Fuel bundle with twisted ribbon fuel rodlets for nuclear thermal propulsion applications, structures for manufacture, and methods of manufacture

Abstract

Fuel bundle has plurality of twisted ribbon fuel rodlets arranged hexagonal packing or circle packing arrangement in a reactor core encased in a multilayer casing. Arrangement of twisted ribbon fuel rodlets is facilitated by rodlet seating fixture with seating surface having a plurality of protrusions that form a receiving space for ends of the twisted ribbon fuel rodlets. Manufacture of the fuel bundle incorporates fiber manufacturing technologies and, optionally, infiltration of spaces in the reactor core by infiltrant. Twisted ribbon fuel rodlet manufacturing system has sub-systems that impart twist periodicity to extruded ribbons, inspect twisted extruded ribbons, and cut twisted extruded ribbons to length. Inspection sorts twisted ribbon fuel rodlets as well as provides feedback to adjust operation of sub-systems. The fuel bundle (and optional fuel bundle support) can be incorporated into a fuel assembly of nuclear propulsion fission reactor structure of, for example, a nuclear thermal propulsion engine.

What is claimed is: 
     
         1 . A twisted ribbon fuel rodlet manufacturing system, comprising:
 a ribbon initial cooling zone;   a ribbon tensioning sub-system;   a ribbon twisting sub-system;   a ribbon cutting sub-system;   a ribbon inspection zone;   a length sensor sub-system; and   a rodlet sorting and collection sub-system.   
     
     
         2 . The twisted ribbon fuel rodlet manufacturing system according to  claim 1 , wherein the twisted fuel rodlet manufacturing system is enclosed in an inert atmosphere chamber. 
     
     
         3 . The twisted ribbon fuel rodlet manufacturing system according to  claim 2 , wherein an exit of a die of an extruder is enclosed in the inert atmosphere chamber. 
     
     
         4 . The twisted ribbon fuel rodlet manufacturing system according to  claim 3 , wherein the ribbon tensioning sub-system includes tensioning rollers, wherein surfaces of the tensioning rollers form a nip that is configured to contact surfaces of an extruded ribbon, and wherein one or both tensioning rollers are spring mounted in a direction parallel to a processing path of the extruded ribbon. 
     
     
         5 . The twisted ribbon fuel rodlet manufacturing system according to  claim 4 , wherein the ribbon twisting sub-system includes a stage, wherein the stage is configured for rotation about an axis of the processing path of the extruded ribbon, and wherein the stage has a shape with a center opening that is configured to accommodate passage of the extruded ribbon. 
     
     
         6 . The twisted ribbon fuel rodlet manufacturing system according to  claim 5 , wherein the ribbon tensioning sub-system is mounted on the ribbon twisting sub-system. 
     
     
         7 . The twisted ribbon fuel rodlet manufacturing system according to  claim 6 , wherein:
 the ribbon cutting sub-system includes cutting surfaces mounted on either side of the processing path and configured for reciprocating cutting action in an actuation zone and a funnel located upstream from the actuation zone in the processing path, and   the ribbon inspection zone includes one or more non-destructive inspection devices.   
     
     
         8 . The twisted ribbon fuel rodlet manufacturing system according to  claim 7 , wherein the one or more non-destructive inspection devices include a visual inspection system for optical analysis, a radiography system, a computed tomography system, and an ultrasound system. 
     
     
         9 . The twisted ribbon fuel rodlet manufacturing system according to  claim 8 , where the length sensor sub-system includes a laser line scanner and a photodiode detector, and the length sensor sub-system is configured to detect when an extruded ribbon traveling along the processing path breaks a plane of detection. 
     
     
         10 . The twisted ribbon fuel rodlet manufacturing system according to  claim 9 , wherein the rodlet sorting and collection sub-system includes a sorting device and a sorting tray, wherein the sorting device is movable from a first position to a second position, wherein in the first position the sorting device is configured to receive a first cut twisted ribbon fuel rodlet and deliver the first cut twisted ribbon fuel rodlet to a first location of the sorting tray, and wherein in the second position the sorting device is configured to receive a second cut twisted ribbon fuel rodlet and deliver it to a second location of the sorting tray. 
     
     
         11 . The twisted ribbon fuel rodlet manufacturing system according to  claim 1 , wherein the ribbon tensioning sub-system includes tensioning rollers, wherein surfaces of the tensioning rollers form a nip that is configured to contact surfaces of an extruded ribbon, and wherein one or both tensioning rollers are spring mounted in a direction parallel to a processing path of the extruded ribbon. 
     
     
         12 . The twisted ribbon fuel rodlet manufacturing system according to  claim 1 , wherein the ribbon twisting sub-system includes a stage, wherein the stage is configured for rotation about an axis of the processing path of the extruded ribbon, and wherein the stage has a shape with a center opening that is configured to accommodate passage of the extruded ribbon. 
     
     
         13 . The twisted ribbon fuel rodlet manufacturing system according to  claim 12 , wherein the ribbon tensioning sub-system is mounted on the ribbon twisting sub-system. 
     
     
         14 . The twisted ribbon fuel rodlet manufacturing system according to  claim 1 , wherein:
 the ribbon cutting sub-system includes cutting surfaces mounted on either side of the processing path and configured for reciprocating cutting action in an actuation zone and a funnel located upstream from the actuation zone in the processing path, and   the ribbon inspection zone includes one or more non-destructive inspection devices.   
     
     
         15 . The twisted ribbon fuel rodlet manufacturing system according to  claim 14 , wherein the one or more non-destructive inspection devices include a visual inspection system for optical analysis, a radiography system, a computed tomography system, and an ultrasound system. 
     
     
         16 . The twisted ribbon fuel rodlet manufacturing system according to  claim 14 , where the length sensor sub-system includes a laser line scanner and a photodiode detector, and the length sensor sub-system is configured to detect when an extruded ribbon traveling along the processing path breaks a plane of detection. 
     
     
         17 . The twisted ribbon fuel rodlet manufacturing system according to  claim 1 , wherein the rodlet sorting and collection sub-system includes a sorting device and a sorting tray, wherein the sorting device is movable from a first position to a second position, wherein in the first position the sorting device is configured to receive a first cut twisted ribbon fuel rodlet and deliver the first cut twisted ribbon fuel rodlet to a first location of the sorting tray, and wherein in the second position the sorting device is configured to receive a second cut twisted ribbon fuel rodlet and deliver it to a second location of the sorting tray. 
     
     
         18 . A method of manufacturing a twisted ribbon fuel rodlet, the method comprising:
 mixing a carbon source and a plurality of oxide powders to form a mixture, wherein at least one oxide powder has a composition including an oxide of a fissionable fuel component;   forming the mixture into an intermediate powder;   subjecting the intermediate powder to carbothermal reduction;   mechanical processing the carbothermally reduced intermediate powder to form a feedstock of solid solution carbide powders containing the fissionable fuel component;   forming the feedstock into a billet, wherein forming the feedstock includes the step of heated thermoplastic mixing;   extruding the billet to form an extruded ribbon; and   processing the extruded ribbon to form a twisted ribbon fuel rodlet.   
     
     
         19 . The method of manufacturing according to  claim 18 , wherein the carbon source is a phenolic resin, and wherein forming the mixture into the intermediate powder includes curing the mixture to form an intermediate body, pyrolyzing the intermediate body in inert atmosphere or vacuum, and mechanically processing the pyrolyzed intermediate body into the intermediate powder. 
     
     
         20 . The method of manufacturing according to  claim 19 , wherein the plurality of oxide powders include zirconium oxide nano-powder and niobium oxide,
 wherein the feedstock has a composition including (U a Zr b Nb c )C d , where 0.05<a<0.4, 0<b<0.95, 0<c<0.4, and 0.7<d<1, and   wherein processing the extruded ribbon to form the twisted ribbon fuel rodlet includes:
 contacting surfaces of the extruded ribbon in a nip of tensioning rollers of the ribbon tensioning sub-system, wherein one or both tensioning rollers are spring mounted in a direction parallel to a processing path of the extruded ribbon, and 
 rotating a ribbon tensioning sub-system about an axis of the processing path of the extruded ribbon while maintaining tension on the extruded ribbon to impart a twist to the extruded ribbon. 
   
     
     
         21 . The method of manufacturing according to  claim 20 , wherein processing the extruded ribbon to form the twisted ribbon fuel rodlet further includes:
 cutting the twisted extruded ribbon to form a twisted ribbon fuel rodlet, wherein cutting occurs in response to a length signal.   
     
     
         22 . The method of manufacturing according to  claim 21 , wherein processing the extruded ribbon to form the twisted ribbon fuel rodlet further includes:
 conducting image analysis on the twisted extruded ribbon to identify defects, and sorting the twisted ribbon fuel rodlet based on a result of the image analysis.   
     
     
         23 . The method of manufacturing according to  claim 18 , wherein the carbon source is carbon black, and wherein forming the mixture into the intermediate powder includes drying the mixture to form an intermediate body and mechanically processing the intermediate body into the intermediate powder. 
     
     
         24 . The method of manufacturing according to  claim 23 , wherein the plurality of oxide powders include zirconium oxide nano-powder and niobium oxide,
 wherein the feedstock has a composition including (U a Zr b Nb c )C d , where 0.05<a<0.4, 0<b<0.95, 0<c<0.4, and 0.7<d<1, and   wherein processing the extruded ribbon to form the twisted ribbon fuel rodlet includes:
 contacting surfaces of the extruded ribbon in a nip of tensioning rollers of the ribbon tensioning sub-system, wherein one or both tensioning rollers are spring mounted in a direction parallel to a processing path of the extruded ribbon, and 
 rotating a ribbon tensioning sub-system about an axis of the processing path of the extruded ribbon while maintaining tension on the extruded ribbon to impart a twist to the extruded ribbon. 
   
     
     
         25 . The method of manufacturing according to  claim 24 , wherein processing the extruded ribbon to form the twisted ribbon fuel rodlet further includes:
 cutting the twisted extruded ribbon to form a twisted ribbon fuel rodlet, wherein cutting occurs in response to a length signal.   
     
     
         26 . The method of manufacturing according to  claim 25 , wherein processing the extruded ribbon to form the twisted ribbon fuel rodlet further includes:
 conducting image analysis on the twisted extruded ribbon to identify defects, and sorting the twisted ribbon fuel rodlet based on a result of the image analysis.   
     
     
         27 . The method of manufacturing according to  claim 18 , wherein the plurality of oxide powders include zirconium oxide nano-powder and niobium oxide. 
     
     
         28 . The method of manufacturing according to  claim 18 , wherein the feedstock has a composition including (U a Zr b Nb c )C d , where 0.05<a<0.4, 0<b<0.95, 0<c<0.4, and 0.7<d<1. 
     
     
         29 . The method of manufacturing according to  claim 18 , wherein processing the extruded ribbon to form the twisted ribbon fuel rodlet includes:
 contacting surfaces of the extruded ribbon in a nip of tensioning rollers of the ribbon tensioning sub-system, wherein one or both tensioning rollers are spring mounted in a direction parallel to a processing path of the extruded ribbon, and   rotating a ribbon tensioning sub-system about an axis of the processing path of the extruded ribbon while maintaining tension on the extruded ribbon to impart a twist to the extruded ribbon.   
     
     
         30 . The method of manufacturing according to  claim 29 , wherein processing the extruded ribbon to form the twisted ribbon fuel rodlet further includes:
 cutting the twisted extruded ribbon to form a twisted ribbon fuel rodlet, wherein cutting occurs in response to a length signal.   
     
     
         31 . The method of manufacturing according to  claim 29 , wherein processing the extruded ribbon to form the twisted ribbon fuel rodlet further includes:
 conducting image analysis on the twisted extruded ribbon to identify defects, and   sorting the twisted ribbon fuel rodlet based on a result of the image analysis.   
     
     
         32 . A method of controlling twist rate during manufacture of twisted ribbon fuel rodlets, the method comprising:
 receiving an image of a twisted ribbon;   converting the received image to a binary ribbon profile by comparing each pixel in the received image to a predefined threshold;   generating a theoretical ribbon profile according to a ribbon model that includes a target twist rate;   generating a plot by convolving the ribbon profile with the theoretical ribbon profile for a range of twist rates; and   determining a calculated twist rate for the twisted ribbon as an x-coordinate of a point in the plot having maximum value.