REMARKS PREPARED BY DR. WILLARD F. LIBBY * Commissioner, United States Atomic Energy Commission 1 INTRODUCTION The whole world is concerned over the question of radioactive fallout, particularly that from the testing of nuclear weapons. This has focused worid-wide attention on the problem of the effects of radiation, whether it be from atomic fallout or medical X rays, and a field of knowledge formerly known to only a limited group of scientists is becoming a matter of general concern, thought about and discussed by millions of people. The widespread concern may be due to the general fear of the unknown which has always been a basic humaninstinct. If the knowledge of the effects of radiation and the magnitude of the doses from fallout were more widely known, this would considerably allay the apprehension. So the first problem is the dissemination of the knowledge of fallout and radiation effects which has been gained over the last several years, and it is for this reason that this paper is presented. Last June the Congress of the United States held extensive hearings on radioactive fallout and radiation, and the minutes of these hearings are one of the best sources of information about the whole subject. In addition, a considerable number of articles have been published since last June which present more recent data and considerations. I hope to refer to some of these in the present paper. Since there is every reason for the information on radioactive fallout and radiation to be anown to any interested person, the United States Atomic Energy Commission hasthe policy of publishing promptly and completely on this subject, and this paper serves this function also. Before beginning a main subject of Radioactive Fallout, I would like to mention a new develop- ment which though related is not entirely germane. During the recent test operations of the U. 8. Atomic Energy Commission and the U. S. Department of Defense, in Nevada, Operation Plumbbob, a bomb wasfired underground which had no radioactive fallout because its fireball was sealed in molten rock. The fireball consisted largely of vaporized rock which congealed and totally contained the radioactivity. Essentially no radioactivity, even that belonging to such a volatile material as radioactive krypton, escaped to any considerable degree. The entirety of the radioactive material was found in some 700 tons of rock which had been fused and then cooled and crushed. Apparently the bomb, which had the power of 1700 tons of ordinary chemical explosive, blew itself a bubble of vaporized rock about 55 ft in radius, which had a skin about 3 or 4 in, thick. The shock wave crushed rock out to about 130 ft so the weight of the crushed rock overhead crushed the thin eggshell when it cooled and brokeit into fragments. These fragments contain the bomb debris essentially in its entirety. This means it is possible, at least in the small yield range, to contain and eliminate radioactive fallout in certain types of weapons tests. Of course, effects tests where such materials as structures and military equipment are being checked against atomic blast cannot be conducted in this manner, but these tests could conceivably be done with the special type of bomb with reduced radioactivity. *For delivery before The Swiss Academy of Medical Sciences Symposium on Radioactive Fallout, Lausanne, Switzerland, March 27, 1958. 293