"Much of the oil shale program effort at the Los Alamos Scientific Laboratory during the past quarter involved preparation for the intermediate-scale field tests that are due to begin in July 1978 at the Colony Mine. Laboratory work in material studies, explosive characterization and computer predictive modeling development have therefore proceeded at a slower rate. Considerable effort has been devoted to performing and interpreting flash x-radiographic studies of cavity formation in a spherical geometry. The experimental results are not yet understood, but anisotropic effects seem to play a strong role both in wave propagation and plastic deformation. These studies will continue. Also, computer simulation studies of rubbling caused by different explosives in the same material and geometry have been performed. Although the fracture criterion for rubbling is not sophisticated enough to allow quantitative comparison of rubbling efficiency the general features of the calculations do allow at least a qualitative comparison and therefore are useful for determining emplacement geometry, timing. and boostering."