405479 APPENDIX ITI Radiation Dose Prediction for Underground Nuclear Detonations H. Mueller (ARL, Las Vegas) Introduction The detonation of a nuclear device beneath the earth's surface may be Boe Aa accompanied by a release of radioactivity to the atmosphcre. Whether a release will or will not occur depends on a number of factors. Expertence has shown that for certain types of device emplacements, releases are to be expected, e.g. cratering detonations. For other types of emplacements, releases are not expected and do not normally occur. The quantities of radioactive materials which have been released from individual underground explosions have varied over many orders of magnitude. The physical character- istics of the releases and the composition of the released materials have also varied greatly. In some instances only small releases, or seepages ‘of primarily noble gases have been observed. On the other hand, releases of large quantities of radioactive material have been experienced, consisting of both gaseous and refractory materials, resulting in considerable local radioactive fallout and in airborne activity being detected at great downwind distances. A radionuclide of particular interest is radioiodine, particularly itodine-131. The quantities of this nuclide released during a seepage is rather small and does not constitute an off-site hazard. For prompt massive ventings, however, relatively large quantities may be released, later appear in the milk of dairy cattle, and potentially result in exposures to the thyroids of those who consume the milk. It is this latter type of release and the prediction of its related potential exposures to man which is the subject of what follows.