text: Let us assume that the resonant neutrons move in an infinite system consisting of a moderator and U. When colliding with the moderator nuclei, the neutrons are scattered, and with the U nuclei, they are absorbed. The former collisions favor the retention and removal of resonant neutrons from the danger zone, while the latter lead to their loss.
  The probability of avoiding resonance capture (coefficient φ) is related to the density of nuclei N and the moderating power of the medium ξΣ by the relationship below,
  The J value is called the effective resonance integral. It characterizes the absorption of neutrons by a single nucleus in the resonance region and is measured in barnes. The use of the effective resonance integral simplifies quantitative calculations of resonance absorption without detailed consideration of neutron interaction at deceleration. The effective resonance integral is usually determined experimentally. It depends on the concentration of U and the mutual arrangement of uranium and the moderator.