Safe and Secure Decommissioning Act of 2018 This bill amends the Atomic Energy Act of 1954 to prohibit the Nuclear Regulatory Commission from approving the request of a licensee for a waiver of, or exemption from, a covered regulation applicable to a civilian nuclear power reactor that has permanently ceased to operate. A covered regulation includes: (1) an emergency preparedness or response regulation or requirement, or (2) a security regulation or requirement applicable to spent nuclear fuel. This prohibition shall not apply to a civilian nuclear power reactor at which all spent nuclear fuel has been transferred to spent nuclear fuel dry casks.