The U.S. power grid regulator on Monday rejected a directive by Energy Secretary Rick Perry to prop up aging coal and nuclear power plants but said it had embarked on a new plan to determine whether the power grid is reliable. The move was a blow to Perry who wanted the Federal Energy Regulatory Commission (FERC) to act quickly to support the coal and nuclear power plants. In a filing, FERC asked grid operators to submit their concerns about the resiliency of the power system. Once it reviews the information, the commission will “promptly decide” whether additional action is warranted to address grid resilience, FERC said.