The Bravo test, the testiong of a nuclear bomb on March 1, 1954, in the Bikini Atoll of the Marshall Islands resulted in an explosion that was 2½ times larger than expected. Radioactive ash dropped more than 7,000 square miles from the bomb site, caking the nearby inhabited islands.  “Within hours, the atoll was covered with a fine, white, powder-like substance,” the Marshall Islands health minister would later testify, according to the Atomic Heritage Foundation. “No one knew it was radioactive fallout. The children played in the ‘snow.’ They ate it.”

The 1954 explosion was part of nuclear tests conducted as the American military lurched into the nuclear age. From 1946 o 1958, 67 U.S. nuclear tests were conducted in the Marshall islands….From 1977 to 1980, loose waste and top soil debris scraped off from six different islands in the Enewetak Atoll was transported to Runit island and was mixed with concrete and buried in nuclear blast crater. 4,000 US servicemen were involved in the cleanup that took three years to complete. The waste-filled crater was finally entombed in concrete.  The Runit Dome, also called locally “The Tomb”, is a 46 cm (18 in) thick dome of concrete at sea level, encapsulating an estimated 73,000 m3 (95,000 cu yd) of radioactive debris, including some plutonium-239. …The structure, however, was never meant to last. Today, due to disrepair and rising sea tides, it is dangerously vulnerable. A strong storm could breach the dome, releasing the deadly legacy of America’s nuclear might….

Cracks have reportedly started to appear in the dome. Part of the threat is that the crater was never properly lined, meaning that rising seawater could breach the structural integrity. “The bottom of the dome is just what was left behind by the nuclear weapons explosion,” Michael Gerrard, the chair of Columbia University’s Earth Institute, told the ABC. “It’s permeable soil. There was no effort to line it. And therefore, the seawater is inside the dome. 

According to Guterres, UN Secretary General, who refers to Runit Dome as nuclear coffin: The Pacific was victimized in the past as we all know, The consequences of these have been quite dramatic, in relation to health, in relation to the poisoning of waters in some areas.”

Excerpts from Kyle Swenson , The U.S. put nuclear waste under a dome on a Pacific island. Now it’s cracking open, Washington Post, May 20, 2019 and Wikipedia