Revisiting the 238U thermal capture cross section and gamma-ray emission probabilities from 239Np decay

The precise value of the thermal capture cross section of 238 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. Because of the strong correlations in activation measurements, the gamma-ray emission probabilities from the, beta(-) decay of Np-239 were also analyzed. As a result of the analysis, a value of 2.683 +/- 0.012 b was derived for the thermal capture cross section of U-238. A new evaluation of the gamma-ray emission probabilities from Np-239 decay was also undertaken.