Nuclear weapon

A nuclear weapon was a device that worked by altering the structure of atomic nuclei. This produced far more energy than the chemical changes that powered conventional explosives. Primitive atomic weapons split uranium or plutonium atoms. More sophisticated ones fused isotopes of hydrogen into helium. Nuclear weapon yield was measured in thousands or millions of tonnes of TNT (equivalent), typically producing an intense burst of radiation and lingering contamination ('fallout') as well as thermal and blast effects. Earth's first nuclear weapons were produced by the United States in 1945.

Nuclear weapons on Earth
In the 1970s, nuclear missiles were used against Eldrad when she took over the Nunton Experimental Complex, but they had no effect on her. (DW: The Hand of Fear)

In 2008, agents of Cell 114 attempted to explode nuclear missiles stored in an old mine near Cardiff, but were thwarted by members of Torchwood Three. (TW: Sleeper)

In 2009, UNIT attempted to fire nuclear weapons at the Sontaran flagship to prevent the Sontaran invasion of Earth, but this was thwarted by a clone of Martha Jones. (DW: The Poison Sky)

At an unknown point in history, in the wake of an unspecified event known as the Southport Incident, the world governments stopped stockpiling nuclear weapons. (NA: Just War) However, Zoe Heriot recognised the effects of an atomic blast on the Island of Death, likely indicating that nuclear weapons were still around in her time. (DW: The Dominators)

Nuclear weapons on other planets
On Skaro, nuclear weapons were used early on in the Thousand Year War. In the later years of the war, the combatants were reduced to primitive weaponry. (DW: Genesis of the Daleks)

On Dulkis, the Dulcians tested nuclear weapons on the Island of Death, and were so horrified by their destructive capabilities that they outlawed war. (DW: The Dominators)

Nuclear weapons were also used in the war between the Argolins and the Foamasi. (DW: The Leisure Hive)

The Marshal of Atrios attempted to end the war between Atrios and Zeos by firing a nuclear missile from his Command Capsule at Zeos, but the Fourth Doctor redirected his attack onto the Third planet. (DW: The Armageddon Factor)

On Alrakis, Tonska rebels used a nuclear bomb to destroy Zaniah's laboratories, inadvertently allowing a Cerunnos to escape to Earth. (VD: ...And Eternity in an Hour)

On Mars, a nuclear device was used by Adelaide Brooke to destroy Bowie Base One after an infection known as the Flood broke loose. (DW: The Waters of Mars)

On Sunday, a Swamp Monster attempted to blow itself up with a nuclear weapon, thus spreading itself across the Galaxy. (NSA: Wetworld)