“Within about 1ms after the explosion, some 70-80% of the explosion energy…
\n is emitted as primary thermal radiation, most of which consists of soft
\n X-rays.”<\/p>\n
\t\t\t\tGlasstone, The Effects of Nuclear Weaponns<\/p>\n
FISSION PRINCIPLES<\/p>\n
The binding energy per nucleon versus atomic mass has a turning point around
\nFe-56. Iron is the most stable element. Elements with atomic masses less
\nthan iron tend to combine, and those with masses greater than iron tend to
\nsplit. Radioactivity is an indication of this instability. The problem is that
\nprotons in the nucleus tend to repel each other. There comes a stage where
\nthe nuclear binding energy cannot compete with this repelling force, even if
\nyou add more and more neutrons to the nucleus. Take as an example, the highest
\nZ naturally occuring element – uranium.<\/p>\n
U has many radioactive isotopes. These include U-234, U-235 and U-238. They are
\namong the longest-living elements in a table of radioactive isotopes.<\/p>\n
The U-235 isotope is used in weapons since it has the highest fission cross
\nsection of all the U isotopes, for thermal neutrons.<\/p>\n
If you bombard U-238 with thermal neutrons, you might just cause
\na transuranic beta decay to Pu-239. Pu does not occur naturally, and is of
\nuse in weapons. If you bombard the radioactive isotopes with slow neutrons
\nthere is a chance that you will split the nuclei in half. In the process, you
\nrelease some binding energy, and some more neutrons. For an explosion, you
\nneed a self-sustaining chain reaction which keeps on generating more and more
\nneutrons. In effect, you need a critical mass of fissionable material to
\noffset any loss of neutrons. (Instead of hitting other isotopic nuclei, the
\nneutrons might just wander off.) A sphere of material is used to provide the
\nleast surface area for neutron loss. If the sphere is large enough, neutron
\nloss will be balanced by neutron generation, resulting in a self-sustaining
\nreaction. You have an energy release in fission since the mass of the original
\natom doesn’t equal the mass of the two reaction atoms. The lost energy is
\nconverted to radiation and kinetic energy of the atoms via mass-energy
\nequivalence. The fission products are around equal size, and are highly
\nradioactive. Products include Sr, which is absorbed into human bones and
\nstays there, since it is chemically similar to calcium. Other harmful
\nproducts include cesium, similar to potassium. Cesium is distributed
\nuniformly throughout the body.<\/p>\n
The number of fissioning nuclei increases as a geometric progression, with
\neach generation. Most of the energy in a bomb is released during around the
\n80th generation.<\/p>\n
It is estimated in 10^-6 secs, about 2×10-24 U-235 nuclei split, releasing
\nHUGE amounts of energy. A single split gives you about 170MeV on average,
\nwhereas a chemical reaction only gives you a few eV.<\/p>\n
An example of a fission reaction is:<\/p>\n
\tU-235 + n -> Kr-92 + Xe-142 + 2n + 207 MeV.<\/p>\n
The released energy is many orders of magnitude greater than that released
\nby a chemical reaction using the same amount of matter.<\/p>\n
A solid Pu sphere of 6.2kg mass is about 3.3″ in diameter. It would be as
\nbig as a tennis ball, but as massive as a bowling ball. The sphere would be
\nbigger if there was a Po-Be core inside.<\/p>\n
Uranium & Plutonium
\n ——————-<\/p>\n
Uranium-235 is very difficult to extract. In fact, for every 25,000 tons
\nof Uranium ore that is mined from the earth, only 50 tons of Uranium metal can
\nbe refined from that, and 99.3% of that metal is U-238 which is too stable to
\nbe used as an active agent in an atomic detonation. To make matters even more
\ncomplicated, no ordinary chemical extraction can separate the two isotopes
\nsince both U-235 and U-238 possess precisely identical chemical
\ncharacteristics. The only methods that can effectively separate U-235 from
\nU-238 are mechanical methods.<\/p>\n
U-235 is slightly, but only slightly, lighter than its counterpart,
\nU-238. A system of gaseous diffusion is used to begin the separating process
\nbetween the two isotopes. In this system, Uranium is combined with fluorine
\nto form Uranium Hexafluoride gas. This mixture is then propelled by low-
\npressure pumps through a series of extremely fine porous barriers. Because
\nthe U-235 atoms are lighter and thus propelled faster than the U-238 atoms,
\nthey could penetrate the barriers more rapidly. As a result, the
\nU-235’s concentration became successively greater as it passed through each
\nbarrier. After passing through several thousand barriers, the Uranium
\nHexafluoride contains a relatively high concentration of U-235 — 2% pure
\nUranium in the case of reactor fuel, and if pushed further could
\n(theoretically) yield up to 95% pure Uranium for use in an atomic bomb.<\/p>\n
Once the process of gaseous diffusion is finished, the Uranium must be
\nrefined once again. Magnetic separation of the extract from the previous
\nenriching process is then implemented to further refine the Uranium. This
\ninvolves electrically charging Uranium Tetrachloride gas and directing it past
\na weak electromagnet. Since the lighter U-235 particles in the gas stream are
\nless affected by the magnetic pull, they can be gradually separated from the
\nflow.<\/p>\n
Following the first two procedures, a third enrichment process is then
\napplied to the extract from the second process. In this procedure, a gas
\ncentrifuge is brought into action to further separate the lighter U-235 from
\nits heavier counter-isotope. Centrifugal force separates the two isotopes of
\nUranium by their mass. Once all of these procedures have been completed, all
\nthat need be done is to place the properly molded components of Uranium-235
\ninside a warhead that will facilitate an atomic detonation.<\/p>\n
Supercritical mass for Uranium-235 is defined as 110 lbs (50 kgs) of
\npure Uranium.<\/p>\n
Depending on the refining process(es) used when purifying the U-235 for
\nuse, along with the design of the warhead mechanism and the altitude at which
\nit detonates, the explosive force of the A-bomb can range anywhere from 1
\nkiloton (which equals 1,000 tons of TNT) to 20 megatons (which equals 20
\nmillion tons of TNT — which, by the way, is the smallest strategic nuclear
\nwarhead we possess today. {Point in fact — One Trident Nuclear Submarine
\ncarries as much destructive power as 25 World War II’s}).<\/p>\n
While Uranium is an ideally fissionable material, it is not the only one.
\nPlutonium can be used in an atomic bomb as well. By leaving U-238 inside an
\natomic reactor for an extended period of time, the U-238 picks up extra
\nparticles (neutrons especially) and gradually is transformed into the element
\nPlutonium.<\/p>\n
Plutonium is fissionable, but not as easily fissionable as Uranium.
\nWhile Uranium can be detonated by a simple 2-part gun-type device, Plutonium
\nmust be detonated by a more complex 32-part implosion chamber along with a
\nstronger conventional explosive, a greater striking velocity and a
\nsimultaneous triggering mechanism for the conventional explosive packs. Along
\nwith all of these requirements comes the additional task of introducing a fine
\nmixture of Beryllium and Polonium to this metal while all of these actions are
\noccurring.<\/p>\n
Supercritical mass for Plutonium is defined as 35.2 lbs (16 kgs). This
\namount needed for a supercritical mass can be reduced to a smaller quantity of
\n22 lbs (10 kgs) by surrounding the Plutonium with a U-238 casing.<\/p>\n
============================================================================<\/p>\n
– Diagram of a Chain Reaction –
\n ——————————-<\/p>\n
|
\n |
\n |
\n |
\n [1]——————————> o<\/p>\n
. o o .
\n . o_0_o . . o_0_o”o_0_o .
\n . o 0 o~o 0 o .
\n . o o.”.o o .
\n |
\n \/ |
\n |\/_ | _|
\n ~~ | ~~
\n |
\n o o | o o
\n [4]—————–> o_0_o | o_0_o <—————[5]
\n o~0~o | o~0~o
\n o o ) | ( o o
\n \/ o
\n \/ [1]
\n \/
\n \/
\n \/
\n o [1] [1] o
\n . o o . . o o . . o o .
\n . o_0_o . . o_0_o . . o_0_o .
\n . o 0 o . . o 0 o . . o 0 o .
\n . o o . . o o . . o o .<\/p>\n
\/ |
\n |\/_ |\/ _|
\n ~~ ~ ~~<\/p>\n
. o o. .o o . . o o. .o o . . o o. .o o .
\n . o_0_o”o_0_o . . o_0_o”o_0_o . . o_0_o”o_0_o .
\n . o 0 o~o 0 o . . o 0 o~o 0 o . . o 0 o~o 0 o .
\n . o o.”.o o . . o o.”.o o . . o o.”.o o .
\n . | . . | . . | .
\n \/ | \/ | \/ |
\n : | : : | : : | :
\n : | : : | : : | :
\n :\/ | :\/ :\/ | :\/ :\/ | :\/
\n ~ | ~ ~ | ~ ~ | ~
\n [4] o o | o o [5] [4] o o | o o [5] [4] o o | o o [5]
\n o_0_o | o_0_o o_0_o | o_0_o o_0_o | o_0_o
\n o~0~o | o~0~o o~0~o | o~0~o o~0~o | o~0~o
\n o o ) | ( o o o o ) | ( o o o o ) | ( o o
\n \/ | \/ | \/ |
\n \/ | \/ | \/ |
\n \/ | \/ | \/ |
\n \/ | \/ | \/ |
\n \/ o \/ o \/ o
\n \/ [1] \/ [1] \/ [1]
\n o o o o o o
\n [1] [1] [1] [1] [1] [1]<\/p>\n
============================================================================<\/p>\n
– Diagram Outline –
\n ———————<\/p>\n
[1] – Incoming Neutron
\n [2] – Uranium-235
\n [3] – Uranium-236
\n [4] – Barium Atom
\n [5] – Krypton Atom<\/p>\n
===========================================================================<\/p>\n
I. The History of the Atomic Bomb
\n ——————————<\/p>\n
On August 2nd 1939, just before the beginning of World War II, Albert
\nEinstein wrote to then President Franklin D. Roosevelt. Einstein and several
\nother scientists told Roosevelt of efforts in Nazi Germany to purify U-235
\nwith which might in turn be used to build an atomic bomb. It was shortly
\nthereafter that the United States Government began the serious undertaking
\nknown only then as the Manhattan Project. Simply put, the Manhattan Project
\nwas committed to expedient research and production that would produce a viable
\natomic bomb.<\/p>\n
The most complicated issue to be addressed was the production of ample
\namounts of `enriched’ uranium to sustain a chain reaction. At the time,
\nUranium-235 was very hard to extract. In fact, the ratio of conversion from
\nUranium ore to Uranium metal is 500:1. An additional drawback is that the 1
\npart of Uranium that is finally refined from the ore consists of over 99%
\nUranium-238, which is practically useless for an atomic bomb. To make it even
\nmore difficult, U-235 and U-238 are precisely similar in their chemical
\nmakeup. This proved to be as much of a challenge as separating a solution of
\nsucrose from a solution of glucose. No ordinary chemical extraction could
\nseparate the two isotopes. Only mechanical methods could effectively separate
\nU-235 from U-238. Several scientists at Columbia University managed to solve
\nthis dilemma.<\/p>\n
A massive enrichment laboratory\/plant was constructed at Oak Ridge,
\nTennessee. H.C. Urey, along with his associates and colleagues at Columbia
\nUniversity, devised a system that worked on the principle of gaseous
\ndiffusion. Following this process, Ernest O. Lawrence (inventor of the
\nCyclotron) at the University of California in Berkeley implemented a process
\ninvolving magnetic separation of the two isotopes.<\/p>\n
Following the first two processes, a gas centrifuge was used to further
\nseparate the lighter U-235 from the heavier non-fissionable U-238 by their
\nmass. Once all of these procedures had been completed, all that needed to be
\ndone was to put to the test the entire concept behind atomic fission.<\/p>\n
Over the course of six years, ranging from 1939 to 1945, more than 2
\nbillion dollars were spent on the Manhattan Project. The formulas for
\nrefining Uranium and putting together a working bomb were created and seen to
\ntheir logical ends by some of the greatest minds of our time. Among these
\npeople who unleashed the power of the atomic bomb was J. Robert Oppenheimer.<\/p>\n
Oppenheimer was the major force behind the Manhattan Project. He
\nliterally ran the show and saw to it that all of the great minds working on
\nthis project made their brainstorms work. He oversaw the entire project from
\nits conception to its completion.<\/p>\n
Finally the day came when all at Los Alamos would find out whether or not
\nThe Gadget (code-named as such during its development) was either going to be
\nthe colossal dud of the century or perhaps end the war. It all came down to
\na fateful morning of midsummer, 1945.<\/p>\n
At 5:29:45 (Mountain War Time) on July 16th, 1945, in a white blaze that
\nstretched from the basin of the Jemez Mountains in northern New Mexico to the
\nstill-dark skies, The Gadget ushered in the Atomic Age. The light of the
\nexplosion then turned orange as the atomic fireball began shooting upwards at
\n360 feet per second, reddening and pulsing as it cooled. The characteristic
\nmushroom cloud of radioactive vapor materialized at 30,000 feet. Beneath the
\ncloud, all that remained of the soil at the blast site were fragments of jade
\ngreen radioactive glass. …All of this caused by the heat of the reaction.<\/p>\n
The brilliant light from the detonation pierced the early morning skies
\nwith such intensity that residents from a faraway neighboring community would
\nswear that the sun came up twice that day. Even more astonishing is that a
\nblind girl saw the flash 120 miles away.<\/p>\n
Upon witnessing the explosion, reactions among the people who created
\nit were mixed. Isidor Rabi felt that the equilibrium in nature had been
\nupset — as if humankind had become a threat to the world it inhabited.
\nJ. Robert Oppenheimer, though ecstatic about the success of the project,
\nquoted a remembered fragment from Bhagavad Gita. “I am become Death,” he
\nsaid, “the destroyer of worlds.” Ken Bainbridge, the test director, told
\nOppenheimer, “Now we’re all sons of bitches.”<\/p>\n
Several participants, shortly after viewing the results, signed petitions
\nagainst loosing the monster they had created, but their protests fell on deaf
\nears. As it later turned out, the Jornada del Muerto of New Mexico was not
\nthe last site on planet Earth to experience an atomic explosion.<\/p>\n
As many know, atomic bombs have been used only twice in warfare. The
\nfirst and foremost blast site of the atomic bomb is Hiroshima. A Uranium
\nbomb (which weighed in at over 4 & 1\/2 tons) nicknamed “Little Boy” was
\ndropped on Hiroshima August 6th, 1945. The Aioi Bridge, one of 81 bridges
\nconnecting the seven-branched delta of the Ota River, was the aiming point of
\nthe bomb. Ground Zero was set at 1,980 feet. At 0815 hours, the bomb was
\ndropped from the Enola Gay. It missed by only 800 feet. At 0816 hours, in
\nthe flash of an instant, 66,000 people were killed and 69,000 people were
\ninjured by a 10 kiloton atomic explosion.<\/p>\n
The point of total vaporization from the blast measured one half of a
\nmile in diameter. Total destruction ranged at one mile in diameter. Severe
\nblast damage carried as far as two miles in diameter. At two and a half
\nmiles, everything flammable in the area burned. The remaining area of the
\nblast zone was riddled with serious blazes that stretched out to the final
\nedge at a little over three miles in diameter.<\/p>\n
On August 9th 1945, Nagasaki fell to the same treatment as Hiroshima.
\nOnly this time, a Plutonium bomb nicknamed “Fat Man” was dropped on the city.
\nEven though the “Fat Man” missed by over a mile and a half, it still leveled
\nnearly half the city. Nagasaki’s population dropped in one split-second from
\n422,000 to 383,000. 39,000 were killed, over 25,000 were injured. That
\nblast was less than 10 kilotons as well. Estimates from physicists who have
\nstudied each atomic explosion state that the bombs that were used had utilized
\nonly 1\/10th of 1 percent of their respective explosive capabilities.<\/p>\n
While the mere explosion from an atomic bomb is deadly enough, its
\ndestructive ability doesn’t stop there. Atomic fallout creates another hazard
\nas well. The rain that follows any atomic detonation is laden with
\nradioactive particles. Many survivors of the Hiroshima and Nagasaki blasts
\nsuccumbed to radiation poisoning due to this occurance.<\/p>\n
The atomic detonation also has the hidden lethal surprise of affecting
\nthe future generations of those who live through it. Leukemia is among the
\ngreatest of afflictions that are passed on to the offspring of survivors.<\/p>\n
While the main purpose behind the atomic bomb is obvious, there are many
\nby-products that have been brought into consideration in the use of all
\nweapons atomic. With one small atomic bomb, a massive area’s communications,
\ntravel and machinery will grind to a dead halt due to the EMP (Electro-
\nMagnetic Pulse) that is radiated from a high-altitude atomic detonation.
\nThese high-level detonations are hardly lethal, yet they deliver a serious
\nenough EMP to scramble any and all things electronic ranging from copper wires
\nall the way up to a computer’s CPU within a 50 mile radius.<\/p>\n
At one time, during the early days of The Atomic Age, it was a popular
\nnotion that one day atomic bombs would one day be used in mining operations
\nand perhaps aid in the construction of another Panama Canal. Needless to say,
\nit never came about. Instead, the military applications of atomic destruction
\nincreased. Atomic tests off of the Bikini Atoll and several other sites were
\ncommon up until the Nuclear Test Ban Treaty was introduced. Photos of nuclear
\ntest sites here in the United States can be obtained through the Freedom of
\nInformation Act.<\/p>\n
[See Smyth Report for fuller details. Goin’s book in References has photos
\n of nuke sites.]<\/p>\n
============================================================================<\/p>\n
1994<\/p>\n
