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Resonance Parameters and Uncertainties Derived from Epithermal Neutron Capture and Transmission Measurements of Natural Molybdenum

G. Leinweber, D. P. Barry, J. A. Burke, N. J. Drindak, Y. Danon, R. C. Block, N. C. Francis, B. E. Moretti

Nuclear Science and Engineering / Volume 164 / Number 3 / March 2010 / Pages 287-303

Technical Paper / dx.doi.org/10.13182/NSE08-76

The electron linear accelerator facility at the Rensselaer Polytechnic Institute was used to explore neutron interactions with molybdenum in the energy region from 10 eV to 2 keV. Neutron capture and transmission measurements were performed by the time-of-flight technique. Resonance parameters were extracted from the data using the multilevel R-matrix Bayesian code SAMMY. A table of resonance parameters and their uncertainties is presented. Two transmission measurements were performed at a flight path of 25 m with a 6Li glass scintillation detector. The neutron capture measurements were performed at a flight path of 25 m with a 16-segment sodium iodide multiplicity detector. Nine different thicknesses of elemental molybdenum metal samples ranging from 0.051 mm (0.002 in.) to 6.35 mm (0.250 in.) were measured in either capture or transmission. Reductions in resonance integrals were observed when compared to ENDF/B-VII.0 for six of the seven stable isotopes. The largest reductions were 9% in 97Mo and 11% in 100Mo. The one measured increase in resonance integral relative to ENDF/B-VII.0 occurred in 95Mo, and it was significant (10%). The measured distribution of neutron widths for 95Mo and 97Mo are a better match to a Porter-Thomas distribution than those of ENDF/B-VII.0. Neutron strength functions for 95Mo and 97Mo were measured and compared to ENDF/B-VII.0. The strength of 95Mo and 97Mo are within uncertainties of each other. The measured radiation width distribution for 95Mo and 97Mo are compared to those of ENDF/B-VII.0 and to 2 distributions. Significant aspects of this analysis are the assignment of radiation widths, the determination of the transmission resolution function, and the propagation of experimental uncertainties into resonance parameter uncertainties.

 
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