Hi, Dr. Zoomie! What’s this I heard about radioactive wasps at some nuclear site in the South? What’s that about?
Huh – this is right up there with the radioactive deer near the Rocky Flats plant in Colorado and some radioactive frogs at a site I used to work at. First of all, it’s not dangerous. Second – it’s actually not all that surprising. Here’s what happened.
Last month (July, 2025) some radiation safety technicians were performing routine radiological surveys and they stumbled on a wasp nest (and then three more) that gave them elevated readings. The techs responded as techs are wont to do – they surveyed and found some hot stuff; they surveyed a little further and found less hot stuff; the found the end of the hot stuff; they cleaned up and disposed of the waste.
The Savannah River Site dates back to the 1950s, built to produce plutonium and tritium (a radioactive isotope of hydrogen) for nuclear and thermonuclear weapons, producing them in nuclear reactors. Ultimately, the site grew to hold five nuclear reactors, each accompanied by chemical processing plants to extract the plutonium from spent reactor fuel slugs and the tritium from the lithium targets from which it was produced. The site produced plutonium and tritium into the 1980s, at which point the end of the Cold War and a reduction in nuclear weapons inventory reduced the need for its production.
After four decades of urgent Cold War-era operations the site contained all of the nuclear reactors and associated chemical processing facilities, along with nearly four decades of producing and accumulating radioactive waste, the site was loaded with radioactivity – spent reactor fuel, waste from the chemical processing, contaminated work areas, waste ponds, on-site radioactive waste burial pits, as well as a lot of environmental contamination. For over 30 years the site has been in remediation and there are likely a few decades of remediation remaining.
With so much environmental contamination it’s hard to contain – contaminated soil and water can spread radioactivity into plants, contaminated sediments can be bioperturbed by crayfish and other burrowing aquatic organisms, insects can carry contaminated sediments into “clean” areas, and more. And that’s where the wasps come in. Wasps fly, but they also crawl over contaminated soils and plants, they eat contaminated food, and they collect contaminated materials to make their nests. At least, that’s what likely occurred here. Whether the nests were built a decade ago or last spring, the materials from which they were made contained some radioactivity and the wasps likely tracked more contamination in, picked up during their routine foraging and whatever else it is that wasps do in the course of their days.
The reason this hit the news is that routine radiological surveys found “legacy radioactive contamination greater than 10 times to total contamination values” permitted under federal regulations – up to 100,000 dpm / 100 square centimeters of beta/gamma-emitting contamination in the form of a wasp nest close to F-area Tank Farm. The occurrence report notes that “The wasp nest was sprayed to kill the wasps, then bagged as radiological waste,” noting that no contamination was found on the ground in the surrounding area. The occurrence noted a similar incident several years earlier; in 2017 contaminated bird feces were found on the roof railing of another building on-site.]
Neither of these incidents involved potentially harmful levels of contamination – 100,000 dpm is about 0.05 microCuries of radioactivity. While the exact radionuclide wasn’t identified, beta and gamma radiation have the lowest relative biological effectiveness and the longer-lived beta-gamma emitters don’t tend to be highly radiotoxic. As one example a person would have to ingest 40 microCuries of Cs-137 to get a dose of 5 rem to the whole body, about 800 times as much radioactivity as was reported for a wipe over 100 square cm in the wasp nest. For that amount of radioactivity to give a dose of 5 rem, the nest would need to have at least 80,000 square cm – about 85 square feet – and a person would need to ingest it. This is not a plausible scenario…at least, I hope it’s not!
The bottom line is that the contamination exceeded regulatory limits, but doesn’t appear to pose any risk to workers at the site. And, because wasps don’t tend to travel far from home – and the Savannah River Site is huge (310 square miles) – this doesn’t pose a risk to people living nearby either. And I guess that’s one good thing about having regulatory control limits that are very much lower than the levels needed to put anyone at risk – they can be exceeded without hurting anyone. Which is something to try to keep in mind the next time something like this happens.