tailieunhanh - Material Science_ Vol 2 of 2 - US DOE (1993) WW part 10

Tham khảo tài liệu 'material science_ vol 2 of 2 - us doe (1993) ww part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Plant Materials DOE-HDBK-1017 2-93 CLADDING AND REFLECTORS In the case of a fast reactor neutron thermalization is not desirable and the reflector will consist of a dense element of high mass number. Materials that have been used as reflectors include pure water heavy water deuterium oxide beryllium as metal or oxide carbon graphite and zirconium hydride. The selection of which material to use is based largely on the nuclear considerations given above and the essential neuronic properties of the materials. Most power reactors use water as both the moderator and reflector as well as the coolant. Graphite has been used extensively as moderator and reflector for thermal reactors. Beryllium is superior to graphite as a moderator and reflector material but because of its high cost and poor mechanical properties it has little prospect of being used to any extent. Beryllium has been used in a few instances such as test reactors but is not used in any power reactors. Reactors using heavy water as the moderator-reflector have the advantage of being able to operate satisfactorily with natural uranium as the fuel material enriched uranium is then not required. Zirconium hydride serves as the moderator in the Training Research Isotopes General Atomic TRIGA reactor. The zirconium hydride is incorporated with enriched uranium metal in the fuel elements. Rev. 0 Page 13 MS-05 CLADDING AND REFLECTORS DOE-HDBK-1017 2-93 Plant Materials Summary The important information in this chapter is summarized below. Cladding and Reflectors Summary Major characteristics required for cladding material Mechanical properties such as ductility impact strength tensile strength creep and ease of fabrication Physical properties include high corrosion resistance and high melting temperature High thermal conductivity Nuclear properties such as small absorption cross section Four materials suitable for cladding Aluminum is used for low power water-cooled research training and materials test reactors in .