VARIABLE MODERATOR REACTOR DEVELOPMENT PROGRAM. Quarterly Progress Report NO. 3

The hydrodyraruios code BOCH and the physics code PUREE' were used in the anaiysis of specific VMR cores. Eight core designs of different geometries were selected for initial evaluation. Extensive analysis of the first of these cores was completed. aid more general analysis of the other cores is in progress. The analog representation of the VMR kinetics was completed and applied to the aaalysis of the VMR over a large range of parameters for curves of positive void versus reactivity. Funiner checks of the first three energy groups of PUREE' against experinnental data were completed. The P/sub 3/-POP method of computing the thermal group constants was used in conjunction with the first three groups to analyze the reference core designs and the critical experiment. The more complex blackness method of computing the PUREE' thermal group constants appeared to be functioning properly and is being checked on very tight lattices to determine the magnitude of the change in fuel-pin blackness due to incident neutron distortion by neighboring fuel pins. Mechanical and system design of selected cores was started. Corrosion rate of the moderator systems was computed. and preliminary analysis of a clean-up system was started. (For preceding period see ATL-A-103.) (W.D.M.