Calculation of the Effective Resonance Integral of U²³⁸

Methods for determining an effective resonance integral from available resonance parameter data are examined and applied to lumped systems where the absorber is U²³⁸. Agreement with experiment is satisfactory in view of an uncertainty of about 10% introduced by probable errors of the parameter data. The empirical formula is expected to represent the geometric behavior of I better than other two-parameter formulas when applied to a variety of fuel element compositions. For uranium metal the formula is virtually indistinguishable from the formula of Gurevich and Pomeranchouk: Quantitative results describing the temperature and energy dependence of resonance captures are also given.