Integral tests of evaluated ENDF/B high-energy cross sections have been made by comparing measured and calculated neutron leakage flux spectra from spheres of various materials. An Am-Be (of,n) source was used to provide fast neutrons at the center of the test spheres of Be, CHg, Pb, Nb, Mo, Ta, and W. The absolute leakage, flux spectra were measured in the energy range 0. 5 to 12 MeV using a calibrated NE213 liquid scintillator neutron spectrometer. Absolute calculations of the spectra were made using version HI ENDF/B cross sections and an S discrete ordinates multigroup transport code. Generally excellent agreement was obtained for Be, CHg, Pb, and Mo, and good agreement was observed for Nb although discrepancies were observed for some energy ranges. Poor comparative results, obtained for Ta and W, are attributed to unsatisfactory nonelastic cross sections. The experimental sphere leakage flux spectra are tabulated and serve as possible benchmarks for these elements against which reevaluated * cross sections may be tested.
Key Words (Suggested by Author(s))Sphere leakage spectra; Scintillator measurements; Neutron flux spectra; Nuclear reactors; Neutron cross sections
SUMMARYIntegral tests of evaluated ENDF/B high-energy cross sections have been made by comparing measured and calculated neutron leakage flux spectra from spheres of various materials. An americium-beryllium (Am-Be (a, n)) source was used to provide fast neutrons at the center of the test spheres of beryllium (Be), polyethylene (CH 2 ), lead (Pb), niobium (Nb), molybdenum (Mo), tantalum (Ta), and tungsten (W). The absolute leakage flux spectra were measured in the energy range 0. 5 to 12 MeV using a calibrated NE213 liquid scintillator neutron spectrometer. Absolute calculations of the spectra were made using version in ENDF/B cross sections and an S discrete ordinates multigroup transport code.Generally excellent agreement was obtained for Be, CHg, Pb, and Mo, and good agreement was observed for Nb, although discrepancies were observed for some energy ranges. Poor comparative results, obtained for Ta and W, are attributed to unsatisfactory nonelastic cross sections. The experimental sphere leakage flux spectra arer, tabulated and serve as possible benchmarks for these elements against which reevaluated cross sections may be tested.
