Revisiting the U-238 Thermal Capture Cross Section and Gamma-ray Emission Probabilities from Np-239 Decay

The precise value of the thermal capture cross section of U is uncertain, and evaluated cross sections from various sources differ by more than their assigned uncertainties. A number of the original publications have been reviewed to assess the discrepant data, corrections were made for more recent standard cross sections and other constants, and one new measurement was analyzed. Due to the strong correlations in activation measurements, the gamma-ray emission probabilities from decay of Np were also analyzed. As a result of the analysis, a value of 2.683 ± 0.012 barns was derived for the thermal capture cross section of U. A new evaluation of the gamma-ray emission probabilities from Np decay was also undertaken.

[1]  V. S. Crocker.  The thermal neutron activation cross-section of U238 and Th232 , 1955 .

[2]  A. Bresesti,et al.  A method for absolute determination of 238U capture rates , 1969 .

[3]  H. Pomerance,et al.  THERMAL NEUTRON CAPTURE CROSS SECTIONS , 1951 .

[4]  F. Corte.  Problems and solutions in the standardization of reactor neutron activation analysis , 1992 .

[5]  R. W. Durham,et al.  A direct measurement of the thermal neutron conversion ratio of natural uranium , 1969 .

[6]  P. A. Egelstaff.  The neutron absorption cross sections of U238 and U235 at 2,200 m/sec , 1954 .

[7]  M. Wahlgren,et al.  Long-lived standards for the efficiency calibration of Ge(Li) detectors , 1972 .

[8]  V. G. Small.  The thermal neutron absorption cross-sections of U238 and Th232 , 1955 .

[9]  F. Corte,et al.  k0-Measurements and related nuclear data compilation for (n, γ) reactor neutron activation analysis , 1989 .

[10]  Selected Cryogenic,et al.  Brookhaven National Laboratory , 1957, Nature.

[11]  I. Ahmad.  Alpha-emitting nuclides as absolute efficiency calibration sources for germanium detectors , 1982 .

[12]  C. Walsh,et al.  Standardisation and measurement of the decay scheme data of 243Am and 239Np , 1996 .

[13]  Tyler B. Coplen,et al.  Atomic Weights of the Elements 1999 , 2001 .

[14]  S. Mughabghab.  Thermal neutron capture cross sections resonance integrals and g-factors , 2003 .

[15]  P. D. P. Taylor,et al.  Isotopic Compositions of the Elements 1997 , 1998 .

[16]  J. O. Blomeke,et al.  EFFECTIVE REACTOR CROSS SECTIONS IN MTR FUEL ASSEMBLIES , 1958 .

[17]  Dennis Saleh.  Zs , 2001 .

[18]  S. Harris,et al.  Thermal neutron absorption cross section of U238 , 1953 .

[19]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[20]  T. B. Ryves,et al.  A measurement of the thermal neutron radiative capture cross section of 238U , 1969 .

[21]  A. Bardell,et al.  A technique for the absolute counting of nuclear fission events , 1969 .

[22]  V. Petrov,et al.  Measurement of the absolute intensity of the 27S keV line of Np239 , 1974 .

[23]  G. Bortels,et al.  Alpha-particle-emission probabilities in the decay of 234U and photon-emission probabilities in the decays of 234U, 239Np and 243Am , 1984 .