cant fallout area for the first twenty-four hour period, taking into account changes in the wind patterns with time and displacement of the atomic cloud. No basic change was made in the fallout forecast- ing techniques as planned prior to|s/077,\ rather the new method was used and presented at briefings to augment and modify results from the original methods. Also, MIKE shot indicated that the current methods of predict-— ing fallout on the assumption of a point source (or at best, a very small source) were net acceptable for high yields. Consequently, CASTLE forecasting was originally made on the basis of a circular source approximately fifteen miles in radius (i.e., the approximate radius of fallout crosswind and upwind from MIKE). The results of HT1\ however, indicated this to be somewhat small, and the shape was probably more elliptical with a semi-minor axis of about twenty-~five miles. For the barge shots, the fifteen mile circular ra- dius (again more elliptical than circular) appeared to be more than adequate, E. Constructicn of RADEXES and Fallout Plots. Generally speaking the radiological exclusion area (RADEK area) was considered to be a limited fallout area for the first six hours post-shot in the vicinity of the test site and for the primary use of test personnel and equipment. The RADEX was used as an operational device to define dangerous areas and to deny entry of Task Force units into certain areas except under specific authorization. As a consequence, it was given wide dissemination through- 184