- 80 situation are made. purposes. However, these calculations are made for planning Tests would not be conducted unless it can be shown that safety of on~ and off-site personnel can be assured even if the maximum credible accident should occur. By virtue of experiences gained over the past several years, containment techniques have been vastly improved and further improvement is anticipated. During the period August 5, 1963, through October 31, 1969, the Atomic Energy Commission announced the detonation of 180 nuclear tests which were designed to completely contain resulting radioactivity underground. Of these 180 underground tests, only 15 (all of low or low-intermediate yield) released radicactivity to the atmosphere which was detected by ground monitors or ground monitoring equipment off the site. There have been no releases of radioactivity from high-yield tests. Part C Question 17 Is it possible to determine the direction and velocity of contaminated underground water from a Plowshare cavity in an unfamiliar region, when there seems still to be some uncertainty about its direction and velocity even in Nevada? Part C Answer Question 17 The direction of ground water flow under natural conditions or in the vicinity of a cavity formed by the explosion of a deeply buried nuclear device can be predicted by knowledge of the pressure of hydraulic gradient acting on the water bearing formation. Ground water, like water on the surface of the earth, moves from points of higher elevation or pressure to