SYNTHESIS AND FABRICATION OF REFRACTORY URANIUM COMPOUNDS. Monthly Progress Report No. 8 for April 1 through April 31, 1960

The effort on uranium silicide during the repent period was equally divided between synthesis and fabrication. The goal for the synthesizing effort was to make U/sub 3/8i/sub 2/ of higher purity than that made in the past, and the goal for the fabrication effort was to make pellets of density higher than 93%. Both goals were achieved. Experiments in simultaneous synthesis and fabrication of uranium monocarbide are reported in which mixtures of uranium powder and carbon were hot pressed. Sintering experiments on uranium monocarbide produced pellets of 91 to 91% theoretical density; however, cracking and oxidation were observed. Further experiments are planned in which oxidation will be reduced to a minimum. (J.R.D.

Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

Synthesis and Fabrication of Refractory Uranium Compounds. Monthly Progress Report No. 6 for January 1 Through January 31, 1960

Preparation of about 1200 g of uranium nitride powder is reported. Experiments indicated that synthesis of mononitride by decomposition of higher nitrides required pro longed heating at high temperature. Chemical analysis of uranium nitride for nitrogen was found to be difficult. Data from analysis of these compounds are tabulated for comparison with calculated composition. Sintering studies of uranium mononitride continued during the report period. Work on uranium silicide formation from the elements without quenching was continued, and effects of crucible material on the synthesis of the material were investigated. (For preceding period see ORC-254.) (J.R.D.