Improved graphite neutron reflectors containing beryllium oxide inclusions.

Abstract

A nuclear reactor (100) is disclosed that includes a reactor core (102) and a reflector assembly (150) surrounding the reactor core. The reflector assembly includes a stationary reflector component (152) that includes a graphite support structure (156) having a plurality of channels (158) defined therein and a plurality of beryllium oxide pins (160) positioned within the channels.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Non-provisional Application No. 17 / 080,241, filed October 26, 2020, entitled "ENHANCED GRAPHITE NEUTRON REFLECTOR WITH BERYLLIUM OXIDE INCLUSIONS," the contents of which are incorporated herein by reference in their entirety.

[0002] Government support This invention was made with government support under Contract DE-NE0008853 awarded by the U.S. Department of Energy. The government has certain rights in this invention. [Background technology]

[0003] The present invention relates generally to nuclear reactors, such as small modular reactors (SMRs) and microreactors, and more particularly to the arrangement of a reflector surrounding the reactor core.

[0004] Electricity energy markets are divided into centralized and decentralized markets. Centralized markets are based on large-scale generators (in the hundreds of MWe range) and high-capacity, dense transmission and distribution networks. Decentralized, or off-grid, markets instead rely on small generators (<15 MWe), typically connected to smaller, localized distribution networks or microgrids. Currently, remote artic communities, remote mines, military bases, and island communities are examples of decentralized markets. Currently, the energy needs of off-grid markets are primarily met by diesel generators. This leads to high electricity costs, dependence on fossil fuels, load shedding, complex fuel supply logistics, and aging infrastructure. The stringent requirements of off-grid markets include affordability, reliability, flexibility, resiliency, sustainability (clean energy), energy security, and rapid installation and minimal maintenance. All of these demands can be addressed with nuclear energy.

[0005] Microreactors are nuclear reactors capable of generating less than 10 MWe and can be deployed in remote applications. These microreactors are packaged in relatively small vessels, operate without active human involvement, and can operate without refueling / replacing for longer periods of time than conventional nuclear power plants.

[0006] One such micro-reactor is the eVinci™ micro-reactor system, designed by Westinghouse Electric Company. These micro-reactors are packaged in a relatively small container, operate without active personnel involvement, and can operate without refueling / replacing for longer periods of time than conventional nuclear power plants. Other examples of micro-reactors are described in commonly owned U.S. Provisional Application Publication No. 62 / 984,591, entitled "HIGH TEMPERATURE HYDRIDE MODERATOR ENABLING COMPACT AND HIGHER POWER DENSITY CORES IN NUCLEAR MICRO-REACTORS," and U.S. Patent Application No. 14 / 773,405, entitled "MOBILE HEAT PIPE COOLED FAST REACTOR SYSTEM," published as U.S. Patent Application Publication No. 2016 / 0027536, both of which are incorporated herein by reference in their entireties.

[0007] The use of an effective neutron reflector is required to ensure the small size of the reactor. The reflector material and its dimensions affect the fuel mass, core size, mass, and thermal power of the microreactor. The neutron reflector also contributes to neutron shielding. Therefore, the selection of the reflector design is an important part of the microreactor design development.

[0008] Existing manufacturing techniques for beryllium-based reflectors impose significant limitations when attempting to maximize the size of the beryllium oxide components. Currently, hundreds of reflector pieces must be combined and placed with materials that do not have good neutron properties, which is labor intensive and negatively impacts the overall performance of the neutron reflector.

[0009] In addition to beryllium-based reflectors, graphite reflectors are known and widely used, however, they are less neutron efficient than beryllium-based reflectors and cannot meet the size, mass, and power output requirements of microreactors imposed in some applications.

[0010] Additionally, thermo-mechanical performance is another aspect that requires consideration when considering neutron reflector material and design selection. There is a significant temperature gradient in the radial direction of the radial reflector from the inner edge of the reflector where the core is located to the outer edge of the reflector. Therefore, temperature-induced stresses must be taken into account and minimized through design and material selection.

[0011] Various aspects of the present disclosure provide improved reflector designs to improve furnace efficiency. Summary of the Invention

[0012] In various embodiments, a nuclear reactor is disclosed that includes a reactor core and a reflector assembly surrounding the reactor core. The reflector assembly includes a stationary reflector component that includes a graphite support structure having a plurality of channels defined therein and a plurality of beryllium oxide pins positioned within the channels.

[0013] In various embodiments, a reflector assembly usable in a nuclear reactor is disclosed. The nuclear reactor includes a reactor core. The reflector assembly is configured to surround the reactor core. The reflector assembly includes a graphite support structure having a plurality of channels defined therein and a plurality of beryllium oxide inclusions positioned within the channels.

[0014] In various embodiments, a nuclear reactor is disclosed that includes a reactor core and a reflector assembly surrounding the reactor core. The reflector assembly includes a stationary reflector portion and a movable reflector portion. The stationary reflector portion includes a graphite support structure having a plurality of channels defined therein and a plurality of beryllium oxide inserts positioned within the channels. The movable reflector portion includes a plurality of control drums rotatable relative to the stationary reflector portion.

[0015] The various features of the embodiments described herein, together with their advantages, may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which: [Brief explanation of the drawings]

[0016] [Figure 1] 1 illustrates a micro-fuel reactor having an improved neutron reflector assembly in accordance with at least one embodiment of the present disclosure. [Figure 2] 2 illustrates an expanded perspective view of the micro-furnace of FIG. 1 in accordance with at least one embodiment of the present disclosure.

[0017] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set forth herein illustrate various embodiments of the present invention in one form, and such exemplifications should not be construed as limiting the scope of the present invention in any manner. DETAILED DESCRIPTION OF THE INVENTION

[0018] Numerous specific details are set forth to provide a thorough understanding of the overall structure, function, manufacture, and use of the embodiments described herein and illustrated in the accompanying drawings. Well-known operations, components, and elements have not been described in detail so as not to obscure the embodiments described herein. The reader will understand that the embodiments described and illustrated herein are non-limiting examples, and therefore, it will be understood that specific structural and functional details disclosed herein may be representative and exemplary. Variations and modifications thereto may be made without departing from the scope of the claims.

[0019] 1 and 2 , a microreactor 100 is provided in accordance with at least one aspect of the present disclosure. The microreactor 100 may include a core 102 that may contain fuel, moderator channels, heat pipes, and reactivity control channels (stop rods). In various embodiments, the core 102 may be similar to the cores described in U.S. Provisional Application Publication No. 62 / 984,591 and U.S. Patent Application No. 14 / 773,405, both of which are incorporated by reference above. In various embodiments, the core 102 may include a core housing, or shell 104, that may contain fuel, multiple heat pipes, multiple moderator channels, and multiple reactivity control channels within the core 102. The fuel may be encapsulated within the core 102, while the heat pipes, moderator channels, and reactivity control channels may extend outside the core 102 to a secondary side of the microreactor 100 to allow extraction of heat generated by the fuel.

[0020] In various embodiments, the microreactor 100 can include a modified neutron reflector assembly 150 that surrounds the reactor core 102. With particular reference to Figure 2, the reflector assembly 150 can include both a stationary reflector component 152 and a movable reflector component 154.

[0021] In one aspect, with continued reference to FIG. 2 , the stationary reflector component 152 may include a graphite support structure 156 that may include a plurality of channels 158 defined therein. In various embodiments, the graphite support structure 156 may be a unitary structure. In various other embodiments, the graphite support structure 156 may be assembled from a plurality of smaller graphite support structures spliced ​​together to form the graphite support structure 156. Forming the graphite support structure 156 from a plurality of smaller graphite support components facilitates the manufacturing process. Additionally, as described in more detail below, the graphite support structure may be used to adjust the spacing for other components within the stationary reflector component 152, such as the movable reflector component 154. In various embodiments, the graphite support structure 156 may be formed from a plurality of smaller graphite support components, and the individual components may be positioned to sequentially reflect neutrons. In one exemplary embodiment, multiple smaller graphite support components may be positioned both radially and axially relative to the core 102 to continuously reflect neutrons. Additionally, assembling the graphite support structure 156 from multiple smaller graphite support structural components allows for overlapping gaps remaining between the individual components. Selecting these gaps between the smaller graphite support components allows for continuous neutron reflection despite differential thermal expansion of the core 102 and the reflector assembly 150, while also assisting in mechanical load transfer and heat removal. In various embodiments, the radial thickness of the graphite support structure 156 may range from about 0.3 meters to about 1.0 meters. Other embodiments are contemplated in which the radial thickness of the graphite support structure 156 may be greater than 1.0 meters or less than 0.3 meters.

[0022] In one aspect, reflector assembly 150 may further include a plurality of beryllium oxide inclusions, pins, or inserts 160 that may be removably positioned within channels 158 defined by graphite support structure 156. In one aspect, any type of beryllium-based or beryllium oxide inclusion may be used. In various embodiments, graphite support structure 156 may act as a support structure for supporting beryllium oxide inclusions 160, such as within channels 158, while also supporting neutron reflection from core 102 and providing mechanical and thermal load transfer.

[0023] As described above, the microreactor 100 may further include a movable reflector component 154. In various embodiments, the movable reflector component 154 may include a plurality of control drums 106 that may be rotatably positioned within the stationary reflector component 152. In one aspect, the control drum 106 may include a neutron absorber portion 110 and a neutron reflector portion 108. In various embodiments, the control drums 106 may each be rotatable relative to the stationary reflector component 152 between a neutron reflecting position and a neutron absorbing position. In the neutron reflecting position, the neutron reflector portion 108 of the control drum 106 faces the core 102 and may therefore increase the reactivity of the core 102. In the neutron absorbing position, the neutron absorber portion 110 faces the core 102 and may limit or stop the reaction within the core 102. In various embodiments, the neutron reflector portion 108 may include beryllium oxide. In one exemplary embodiment, the neutron reflector portion 108 may be fabricated from graphite and may include channels defined therein, similar to the graphite support structure 156. In such an embodiment, beryllium oxide may be positioned within channels defined in the graphite control drum. In various other embodiments, the neutron reflector portion 108 of the control drum 106 may be fabricated substantially, if not entirely, from beryllium oxide.

[0024] In one aspect, the control drum 106 may be the only moving component within the reactor core 102. In one embodiment, all of the control drums 106 may rotate together such that all of the control drums 106 are in either a neutron reflecting position or a neutron absorbing position. In other embodiments, the control drums 106 may be independently rotatable relative to one another. In other embodiments, the control drum 106 may be rotated to a partially rotated position such that a portion of both the neutron absorber portion 110 and the neutron reflector portion 108 at least partially faces the reactor core, thus providing an intermediate level of reactivity within the reactor core 102. In another embodiment, the control drum 106 may automatically rotate between the neutron reflecting position and the neutron absorbing position depending on various factors, such as the temperature within the reactor core 102. In one aspect, the control drum 106 may automatically rotate to the neutron absorbing position when the temperature within the reactor core 102 meets or exceeds a threshold temperature. In another aspect, the control drum 106 may automatically rotate to the neutron reflecting position when the temperature within the reactor core 102 drops below a threshold temperature. Various other embodiments are contemplated in which the control drum 106 may rotate between the neutron absorbing position and the neutron reflecting position based on other measured parameters within the reactor. As one example, the control drum 106 may be rotatable between the neutron absorbing position and the neutron reflecting position based on the measured neutron flux within the microreactor 100.

[0025] In various embodiments, the core 102 and improved neutron reflector assembly 150 may be housed within a container structure 112, a neutron absorber vessel 122, and a boron carbide, or gamma-neutron, shielding 114. Additionally, a gap 116 may be provided between the neutron absorber vessel 122 and the boron carbide shielding 114 for shield cooling and gamma ray shielding. All of these components may be located inside the outer canister structure 120. In various other embodiments, the core 102 and improved neutron reflector assembly 150 may also be housed in a housing described in U.S. Provisional Application Publication No. 62 / 984,591 and U.S. Patent Application No. 14 / 773,405, which are incorporated by reference above in their entireties. In various embodiments, the core housing 104 may also comprise beryllium oxide.

[0026] In one aspect, the channels 158 defined in the graphite support structure 156 can be sized and positioned such that good neutronic performance of the reflector assembly 150 can be achieved through the beryllium oxide inclusions 160. In various embodiments, the selection of the diameter, pitch, and spacing of the channels 158 relative to adjacent channels 158 can be varied to optimize the performance of the reflector assembly 150. In one exemplary embodiment, the channels 158 can be arranged with a triangular or rectangular pitch as substantially uniform as possible, taking into account the movable reflector component 154 and the segmented stationary reflector parts, as well as assumptions about the thermal evaluation of the reactor core. In various embodiments, the pitch of the channels 158 can be in the range of about 0.013 meters to about 0.07 meters. In various embodiments, the diameter of the channels 158, and therefore the diameter of the beryllium oxide inclusions 160, can be in the range of about 0.005 meters to about 0.05 meters. In other embodiments, the diameter of the beryllium oxide inclusions 160 and the diameter of the channels 158 can be different. In various embodiments, the channels 158 defined in the graphite support structure 156 may be spaced apart from adjacent channels 158 at intervals ranging from 0.001 meters to about 0.06 meters. In one aspect, the spacing between channels 158 may be defined as the space between the outer edge of one channel 158 and the outer edge of an adjacent channel 158. In various embodiments, the above-mentioned parameters (diameter, pitch, and channel spacing) of the graphite support structure 156 may vary from channel to channel.

[0027] While the neutron reflection efficiency of the above-described concept is strictly inferior to that of a beryllium oxide reflector, the difference is not substantial and does not affect the required microreactor power output. Nevertheless, the above-described concept improves the thermomechanical performance of the reflector while simplifying the manufacturing and assembly process. Furthermore, taking into account the density difference between graphite and beryllium oxide, this concept is expected to reduce the overall mass of the small-scale reflector. A reflector based on the above-described concept can also reduce costs due to the simplified beryllium oxide geometry and the reduction in the number of beryllium oxide components. Advantages of this concept include, but are not limited to, keeping the dimensions of the neutron reflector itself relatively small, keeping the fuel required to provide the required thermal power relatively small, improving the manufacturability and assembly of the reflector, improving thermomechanical performance, and lowering the cost of the reflector. Thus, the combination of materials (graphite and beryllium oxide) that provides good neutron reflection, acceptable thermomechanical performance, and ease of manufacturing and assembly is highly beneficial.

[0028] Various aspects of the subject matter described herein are illustrated in the following examples.

[0029] [Example]

[0030] [Example 1] 1. A nuclear reactor comprising: a core; and a reflector assembly surrounding the core, the reflector assembly including a stationary reflector component including a graphite support structure having a plurality of channels defined therein; and a plurality of beryllium oxide pins positioned within the channels.

[0031] [Example 2] 2. The nuclear reactor of embodiment 1, wherein the reflector assembly further comprises a movable reflector component, the movable reflector component including a plurality of control drums rotatable relative to the stationary reflector component.

[0032] [Example 3] 3. The nuclear reactor of example 2, wherein each of the control drums includes a reflector portion and an absorber portion, and the reflector portion includes beryllium oxide.

[0033] [Example 4] 4. The nuclear reactor of any one of embodiments 1-3, further comprising a core housing, the core being positioned within the core housing, the core housing comprising beryllium oxide.

[0034] [Example 5] The reactor of any one of Examples 1-4, wherein the radial thickness of the graphite support structure is from about 0.3 meters to about 1.0 meters.

[0035] [Example 6] The reactor of any one of Examples 1-5, wherein each of the plurality of channels has a diameter of about 0.005 meters to about 0.05 meters.

[0036] [Example 7] The reactor of any one of Examples 1-6, wherein the pitch of each of the plurality of channels is between about 0.013 meters and about 0.07 meters.

[0037] [Example 8] The reactor of any one of Examples 1-7, wherein each of the plurality of channels is spaced apart from one another by between about 0.001 meters and about 0.06 meters.

[0038] [Example 9] The nuclear reactor of any one of Examples 1-8, wherein the graphite support structure is an assembly of multiple graphite support structures positioned to sequentially reflect neutrons.

[0039] [Example 10] 1. A reflector assembly usable in a nuclear reactor having a reactor core, the reflector assembly being configured to surround the reactor core, the reflector assembly comprising: a graphite support structure having a plurality of channels defined therein; and a plurality of beryllium oxide inclusions positioned within the channels.

[0040] [Example 11] The reflector assembly of Example 10, further comprising a plurality of control drums rotatable relative to the graphite support structure.

[0041] [Example 12] The reflector assembly of example 11, wherein each of the control drums includes a reflector portion and an absorber portion, and the reflector portion includes beryllium oxide.

[0042] [Example 13] The reflector assembly of any one of Examples 10-12, wherein the radial thickness of the graphite support structure is between about 0.3 meters and about 1.0 meters.

[0043] [Example 14] The reflector assembly of any one of Examples 10-13, wherein each of the plurality of channels has a diameter of about 0.005 meters to about 0.05 meters.

[0044] [Example 15] The reflector assembly of any one of Examples 10-14, wherein the pitch of each of the plurality of channels is between about 0.013 meters and about 0.07 meters.

[0045] [Example 16] The reflector assembly of any one of Examples 10-15, wherein each of the plurality of channels is spaced apart from one another by between about 0.001 meters and about 0.06 meters.

[0046] [Example 17] The reflector assembly of any one of Examples 10-16, wherein the graphite support structure is an assembly of multiple graphite support structures positioned to sequentially reflect neutrons.

[0047] [Example 18] 1. A nuclear reactor comprising: a core; and a reflector assembly surrounding the core, the reflector assembly including a stationary reflector portion and a movable reflector portion, the stationary reflector portion including a graphite support structure having a plurality of channels defined therein and a plurality of beryllium oxide inserts positioned within the channels, the movable reflector portion including a plurality of control drums rotatable relative to the stationary reflector portion.

[0048] [Example 19] 19. The nuclear reactor of Example 18, wherein each of the control drums includes a reflector portion and an absorber portion, and the reflector portion includes beryllium oxide.

[0049] [Example 20] 20. The nuclear reactor of example 18 or 19, further comprising a core housing, the core being positioned within the core housing, the core housing comprising beryllium oxide.

[0050] Unless otherwise specifically stated as is apparent from the above disclosure, throughout the above disclosure, discussions using terms such as "processing," "computing," "calculating," "determining," "displaying," and the like refer to the actions and processes of a computer system or similar electronic computing device that manipulates and transforms data represented as physical (electronic) quantities in the computer system's registers and memory into other data similarly represented as physical quantities in the computer system's memory or registers, or other such information storage, transmission, or display device.

[0051] One or more components may be referred to herein as "configured to," "configurable to," "operable to," "adapted to," "capable to," "adaptable to," etc. Those skilled in the art will recognize that "configured to" can generally encompass active state components and / or inactive state components and / or standby state components, unless the context requires otherwise.

[0052] Those skilled in the art will recognize that the terms used in this specification, generally, and in the appended claims in particular (e.g., the body of the appended claims), are generally intended as "open" terms (e.g., the term "comprising" should be interpreted as "including, but not limited to," the term "having" should be interpreted as "having at least," the term "including" should be interpreted as "including, but not limited to," etc.). Where a specific number of claims to be introduced is intended, such intention will be expressly recited in the claims; it will further be understood by those skilled in the art that, in the absence of such recitation, no such intention exists. For example, as an aid to understanding, the following appended claims may contain the use of the introductory phrases "at least one" and "one or more" to introduce the recitation of claims. However, the use of such phrases should not be construed as implying that introducing a claim recitation with the indefinite article "a" or "an" limits any particular claim containing such an introduced claim recitation to claims containing only one such recitation, even when that same claim includes the introductory phrase "one or more" or "at least one" and an indefinite article such as "a" or "an" (e.g., "a" and / or "an" should typically be construed to mean "at least one" or "one or more"), nor should the use of a particular article be used to introduce a claim recitation.

[0053] Additionally, even if a specific number of enumerations in an introduced claim are explicitly recited, those skilled in the art will understand that such enumeration should typically be interpreted to mean at least the recited number (e.g., the literal recitation of "two enumerations," without other modifiers, means at least two enumerations, or more than two enumerations). Furthermore, in such cases where a convention similar to "at least one of A, B, and C, etc." is used, such structure is generally intended in the sense that those skilled 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 having 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 cases where a convention similar to "at least one of A, B, or C, etc." is used, such construction is generally intended in the sense that one of ordinary skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include, but is not limited to, systems having 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 of ordinary skill in the art that typical disjunctive words and / or phrases presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibility of including one of the terms, either of the terms, or both terms, unless the context dictates otherwise. For example, the phrase "A or B" would typically be understood to include the possibilities of "A" or "B" or "A and B."

[0054] With respect to the appended claims, those skilled in the art will understand that the operations recited therein may generally be performed in any order. Also, while various operational flow diagrams are presented in sequences, it should be understood that various operations may be performed in other orders than those illustrated, or may be performed simultaneously. Examples of such alternative orderings may include overlapping, interleaved, interrupted, reordered, incremental, preliminary, supplemental, simultaneous, reverse, or various other orderings, unless the context dictates otherwise. Furthermore, unless the context dictates otherwise, terms such as "responsive," "related," or other past tense adjectives are generally not intended to exclude such variations.

[0055] It should be noted that any reference to "one embodiment," "one embodiment," "one exemplary embodiment," "one example," etc. means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment. Thus, the appearances of the phrases "in one embodiment," "in one embodiment," "in one exemplary embodiment," and "in one exemplary embodiment" 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 one or more embodiments.

[0056] Any patent application, patent, non-patent publication, or other disclosure material referenced herein and / or listed in any Application Data Sheet is incorporated herein by reference and, to the extent that it does not conflict with the material incorporated herein. Accordingly, the disclosure set forth herein supersedes, to the extent necessary, any conflicting material incorporated herein by reference. All material, or portions thereof, that is referred to as being incorporated herein by reference that conflicts with existing definitions, descriptions, or other disclosure material set forth herein will be incorporated only to the extent that there is no conflict between the incorporated material and the existing disclosure material.

[0057] 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. Consequently, 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. Similarly, an element of a system, device, or apparatus that "includes," "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.

[0058] The terms "substantially," "about," or "approximately," as used in this disclosure, unless otherwise specified, refer to 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 terms "substantially," "about," or "approximately" mean within 1, 2, 3, or 4 standard deviations. In certain embodiments, the terms "substantially," "about," or "approximately" mean 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.

[0059] In summary, numerous benefits resulting from employing the concepts described herein have been described. The foregoing description of one or more embodiments has been presented for purposes of illustration and description. It is not intended to be exhaustive or to be limited to the precise form disclosed. Modifications or variations are possible in light of the above teachings. One or more embodiments have been selected and described in order to illustrate the principles and practical applications, thereby enabling those skilled in the art to utilize various embodiments and with various modifications suitable for the particular use contemplated. The claims submitted herein are intended to define the overall scope.

Claims

1. A nuclear reactor, The reactor core and a reflector assembly surrounding the reactor core and including stationary reflector components; the stationary reflector component is a graphite support structure having a plurality of channels defined therein; a plurality of beryllium oxide pins positioned within the channel.

2. 10. The nuclear reactor of claim 1, wherein said reflector assembly further comprises a movable reflector component, said movable reflector component including a plurality of control drums rotatable relative to said stationary reflector component.

3. 3. The nuclear reactor of claim 2, wherein each of said control drums includes a reflector portion and an absorber portion, said reflector portions including beryllium oxide.

4. further comprising a core housing; the core is positioned within the core housing; 10. The nuclear reactor of claim 1, wherein the core housing comprises beryllium oxide.

5. 10. The nuclear reactor of claim 1, wherein the graphite support structure has a radial thickness of from about 0.3 meters to about 1.0 meters.

6. 10. The nuclear reactor of claim 1, wherein each of said plurality of channels has a diameter of between about 0.005 meters and about 0.05 meters.

7. 10. The nuclear reactor of claim 1, wherein the pitch of each of the plurality of channels is between about 0.013 meters and about 0.07 meters.

8. 10. The nuclear reactor of claim 1, wherein each of the plurality of channels is spaced apart from one another by between about 0.001 meters and about 0.06 meters.

9. 10. The nuclear reactor of claim 1, wherein the graphite support structure is an assembly of a plurality of graphite support structures positioned to sequentially reflect neutrons.

10. A reflector assembly usable in a nuclear reactor having a reactor core, the reflector assembly configured to surround the reactor core, the reflector assembly a graphite support structure having a plurality of channels defined therein; and a plurality of beryllium oxide inclusions positioned within the channels.

11. The reflector assembly of claim 10 further comprising a plurality of control drums rotatable relative to the graphite support structure.

12. 12. The reflector assembly of claim 11, wherein each of the control drums includes a reflector portion and an absorber portion, the reflector portion including beryllium oxide.

13. The reflector assembly of claim 10, wherein the radial thickness of the graphite support structure is from about 0.3 meters to about 1.0 meters.

14. 11. The reflector assembly of claim 10, wherein each of the plurality of channels has a diameter of about 0.005 meters to about 0.05 meters.

15. The reflector assembly of claim 10, wherein the pitch of each of the plurality of channels is between about 0.013 meters and about 0.07 meters.

16. The reflector assembly of claim 10, wherein each of the plurality of channels is spaced apart from one another by between about 0.001 meters and about 0.06 meters.

17. 11. The reflector assembly of claim 10, wherein the graphite support structure is an assembly of a plurality of graphite support structures positioned to sequentially reflect neutrons.

18. A nuclear reactor, The reactor core and a reflector assembly surrounding the reactor core, the reflector assembly comprising: A stationary reflector portion, a graphite support structure having a plurality of channels defined therein; and a stationary reflector portion including a plurality of beryllium oxide inserts positioned within the channel; a movable reflector portion including a plurality of control drums rotatable relative to said stationary reflector portion.

19. 20. The nuclear reactor of claim 18, wherein each of the control drums includes a reflector portion and an absorber portion, the reflector portions including beryllium oxide.

20. further comprising a core housing; the core is positioned within the core housing; 20. The nuclear reactor of claim 18, wherein the core housing comprises beryllium oxide.

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