1.   The events included radioactive leaks, unplanned shutdowns and component failures, as well as vandalism, drug abuse and unauthorized use of firearms.

2.   Any unplanned shutdown is riskier, but the successful activation of all those flares would be the best outcome, because they burn gases that otherwise might escape disastrously.

3.   He said an unexpected electrical shutdown caused the leak, adding that the Canadian company has installed additional back-up generators to help prevent more unplanned shutdowns.

4.   The absence of unplanned shutdowns is an indication of safe performance, according to federal regulators.

5.   Outages of power supplies from outside the plants could also cause unplanned shutdowns, he said.

6.   Power plants where unplanned shutdowns have happened also were visited to examine operations and maintenance records, Lynch said.