Regulators and congressional investigators clashed Wednesday over a new report warning that in the event of an accident at a nuclear plant, frightened residents from outside the official evacuation zone might jam highways and prevent others from escaping.
The report by the Government Accountability Office, which acts as the investigative arm of Congress, challenges a three-decade-old fundamental of emergency planning around US nuclear power plants: that preparations for evacuation should focus on people who live within 10 miles of the site.
The GAO found that people living beyond the official 10-mile evacuation zone might be so panicked by the prospect of spreading radiation that they would also flee, clog highways, and delay the escape of others.
The investigators said regulators have never properly studied how many people beyond 10 miles would make their own decisions to take flight, prompting what is called a ‘‘shadow evacuation.’’
As a result, the GAO report says, ‘‘evacuation time estimates may not accurately consider the impact of shadow evacuations.’’
However, Neil Sheehan, a spokesman for the federal Nuclear Regulatory Commission, said in an e-mail statement: ‘‘We disagree with the view that evacuations cannot be safely carried out.’’
The investigation was requested by four US senators: Democrats Barbara Boxer of California, Robert P. Casey Jr. of Pennsylvania, and Sheldon Whitehouse of Rhode Island, and independent Bernard Sanders of Vermont.
They asked for the report in 2011 in response to an Associated Press investigative series reporting weaknesses in community planning for nuclear accidents, including the likelihood of surprisingly large shadow evacuations.
In an interview Wednesday, Casey said the report suggests that ‘‘we need to do more to ensure that these residents who live outside of the 10-mile radius have access to and understand evacuation procedures.’’
He said legislation may be needed but he gave no further details.