U.S. nuclear plants recorded 2,957 mishaps in 1986, a slight improvement over the 1985 record of 2,997, a study by Public Citizen's Critical Mass Energy Project said. The total included 11 incidents considered serious enough by the Nuclear Regulatory Commission that they were reported to Congress as "abnormal occurrences." Two occurred in December, 1985, but were reported in 1986. There were 678 emergency shutdowns at the more than 100 licensed reactors. The Ralph Nader-affiliated group acknowledged that most incidents were minor but said they indicated continuing safety problems. The report counts as mishaps several cases in which marijuana was confiscated from employees, security breaches in which workers were carrying weapons and such "acts of God" as earthquakes.