Latin American Nuclear-Weapon-Free Zone

This treaty created a nuclear-weapon-free zone in Latin America and the Caribbean. The Treaty of Tlatelolco was the first international agreement that aimed at excluding nuclear weapons from an inhabited region of the globe. In addition to prohibiting nuclear testing by all States Parties, Member States also accept the application of International Atomic Energy Agency safeguards for all their nuclear activities to assist in verifying compliance with the treaty. The treaty also establishes a regional organization, the Agency for the Prohibition of Nuclear Weapons in Latin America (OPANAL), to help ensure compliance with its provisions. The treaty was opened for signature on 14 February 1967 and entered into force on 25 April 1969. It has since been signed and ratified by all 33 nations of Latin America and the Caribbean, with  Cuba being the last country to ratify it on 23 October 2002. China, France, the Netherlands, the Russian Federation, the United Kingdom and the United States have all signed the relevant protocols of the treaty.

Léo Szilárd

Hungarian-born scientist noted for his contributions to the fields of thermodynamics, biophysics, nuclear physics, and the development of atomic energy. In August 1939,  Szilárd sent a confidential letter, which was also signed by Albert Einstein,  to Franklin D. Roosevelt, warning of the possibility of creating an atomic weapon and urging the US government to develop this weapon before Germany. This letter was a catalyst in initiating the US government’s atomic research programme, which led to the establishment of the Manhattan Project. In 1942, Szilárd and Enrico Fermi were successful in creating the first controlled nuclear chain reaction. Szilárd later became a leading campaigner in favour of international nuclear weapons control.

Lethal dose

The dose of radiation expected to cause death to an exposed population within 30 days to 50 percent of those exposed.

Limited Test Ban Treaty

Another name for the Partial Test Ban Treaty.

Lisbon Protocol

The protocol, opened for signature in 1992 by Belarus, Kazakhstan, Russia and Ukraine, made these states parties to the 1991 Strategic Arms Reduction Treaty as successors to the former Soviet Union. Belarus, Kazakhstan, and Ukraine also committed themselves in this protocol to adhere to the nuclear Nonproliferation Treaty (NPT) as non-nuclear weapon states.

Long period

A passband of interest for studying seismic events, often for the study of surface waves. Normally refers to low frequencies (i.e. those below 0.1 Hz).

Low enriched uranium (LEU)

Uranium in which the naturally occurring U235 isotope is increased, to less than 20 percent and usually between two and four percent. LEU is used in nuclear fuel for reactors using natural (light) water as a moderator and coolant.