Backgrounder on Force-on-Force Security Inspections

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The Nuclear Regulatory Commission has carried out force-on-force inspections regularly at commercial operating nuclear power plants since 1991 as part of its comprehensive security program. These inspections are an important way to evaluate and improve the effectiveness of plant security programs under NRC regulations (10 CFR Part 73) to prevent radiological sabotage.

FOF inspections assess a nuclear plant's physical protection measures to defend against the "design basis threat," or DBT. The DBT describes an adversary that plant owners must protect against with physical protection systems and response strategies. The NRC periodically reassesses the DBT and makes revisions as necessary.

A New, Stronger Force-on-Force Program

Before Sept. 11, 2001, NRC conducted FOF inspections about once every eight years at all U.S. commercial nuclear plant sites, in addition to regular baseline security inspections. Following the Sept. 11 attacks, the NRC strengthened its FOF program, requiring plants to defend against a tougher DBT that reflected the new threat environment and increasing the level of realism.


The NRC’s redesigned FOF program was fully implemented by late 2004. Today, the NRC evaluates each plant site every three years. All licensees conduct tactical security exercises in the intervening years. (The details of the FOF inspections are Safeguards Information, which is protected from public disclosure under the Atomic Energy Act.)

The NRC gives plant operators advance notice of FOF inspections for safety and logistical purposes and to provide for coordination of two sets of security officers — one for maintaining actual security, another for participating in the inspection. A key goal is to balance personnel safety, while maintaining actual plant security during exercises that are as realistic as possible.

Inspectors preparing FOF exercises use information from table-top drills, previous inspection reports and security plan reviews to design commando-style attacks to probe potential weaknesses in the plant’s defenses. The site’s defenders aim to keep the attackers from destroying or damaging key equipment. Any potentially significant weaknesses in the protective strategy identified during FOF inspections are promptly addressed. FOF inspection teams include active duty military advisors from the U.S. Special Operations Command. They help evaluate site security forces and systems, and provide an independent evaluation of the adversary force’s performance.

Mock Adversary Forces in Force-on-Force Exercises at Nuclear Power Plants

The NRC conducts force-on-force (FoF) exercises (simulated terrorist attacks on nuclear power plants using a mock adversary force to replicate design basis threat (DBT) characteristics during the attacks). These exercises are used to assess and improve, as necessary, the defensive strategies at licensed facilities.

A credible, well-trained, and consistent mock adversary force (MAF) is vital to the FoF program. Licensee employees have been used in the role of the mock adversary since FoF testing was initiated in 1982. Prior to 2004, plant operators used a MAF that included security officers from their own sites, officers from other licensees, and state police tactical team members. However, using these diverse sources to constitute a MAF caused inconsistencies during FoF exercises, as not all of the forces were trained to the same standard. In 2004, the NRC approved use of the Nuclear Energy Institute (NEI)-managed Composite Adversary Force (CAF) as the mock adversary in FoF exercises for the entire fleet of operating reactors. In February 2018, when Entergy and NextEra ended their membership with NEI, they formed a Joint Composite Adversary Force (JCAF) to serve as the MAF at Entergy and NextEra facilities.

Following Entergy's and NextEra's decision to discontinue membership with NEI, the Commission approved the staff's recommendation to institute long-term use of one or more industry-managed MAFs and to permit industry to implement and manage the MAFs for use during NRC-conducted FoF exercises. The Commission further directed that the approval of any new MAF beyond the existing CAF and JCAF would involve NRC staff's review of the associated proposal and implementation plan. NRC would also need to provide approval prior to the new MAF being utilized in an NRC-conducted FoF exercise.

The NRC maintains operational oversight of FoF exercises, including the MAF actions during all exercises. NRC will continue to provide oversight to ensure that MAF teams meet the NRC performance standards and can provide a credible adversary force that can replicate the characteristics outlined in the DBT. The NRC will also continue to ensure separation and independence between the MAF team and a site's guard force during exercises.

Photo of Force on Force Exercises

Composite Adversary Force

A credible, well-trained, and consistent mock adversary force is vital to the FOF program. Prior to Sept. 11, power plant operators used a mock adversary force that often included security officers from their own sites, other licensees, and state police tactical team members. Using these diverse sources caused inconsistencies. The revised FOF program uses a mock adversary force specifically trained to NRC standards, which cover the skills and physical fitness qualifications of team members; team tactics, communications and planning; firearms knowledge and proficiency; and exercise simulation equipment.


To avoid any conflict of interest, the NRC requires a clear separation of functions between the mock adversary forces and plant security forces. The NRC also maintains control over the design and implementation of the FOF inspections.

NRC's Overall Security Program

FOF inspections are an essential part of NRC's oversight of plant owners’ security programs and their compliance with NRC security requirements. The agency continues to evaluate and strengthen its overall security program in response to changes in the threat environment, technological advancements and lessons learned. As a result, substantial improvements to nuclear plant security have been made to protect against terrorism and radiological sabotage. These include well-trained security forces, robust physical barriers, intrusion detection systems, surveillance systems and plant access controls.


Together, these efforts help make nuclear power plants among the best protected private sector facilities in the nation.

Additional information is available on NRC's website.

March 2019

Page Last Reviewed/Updated Saturday, August 29, 2020