Some Effects of Packaging Materials on Critical Arrays of Fissile Materials

The surface density representation of array criticality provides a comprehensive display of criticality parameters of arrays of packaged fissile materials. The study leads to the following conclusions: (1) The mass limits established by the N 16.5 standard for air-spaced spherical units in water-reflected arrays may be adequate for transportation packages; (2) criticality assessments made for one fissile material can be extended to other materials which have defined equivalent masses for array criticality of air-spaced units; and (3) a uniform minimum margin of subcriticality can be established for transportation of packaged fissile materials.