Nuclear Security Act of 2003

Nuclear Security Act of 2003 - Amends the Atomic Energy Act of 1954 to establish a task force on nuclear infrastructure security to protect sensitive nuclear facilities from potential terrorist threats.

Instructs the Nuclear Regulatory Commission (NRC) to promulgate regulations that: (1) identify the threats that sensitive nuclear facilities must protect against to prevent radiological sabotage and theft of special nuclear material; and (2) establish a system to determine multiple threat levels in order to describe threat conditions.

Prescribes guidelines for mandatory NRC review of security plans and emergency response plans.

Directs the President to: (1) promulgate regulations establishing the Nuclear Infrastructure Antiterrorism Team to protect sensitive nuclear facility perimeters; and (2) establish a training program for National Guard, State and local law enforcement agency response to threats against a sensitive nuclear facility.

Amends the Energy Reorganization Act of 1974 to establish: (1) the Office of Nuclear Security and Incident Response; and (2) a Security Response Unit, including a mock terrorist team.

Instructs the NRC to: (1) establish a security response evaluation program for sensitive nuclear facilities; and (2) conduct emergency response exercises to evaluate emergency personnel response to a radiological emergency at those facilities.

Amends the Atomic Energy Act of 1954 to authorize trained security guards and employees of NRC certificate holders to carry firearms, other weapons, devices, or ammunition at NRC facilities.

Prescribes guidelines for such personnel to detain or arrest without a warrant.

Subjects to a criminal penalty: (1) any attempt or conspiracy to commit sabotage of nuclear facilities or fuel (the current standard is intentional or willful attempt); and (2) sabotage committed during construction of certain NRC facilities if the sabotage could adversely affect public health and safety during facility operation.

Amends the Energy Reorganization Act of 1974 to extend whistleblower protections to an employee of an NRC contractor or subcontractor.