and few survive to enter the cavity
View of bed taken through bottom plate: 500-µm glass beads, 1,000 rpm, 170 m3/min.
illustrating J. R. Powell and T. E. Botts, Brookhaven National Laboratory, "Particle Bed Reactors and Related Concepts." in Proceedings of a Symposium, Advanced Compact Reactor Systems. National Academy of Sciences, Washington, D.C. November 15-17, 1982 (National Academy Press, 1983): 95-153
This appears to belong to a Rotating Bed Reactor (RBR), in which particulate fuel is held inside a "cold rotating porous cylindrical frit." The article concerns nuclear reactors for use in space.
...insensitivity to thickness is a result of the "blackness" of the reactor core. Almost all thermalized neutrons that diffuse back from the reflector are absorbed in the fuel bed, and few survive to enter the cavity… (p107)
tags: J. R. Powell; T. E. Botts; black; blackness; related concepts; survival