means an acceptable error for a particular value as determined by one of ordinary skill in the art, which depends in part on how the value is measured or determined. In certain embodiments, the term “substantially”, “about”, or “approximately” means within 1, 2, 3, or 4 standard deviations. In certain embodiments, the term “substantially”, “about”, or “approximately” means within 50%, 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, or 0.05% of a given value or range. [0069] In summary, numerous benefits have been described which result from employing the concepts described herein. The foregoing description of the one or more forms has been presented for purposes of illustration and description. It is not intended to be exhaustive or limiting to the precise form disclosed. Modifications or variations are possible in light of the above teachings. The one or more forms were chosen and described in order to illustrate principles and practical application to thereby enable one of ordinary skill in the art to utilize the various forms and with various modifications as are suited to the particular use contemplated. It is intended that the claims submitted herewith define the overall scope.

Claims

CLAIMS WHAT IS CLAIMED IS: 1. A device for producing gamma radiation, the device comprising: a neutron generator configured to generate a neutron flux field; and a neutron capture reservoir comprising a neutron capture material, the neutron capture material configured to emit gamma radiation in response to exposure to the neutron flux field; wherein the neutron capture reservoir is configured to be positioned between the neutron generator and an irradiation target to irradiate the irradiation target with the emitted gamma radiation. 2. The device of claim 1, wherein the neutron capture material comprises a gadolinium material. 3. The device of claim 2, wherein the gadolinium material is enriched in gadolinium-157. 4. The device of claim 1, wherein the neutron capture reservoir is configured to allow the replacement of the neutron capture material. 5. The device of claim 1, wherein the gamma radiation emitted by the neutron capture material has an energy of no less than 2 MeV. 6. The device of claim 1, further comprising a neutron moderator positioned between an end of the neutron generator and the neutron capture reservoir, wherein the neutron moderator is configured to optimize the exposure of the neutron capture material to the neutron flux field. 7. The device of claim 6, wherein the neutron moderator comprises a neutron moderator material, and wherein the neutron moderator material comprises graphite, water, or a combination thereof. 8. The device of claim 1, further comprising shielding surrounding at least a portion of the neutron generator; wherein the shielding is configured to maximize the containment of the neutron flux field within the device; and wherein the shielding is configured to minimize an amount of gamma radiation that escapes the device from the neutron capture reservoir in a direction away from the irradiator target. 9. A system for producing gamma radiation, the system comprising: a plurality of devices, each of the plurality of devices comprising: a neutron generator configured to generate a neutron flux field; and a neutron capture reservoir comprising a neutron capture material, the neutron capture material configured to emit gamma radiation in response to exposure to the neutron flux field; wherein the neutron capture reservoir is positioned proximate to an end of the neutron generator that generates the neutron flux field; and wherein each of the plurality of devices is positioned to irradiate a common irradiation target with the emitted gamma radiation 10. The system of claim 9, wherein the neutron capture material comprises a gadolinium material. 11. The system of claim 10, wherein the gadolinium material is enriched in gadolinium-157. 12. The system of claim 9, wherein gamma radiation emitted by the neutron capture material has an energy of no less than 2 MeV. 13. The system of claim 9, wherein each of the plurality of devices further comprises a neutron moderator positioned between an end of the neutron generator and the neutron capture reservoir, wherein the neutron moderator is configured to optimize the exposure of the neutron capture material to the neutron flux field. 14. A method for producing gamma radiation, the method comprising: generating, by a neutron generator, a neutron flux field; exposing a neutron capture reservoir comprising a neutron capture material to the neutron flux field; emitting, by the neutron capture material, gamma radiation; positioning the neutron capture reservoir between the neutron generator and an irradiation target; and irradiating the irradiation target with the emitted gamma radiation. 15. The method of claim 14, wherein the neutron capture material comprises enriched in gadolinium-157. 16. The method of claim 14, further comprising replacing the neutron capture material. 17. The method of claim 14, wherein emitting gamma radiation by the neutron capture material comprises emitting gamma radiation having an energy of no less than 2 MeV. 18. The method of claim 14, wherein irradiating the irradiation target with the emitted gamma radiation comprises sterilizing a food product or sterilizing a medical device. 19. The method of claim 14, wherein irradiating the irradiation target with the emitted gamma radiation comprises delivering a gamma radiation dose of no less than 25 kGy to the irradiation target in less than 1.5 hours. 20. The method of claim 15, wherein irradiating the irradiation target with the emitted gamma radiation comprises delivering a gamma radiation dose of no less than 25 kGy to the irradiation target in less than 1 minute.