An investigation by the US Better Government Association (BGA) found that Illinois NPPs reported at least 35 accidental releases of water contaminated with radioactive tritium over the past decade. The BGA said on 17 November that at least seven of the 35 documented accidents since 2007 involved contamination of groundwater near the plants at levels dozens of times higher than federal safe drinking water standards. 

The report notes a leak at Exelon’s Dresden nuclear plant sent radioactive contaminants into a sewage treatment plant, a leak at Quad Cities, which took eight months to plug, and a leak that was occurring at Braidwood while state inspectors onsite. 

Representatives of Exelon and the US Nuclear Regulatory Commission, the Illinois Emergency Management Agency and the Illinois Environmental Protection Agency said the leaks posed no public danger and did not contaminate drinking water. Exelon said that to prevent leaks, it has spent $100m in the past decade on upgrades at all of its US plants.

The accidents included in the BGA analysis are separate from government-approved releases into large bodies of water," said David Lochbaum, an analyst with the nonprofit Union of Concerned Scientists. "The state allows Exelon to discharge controlled amounts of tritium into rivers and lakes, where radioactive material gets diluted..."Leaks aren't supposed to happen."