The most difficult nuclear weapons riddles

Russia - 7000, USA - 6800, China - 270, North Korea - unknown.

In 1977, the United States military began decontamination of Enewetak and other islands. During the three-year, $100 million cleanup process, the military mixed more than 111,000 cubic yards (85,000 m3) of contaminated soil with Portland cement and buried it in an atomic blast crater. Today, a concrete dome covers the material.

Lake Chagan, Kazakhstan, is a lake created by the Chagan nuclear test fired on January 15, 1965, part of the Nuclear Explosions for the National Economy. A 140 kiloton device was placed in a 178-metre (584 ft) deep hole in the dry bed of the Chagan River. The blast created a crater 400 m (1,300 ft) across and 100 m (330 ft) deep with a lip height of 20 to 38 m (66 to 125 ft).; it is often referred to as "Atomic Lake".