The group has had a long-term program for the measurement of one of the most important of these cross sections-the neutron-induced fission cross section of /sup 235/U. The primary mission of the Neutron Interactions and Dosimetry Group at the National Bureau of Standards (NBS) is the measurement of the standard neutron cross sections. A computed value of 1245 mb is obtained using an evaluated /sup 252/Cf fission neutron spectrum and ENDF/B-IV for the /sup 235/U(n,f) cross section. The observed /sup 235/U fission cross section is 1204 - 29 mb. Five scattering corrections were applied to the data source capsule (0.6 - 0.8) percent, fission chamber (1.1 - 0.4) percent, support structure (0.6 - 0.5) percent, platinum deposit backing (1.3 - 0.8) percent and total room return (0.5 - 0.2) percent. ![]() Uncertainty in the Manganous Bath comparison of NBS-I and the Cf source was -0.4 percent the /sup 235/U fissionable deposit masses have been ascertained to -1.3 percent. The /sup 252/Cf neutron source strength was determined with a Manganous Sulfate Bath relative to the internationally compared Ra-Be photoneutron standard neutron source, NBS-I, presently more ยป known to -1.1 percent. In this geometry the effect of source position errors is small. The fission chambers are mounted 10 cm apart on opposite sides of a small volume, single encapsulated /sup 252/Cf source (4 x 10/sup 9/ n/sec, 0.34 cm/sup 3/ capsule vol approximately 2 g steel and aluminum). (United States) Additional Journal Information: Journal Volume: 81:2 Country of Publication: United States Language: English Subject: 73 NUCLEAR PHYSICS AND RADIATION PHYSICS NEUTRON REACTIONS FAST FISSION URANIUM 235 TARGET BERYLLIUM 7 CROSS SECTIONS DATA COVARIANCES EXPERIMENTAL DATA FISSION CHAMBERS FISSION NEUTRONS FISSION SPECTRA FISSIONABLE MATERIALS KEV RANGE 100-1000 LABORATORIES LITHIUM 7 MEASURING METHODS MEV RANGE 01-10 NEUTRON FLUX NEUTRON SOURCES PLASTIC SCINTILLATORS PULSE TECHNIQUES STANDARDS TIME-OF-FLIGHT METHOD US NBS ALKALI METAL ISOTOPES ALKALINE EARTH ISOTOPES BARYON REACTIONS BARYONS BERYLLIUM ISOTOPES BETA DECAY RADIOISOTOPES DATA DAYS LIVING RADIOISOTOPES ELECTRON CAPTURE RADIOISOTOPES ELEMENTARY PARTICLES ENERGY RANGE EVEN-ODD NUCLEI FERMIONS FISSION HADRON REACTIONS HADRONS INFORMATION IONIZATION CHAMBERS ISOTOPES KEV RANGE LIGHT NUCLEI LITHIUM ISOTOPES MATERIALS MEASURING INSTRUMENTS MEV RANGE NATIONAL ORGANIZATIONS NEUTRON DETECTORS NEUTRONS NUCLEAR REACTIONS NUCLEI NUCLEON REACTIONS NUCLEONS NUMERICAL DATA ODD-EVEN NUCLEI PARTICLE SOURCES PHOSPHORS RADIATION DETECTORS RADIATION FLUX RADIATION SOURCES RADIOISOTOPES SPECTRA STABLE ISOTOPES TARGETS US DOC US ORGANIZATIONS 652026* - Nuclear Properties
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