Atomic bomb


Nuclear weapon using the energy released during the fission of U-235 or Pu-239. The explosive force of a nuclear weapon is indicated in kilotonnes (kt) or megatonnes (Mt) of TNT equivalents (TNT (trinitrotoluol) is a chemical explosive). The bombs dropped on Hiroshima (U-235 bomb) and Nagasaki (Pu-239 bomb) had an explosive energy equal to 13 and 22 kt TNT. In each case about 1 kg fission material was fissioned in one millionth of a second. A minimum mass of fission material is required for a nuclear blasting charge, e.g. 52 kg of U-235. The highly developed weapon technology in the nuclear weapon countries partly enables lower values, e.g. 15 kg and less for metallic U-235. An ignition device is also required to shoot these fission materials together to a critical configuration within a very short period so as to initiate the chain reaction. Experts quote a velocity of some kilometres per second for weapon plutonium and a multiple of this impact velocity is necessary for reactor plutonium with its high share of other plutonium isotopes. See 'hydrogen bomb'.

Type of fission material

Quantity in kg

as a metal

as an oxide

Weapon plutonium



Reactor plutonium



93% enriched U-235



3% enriched U-235 (LWR-fuel)

not possible

not possible




Estimated minimum quantity of fission material for nuclear blasting charges

According to UNSCEAR 504 atmospheric explosion (plus 39 safety tests) and 1879 underground explosions were carried out till mid of Februar 2013.

Nuclear explosions by year

Nuclear explosions by country








ENS conferences

TopSafe 2017

TopSafe 2017
12-16 Feb. 2017
Vienna, Austria

PIME 2017

PIME 2017
19 - 22 March 2017, Middelburg Netherlands

RRFM 2017

RRFM 2017
14 - 18 May 2017 in Rotterdam, Netherlands

ETRAP 2017

ETRAP 2017
30 May - 2 June 2017, Valencia, Spain