* All terms are followed by their source.

  • Amendment to the Convention on the Physical Protection of Nuclear Material

    "The amended Convention makes it legally binding for States Parties to protect nuclear facilities and material in peaceful domestic use, storage as well as transport. It also provides for expanded cooperation between and among States regarding rapid measures to locate and recover stolen or smuggled nuclear material, mitigate any radiological consequences of sabotage, and prevent and combat related offences." (IAEA

  • Chain Reaction

    "A process in which neutrons are absorbed by fissionable material and the neutrons released as a result of fission go on to cause more fissions.  A self-sustaining chain reaction is one where the number of neutrons released from fission in one period of time (or generation) is enough to cause the same number of fissions in the following generation, taking into account that some neutrons will be absorbed by non-fissionable material or escape the region of fissionable material.  Nuclear reactors, as well as nuclear weapons, utilize chain reactions." (NTI)

  • Convention on the Physical Protection of Nuclear Material (CPPNM)

    "Obliges parties to ensure that during international transport across their territory, or on ships or aircraft under their jurisdiction, civil nuclear materials are protected according to agreed standards. The convention also provides a framework for international cooperation on the protection, recovery, and return of stolen nuclear material, and on the application of criminal sanctions against persons who commit crimes involving nuclear material. The CPPNM opened for signature on 3 March 1980 and entered into force on 8 February 1987. The Amendment to the CPPNM extended the convention’s scope to also cover the physical protection of nuclear material in domestic use, in storage, and during transport, and of nuclear facilities used for peaceful purposes, and provided for additional cooperation between states." (NTI)

  • Cooperative Threat Reduction (Nunn-Lugar) Program

    "A U.S. Department of Defense (DOD) program established in 1992 by the U.S. Congress, through legislation sponsored primarily by Senators Sam Nunn and Richard Lugar. It was the largest and most diverse U.S. program addressing former Soviet Union weapons of mass destruction threats. The program focused primarily on: (1) destroying vehicles for delivering nuclear weapons (e.g., missiles and aircraft), their launchers (such as silos and submarines), and their related facilities; (2) securing former Soviet nuclear weapons and their components; and (3) destroying Russian chemical weapons. The term is often used generically to refer to all U.S. nonproliferation programs in the former Soviet Union—and sometimes beyond— including those implemented by the U.S. Departments of Energy, Commerce, and State. The program’s scope has expanded to include threat reduction efforts in geographical areas outside the Former Soviet Union." (NTI)

  • Design Basis Threat (DBT)

    "A states' DBT is a description of the attributes and characteristics of potential insider and/or external adversaries who might attempt unauthorized removal of nuclear material or sabotage against which a physical protection system is designed and evaluated." (IAEA)

  • Dirty Bomb

    "A “dirty bomb” is one type of a radiological dispersal device that combines conventional explosives, such as dynamite, with radioactive material." (NRC)

  • Downblending

    "Refers to the process of blending down HEU to LEU. This is done by mixing HEU and the blendstock (of natural, depleted, or slightly enriched uranium) in either liquid or gas form." (NTI)

  • Export Controls

    "National laws or international arrangements established to restrict the sale of certain goods to certain countries, or to ensure that safeguards or end-use guarantees are applied to the export and sale of sensitive and dual-use technologies and materials." (NTI)

  • Fissile Material

    "A type of fissionable material capable of sustaining a chain reaction by undergoing fission upon the absorption of low-energy (or thermal) neutrons.  Uranium-235, Plutonium-239, and Uranium-233 are the most prominently discussed fissile materials for peaceful and nuclear weapons purposes." (NTI)

  • Force-on-Force (FOF)

    "Inspections designed to evaluate and improve the effectiveness of a licensee's security force and ability to defend a nuclear power plant and other nuclear facilities against a design-basis threat. An essential part of the security program instituted by the NRC, a full force-on-force inspection spans 2 weeks and includes tabletop drills and multiple simulated combat exercises between a mock commando-type adversary force and the plant's security force." (NRC)

  • Fuel Cycle

    "A term for the full spectrum of processes associated with utilizing nuclear fission reactions for peaceful or military purposes.  The “front-end” of the uranium-plutonium nuclear fuel cycle includes uranium mining and milling, conversion, enrichment, and fuel fabrication.  The fuel is used in a nuclear reactor to produce neutrons that can, for example, produce thermal reactions to generate electricity or propulsion, or produce fissile materials for weapons. The “back-end” of the nuclear fuel cycle refers to spent fuel being stored in spent fuel pools, possible reprocessing of the spent fuel, and ultimately long-term storage in a geological or other repository." (NTI)

  • Fuel Reprocessing

    "The processing of reactor fuel to separate the unused fissionable material from waste material. Reprocessing extracts isotopes from spent nuclear fuel so they can be used again as reactor fuel. Commercial reprocessing is not practiced in the U.S., although it has been practiced in the past." (NRC)


  • Global Initiative to Combat Nuclear Terrorism (GICNT)

    "The GICNT was announced by U.S. President George W. Bush and Russian President Vladimir Putin on 15 July 2006 in St. Petersburg, Russia. The initiative’s missions is to strengthen global capacity to prevent, detect, and respond to nuclear terrorism by conducting multilateral activities that strengthen the plans, policies, procedures, and interoperability of partner nations." (NTI)

  • Global Threat Reduction Initiative (GTRI)

    "A program established by the U.S. National Nuclear Security Administration in May 2004 to identify, secure, remove, and/or facilitate the removal of vulnerable nuclear and radiological materials around the world. The GTRI incorporated, among other programs, longstanding U.S. efforts under the RERTR program to convert domestic and foreign research reactors from highly enriched uranium fuel to low-enriched uranium fuel." (NTI)

  • Graded Approach

    "The application of nuclear security measures proportionate to the potential consequences of criminal or intentional unauthorized acts involving or directed at nuclear material, other radioactive material, associated facilities or associated activities or other acts determined by the State to have an adverse impact on nuclear security." (IAEA)

  • Highly Enriched Uranium (HEU)

    “Uranium contain­ing 20 percent or more of the fissile isotope U-235. Weapons-grade uranium is usually enriched to 90 per­cent or higher levels of U-235.” (Nuclear Iran: A Glossary of Terms)

  • International Atomic Energy Agency (IAEA)

    Considered the world’s nuclear “watchdog,” the IAEA “independently verifies the correctness and completeness of the declarations made by States about their nuclear material and activities.” (IAEA)

  • International Nuclear Material Protection and Control (IMPC)

    "IMPC began in 1994 as a task force to mitigate the security vulnerabilities of special nuclear material arising from the collapse of the Soviet Union.  Since that time, the program has evolved into a global effort, engaging over 40 countries to deny terrorists the vital materials needed to engage in acts of nuclear terror." (NNSA)

  • International Nuclear Security Education Network (INSEN)

     "INSEN is a Non-Governmental Organization whose mission is to enhance global nuclear security by developing, sharing and promoting excellence in nuclear security education." (IAEA

  • International Physical Protection Advisory Service Inspections (IPPAS)

     "IPPAS provides peer advice on implementing international instruments, and Agency guidance on the protection of nuclear and other radioactive material and associated facilities. During the IPPAS mission, the State’s physical protection system is reviewed and compared with international guidelines and internationally recognized best practices." (IAEA)

  • Insider

    "An individual with authorized access to associated facilities or associated activities or to sensitive information or sensitive information assets, who could commit, or facilitate the commission of criminal or intentional unauthorized acts involving or directed at nuclear material, other radioactive material, associated facilities or associated activities or other acts determined by the State to have an adverse impact on nuclear security." (IAEA)

  • Kiloton

    "A measure of the explosive power of an atomic bomb, equivalent to one thousand tons of TNT. The bomb tested at Alamogordo, New Mexico, in July 1945 was 20 kilotons. The one dropped on Hiroshima was 12 to 15 kilotons; the one dropped on Nagasaki was 20 to 22 kilotons. The destructive power of the much more powerful hydrogen bomb is rated in megatons, equivalent to millions of tons of TNT." (Nuclear Iran: A Glossary of Terms)

  • Low Enriched Uranium (LEU)

    "Uranium contain­ing between 0.7 and 20 percent of the isotope U-235 found in the natural metal. At 20 percent the material becomes known as high-enriched uranium." (Nuclear Iran: A Glossary of Terms)

  • Material Consolidation and Conversion

    This is a cooperative program between Russia and the U.S. National Nuclear Security Administration “designed to simplify the task of protecting Russia's weapons-usable nuclear materials by reducing the number buildings, and if possible, sites that contain such material.” (NNSA)

  • Material Protection, Control, and Accountability (MPC&A)

    "An integrated system of physical protection, material accounting, and material control measures designed to deter, prevent, detect, and respond to unauthorized possession, use, or sabotage of nuclear materials. The U.S. Department of Energy's MPC&A program was implemented in cooperation with the Russian Atomic Energy Ministry and other agencies to install and upgrade physical protection systems at the nuclear energy and weapons production facilities in the successor states of the former Soviet Union." (NTI)

  • Megaton

    "A measure of the explosive power of a hydrogen bomb, equivalent to one million tons of TNT. Atomic bombs are much less powerful and are therefore rated in kilotons." (Nuclear Iran: A Glossary of Terms)

  • Megaton To Megawatts

    "The Megatons to Megawatts™ Program was a unique, commercially financed government-industry partnership in which bomb-grade uranium from dismantled Russian nuclear warheads is being recycled into low enriched uranium (LEU) used to produce fuel for American nuclear power plants." (United States Enrichment Corporation)

  • Framework Agreement on a Multilateral Nuclear Environmental Programme in the Russian Federation (MNEPR)

    "MNEPR is an international programme designed to facilitate cooperation and assistance to the Russian Federation in the field of spent nuclear fuel safety and radioactive waste management. Projects covered by MNEPR include securing and cleaning up spent nuclear fuel storage sites and dismantling old decommissioned nuclear submarines." (Organization for Economic Co-operation and Development)

  • Molybdenum-99

    Also referred to as Moly 99, this is an isotope often used in medical diagnostic procedures.

  • Nuclear Cooperation (Section 123) Agreement

    "Named after Section 123 of the U.S. Atomic Energy Act of 1954, this type of agreement governs U.S. peaceful nuclear cooperation with foreign states, and must be in place for certain types of transactions to occur." (NTI)

  • Nuclear Nonproliferation Treaty (NPT)

    "A global treaty designed to halt the spread of nuclear weap­ons, promote the spread of peaceful nuclear technol­ogy, and further the goal of disarmament. The NPT, which went into force in 1970, divides its signatories into two categories: nuclear weapons states and non-nuclear weapons states. The five official nuclear weap­ons states are the United States, Russia, Britain, France, and China. The non-nuclear weapons states…agree not to pursue nuclear weapons in exchange for access to peaceful nuclear technologies. The nuclear weapons states are obligated to assist in the development of nuclear energy while also working in good faith toward nuclear disarmament." (Nuclear Iran: A Glossary of Terms)

  • Nuclear Material

    Nuclear Material is matter that can sustain a chain reaction (when an atom’s nucleus splits, releasing a massive amount of energy). It is the essential ingredient required to produce the chain reaction that causes a nuclear explosion. (Nuclear Terrorism: The Ultimate Preventable Catastrophe

  • Nuclear Regulatory Commission (NRC)

    "The NRC is a U.S. federal agency that regulates commercial nuclear power plants and other uses of nuclear materials, such as in nuclear medicine, through licensing, inspection and enforcement of its requirements." (NRC)

  • Nuclear Security

    "The prevention and detection of, and response to, theft, sabotage, unauthorized access, illegal transfer or other malicious acts involving nuclear material, other radioactive substances or their associated facilities." (IAEA)

  • Nuclear Security Culture

    "The assembly of characteristics, attitudes and behaviours of individuals, organizations and institutions which serve as a means to support, enhance, and sustain nuclear security." (IAEA)

  • Nuclear Security Summits

    "A series of international summits that emerged out of U.S. President Barack Obama's call in April 2009 to "secure all vulnerable nuclear material around the world within four years." The summit process focuses on strengthening international cooperation to prevent nuclear terrorism, thwarting nuclear materials trafficking, and enhancing nuclear materials security." (NTI)

  • Nuclear Suppliers Group (NSG)

    "The NSG was established in 1975, and its members commit themselves to exporting sensitive nuclear technologies only to countries that adhere to strict non-proliferation standards." (NTI)

  • Nuclear Terrorism

    Occurs when a terrorist detonates a nuclear explosive, disperses radioactive material in a so-called “dirty bomb,” or sabotages a major nuclear facility.

  • Plutonium (Pu)

    "A radioactive element that occurs in only trace amounts in nature. When produced by irradiating uranium fuels, plutonium contains varying percentages of the isotopes Pu-238, 239, 240, 241, and 242. Plutonium containing any Pu-239 is considered a special fissionable material. The International Atomic Energy Agency has defined 8 kg of plutonium as a ‘sig­nificant quantity,’ that is, the amount sufficient for a nuclear bomb." (Nuclear Iran: A Glossary of Terms)

  • Proliferation Security Initiative

    "Announced by U.S. President George W. Bush in May 2003, PSI is a U.S.- led effort to prevent the proliferation of WMD, their delivery systems, and related materials through the use of information sharing and coordination of diplomatic and military efforts. Members of the initiative share a set of 13 common principles, which guide PSI efforts." (NTI)

  • Radiological Dispersal Device (RDD)

    A device pairing conventional explosives with radiological materials. Once detonated, the conventional explosives disperse the radioactive material, radioactively contaminating the target area. Informally referred to as a “dirty bomb.” (NTI)

  • Repatriation

    "In the context of threat reduction, repatriation refers to the process of returning nuclear materials (e.g., fresh or spent HEU fuel), to the state that originally exported them." (NTI)

  • Reduced Enrichment for Research and Test Reactors (RERTR) Program

    The Reduced Enrichment for Research and Test Reactors (RERTR) program, conceived in the wake of India’s first nuclear test in 1974, is a U.S.-led effort to reduce the use of HEU in civil research reactors exported during the Atoms for Peace Program. Under the program, the United States has worked to develop new LEU fuels, and to convert research reactors and critical assemblies to these fuels at home and abroad. The RERTR program was folded into the Global Threat Reduction Initiative (GTRI) in 2004. (NTI)

  • Research Reactor

    "A small fission reactor designed to produce neutrons for a variety of purposes, including scientific research, training, and medical isotope production. Significantly less powerful than commercial power reactors, research reactors use smaller amounts of uranium for neutron production. Most of the research reactors that are powered by HEU have been undergoing conversion to LEU, initially as part of the RERTR program and subsequently as part of the Global Threat Reduction Initiative." (NTI)

  • Revision 5 of Nuclear Security Recommendation on Physical Protection of Nuclear Material and Nuclear Facilities

    "This is an IAEA publication intended to provide guidance to States and their competent authorities on how to develop or enhance, implement and maintain a physical protection regime for nuclear material and nuclear facilities, through the establishment or improvement of their capabilities to implement legislative and regulatory programmes. The recommendations presented in this publication reflect a broad consensus among IAEA Member States on the requirements which should be met for the physical protection of nuclear materials and nuclear facilities." (IAEA)

  • Second Line of Defense

    "This DOE NNSA program works to prevent illicit trafficking in nuclear and radiological materials by securing international land borders, seaports and airports that may be used as smuggling routes for materials needed for a nuclear device or a radiological dispersal device. SLD has two main parts, the Core Program and the Megaports Initiative." (NTI)

  • Self Protecting

    "Fuel is considered “self protecting” if it is sufficiently radioactive that those who might seek to divert it would not be able to handle it directly without suffering acute radiation exposure." (NTI)

  • Sensitive Information

    "Information, in whatever form, including software, the unauthorized disclosure, modification, alteration, destruction, or denial of use of which could compromise nuclear security." (IAEA)

  • Significant Quantity

    “The approximate minimum quantity of nuclear material required for the manufac­ture of a nuclear explosive device. . . . The IAEA has defined 25 kg of U-235 for high-enriched uranium (U-235≥20 %), 75 kg U-235 for low-enriched uranium (U-235<20%), or 8 kg of Pu-239 or U-233 as a ‘significant quantity.’ Some outside experts argue that an aspiring nuclear weapons state could construct a simple fission weapon with as little as 3 kg of weapons-grade plutonium, or between 2 and 7 kg of HEU.” (Nuclear Iran: A Glossary of Terms)

  • Spent Nuclear Fuel

    "Nuclear reactor fuel that has been used to the extent that it can no longer effectively sustain a chain reaction. For related information, see Storage of Spent Nuclear Fuel and Transportation of Spent Nuclear Fuel." (NRC)

  • UN Security Council Resolution 1540

    "Resolution 1540 was passed by the UN Security Council in April 2004, calling on all states to refrain from supporting, by any means, non-state actors who attempt to acquire, use, or transfer chemical, biological or nuclear weapons or their delivery systems. The resolution also called for a Committee to report on the progress of the resolution, asking states to submit reports on steps taken towards conforming to the resolution. In April 2011, the Security Council voted to extend the mandate of the 1540 Committee for an additional 10 years." (NTI)

  • UN Security Council Resolution 1887

    "In September 2009, the UN Security Council committed to working toward the reduction of nuclear weapons and global nuclear dangers by adopting UNSCR 1887. In addition to calling for nuclear arms reductions, a strengthened NPT, greater support for the IAEA, and more robust export controls, the resolution also encouraged states to share best practices for improving nuclear safety and security standards, in order to reduce the risk of nuclear terrorism and to secure vulnerable nuclear materials within four years. The resolution also called on states to "minimize to the greatest extent that is technically and economically feasible the use of highly enriched uranium for civilian purposes, including by working to convert research reactors and radioisotope production processes to the use of low enriched uranium fuels and targets.” UNSCR 1887 also reaffirmed the need for full implementation of UNSCR 1540." (NTI)

  • Uranium

    "A naturally occurring radioactive element with atomic number 92. Natural uranium contains the isotopes U-234, 235, and 238; the isotopes U-232, 233, and 236 are produced by radioactive decay." (Nuclear Iran: A Glossary of Terms)

  • Weapons-Grade Material

    "Refers to the nuclear materials that are most suitable for the manufacture of nuclear weapons, e.g., uranium (U) enriched to 90% U-235 or plutonium (Pu) that is primarily composed of Pu-239 and contains less than 7% Pu-240. Crude nuclear weapons (i.e., improvised nuclear devices), could be fabricated from lower-grade materials." (NTI)

  • World Institute for Nuclear Security (WINS)

    WINS is an International Non-Governmental Organization whose mission is to provide an international forum for those accountable for nuclear security to share and promote the implementation of best security practices. (WINS)

  • Y-12

    This is a U.S. nuclear weapons facility located in Oak Ridge, Tennessee that stores most of the Highly Enriched Uranium in the United States, enough to make thousands of nuclear weapons.