USSR naval mines were exposed to the underwater effects of Shot 4: Mk 6-0, Mk 10-9, Mk 18-0, Mk 25-0, Mk 36-2, Mk 36-3, Mk 39-0, and USSR R-1A. The statistical validity of the results may be questionable, since only 121 mines cf all types were exposed. These results indicated a 95-percent probability thut 1 surfacedetonated 7.0-Mt weapon will aeutralize 70 to 93 percent of all Mk 18-0, Mk 25-C, Mk 36-2, uf]: 36-2, and USSR R-1A mines within a radius of 4,500 feet from site z-ro, if the mines are in water approximately 180 feet deep. With identical conditions of yieid, height-of-burst, and water depth, results also indicated a 95-percent probability chat 72 to 96 percent cf al! Mk 5-0 und Mk 10-9 mines within a radius of 7 000 feet mili he neutralized. For Mk 39-4 mines laid in 180 feet of warer, an approx:mate range of 2.800 fect was established as the maximum distance from a 7.0-Mt sucface detonation at which lethal damage will occur. Table 4.2 presents a summary of the blast erfects of Shot 4 oa the minefieid. The radii of destruction obtained with the 7.0-Mt yield of Shot 4 are impressive however, for a 20-kt weapon, assuming that cube-root scaling is valid to a first approx.mation, these radii would be only one seventh as large. The limited clearance range3 ¢obtaine:) indicate that use of surface-detonated nuclear weapons for nava.~minetield clearence is not feasible. 70