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1.1 This document is a guide to preparing material specifications for fiber reinforced carbon-carbon (C-C) composite structures (flat plates, rectangular bars, round rods, and tubes) manufactured specifically for structural components in nuclear reactor core applications. The carbon-carbon composites consist of carbon/graphite fibers (from PAN, pitch, or rayon precursors) in a carbon/graphite matrix produced by liquid infiltration/pyrolysis and/or by chemical vapor infiltration.

1.2 This guide provides direction and guidance for the development of a material specification for a specific C-C composite component or product for nuclear reactor applications. The guide considers composite constituents and structure, physical and chemical properties, mechanical properties, thermal properties, performance durability, methods of testing, materials and fabrication processing, and quality assurance. The C-C composite materials considered here would be suitable for nuclear reactor core applications where neutron irradiation-induced damage and dimensional changes are a significant design consideration. (1-4)2

1.3 The component specification is to be developed by the designer/purchaser/user. The designer/purchaser/user shall define and specify in detail any and all application-specific requirements for necessary design, manufacturing, and performance factors of the ceramic composite component. This guide for material specifications does not directly address component/product-specific issues, such as geometric tolerances, permeability, bonding, sealing, attachment, and system integration.

1.4 This guide is specifically focused on C-C composite components and structures with flat panel, solid rectangular bar, solid round rod, or tubular geometries.

1.5 This specification may also be applicable to C-C composites used for other structural applications discounting the nuclear-specific chemical purity and irradiation behavior factors.

1.6 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

4.1 Composite materials consist by definition of a reinforcement phase in a matrix phase. In addition, carbon-carbon composites often contain measurable porosity which interacts with the reinforcement and matrix. The composition and structure of the C-C composite are commonly tailored for a specific application with detailed performance requirements. The tailoring involves the selection of the reinforcement fibers (composition, properties, morphology, etc), the matrix (composition, properties, and morphology), the composite structure (component fractions, reinforcement architecture, porosity structure, microstructure, etc.), and the fabrication conditions (forming, assembly, forming, densification, finishing, etc.). The final engineering properties (physical, mechanical, thermal, electrical, etc.) can be tailored across a broad range with major directional anisotropy in the properties.

4.2 Specifications for specific C-C composite components covering materials, material processing, and fabrication procedures are developed to provide a basis for fabricating reproducible and reliable structures. Designer/users/producers have to write C-C composite specifications for specific applications with well-defined composition, structure, properties and processing requirements. But with the extensive breadth of selection in composition, structure, and properties in C-C composites, it is virtually impossible to write a "generic" composite specification applicable to any and all C-C composite applications that has the same type of structure and details of the commonly-used specifications for metal alloys. This guide is written to assist the designer/user/producer in developing a comprehensive and detailed material specification for a specific CMC application/component with a particular focus on nuclear applications.

4.3 The purpose of this guide is to provide guidance on how to specify the constituents, the structure, the desired engineering properties (physical, chemical, mechanical, durability, etc), methods of testing, manufacturing process requirements, the quality assurance requirements, and traceability for C-C composites for nuclear reactor applications. The resulting specification may be used for the design, production, evaluation, and qualification of C-C composites for structures in nuclear reactors.

4.4 The guide is applicable to C-C composites with flat plate, rectangular bar, round rod, and round tube geometries.

4.5 This guide may also be applicable to the development of specifications for C-C composites used for other structural applications, discounting the nuclear-specific chemical purity and irradiation behavior requirements.