Here are excerpts from Section V.

T272 forces to choose any energy to achieve required density and required IQI, no matter what kind of source (X-Ray and Gamma Ray) we do use

Article 22, E-94 of section V provides guideline to use for achieve the requirement of T272 of Section V. It tells that gamma should be used from the thickness 8.9 mm to 89 mm from gamma but again it is only guideline. If Sensitivity and Density requirements are met, any source (X-Ray or Gamma Ray) can be used.