Nuclear instrumentation cable end seal
AssigneeThe United States of America as represented by the United States Department of Energy
InventorsCollins P. Cannon, Donald P. Brown
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Abstract
An improved coaxial end seal for hermetically sealed nuclear instrumentation cable exhibiting an improved breakdown pulse noise characteristic under high voltage, high temperature conditions. A tubular insulator body has metallized interior and exterior surface portions which are braze sealed to a center conductor and an outer conductive sheath. The end surface of the insulator body which is directed toward the coaxial cable to which it is sealed has a recessed surface portion within which the braze seal material terminates.
Claims7
A high voltage, high temperature coaxial end seal for hermetically sealed nuclear instrumentation cable which exhibits an improved breakdown pulse noise characteristic, which end seal comprises a generally tubular insulator body portion with selected portions of the interior and exterior surfaces of the tubular insulator body being metallized, a conductive central tube passing through the tubular insulator and sealed thereto, an outer conductive sheath disposed about one end of the tubular insulator and sealed thereto, with a conductive end cap disposed about the other end of the tubular insulator and sealed to the metallized exterior surface of the tubular insulator and the conductive central tube, and wherein the other end surface of the tubular insulator body has a first radial surface portion of a predetermined minimum dimension extending from the tubular insulator body interior surface to an axial surface portion coaxial about the conductive central tube, with a second radial surface portion extending from the axial surface portion to the tubular insulator body exterior surface, with the radial and axial surface portions free of metallized layer, and wherein sealing braze material is provided between the conductive central tube and the metallized interior surface of the tubular insulator body with the braze material terminating along the first radial surface portion.
An insulator-to-metal hermetic end seal structure for use with coaxial instrumentation cable subject to high voltage and high temperature which end seal structure comprises a generally tubular insulator body with a central passage provided through the insulator body along the longitudinal axis of the body, a metallized layer provided on the interior surface of the central passage and on the exterior surface of the insulator body, a central conductor exterior surface of the insulator body, a central conductor disposed within the central passage braze sealed to the metallized interior surface of the passage and a tubular metal outer sheath about and braze sealed to the metallized exterior surface of the insulator body, wherein the end surface of the insulator body facing the end of the coaxial instrumentation cable to which it is sealed has a radial portion and a stepped axial recess portion at the interior surface about the center conductor providing a predetermined gap between the center conductor and the stepped axial recess with a braze seal provided between the center conductor and the metallized interior surface of the insulator body which braze seal terminates at the axial recess portion of the tubular insulator body, and the predetermined gap between the center conductor and the axial recess portion is at least 0.01 inch.
Dependencies are inferred from the claim text.