Advanced Beryllium Gyro Technology

This paper describes the process developed for fabricating beryllium gyro components by hot isostatic pressing. Five different components, an inner gimbal, a gyro sleeve, an accelerometer sleeve, an inner cylinder, and an inner cylinder cover, were fabricated. Although the process varied somewhat for each type of specimen, it consisted primarily of vibratory packing, hydrostatic pressing, hot isostatic pressing, and leaching. Since the most challenging component to be fabricated was the inner gimbal, this paper is devoted primarily to the process development of this particular component. Two key developments associated with the fabrication of the inner gimbal were the use of a deformable mandrel and the use of a new type of pressure-transmitting medium. The use of a porous copper mandrel allowed even deformation of the preform during cold hydropressing and, as a result, very accurate pressings could be made. A sodium chloride pressure-transmitting layer around the green compact allowed sealing of the irregular shape in a cylindrical pressing container

GAS-PRESSURE BONDING OF ZIRCALOY-CLAD FLAT-PLATE URANIUM DIOXIDE FUEL ELEMENTS

A solid-state bonding technique involving the use of gas pressure at elevated temperatures was investigated for the preparation of compartmented Zircaloy-clad flat-plate uranium dioxide fuel elements. These investigations involved development of methods for the surface preparation and assembly of fuel- element components for bonding, determination of optimum bonding parameters, development of barrier coatings for uranium dioxide to prevent reaction with Zircaloy, and extensive testing and evaluation of the bonded fuel elements. During the course of this work, the process was continually modified and refined in an effort to improve the quality of the bonded element and decrease the cost of fabrication. The surface-preparation studies indicated that satisfactory bonding could be obtained consistently with both machined and belt-abraded components. Belt abrasion is more economical and was used as the standard technique in the development phases of the program. Initially the elements were assembled into a stainless steel or Ti-Namel envelope which was evacuated and sealed prior to bonding. Later studies showed that the quality of bonded elements could be improved and process costs decreased by edge welding the Zircaloy components to form a gastight assembly that was then bonded without use of a protective envelope. Further cost reductions were incorporated into the process by the use of piece Zircaloy components to form the picture frame. Optimum bending with a minimum core-to-cladding reaction was achieved by pressure bonding at 1500 to 1550 deg F for 4 hr using a helium gas pressure of 10,000 psi. A postbonding heat treatment for 5 min at 1850 deg F in a salt bath promoted additional grain growth at the bond interface during the alpha-to-beta transformation. Barrier layers of graphite. chronaium, iron. molybdenum, nickel, niobium, palladium, and various oxides were investigated to prevent reaction between the UO/sub 2/ core and Zircaloy cladding. Graphite, in the form of a sprayed and buffed coating, and chromium were found to be relatively effective barriers. The graphite coating was easy to apply and less expensive than a chromium electroplate. (auth

FURTHER DEVELOPMENT OF GAS-PRESSURE BONDING OF ZIRCALOY-CLAD FLAT-PLATE URANIUM DIOXIDE FUEL ELEMENTS

The effects of core barrier coatings, void spaces, and surface-cleaning techniques on the quality of Zircaloyclad flat-plate UO/sub 2/ fuel elements prepared by gas-pressure bonding were investigated. Techniques were developed for the application of barrier layers of chromium by a vapordeposition process and of crystalline carbon by a pyrolytic process. These coatings, together with a graphite coating previously developed, were evaluated in pressure-bonded fuel elements for their effectiveness in preventing coreto-cladding reaction and for their general production feasibility. Crystalline carbon coatings 15 to 40 mu in. thick and chromium coatings 25 to 40 mu in. thick were determined to be satisfactory. In the stady of the flow of cladding-plate material into void spaces in the picture-frame assembly, it was established that excessive flow, and consequent thinning of the cladding, can be minimized by individually compartmentalizing the cores with Zircaloy ribs. This design resulted in maximum restriction of the effects of a cladding failure in service. Quantitative data on the maximum amount of void space resulting from manufucturing tolerances or from chipped fuel cores that is tolerable in cladding failure in service. Quantitative data on the maximum amount of void space resulting from manufucturing tolerances or from chipped fuel cores that is tolerable in elements of this design were obtained. In stadies of surface-cleaning technlques, it was found that a final multistep rinsing cycle resulted in bonds consistently free of evidence of contamination. (See also BMI-1374.) (auth

Gas-pressure bonding of zircaloy-clad flat-plate uranium dioxide fuel elements /

"Contract No. W-7405-eng-92.""UC-25 Metallurgy and Ceramics (TID-4500, 14th Ed.).""August 28, 1959.""Report No. BMI-1374."Includes bibliographical references (p. 105-106).Work performed by the Battelle Memorial InstituteMode of access: Internet

Further development of gas-pressure bonding of zircaloy-clad flat-plate uranium dioxide fuel elements /

"Contract No. W-7405-eng-92.""UC-25 Metallurgy and Ceramics (TID-4500, 15th Ed.).""May 11, 1960.""Report No. BMI-1436."Includes bibliographical references (p. 57).Work performed by the Battelle Memorial InstituteMode of access: Internet