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PULSED NEUTRON EXPERIMENTS WITH FAST ASSEMBLIES

Technical Report ·
OSTI ID:4342475
This is a slight revision of the paper presented at the Theoretical Reactor Physics Conference in Sun Valley, Idaho on Sept. 25, 1957. The pulsed source technique consists of introducing repeated shont bursts of neutrons into a subcritical assembly, and following the decay of the leakage flux as a function of time. This technique is shown to be complementary to the Rossi alpha'' method, being more satisfactory than the latter for slower systems and further from prompt critical. The normal mode decay constants for a number of bare subcritical highly enriched assemblies thus obtained serve as additional normalization data for multigroup cross-sections. Analysis of the data for a set of emriched U spheres indicates that a satisfactory fit cannot be obtained with one group constants, and that the neutron spectrum is slower for smaller assemblies. It is noted that plotting the decay conntant as a function of buckling gives an apparently accurate way to extrapolate to prompt critical. The pulsed source technique can also be used to calibrate control rod and poison worth, and will give some estimate of the prompt neutron lifetime. (auth)
Research Organization:
California. Univ., Livermore' Radiation Lab.
DOE Contract Number:
W-7405-ENG-48
NSA Number:
NSA-12-004465
OSTI ID:
4342475
Report Number(s):
UCRL-4998
Country of Publication:
United States
Language:
English