Patent Application
20150040727
1. Field
The present disclosure relates to systems and methods for removing salts from electrolytically-reduced metals.
2. Description of Related Art
During a fuel fabrication process, metal oxides may be obtained from spent nuclear material and electrolytically reduced to their metallic form. The resulting metal from the electrolytic reduction step may be in the form of a dendritic structure (e.g., cake), which resembles a porous metal sponge with a relatively high surface area. As a result, the dendritic structure will also have a relatively large amount of salt adhered to and included therein from the electrolytic reduction step.
To remove the salt from the dendritic structure, a cathode processor is conventionally used to subject the mixture to relatively high temperatures to vaporize the salt. However, the relatively high temperatures will also vaporize volatile contaminants and radioactive materials within the mixture, which requires relatively expensive equipment to clean up the offgas from such a process while also increasing the risk of an accidental release of such materials.
A mechanical press system may include an upper press body including a curved bottom portion and an upper lip portion surrounding the curved bottom portion; a first heater within the upper press body; a lower press body aligned below the upper press body, the lower press body including a top portion and a lower lip portion surrounding the top portion, the upper press body and lower press body configured to come together during a compression state and configured to move apart during a decompression state; a second heater within the lower press body; and a containment band configured to rest on the lower lip portion of the lower press body and to surround the upper lip portion of the upper press body during the compression state and configured to separate from the upper press body and the lower press body during the decompression state.
A method of removing salt from a dendritic mixture may include loading the dendritic mixture into a mechanical press system, the dendritic mixture including a metallic dendrite and the salt dispersed within the metallic dendrite; heating the dendritic mixture to liquefy the salt without volatilizing one or more metals of the metallic dendrite; and compressing the dendritic mixture to obtain a fluidic mixture and an ingot of the metallic dendrite, the fluidic mixture including molten salt and residual metallic dendrite.
The various features and advantages of the non-limiting embodiments herein may become more apparent upon review of the detailed description in conjunction with the accompanying drawings. The accompanying drawings are merely provided for illustrative purposes and should not be interpreted to limit the scope of the claims. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. For purposes of clarity, various dimensions of the drawings may have been exaggerated.
It should be understood that when an element or layer is referred to as being “on,” “connected to,” “coupled to,” or “covering” another element or layer, it may be directly on, connected to, coupled to, or covering the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout the specification. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
It should be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of example embodiments.
Spatially relative terms (e.g., “beneath,” “below,” “lower,” “above,” “upper,” and the like) may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It should be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the term “below” may encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
The terminology used herein is for the purpose of describing various embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Example embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of example embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, example embodiments should not be construed as limited to the shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an implanted region illustrated as a rectangle will, typically, have rounded or curved features and/or a gradient of implant concentration at its edges rather than a binary change from implanted to non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation takes place. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of example embodiments.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, including those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
In further detail,
The top portion and the lower lip portion 112 of the lower press body 110 form a notch therebetween. The notch is configured to receive and hold the containment band 106 during the loading state (
The head of the lower press body 110 may be in a form of a disc, wherein the area of the top surface is less than that of the opposing bottom surface. As a result, a side surface of the head of the lower press body 110 may slope outwards from the top surface to the opposing bottom surface. Consequently, a cross-section of the head of the lower press body 110 may have a trapezoidal shape as shown in
The containment band 106 may be in a form of an open-ended cylinder, although other shapes are possible as long as the containment band 106 fits in the notch formed by the top portion and the lower lip portion 112 of the lower press body 110. The fit between the containment band 106 and the lower press body 110 should be adequate to prevent the metallic dendrite of the dendritic mixture from passing therebetween during the loading state. The containment band 106 also includes a handle structure 108 on an exterior surface of the containment band 106. The handle structure 108 may be in a form of continuous structure that completely surrounds the containment band 106. Alternatively, the handle structure 108 may be in a form of a plurality of intermittent structures that are spaced around the containment band 106. For instance, two or more (e.g., three, four, five, six, seven, eight, etc.) intermittent structures may be evenly spaced around the containment band 106, although example embodiments are not limited thereto. The length of the intermittent structures may be relatively long so as to be greater than the space between them. In another example, the length of the intermittent structures may be relatively short so as to be less than the space between them.
The upper press body 120 may be configured to be stationary, while the lower press body 110 may be configured to move toward the upper press body 120 in a second direction 119 during the compression state (
The curved bottom portion of the upper press body 120 may have a shape that corresponds to a partial surface of a sphere. The upper lip portion of the upper press body 120 is angled so as to point toward the containment band 106 during the compression state. For example, the upper lip portion of the upper press body 120 is angled downwards and outwards toward the containment band 106 during the compression state. The size and shape of the upper press body 120 and the containment band 106 are configured such that the upper press body 120 will fit relatively closely within the interior of the containment band 106 during the compression state. The fit should be adequate such that only a relatively small amount (if any) of the dendritic mixture 102 will forced out from between the upper press body 120 and the containment band 106 during the compression state.
As a result of the heat and compression, the salt within the dendritic mixture 102 will melt and drain away from the upper press body 120 and the lower press body 110 in the form of a fluidic mixture 124. The fluidic mixture 124 includes the molten salt along with residual metallic dendrite of a relatively small size that managed to pass between the containment band 106 and the lower press body 110. The fluidic mixture 124 may be filtered by a sieve 114 that has holes/openings/perforations that are smaller than an average particle size of the residual metallic dendrite so as to capture the residual metallic dendrite 126 while allowing the molten salt 128 to pass. The molten salt 128 may be recycled for reuse in an electrolytic reduction system. The sieve 114 may have a shape that corresponds with the periphery of the lower press body 110. For instance, in an example where the periphery of the lower press body 110 is round, the sieve 114 may be ring-shaped.
A receiving structure 136 is configured to extend in a sixth direction 138 toward the lower press body 110 such that the top portion of the lower press body 110 is aligned with an upper surface of the receiving structure 136. A plow 140 is configured to move in a seventh direction 142 across the top portion of the lower press body 110 so as to transfer the ingot 144 onto the receiving structure 136. The ingot 144 and residual metallic dendrite 126 may be subjected to further processing (e.g., processing pertaining to fuel fabrication).
According to an example embodiment, a method of removing salt from a dendritic mixture includes loading the dendritic mixture into a mechanical press system. The dendritic mixture may be in a form of an electrolytically-reduced cake. The dendritic mixture may include a metallic dendrite and salt dispersed within the metallic dendrite. The metallic dendrite may include at least one of plutonium and uranium. The salt may be lithium chloride. The dendritic mixture is heated to liquefy the salt without volatilizing one or more metals of the metallic dendrite. For example, the heating may be performed at a temperature that does not exceed about 650 degrees Celsius (e.g., 605 to 630 degrees Celsius), although the temperature may vary depending on the melting point of a particular salt and the boiling point of a particular contaminant (e.g., americium (Am)). In particular, the temperature should be above the melting point of the salt but below the boiling point of the contaminant in the dendritic mixture. The dendritic mixture is also compressed to obtain a fluidic mixture and an ingot of the metallic dendrite. The fluidic mixture may include molten salt and residual metallic dendrite. As a result, the fluidic mixture may be filtered to separate the residual metallic dendrite from the molten salt.
The mechanical press system may be formed of materials that act as neutron absorbers (e.g., boron, cadmium, hafnium). By using neutron absorbing materials, larger batch sizes and more throughput are possible, since a greater amount of dendritic material may be loaded into the mechanical press system without criticality concerns. Unlike the conventional art, the system and method of the present disclosure does not involve a cathode processor. Consequently, the system and method of the present disclosure are simpler and cheaper in design and operation.
While a number of example embodiments have been disclosed herein, it should be understood that other variations may be possible. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
