The Central Neutron Spectrum of the Fast Critical Assembly BIG-TEN

The BIG-TEN critical assembly at the Los Alamos Scientific Critical Experiments Facility was designed to provide a neutron spectrum somewhat like that expected in the liquid-metal fast breeder reactor. The relatively uncomplicated configuration of this assembly makes it useful for comparison of measured and calculated neutronic characteristics, and the high precision reproducibility of reactivity makes it valuable for intercomparisons of reaction rates. The central neutron spectrum was measured using protonrecoil proportional-counting techniques with pulse shape discrimination capability for the energy range from 27 to 1200 keV.