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4. Nuclear World - Chapter 4 NUCLEAR WORLD © M Ragheb 4.1...

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Unformatted text preview: Chapter 4 NUCLEAR WORLD © M. Ragheb 2/24/2009 4.1 INTRODUCTION The success of the first man made self sustained chain reaction in the Chicago Pile Number 1 (CP1) was followed by the Manhattan Project, which culminated into the Trinity first nuclear test (Fig. 1) then the first use of nuclear weapons by the USA against Japan. This was succeeded by a frantic period of atmospheric nuclear testing and a nuclear arms race then by attempts by humans, who have come to realize its tremendous energy release potential, at: 1. Sublimating the new state of knowledge, or: “Turning their swords into plowshares,” toward the peaceful applications of nuclear energy. 2. Containing the possible, yet improbable, use of nuclear weapons through different treaties and international agreements. The accumulated knowledge about nuclear phenomena is the Aladdin's Genie that is out of its bottle, or oil lamp in the story. It could be made as humanity’s servant, or allowed to become its worst nightmare, and like other knowledge cannot be imprisoned into the lamp again. In fact humanity needs it to preserve its existence, since it constitutes the only way to defend life on Earth against possible future meteorites impacts that have led to major extinctions in the past. It is also the only hope for humanity for becoming a space civilization, using nuclear propulsion for freeing itself from being planet bound and spreading life throughout the known universe. 4.2 THE NEW WORLD In January of 1946, The First General Assembly of the United Nations met and created the United Nations Atomic Energy Commission precursor of the International Atomic Energy Agency (IAEA) with a charge of eliminating all weapons of mass destruction. However, nuclear testing continued. In Operation Cross Roads on July 1, 1946, in the Bikini Atoll in the Pacific Ocean an air drop test designated as the Able test was conducted. An underwater device designated as the Baker test, sunk 16 out of 95 World War II decommissioned ships including the American Saratoga and Arkansas and the Japanese Nagato. Figure 2 shows the underwater Baker test surrounded by the fleet of decommissioned naval vessels. Figure 3 shows the military personnel being trained at watching the tests wearing goggles protecting their eyes from the ensuing intense ultraviolet radiation, yet not from the neutron, gamma and x ray radiation. Figure 4 shows the effect of the nuclear blast shock wave and x rays on structures. Fig. 1: Sequence of photographs of the Trinity nuclear test. Fig. 2: The underwater Baker test surrounded by a fleet of decommissioned naval vessels. Fig. 3: Military personnel being trained at watching the tests wearing ski goggles protecting their eyes from the intense ultraviolet radiation. Fig. 4: Effects of the blast wave and x rays on structures The Soviet program, limited in scope during the war starting in 1943 under I. V. Khurchatov, moved forward. Their first reactor was built in 1947, and their first nuclear device was tested on Aug. 29, 1949. The United States found its monopoly on atomic weapons lost. This led to the Super Program advocated by Edward Teller to build a thermonuclear or hydrogen Bomb. Robert Oppenheimer, then Director of the Los Alamos Laboratory, as well as Enrico Fermi and Rabi, opposed the program initially, on the basis that fission weapons boosted with tritium can generate explosive yields in the range of 100 kT TNT. The argument was that such a yield was sufficient for all tactical purposes, that the megaton yield level of thermonuclear weapons was militarily unusable, and that they amounted to city busters: “Since no limit exists to the destructiveness of this weapon, its existence is a danger to humanity as a whole”. The argument was also made that the acquired advantage would be temporary, in that it will induce an arms race. There ensued a personality clash between Edward Teller and Robert Oppenheimer. Robert Oppenheimer’s reputation was smeared. Having had some communist friends he was viciously accused of treason, his security clearance was revoked by the Atomic Energy Commission in 1953, as the Super Program proceeded forward. His innocence was recognized and reputation was later restored, but he was by then a broken and sick man. 4.3 THE SUPER PROJECT Further momentum was acquired when it was discovered that Manhattan Project British scientist Klaus Fucks had passed nuclear secrets, including concepts of a hydrogen device, to Russia. On January 31, 1950, President Truman gave the go ahead to intensify the effort in the pursuit of a thermonuclear device. The Air Force specifically established the Lawrence Livermore National Laboratory (LLNL) for Edward Teller to pursue the Super project. The first fusion device conceptualized the use of a fission device to heat a cylinder of liquid deuterium to start a fusion reaction. The concept stalled initially when calculations indicated that it is unlikely that a fission weapon could generate by itself the hundred of millions of degrees of temperature needed to trigger significant fusion reactions. The reason was that at such high temperatures, most energy will appear as escaping radiation rather than in the form of usable kinetic energy of the nuclei. Some calculations suggested that using a mixture of deuterium and tritium could help the reaction proceed much faster than for deuterium alone before a lot of radiation is emitted and equilibrium with radiation is established. It was quite difficult to postpone radiation equilibrium and obtain a long enough energy confinement time for thermonuclear reactions to proceed. 4.4 RADIATION AND MATERIAL ENERGY DENSITIES OF A BLACK BODY According to the Stefan Boltzmann law, the total amount of energy of all wavelengths contained per cubic centimeter, or radiation energy density, of a black body is related to the absolute temperature, T oK = 273 + oC, by the equation: E radiation = σ T 4 [ ergs cm3 (1) where: σ is the Stefan-Boltzmann constant = 7.65 x 10-15 [ergs/(cm3.oK4)]. On the other hand, the material energy density is related to the temperature by: E material = 3 ergs f NkT [ 3 ] , 2 cm (2) where: k is the Boltzmann constant = 1.38 x 10-16 [erg/oK], f = 1 + r, r = average degree of ionization, N = ρ. Av / M, = atomic density in [nuclei/cm3], Av = 6.025 x 1023 [nuclei/mole] = Avogadro's number, M is the molecular or atomic weight [amu], ρ is the material density [gm/cm3]. The total energy density is the sum of radiation and material energy densities and is given by: E total =E radiation + E material = σ T4 + 3 ergs f NkT [ 3 ] 2 cm Of particular interest is the ratio of the radiation energy density to the material energy density can be deduced as: E radiation 2 σ M T 3 = . E material 3 f.A v .k ρ (3) Or, by substituting the values of the physical constants: E radiation 2 σ M T 3 = E material 3 f.A v .k ρ 2 7.65x10−15 M T3 = 3 6.025x1023x1.38x10-16f ρ = 6.134 x 10 -23 (4) M T3 f ρ A critical temperature of: Tc = 3.5 x 107 οΚ = 6.3 x 107 oF, (5) must be attained in the fusion fuel with the aid of a fission device for the fusion reaction to be self sustaining. Substituting this value in the ratio of energy densities yields: 7 3 E radiation -23 M (3.5 x 10 ) = 6.134 x 10 ρ E material f M 1 = 2.63 . . f ρ (6) To attain an equilibrium between the radiation energy density and material energy density, E radiation ≈ 1, E material (7) suggests that a condition is imposed on the nuclear density as: ρ ≈ 2.63 M f (8) This implies that the fusion fuel has to be compressed to higher than normal density if the material energy density would be in equilibrium with the radiation energy density. The implication for the design of the Super is that precompressing the fusion fuel to higher density is necessary to obtain a thermonuclear burn. There exists an urgent need to strongly compress the thermonuclear fuel, and, in the compressed fuel, radiation would be less important and would not inhibit the reaction. 4.5 INITIATION OF THERMONUCLEAR REACTION Several ideas aroused on how to initiate a thermonuclear reaction, including: 1. 2. 3. One due to Gamow, referred to as: “Squeezing the cat's tail.” One due to Stanislav Ulam, referred to as the “Spittoon.” One due to Edward Teller, referred to as the “Womb.” In a drawing by Gamow in Fig. 5, the Russian leader Josef Stalin is shown carrying the Russian bomb, Robert Oppenheimer, dressed as an angel and a halo above his head, is watching Gamow squeezing a cat’s tail, while Edward Teller is wearing an American Indian fertility necklace in the form of a womb and Stanislav Ulam is spitting into a spittoon. None of these concepts was feasible all by itself, and a test by the Livermore Laboratory of the Teller's womb collimation idea failed to initiate a thermonuclear reaction. Hans Bethe and Enrico Fermi contributed to the effort. John von Neumann, developed one of the first computers, the Eniac to carry out the tedious computations needed to study the process. A new numerical methodology, Monte Carlo sampling was developed to simulate the particles and radiation interactions in such a device. Initially Stanislav Ulam thought that he could use neutrons from a primary fission device to compress the fusion fuel in a secondary charge. Calculations showed this was not feasible. 4.6 HOHLRAUM CONCEPT HOHLRAUM The breakthrough came when Edward Teller suggested the use of radiation from the primary instead of neutrons to compress and implode the fusion fuel in the secondary charge. In this process, the x rays from the primary fill up a cavity filled with a material that is transparent to x rays such as polystyrene. This forms a hohlraum where the x rays uniformly irradiate the fusion fuel casing. The surface of the fusion fuel casing absorbs the x rays ablating its outer surface and generating an inverse rocket driving it inwards. The ablating surface sends a compression shock wave into it. This compression wave propagates into the casing then reflects back as a rarefaction wave further sputtering the surface. The implosion process compresses the fusion charge to a high density, which makes possible the ignition and effective burn of fusion fuel, and prevents radiation from escaping. SPARK PLUG A further embellishment is to include a spark plug at the center of the fusion charge consisting of a subcritical mass of Pu239 becoming upon reaching criticality under compression a source of neutrons to breed fusile fuel such as 1T3 from a fusile breeding material such as natural Li or its isotope 3Li6. Shaping the spark plug as a long cylinder increases the surface leakage of neutrons and allows the use of a large mass of plutonium without initially reaching criticality. DUAL CORE The primary device was later built with a composite inner core of Pu239 and outer core of U . This had two reasons. The U235, even though possessing a larger critical mass than Pu239, was cheaper to produce at the time than Pu239, and the cost advantage compensated for the 235 increased critical mass. In addition, its use to substitute for a larger mass of Pu239 provided a tamper as well as a material with a lower level of spontaneous fission neutrons, avoiding a serious predetonation problem occurring in pure Pu239 cores and in plutonium cores tamped with U238. The Pu239 would also contain some Pu240 adding to the neutron source from the (α, n) reactions with low Z elements impurities such as O and F from the fuel reprocessing process, as well as from spontaneous fission reactions. Table 1: Apportionment of energy release from fission. Distribution of Fission Energy Kinetic energy of fission fragments Prompt gamma rays energy Kinetic energy of fission neutrons Beta particles from fission products Delayed gamma rays from fission products Antineutrinos from the fission products Gammas from radiative capture in structure Energy release per fission event Energy (MeV) 165 7 5 7 6 10 3 _____ Fraction, percent 81.3 3.4 2.5 3.4 3.0 4.9 1.5 _____ 203 100 FISSION ENERGY PARTITION The fission process in the primary device generates fission products, neutrons and prompt and delayed beta and gamma radiation. Some 3 - 5 MeV of energy release per fission event is produced by radiative capture (n, gamma) reactions with the structural material. The energy from the antineutrinos and the beta and gamma particles from the fission products appear at a later time, and are not available to the immediate yield. Thus only 203 – 10 – 6 -7 = 180 MeV are immediately available to the fission yield. The fission products carry 81.3 percent of the approximate energy release of 203 MeV/fission or 165 MeV, and deposit it in the device materials melting and vaporizing them into an ionized state of high temperature plasma. The ionized plasma ions and electrons radiate their energy in the form of x rays. In addition, the prompt gamma radiation interacts with materials through the processes of pair production, Compton scattering, the photo electric effect, and for high energy gammas, through photo fission and photo nuclear reactions. The gamma radiation interacts with materials, loses its energy and turns into x rays. The generated positrons and electrons can annihilate into lower energy gamma rays. The electrons lose their energy through the generation of bremstrahlung x rays. Overall most of the primary device energy at the high obtained temperatures is in the form of x ray radiation. IMPLODING FUSION CHARGE The intense electromagnetic radiation in the form of x rays from the primary fission device permeates almost instantaneously at the speed of light a foam surrounding the secondary fusion device, generating a plasma that encloses the imploding fusion charge fuel liner also called a pusher and compressing it to a higher than normal density. The neutrons contribute to breeding tritium in the fusion fuel in the form of lithium deuteride powder, Li6D, from the lithium contained in it. If lithium is enriched in the Li6 isotope, the reaction is fully exothermic: 0 n1 + 3 Li 6 → 1T 3 + 2 He 4 (9) If natural lithium is used, part of the energy is lost to the endothermic Li7 reaction, but more neutrons are produced: 0 4.7 ABLATIVE REACTION n1 + 3 Li 7 → 0 n1 + 1T 3 + 2 He4 IMPLOSION, EQUILIBRIUM (10) THERMONUCLEAR The complex phenomena involved in the energy transfer from the primary device to the secondary device designated as hetero catalytic processes are almost instantaneous, but they can be sequenced into several modes: 1. The initial impingement of the prompt gamma rays. These constitute just 3.5 percent of the energy release, and to avoid preheating, the secondary material must be shielded from them by interposing a shield along the line of sight between the primary and the secondary. 2. The heated plasma x rays constitute the major part of the 82.5 percent of the energy release in the fission products, and must be considered as the main component in the compression of the secondary. 3. The blast energy in the form of a shock wave carried out by the expanding plasma shell and ionized debris. The x rays move at the speed of light of electromagnetic radiation and deposit their energy before the arrival of the third blast component at the speed of sound in the surface of the secondary and the hohlraum casing surrounding it. The x rays deposit their energy at the surface of the secondary. This deposited radiation forms a shock wave that propagates into it while vaporizing part of the pusher container ablating part of the surface. The shock wave propagates into the pusher and reflects from the free surface of the material’s interior as a rarefaction wave causing spallation. The ablation and spallation combine to form an inverse rocket inwardly imploding the secondary container surface and achieving the needed compression and increase in the density of the fusion charge. Fig. 5: Drawing by Gamow sketching the three processes involved in the design of the Super. Stanislav Ulam is spitting into a spittoon. Edward Teller is wearing a Navajo Indian Naja fertility necklace in the form of an inverted Moor crescent. Gamow is squeezing the tail of a cat. Observing them are Joseph Stalin carrying the Russian atomic device and Robert Oppenheimer as a saint with a halo above his head. Source: Gamow, “The Curve of Binding Energy.” Edward Teller describes the realization of the possibility of this development as: “By the end of 1950, I had the novel and positive answer. Because of the wartime work, we knew how to strongly compress the thermonuclear fuel, and, in the compressed fuel, radiation would be less important and would not inhibit the reaction.” Fig. 6: Crescent shaped Naja Navajo necklace worm by Edward teller showing a squash blossom and healing hands. This was the concept of an equilibrium thermonuclear reaction. Fig. 7: Schematic of assumed Ulam Teller configuration, using a fission primary and a fusion-fission secondary. It must be noted that it is “pressure generated by radiation” rather than just “radiation pressure” that is the key to the fusion fuel compression. This is an esoteric distinction that is important for understanding the process. It is not just the x rays from the primary device that compress the fusion fuel. An analogy has been suggested here to boiling water. Water like radiation, does not turn the blades of a turbine. Instead, it is the steam generated by the boiling water that rotates the blades. 4.8 ULAM TELLER CONFIGURATION In February 1951, Stanislav Ulam came out with the idea that he described in his book “Adventures of a Mathematician” as: “Perhaps the change came with an idea I contributed. I thought of a way to modify the whole approach by injecting a repetition of certain arrangements. Unfortunately the idea or set of ideas involved is still secret and cannot be described here.” This repetition of “certain arrangements” came to be known as the Ulam Teller configuration (Fig. 7) and became the turning point for thermonuclear reactions work. Weapons designers in a handful of other nations have conceived other or similar iterative schemes still shrouded in secrecy. This conveys the immeasurable privilege and prestige to the USA, United Kingdom, France, Russia, and China as Super Powers Status in the World, and reserves them permanent seats and the much desired veto power on the Security Council of the United Nations. Other countries such as India, Pakistan and Israel have developed similar schemes using tritium boosted devices. Those that mastered the knowledge assure their cultures’ invincibility against conventional and nuclear attack and survival against any opponents in any potential future conflicts. Such a configuration would be an extremely complex set of components acting in perfect sequencing as a multistage energy and neutron amplifier. One possibility involves a succession of fission then fusion then fission again amplification stages. Figure 5 shows a drawing by Gamow sketching the three processes involved in the design of the Super. Stanislav Ulam is shown to the left spitting into a spittoon. Edward Teller in the middle is wearing a Navajo Indian Naja fertility necklace in the form of an inverted crescent. Gamow, to the right, is squeezing the tail of a cat. Observing them is Joseph Stalin carrying the Russian first atomic device as well as Robert Oppenheimer as a saint with a halo hovering above his head. Figure 6 shows the pendant worn by Edward Teller. The classic squash blossom necklace features a crescent shaped pendant, called a Naja, which is the Navajo word for “crescent,” and beads with a design resembling a squash blossom. Both the Naja and squash blossom beads designs were adapted from the early Spanish settlers of the American Southwest. The Naja motif was borrowed from the Spanish horse bridle. The Spanish had adopted the Naja design from the crescent moon motif of the Moors of North Africa. The crescent design was common to many early civilizations, particularly the Islamic civilization. The squash blossom design is based on a pomegranate blossom motif originally worn as silver trouser ornaments by the Spanish and, later, by the Mexicans who populated the American Southwest. The Navajo do not use the term “squash blossom,” instead referring to it as “the bead that spreads out.” While the squash blossom necklace is still thought of as primarily a Navajo art form, other Native American silversmiths, including the Zuni, also craft squash blossom necklaces in their own styles. In the Trinity test, electrically fired detonators surrounding a fission primary in a soccer ball configuration with twenty hexagons and twelve pentagons, are set off. They drive shock waves in explosive lenses that convert the spherically divergent waves from the detonators into a spherically convergent shock wave. These convergent shocks simultaneously compress a hollow shell tamper made of high temperature and strength beryllium, which also acts as a neutron multiplier and U238 as an energy multiplier. The tamper is driven inward by the implosion shock toward the fissile core of the primary device. The core is compressed to super criticality by the tamper. It takes a few minutes for a stray neutron from cosmic rays and background radiation to initiate a chain reaction in a critical assembly. For reliability considerations, a neutron source is needed to initiate the reaction once the configuration has reached its supercritical state. An urchin shaped neutron source used the alpha particles generated from Po210 to generate a reaction with beryllium producing neutrons once they came into contact with each other. In modern weapons, for higher reliability, when super-criticality is reached, an accelerator tube generates a beam of high energy charged particles in the form of deuterons that impinge on a target made of tungsten loaded with tritium. The DT reaction releases a pulse of 14.06 MeV DT fusion neutrons that start the chain reaction in a Pu239 fissile pit. A layer of U235 may surround the central Pu239 pit for a dual core configuration, initially reducing the spontaneous fission source from U238. Upon compression, it contributes a neutron source that flattens the neutron flux in the core plutonium region leading to a maximum level of burnup with increased efficiency and yield. 4.9 BOOSTER CHARGE AND NEUTRON MULTIPLICATION The energy release may ignite a thermonuclear reaction in a capsule containing a booster charge of deuterium and tritium gas under high pressure. The energy release from the fission process initiates the DT fusion reaction: 1 D 2 + 1T 3 → 0 n1 (14.06 MeV ) + 2 He 4 (3.54 MeV ) (11) The fusion 14.06 MeV neutrons have a much higher energy than fission neutrons with an average energy of just 1.99 MeV. The fusion neutrons fission plutonium and release an average 4.5 neutrons per reaction at high energy compared with about 2.9 for fission induced neutrons. The fusion neutrons amplify the energy release by increasing the fissioning of fissile isotopes in both the Pu239 and the U235 or U238 tamper. The energy release from these second generation neutrons reactions exceeds the ones from the initial fission process. This made possible the design of devices having yields in the range of 100 kT. Robert Oppenheimer argued that this was sufficient to destroy any conceivable strategic target. This led to a vicious personality clash with Edward Teller who kept pushing for the Super with its potential megaton level energy release. Modern weapons have a yield in the range of 100 kT vindicating Robert Oppenheimer’s perspective. The beryllium used to contain the tritium could also be a source of neutron multiplication through the (n, 2n) reaction: 0 n1 + 4 Be9 → 2 0 n1 + 2 2 He 4 (12) which can be conceived as a fission of the beryllium nucleus. The generated gamma rays are absorbed in the device casing and are reemitted as x rays in addition to the x rays generated from the primary device’s hot plasma. The collimation process may use the concept of a whispering gallery to collimate the soft x rays from the primary at the focus of an ellipsoid of revolution to the other focus containing a DT charge that can be ignited and propagate a thermonuclear burn wave into a cylindrical fusion charge. The hohlraum cylinder length can be arbitrary in length, suggesting that there is no limit on the possible yield that can be generated from such devices; which act like a cigarette ignited at its tip. In fact long cylindrically shaped thermonuclear devices have been used in the Plowshare peaceful nuclear explosives program, in which they were brought down drill holes and exploded to enhance the production from hydrocarbon gas and oil reservoirs. The x rays permeate a paper honeycomb shield to a special polystyrene foam channel filler. The hohlraum is fabricated from foam containing a high Z element, possibly thin sheets of U238 that are 5/1000 of an inch thick. A plasma forms, compressing through inverse rocket action the secondary device composed of a lithium6 deuteride compressed powder encased in a U238 pusher. The compressed plasma in turn compresses an internal core of U235 or Pu239. Neutrons from the internal core transmute the Li6 component of the lithium6 deuteride into tritium, which would interact as a plasma under compression with deuterium. The reaction proceeds under equilibrium since the highly compressed fusion fuel now absorbs the emitted radiation and does not allow it to escape. In addition, the reaction proceeds faster between the deuterium and tritium nuclei with a substantial energy confinement time, leading to a high efficiency in burning the fusion fuel. The high-energy 14.06 MeV neutrons from the DT fusion reaction are capable of fissioning the U238 pusher, generating about 90 percent of the released energy. Thus the secondary contains its own fission trigger in the center. Fig. 8: Setup for the cryogenic deuterium Mike device showing the experimental measuring tubes. Fig. 9: The Mike thermonuclear test whose yield at 10.4 Mt TNT, was 500 times the yield from the Hiroshima device. In enhanced radiation weapons such as a neutron device, no U238 casing is used, and is substituted for with Pb, Be, tantalum, or tungsten. If Be is used the DT fusion 14.6 MeV neutrons do not slow down through radiation capture reactions, and are not lost in fissioning the casing and multiply the neutron flux through (n , 2n) reactions with Be, and possibly to a lesser extent with Pb. The system in fact acts as a multistage energy converter and amplifier of neutrons, electromagnetic radiation and kinetic energy. Designing enhanced radiation devices with different conversion efficiencies and different forms of energy releases in the form of neutrons, x rays, gamma rays, charged particles, and blast, becomes a design possibility, according to the intended usage of the devices. Directed energy devices also have been designed by channeling the device plasma into a heavy or light element propellant disc that under free expansion in space, can evolve into a directed energy cylindrical plug shape. Such process could become useful for pulsed nuclear rocket propulsion for planetary travel. An important application came through a plan of placing such devices in rockets carried by submarines. This suggestion made it impossible for an attack to be launched on the USA without retaliation. A small and efficient primary fission device and a small and efficient secondary fusion device were designed. Since the production of the hydrogen isotope tritium (1T3) was needed for the Super program, president Harry S. Truman assigned the Savannah River Laboratory in South Carolina as a site for producing tritium in 1950. The first Super apparatus weighted 65 tons and was practically a deuterium cryogenic plant built at the Eniwetok Atoll in the South Pacific (Fig. 8). On Oct. 31, 1952 the Mike test was conducted and yielded 10.4 Megatons (Mt) of TNT equivalent. Figure 9 shows the Mike test whose yield was so unexpectedly large that the director of the Los Alamos Laboratory considered keeping the results of the test secret. 4.10 ATMOSPHERE IGNITION AND NUCLEAR TESTING There was a fear that such a thermonuclear reaction could ignite the Earth's atmosphere and turn the Earth into a new star, which obviously did not occur. What happened is that the island of Elugelap in the Marshall Islands in the Pacific Ocean was practically vaporized. The Mike test used the hydrogen isotope deuterium in the form of a cryogenically cooled liquid with the fusion reaction ignited by a fission explosion. This arrangement is fine for a physics experiment, but does not yield a deliverable weapon system. LITHIUM DEUTERIDE, BRAVO TEST In a subsequent deliverable device test designated as Bravo, lithium6 deuteride (Li6D) as a compressed white powdered substance was used. The test was conducted on March 1, 1954, and exceeded its calculated yield by yielding 14.8 Mt TNT, at double its expected release. POSSIBLE EXPLANATION OF THE DOUBLED YIELD An explanation for the doubled yield is necessary to explain for the benefit of future fusion and fusion-fission hybrids designs. One can attempt an explanation on the basis of the secondary fusion reactions that could not have been accounted for in the initial calculations. These would occur at the very high temperatures attained in thermonuclear weapons, but not necessarily under laboratory conditions. For instance, the TT fusion reaction is an efficient neutron multiplier that releases two neutrons per reaction: T 3 + 1T 3 → 2 0 n1 + 2 He 4 + 11.3 MeV 1 (13) At some point the two emitted neutrons were thought to be a “dineutron.” The increased neutron multiplication would have increased the neutron flux, efficiently fissioning the fissile material releasing about 180 MeV per fission event. The DHe3 reaction releases a significant 18.3 MeV per reaction in the form of charged particles: 1 D 2 + 2 He3 → 1 H 1 + 2 He 4 + 18.3 MeV The THe3 reaction has three branches occurring with different branching ratios: (14) 51% T 3 + 2 He3 ⎯⎯⎯ 1 H 1 + 2 He 4 + 0 n1 + 12.1 MeV → 1 43% ⎯⎯⎯ 1 D 2 (9.5MeV ) + 2 He 4 (4.8MeV ) → (15) ⎯⎯ 1 H (11.9 MeV ) + 2 He (2.4 MeV ) → 6% 1 5 The presence of Li6 can also lead to the reaction with deuterium: 1 D 2 + 3 Li 6 → 2 2 He 4 + 22.4 MeV (16) and the reaction with the hydrogen ions: 3 Li 6 + 1 H 1 → 2 He3 (2.3MeV ) + 2 He 4 (1.7 MeV ) (17) If Li7 is present a branching reaction could occur: 1 80% H 1 + 3 Li 7 ⎯⎯⎯ 0 n1 + 4 Be7 − 1.6 MeV → 20% ⎯⎯⎯ 2 2 He 4 + 17.3MeV → (18) One can even envision the occurrence of the He3He3 reaction: 2 He3 + 2 He3 → 2 1 H 1 + 2 He 4 + 12.9 MeV (19) RADIOACTIVE FALLOUT The radioactive fallout from the test, carried by winds beyond its expected range and in an unexpected direction, fell on nearby islands forcing the evacuation of their local inhabitants. The crew of a Japanese fishing vessel, ironically called “Lucky Dragon,” was also affected by the fallout. Figure 10 shows the Mk-17 device, which was the first deliverable thermonuclear weapon. This device required the use of a large bomber to deliver it. This size has been substantially reduced in size as shown in Fig. 11 for the W80-0 device and Fig. 12 for the W85 device. Fig. 10: The Mk-17 device, which was the first deliverable thermonuclear weapon. Fig. 11: Photograph of the W80-0 thermonuclear device. Fig. 12: Schematic of variable yield (5-50 kT) W85 device. Variable yield is achieved through the control of its tritium content. Source: USDOE. Fig. 13: Components of the B83 device. Fig. 14: Assumed schematic of a thermonuclear device. Source: Moreland, “The Secret that Exploded.” These devices are equipped with sophisticated safety, arming and fusing parts as shown in Fig. 13 for the B83 device using the skills of thousand of engineers and technicians used by tens of suppliers constituting a whole industrial suppliers complex. An assumed schematic for the contents is shown in Fig. 14. Inter Continental Ballistic Missiles (ICBMs) can carry Multiple Independently Released Vehicles (MIRVs) as shown in Fig. 15. 4.11 NUCLEAR ARMS RACE OPEN TESTING The nuclear arms race continued escalating. Russia caught up with the American effort and exploded its first fusion device in central Siberia on August 12, 1953. One of the Russian tests at Novaya Zemlya Island on October 23, 1961 yielded a record yield of 58 Mt of TNT. Nikita Khruschchev, the Russian leader boasted about it: “It could have been bigger, but then it might have broken all the windows in Moscow, 4,000 miles away.” In fact, the yield was reduced at the last moment by halving the size of the thermonuclear fuel charge. Khruschchev's boasting notwithstanding, it was a situation where the actual yield exceeded the expected one. Britain caught up and detonated an atomic device on Monte Bello Island off the Australian coast on October 3rd, 1952, which yielded 25 kT of TNT. It conducted 9 more tests in the Great Victoria Desert in Australia from 1952 to 1957. It tested its first hydrogen weapon over the Christmas Island in the Pacific on May 15, 1957. Fig. 15: Multiple Independently Released Vehicles (MIRVs) W87 devices. Fig. 16: British 32 explosive lenses Orange Herald 720 kT device assembly. France used the Sahara Desert in its previous colony, Algeria, for testing its first device on February 13, 1960. It then exploded its first fusion device above the Fangataufa Island in the Pacific on Aug. 24, 1968. Fig. 17: France’s atmospheric testing in the South Pacific. Source: BBC. China's first weapon was exploded at Lop Nor on October 16, 1964. Its first hydrogen bomb was tested in 1967. The world came close to a nuclear exchange between Russia and the USA in the Cuban missile crisis in 1962, when Russia positioned missiles with nuclear warheads close to the USA’s mainland. Russia withdrew its missiles after a naval blockade of Cuba by then President John F. Kennedy, in a horse trade for an already planned closing of American listening posts in Turkey, close to the Russian border. The mutual threats of an unprecedented nuclear exchange generated more efforts towards controlling the spread of nuclear weapons. The Limited Test Ban Treaty (LTBT) was signed in 1963, and was followed by the Comprehensive Test Ban Treaty (CTBT). The radioactive fallout from nuclear testing in the atmosphere spread worldwide, and generated wide protests. Nuclear testing in the atmosphere was replaced by underground tests as shown at the Nevada test site in the USA in Fig. 18. Lately, underground testing has been replaced by computer simulations and laser physics experiments at the National Ignition Facility at Livermore, California. Fig. 18: Underground nuclear test at the Nevada test site in the USA. Fig. 19: Sedan underground cratering explosion, July 6, 1962. However, nuclear weapons continued to proliferate. India tested a 10-15 kT of TNT yield equivalent device in the Rajasthan desert on May 18, 1974. In 1998, it tested new tactical devices, and was followed promptly by its neighbor Pakistan in May 1988 with its own tests. CLANDESTINE TESTING South Africa is suspected of having tested on a barge in collaboration with Israel a tactical device on September 22, 1979. It was inconclusively identified, possibly because of an ingenious disguise of the event to resemble a lightning discharge, by surrounding the exploding device by a Mylar balloon. The balloon would have absorbed the prompt gamma ray emissions from the device and re-emitted them with a time delay. A nuclear explosion is characterized by two gamma ray pulses. One prompt pulse from the fission process, and a delayed pulse from the fission products of the explosion, whereas a lightning pulse involves a single pulse. The Mylar balloon surrounding the device would have merged the two pulses into a single pulse, disguising the explosion to look like a lightning's pulse. It was detected concurrently by the Vela Satellite and by USA Navy ocean hydrophones with a tactical yield of 2-4 kT TNT. Fig. 20: Vela-5 surveillance satellite. Israel, having collaborated with France in building the heavy water plutonium production Dimona reactor in the Negev desert is renown, according to the American Central Intelligence Agency (CIA) reports, to possess 200-400 Nagasaki-sized atomic weapons (20 kT TNT), and possibly more advanced 100 kT TNT tritium boosted hydrogen weapons. It is rumored to have tested its weapons in collaboration with South Africa, but depends primarily on sophisticated computer simulations to maintain its stockpile. Its weapons are mounted on cruise missiles carried on German Dolphin class submarines and are targeted against regional as well as international targets making it another de facto yet intentionally ambiguous superpower. COUNTERPROLIFERATION REPLACING NONPROLIFERATION REGIME The Gulf I campaign and an earlier raid by Israel on the French supplied Osiraq reactor in Iraq may have stopped at its birth a suspected nascent Iraqi effort at acquiring nuclear weapons. The Iraqis then switched to a misinformed U235 enrichment effort using magnetic separation and reportedly centrifugation. They were swindled by various unscrupulous equipment suppliers of their oil money on a grand scale. They dismantled their program under the supervision of the IAEA after the first 1991 Gulf War. Their already dismantled nuclear program was nevertheless used as pretext for invading Iraq in 2001, changing its regime, dividing it along ethnic lines into three Kurdish, Shiite and Sunni entities, hanging its previous president and shooting his children, and plunging it into an irreconcilable civil war for the foreseeable future. South Africa in 1991, voluntarily asked the IAEA to supervise dismantling its program. Lybia, in 2004 under USA pressure and UK brokering agreed to dismantle a failed insignificant program. A uranium enrichment program in Iran for the production of fuel for pressurized power water reactors is suspected to aim towards the production of nuclear weapons. Consequently, a campaign has been planned for bombing and dismantling its nuclear facilities, and awaits a suitable timing for its execution. North Korea withdrew from the Nuclear Nonproliferation Treaty (NPT) and declared that it possessed nuclear weapons, and reportedly tested a device on October 8, 2006. It appears that it was a fizzle generating a low yield; having been constructed of reactor grade rather than from weapons grade plutonium. Ongoing less publicized clandestine Brazilian, Argentinean, and Algerian programs bubble to the surface every once in a while. They sink out of international attention and the eyes are turned away, so as not to embarrass friendly regimes or secure economical ties. Fig. 21: A B-2 stealth airplane drops a mock B83 warhead. Fig. 22: The Ground Launched Cruise Missile used the inactivated W84 warhead. Fig. 23: The Minuteman III Intercontinental Ballistic Missile (ICBM) carrying a W62 warhead. Fig. 24: A Peacekeeper ICBM equipped with the W87 warhead. Fig. 25: Davy Crockett 20 ton TNT tactical device. The superpowers arsenals still remains at a significant level. Table 2 shows the characteristics of some of the USA’s Air Force warheads. The delivery methods range from submarines, bombers aircraft, cruise missiles, ships including submarines, and Intercontinental Ballistic Missiles (ICBMs). Table 2: Characteristics of five of the nine USA Air Force nuclear warheads. Warhead W80 W84 Usage Refurbished Not presently in use Characteristics Cruise Missiles Cruise Missile W87 W62 Surface to Surface Surface to Surface ICBM warhead ICBM warhead B83-0/1 Air to Surface Strategic bomb Missile Carrier Cruise Missiles Ground Launched Cruise Missile Peacekeeper ICBM Minuteman III ICBM B-52, B-2 aircraft The members of the current nuclear club, either with public or with unpublicized weapons programs, are clearly determined individually or collectively on foiling the efforts and denying access of any new members to their exclusive club, with diplomatic and economical pressure, and with military means if necessary. This leads to an a simple mathematical law governing nonproliferation where the probability of a successful nuclear weapons program (p) is inversely proportional to the most current number of the nuclear club membership: p α 1 N (20) As the number of current members N increases, the probability p of being able to join the club decreases. Currently N comprises the USA, Russia, France, the UK and China, as well as Israel, India and Pakistan, and North Korea for a total of 9. Some countries can be considered as latent nuclear weapons states such as Germany, South Africa, Brazil, Argentina, Iran and Japan, in that they possess the science, technology, manpower, knowledge and facilities to initiate nuclear weapons programs on a short notice, should their national security compel them to do so. However, if humanity is to save itself, the nuclear club needs to have a membership of N = 0. 4.12 DISCUSSION Efforts at controlling the proliferation of Nuclear Weapons are nowadays centered on the Non Proliferation Treaty (NPT) joined by 133 nations in 1968. Some states including India, Pakistan China and Israel advanced diverse reasons and have not yet signed nor ratified the treaty. North Korea withdrew from the treaty then is negotiating rejoining it for economical and security incentives. It is supervised by the International Atomic Energy Agency (IAEA) as an arm of the United Nations (UN). The current arms control efforts include a set of global and regional treaties: The Antarctic Treaty, The Sea-Bed Treaty, The Treaty of Tlatelolco in South America, The Outer Space Treaty, The Non-Proliferation Treaty (NPT), The Strategic Arms Limitations Treaty (SALT), The Vladivostok and SALT II treaties. Between the USA and Russia, the following treaties are at different stages of signing and ratification: The Intermediate-range Nuclear Forces Treaty (INF), and the Strategic Arms Reduction Treaty (START). In 2002, USA President George W. Bush and Russian President Vladimir Putin signed the “Moscow Treaty on Strategic Offensive Reductions.” According to that treaty, the USA is to reduce the number of operationally deployed strategic warheads and bombs to 1,700-2,200 by 2012. In 2004, USA President George W. Bush issued a directive to cut the entire USA nuclear stockpile of both deployed and reserve warheads in half by 2012 relative to 2001. The goal was achieved by 2007; five years ahead of schedule. As of 2007, enjoying its status as the sole superpower in the continuously evolving Nuclear World, the USA pursued an active Counter Proliferation Policy which is perceived as competitive to the Non Proliferation Treaty (NPT) substituting cooperation and economical and security incentives with an aggressive pre-emptive disarmament campaign against unfriendly regimes using economical sanctions, as well as coercion and threats of resorting to military means whenever feasible. REFERENCES 1. Stanislav M. Ulam, “Adventures of a Mathematician,” Charles Scribner’s Sons, New York, 1976. 2. A. C. Brown, and B. MacDonald, “The Secret History of the Atomic Bomb,” Dell Publishing Co., New York, 1977. 3. R. G. Hewlett and O. E. Anderson, Jr., “The New World, A History of the United States Atomic Energy Commission,” Volume 1, 1939/1946, U. S. Atomic Energy Commission, 1972. 4. D. S. Saxon et al., “The Effects of Nuclear War,” Office of Technology Assessment, Congress of the United States, Washington D. C., May 1979. ...
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