Nuclear Weapons

The Physics Hypertextbook™
© 1998-2008 by Glenn Elert -- A Work in Progress
All Rights Reserved -- Fair Use Encouraged

prev | up | next

Discussion

introduction

Loose notes and lots of uncited block quotes right now.

http://www.fas.org/nuke/hew/Nwfaq/Nfaq12.html
Convenient Energy Content Approximations (verify)
Fission of U-233: 17.8 kt/kg
Fission of U-235: 17.6 kt/kg
Fission of Pu-239: 17.3 kt/kg
Fusion of pure deuterium: 82.2 kt/kg
Fusion of tritium and deuterium (50/50): 80.4 kt/kg
Fusion of lithium-6 deuteride: 64.0 kt/kg
Fusion of lithium-7 deuteride
Total conversion of matter to energy: 21.47 Mt/kg
Fission of 1.11 g U-235: 1 megawatt-day (thermal)

fission weapons

critical
The minimum mass of a fissionable material that will just maintain a fission chain reaction under precisely specified conditions, such as the nature of the material and its purity, the nature and thickness of the tamper (or neutron reflector), the density, and the physical shape. For an explosion to occur, the system must be supercritical (i.e., the mass of the material must exceed the critical mass under the existing conditions).

supercritical
A term used to describe the state of a given fission system when the quantity of fissionable material is greater than the critical mass under existing conditions. A highly supercritical system is essential for the production of energy at a very rapid rate so that an explosion may occur.

The nuclear blasts that leveled the Japanese cities of Hiroshima and Nagasaki in 1945 had explosive yields of 12,500 and 22,000 tons of TNT, respectively, or twenty and forty times more energy than was released when the World Trade Center towers collapsed in 2001.

Hiroshima Little Boy, enriched uranium, gun type.

Because uranium is more fissionable, the bomb would be based on a gun-type detonator. Basically, a section of uranium would be shaped with a center section missing. The center section, a perfect fit, would be place away from the large uranium mass. A conventional explosive would be used to propel the center section into the large section. Both sections would then weld together and start the reaction. Richard Feynman was responsible for calculating the amount of uranium needed to achieve critical mass. Critical mass is the amount of uranium needed to start the chain reaction. However, if you have more than the required mass to start the reaction, or supercritical mass, the reaction would take place faster and grow exponentially. Feynman calculated about 50 kilograms (110 lb.) of pure uranium. However, the uranium obtained was seldom pure, so a large amount would be needed. Robert Oppenheimer said that the required supercritical mass would be about 100 kilograms ( 220 lb.). The first atomic bomb, a "Fat Man"-style bomb, is detonated at the Trinity test site in central New Mexico. The resulting blast, which is as strong as 18,000 tons of TNT, is felt as far as 250 miles from Trinity.


[magnify]

Trinity Gadget and Nagasaki Fat Man, plutonium, implosion type.

In order to start the chain reaction, the mass of plutonium must be fused together while a radioactive source emitted a neutron. The way the bomb was design was that a Beryllium/Polonium mixture, radioactive elements that release neutrons, would be placed in the center of a sphere. The sphere would be made up of equally spaced and shaped plutonium sections. The sphere looked a lot like a soccer ball. When the bomb was detonated, the sphere would implode, or collapse inward, causing all the plutonium to fuse together, reach supercritical mass, and start the chain reaction. The initial explosion, which caused the implosion, would be made by conventional explosive. All this would occur in a fraction of a second (about one ten-millionth). Richard Feynman and Hans Bethe had calculate the supercritical mass to about 16 kilograms (35.2 lb.). However, it was calculated that this mass could be reduced to 10 kilograms (22 lb.) if the plutonium was surrounded by the U-238 isotope [Dyson, 1997].


[magnify]

fusion weapons

The "super" bomb.The Alarm Clock/Sloika (Layer Cake) Design

Boosted fission, layer cake bombs

In these weapons a few grams of a deuterium/tritium gas mixture are included in the center of the fissile core. The first boosted weapon test was Greenhouse Item (45.5 kt, 24 May 1951), an oralloy design exploded on island Janet at Enewetak. This experimental device used cryogenic liquid deuterium-tritium instead of gas. The boosting approximately doubled the yield over the expected unboosted value. Variants on the basic boosting approach that have been tested including the use of deuterium gas only, and the use of lithium deuteride/tritide, but it isn't known whether any of these approaches have been used in operational weapons.

Staged Radiation Implosion Weapons. Teller-Ulam design

When a neutron is absorbed by a molecule of lithium deuteride (6Li2H), the molecule breaks up into a He, 2H (deuterium) and 3H (tritium). The deuterium can then react with the tritium in fusion. This releases enormous amounts of energy, much greater than you would get in a fission reaction. The end products include a free neutron and a helium atom. Schematically:

6Li + n → 4He + 3H + 4.7 MeV

then

2H + 3H → 4He + n + 17.6 MeV


[magnify]

A bit more modern.


[magnify]

Here comes MIRV!


[magnify]

contamination weapons

"Doomsday Bomb", salted bombs, enhanced fallout

The easiest Doomsday Machine to construct is the cobalt bomb cluster. Each cobalt bomb is an ordinary atomic bomb encased in a jacket of cobalt. When a cobalt bomb explodes, it spreads a huge amount of radiation. If enough of these bombs were exploded, life on Earth would perish.

The idea of the cobalt bomb originated with Leo Szilard who publicized it in February 1950, not as a serious proposal for a weapon, but to point out that it would soon be possible in principle to build a single weapon that would kill everyone on earth. To design such a weapon a radioactive isotope is needed that can be dispersed world wide before it decays. The design would be reminiscent of a fission-fusion-fission weapon. A thick cobalt metal blanket is used to capture the fusion neutrons to maximize the fallout hazard. Instead of generating additional explosive force from fast fission U-238 the cobalt is transmuted into Co-60 which produces energetic and penetrating gamma rays.

summary

Albert Einstein

Nations with nuclear weapons programs


[magnify]

Selected Nuclear Weapon Events
nation date location code name(s) type yield (kt)
United
States		 16 July 1945 Alamogordo
New Mexico
(32.3° N 106.5° W)		 Gadget,
Trinity		 plutonium
fission		 21
" 6 August 1945 Hiroshima
Japan
(34.4° N 132.5° E)		 Little Boy uranium
fission		 12.5
" 9 August 1945 Nagasaki
Japan
(32.7° N 129.9 ° E)		 Fat Man plutonium
fission		 22
" 1 November 1952 Enewetak Atoll
Marshall Islands
(11.7° N 162.2° E)		 Mike two-stage
fusion		 10,400
Soviet
Union		 29 August 1949 Semipalatinsk
Kazakhstan
(48° N 76° E)		 RDS-1* plutonium
fission		 10 - 20
" 12 August 1953 Semipalatinsk
Kazakhstan
(48° N 76° E)		 RDS-4* boosted
fission		 200 - 300
" 22 November 1955 Semipalatinsk
Kazakhstan
(48° N 76° E)		 RDS-37*
"Kuzka's mother" 		two-stage
fusion		 1,600
" 30 October 1961 Novaya Zemlya
Russia
(73° N 55° E)		 Big Ivan,
Tsar Bomba		 two-stage
fusion		 50,000
United
Kingdom		 3 October 1952 Monte Bello Islands
Australia
(20.4° S 115.6° E)		 Hurricane plutonium
fission		 25
" 15 May 1957 Malden Island
Kiribati
(4.0° S 155.0° W)		 Grapple I
Short Granite		 two-stage
fusion
(unsuccesful)		 250
" 8 November 1957 Christmas Island
Kiribati
(2.0° N 157.3° W)		 Grapple X
Round C		 two-stage
fusion		 1,800
France 13 February 1960 Reggane
Algeria
(26.3° N 0.07° W)		 Gerboise Bleu plutonium
fission		 65
" 24 August 1968 Fangataufa Atoll
French Polynesia
(22.2° S 139.1° W)		 Canopus two-stage
fusion		 2,600
China 16 October 1964 Lopnur
Xin Jiang
(42.6° N 88.3° E)		 596 plutonium
fission		 22
" 28 December 1966 Lopnur
Xin Jiang
(42.6° N 88.3° E)		 Test 6 two-stage
fusion		 3,300
India 18 May 1974 Pokhran
Rajasthan
(27.1° N 71.8° E)		 Smiling Buddha plutonium
fission		 5 - 12
" 11 May 1998 Pokhran
Rajasthan
(27.1° N 71.7° E)		 Shakti I boosted
fission		 43
Israel 22 September 1979 International Waters
South Indian Ocean
(47° S 40° E)		 Phenix?
Samson?		 suspected
fission
device		 very low
South
Africa		 24 March 1993 F.W. de Klerk announces existance of now defunct nuclear weapons program. n/a uranium
fission		 n/a
Pakistan 28 May 1998 Koh Kambaran
Chagai
(28.8° N 64.9° E)		 Chagai I uranium
fission		 9 - 12
North Korea 9 October 2006 P'unggye-yok? Kilchu-ŭp? Sumunnae? Chik-tong?
North Hamgyŏng Province
(41.3°N 129.1°E)		 ?? plutonium
fission 		< 1
* RDS (Reaktivniy Dvigatel' Stalina) is a transliteration of the Russian
   РДС (Реактивный двигатель Сталина) or "Stalin's Jet Engine".

Summary

Problems

practice

  1. Write something.
    • Answer it.
  2. Write something.
    • Answer it.
  3. Write something.
    • Answer it.
  4. Write something.
    • Answer it.

numerical

  1. problems

Resources

prev | up | next

Another quality webpage by

Glenn Elert		 eglobe logo home | contact

bent | chaos | eworld | facts | physics