The report faults the Nuclear Regulatory Commission for not protecting facilities such as the Pilgrim Nuclear Generation Station that take in seawater to cool their reactors, The Patriot Ledger in Quincy reported Saturday.
The Pilgrim plant is located on Cape Cod Bay.
The Nuclear Proliferation Prevention Project at the University of Texas at Austin wrote the 33-page report for the Defense Department. It says the NRC's failure to increase security standards at civilian, military and research nuclear reactors has heightened the risk of sabotage and theft of nuclear materials by terrorists.
The report calls for floating barriers -- similar to those used to protect naval ships and submarines -- to be placed at plants located along coastlines.
Carol Wightman, a spokeswoman for Entergy Corp., which owns the Pilgrim plant, said Pilgrim has spent millions of dollars on "enhanced security infrastructure" since the Sept. 11, 2001, terrorist attacks to make the site "one of the most secure and hardened nonmilitary facilities in the world."
Local police briefed on security measures at Pilgrim have assured town leaders the facility is secure from terrorism, said Plymouth Selectman Belinda Brewster.
Peter Stockton, one of the sources for the report, said threat assessments of nuclear facilities underestimate the number of potential adversaries and the lethal capabilities of weapons that could be used.