Runit dome faces water-related threats

The Runit dome on the Enewetak atoll in the Marshall Islands is mainly at risk from water, including rising ocean levels and groundwater seeping into the structure, according to reports from the U.S. Department of Energy and the Los Angeles Times.

History of the Runit dome

The 1958 crater, created by the U.S. atomic test Cactus, was filled with contaminated waste from 43 atomic tests, including plutonium, and covered with a 46 cm thick concrete cap. The structure was meant to be a temporary solution, and the crater was not lined.

Structural concerns and government response

Cracks on the dome’s outer shell are attributed by the U.S. government to the aging of concrete. However, a 2024 study by the Pacific Northwest National Laboratory highlights storm waves and rising sea levels as major factors in the spread of radionuclides in the atoll.

Water seepage and radionuclide migration

The ground of the atoll is made of coral, a porous material, allowing seawater and groundwater to seep under the dome. Radionuclides have percolated into the sediments for decades through open pathways connecting the waste to ocean water and local groundwater.

Lack of data and local concerns

The Department of Energy admits it lacks data to determine how storms would affect the environment. A Marshall Islands leader criticized the agency for downplaying risks and failing to take responsibility for the dome, noting concerns about the radioactivity levels in water flowing from the dome to the lagoon.

Efforts to monitor and assess risks

Congress requested a repair plan and an assessment of the dome’s impact on the lagoon in a 2020 defense bill. From 2013 to 2018, several missions collected water samples for radiochemical analysis, and the Department of Energy proposed a program to measure how storm waves affect groundwater quality.