CRBR reactor structures design. BRC meeting presentation

Some of the more important developments in LMFBR structures design technology are described and the application of the technology to design of the CRBR reactor components is illustrated. The LMFBR is both a high-temperature and a high-ΔT machine. High-temperature operation (up to 1100⁰F) requires that the designer consider the effects of thermal creep as a deformation mechanism and stress rupture as a failure mode. The large ΔT across the core coupled with a low core thermal inertia and the high conductivity of the sodium coolant combine to produce severe temperature gradients during a reactor scram. Structures designed to operate in this environment must be both light and stiff to minimize transient thermal stresses and prevent unacceptable flow-induced vibrations. Thermal shields may be required to protect the load-bearing structure. At CRBR core-component goal fluence levels, the predicted magnitude of core-component dimensional changes due to irradiation swelling and creep is very large compared with the more familiar dimensional changes associated with thermal expansion and thermal creep. The design of the core components, and in particular the core restraint system, is dominated by the need to accommodate the effects of irradiation swelling, creep and utility loss considerations. (author)