The new flash x-ray facility constructed at Site 300 of the Lawrence Livermore National Laboratory has a nominal operating electron energy of 20 MeV. The bremsstrahlung photons from this accelerator will be used for a variety of radiographic investigations of both thick and thin objects under explosively driven conditions. In order to properly design and interpret experiments, it is very useful to have a Monte-Carlo code to simulate the coupled electron-photon processes that occur both in the creation of the bremsstrahlung as well as in the collimation, the materials being radiographed and the detection system. One such code suitable for this purpose in many experimental situations is the SANDYL code, which has been used at this laboratory since 1974. This brief report is written to point out that if one uses the code's default values for some of the parameters involving the electron substep size, the code-predicted bremsstrahlung is higher than experimental data by about 60. This report also shows that as this parameter is made finer, the code prediction approaches the experimental results to within about 10. This report compares the published data of O'Dell et al for bremsstrahlung at 20.9 MeV with our SANDYL calculations. O'Dell et al …

Three different uranium oxide samples have been characterized with respect to the different preparation techniques. Results show that the water reaction with uranium metal occurs cyclically forming laminar layers of oxide which spall off due to the strain at the oxide/metal interface. Single laminae are released if liquid water is present due to the prizing penetration at the reaction zone. The rate of reaction of water with uranium is directly proportional to the amount of adsorbed water on the oxide product. Rapid transport is effected through the open hydrous oxide product. Dehydration of the hydrous oxide irreversibly forms a more inert oxide which cannot be rehydrated to the degree that prevails in the original hydrous product of uranium oxidation with water. 27 figures.