THANS17 si/4AP- 77 BATTELLE $81 NORTHWEST BATTELLE MEMORIAL INSTITUTE 8 0 8OX 999 PACIFIC NORTHWEST LABORATORIES RICHLAND WASHINGTON 99352 March 12, Dr. Rudolf J. Engelmann Chief, Fallout Studies Branch Division of Biology and Medicine U. S. Atomic Energy Commission Washington, D. C. 20545 TELEPHONE 509-942-1111 - 407811 1971 q ( f 7 Dear Rudy: I am replying to your January 21, 1971 letter asking for a reply to G. P. Dix's January 6, 1971 questions to you on particle resuspension for the Transit Program. Very little new experimental resuspension data have been generated since the SNAP-27 Meteorological Working Group report. These results will be discussed together with out additional questions and thoughts on resuspension. The crux of these new questions is the determination of whether we are only interested in the immediate inhalation hazard or are also interested in the long-term particle Migration by saltation and surface creep. These particles may not present an immediate inhalation hazard, but subsequently these larger particles could become the sources for a new inhalation hazard. This long-term surface migration of particles cannot be handled within existing diffusion models unless we also develop a model for describing particle translocation by saltation and surface creep. This new model would require a matching of airborne particle concen- trations and concentration profiles at an interface above which conventional diffusion models are applicable. The following answers are supplied in direct response to the questions which were asked during the review of the Transit Program. 1. Some additional work has been reported on particle resuspension since the November 29, 1968 draft of the SNAP-27 Meteorological Working Group Paper. In Project Schooner, a 31-kt cratering detonation was . OPERATING THE PACIFIC NORTHWEST LABORATORY FOR THE UNITED STATES ATOMIC ENERGY COMMISSION OR1S