Question: What is the yield of the nuclear weapon that was the code name Fat Boy of the first detonation of a nuclear device ?

text: Nuclear weapon yield
Milestone nuclear explosions
The following list is of milestone nuclear explosions . In addition to the atomic bombings of Hiroshima and Nagasaki , the first nuclear test of a given weapon type for a country is included , and tests which were otherwise notable ( such as the largest test ever ) . All yields ( explosive power ) are given in their estimated energy equivalents in kilotons of TNT ( see TNT equivalent ) . Putative tests ( like Vela Incident ) have not been included .
The explosive yield of a nuclear weapon is the amount of energy released when that particular nuclear weapon is detonated, usually expressed as a TNT equivalent (the standardized equivalent mass of trinitrotoluene which, if detonated, would produce the same energy discharge), either in kilotons (kt - thousands of tons of TNT), in megatons (Mt - millions of tons of TNT), or sometimes in terajoules (TJ). An explosive yield of one terajoule is equal to 0.239 kilotonnes of TNT. Because the accuracy of any measurement of the energy released by TNT has always been problematic, the conventional definition is that one kiloton of TNT is held simply to be equivalent to 1012 calories. The yield-to-weight ratio is the amount of weapon yield compared to the mass of the weapon. The practical maximum yield-to-weight ratio for fusion weapons (thermonuclear weapons) has been estimated to six megatons of TNT per metric ton of bomb mass (25 TJ/kg). Yields of 5.2 megatons/ton and higher have been reported for large weapons constructed for single-warhead use in the early 1960s. Since then, the smaller warheads needed to achieve the increased net damage efficiency (bomb damage/bomb mass) of multiple warhead systems have resulted in decreases in the yield/mass ratio for single modern warheads.
Date Name Yield ( kt ) Country Significance
1945-07-16 Trinity 18-20 USA First fission device test , first plutonium implosion detonation
1945-08-06 Little Boy 12-18 USA Bombing of Hiroshima , Japan , first detonation of a uranium gun-type device , first use of a nuclear device in combat
1945-08-09 Fat Man 18-23 USA Bombing of Nagasaki , Japan , second detonation of a plutonium implosion device ( the first being the Trinity Test ) , second and last use of a nuclear device in combat
1949-08-29 RDS-1 22 USSR First fission weapon test by the USSR
1952-10-03 Hurricane 25 UK First fission weapon test by the UK
1952-11-01 Ivy Mike 10,400 USA First cryogenic fusion fuel staged thermonuclear weapon , primarily a test device and not weaponized
1952-11-16 Ivy King 500 USA Largest pure-fission weapon ever tested
1953-08-12 Joe 4 400 USSR First fusion weapon test by the USSR ( not staged )
1954-03-01 Castle Bravo 15,000 USA First dry fusion fuel staged thermonuclear weapon ; a serious nuclear fallout accident occurred ; largest nuclear detonation conducted by United States
1955-11-22 RDS-37 1,600 USSR First staged thermonuclear weapon test by the USSR ( deployable )
1957-05-31 Orange Herald 720 UK Largest boosted fission weapon ever tested . Intended as a fallback in megaton range in case British thermonuclear development failed
1957-11-08 Grapple X 1,800 UK First ( successful ) staged thermonuclear weapon test by the UK
1960-02-13 Gerboise Bleue 70 France First fission weapon test by France
1961-10-31 Tsar Bomba 50,000 USSR Largest thermonuclear weapon ever tested - scaled down from its initial 100 Mt design by 50%
1964-10-16 596 22 PR China First fission weapon test by the People 's Republic of China
1967-06-17 Test No . 6 3,300 PR China First staged thermonuclear weapon test by the People 's Republic of China
1968-08-24 Canopus 2,600 France First staged thermonuclear weapon test by France
1974-05-18 Smiling Buddha 12 India First fission nuclear explosive test by India
1998-05-11 Pokhran-II 45-50 India First potential fusion/boosted weapon test by India ; first deployable fission weapon test by India
1998-05-28 Chagai-I 40 Pakistan First fission weapon ( boosted ) test by Pakistan