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An explosion, in general, results from the very rapid release of a large amount of energy within a limited space. This is true for a conventional "high explosive," such as TNT, as well as for a nuclear (or atomic) explosion although the energy is produced in quite different ways. The sudden liberation of energy causes a considerable increase of temperature and pressure, so that all the materials present are converted into hot, compressed gases. Since these gases are at very high temperatures and pressures, they expand rapidly and thus initiate a pressure wave, called a "shock wave," in the surrounding medium air, water, or earth. The characteristic of a shock wave is that there is (ideally) a sudden increase of pressure at the front, with a gradual decrease behind it, as shown in. A shock wave in air is generally referred to as a "blast wave" because it resembles and is accompanied by a very strong wind. In water or in the ground, however, the term "shock" is used, because the effect is like that of a sudden impact.
Nuclear weapons are similar to those of more conventional types insofar as their destructive action is due mainly to blast or shock. On the other hand, there are several basic differences between nuclear and high-explosive weapons. In the first place, nuclear explosions can be many thousands (or millions) of times more powerful than the largest conventional detonations. Second, for the release of a given amount of energy, the mass of a nuclear explosive would be much less than that of a conventional high explosive. Consequently, in the former case, there is a much smaller amount of material available in the weapon itself that is converted into the hot, compressed gases mentioned above. This results in somewhat different mechanisms for the initiation of the blast wave. Third, the temperatures reached in a nuclear explosion are very much higher than in a conventional explosion, and a fairly large proportion of the energy in a nuclear explosion is emitted in the form of light and heat, generally referred to as "thermal radiation." This is capable of causing skin burns and of starting fires at considerable distances. Fourth, the nuclear explosion is accompanied by highly-penetrating and harmful invisible rays, called the "initial nuclear radiation." Finally the substances remaining after a nuclear explosion are radioactive, emitting similar radiations over an extended period of time. This is known as the "residual nuclear radiation" or "residual radioactivity" It is because of these fundamental differences between a nuclear and a conventional explosion, including the tremendously greater power of the former, that the effects of nuclear weapons require special consideration. In this connection, knowledge and understanding of the mechanical and the various radiation phenomena associated with a nuclear explosion are of vital importance.
BACKGROUND OF NUCLEAR WEAPONS
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission ("atomic") bomb test released the same amount of energy as approximately 20,000 tons of TNT. The first thermonuclear ("hydrogen") bomb test released the same amount of energy as approximately 10,000,000 tons of TNT. A modern thermonuclear weapon weighing little more than 2,400Â pounds (1,100Â kg) can produce an explosive force comparable to the detonation of more than 1.2 million tons (1.1 million metric tons) of TNT. Thus, even a small nuclear device no larger than traditional bombs can devastate an entire city by blast, fire and radiation. Nuclear weapons are considered weapons of mass destruction, and their use and control has been a major focus of international relations policy since their debut.
Based on Issue 1 2008, Nuclear Weapon Journal, Air Force National Laboratories Technical Fellows (AF-NLTF) Program, which operates under the auspices of the Air Force Fellows Program was established to strengthen the chemical, biological, radiological, nuclear, and explosives technical expertise of the USAF's military and civilian personnel. By mentoring officers about the complexities of LANL defense, research and development, and stockpile stewardship issues, the Laboratory helps develop a group of senior officers equipped to understand the Laboratory's approach to its national security commitments especially in developing nuclear weapon.
ATOMIC STRUCTURE AND ISOTOPES
All substances are made up from one or more of about 90 different kinds of simple materials known as "elements." Among the common elements are the gases hydrogen, oxygen, and nitrogen; the solid nonmetals carbon, sulfur, and phosphorus; and various metals, such as iron, copper, and zinc. A less familiar element, which has attained prominence in recent years because of its use as a source of nuclear energy, is uranium, normally a solid metal.
The smallest part of any element that can exist, while still retaining the characteristics of the element, is called an "atom" of that element. Thus, there are atoms of hydrogen, of iron, of uranium, and so on, for all the elements. The hydrogen atom is the lightest of all atoms, whereas the atoms of uranium are the heaviest of those found on earth. Heavier atoms, such as those of plutonium, also important for the release of nuclear energy, have been made artificially frequently, two or more atoms of the same or of different elements join together to form a "molecule."
Every atom consists of a relatively heavy central region or "nucleus," surrounded by a number of very light particles known as "electrons." Further, the atomic nucleus is itself made up of a definite number of fundamental particles, referred to as "protons" and "neutrons." These two particles have almost the same mass, but they differ in the respect that the proton carries a unit charge of positive electricity whereas the neutron, as its name implies, is uncharged electrically, i.e., it is neutral. Because of the protons present in the nucleus, the latter has a positive electrical charge, but in the normal atom this is exactly balanced by the negative charge carried by the electrons surrounding the nucleus.
The essential difference between atoms of different elements lies in the number of protons (or positive charges) in the nucleus; this is called the "atomic number" of the element. Hydrogen atoms, for example, contain only one proton, helium atoms have two protons, uranium atoms have 92 protons, and plutonium atoms 94 protons. Although all the nuclei of a (liven element contain the same number of protons, they may have different numbers of neutrons. The resulting atomic species, which have identical atomic numbers but which differ in their masses, are called "isotopes" of the particular element. All but about 20 of the elements occur in nature in two or more isotopic forms, and many other isotopes, which are unstable, i.e., radioactive, have been obtained in various ways.
Each isotope of a given element is identified by its "mass number," which is the sum of the numbers of protons and neutrons in the nucleus. For example, the element uranium, as found in nature, consists mainly of two isotopes with mass numbers of 235 and 238; they are consequently referred to as uranium-235 and uranium-238, respectively. The nuclei of both isotopes contain 92 protons-as do the nuclei of all uranium isotopes-but the former have in addition 143 neutrons and the latter 146 neutrons. The general term "nuclide" is used to describe any atomic species distinguished by the composition of its nucleus, i.e., by the number of protons and the number of neutrons. Isotopes of a given element are nuclides having the same number of protons but different numbers of neutrons in their nuclei.
In a conventional explosion, the energy released arises from chemical reactions; these involve a rearrangement among the atoms, e.g., of hydrogen, carbon, oxygen, and nitrogen, present in the chemical high-explosive material. In a nuclear explosion, on the other hand, the energy is produced as a result of the formation of different atomic nuclei by the redistribution of the protons and neutrons within the interacting nuclei. What is sometimes referred to as atomic energy is thus actually nuclear energy, since it results from particular nuclear interactions. It is for the same reason, too, that atomic weapons are preferably called "nuclear weapons." The forces between the protons and neutrons within atomic nuclei are tremendously greater than those between the atoms; consequently, nuclear energy is of a much higher order of magnitude than conventional (or chemical) energy when equal masses are considered.
Many nuclear processes are known, but not all are accompanied by the release of energy. There is a definite equivalence between mass and energy, and when a decrease of mass occurs in a nuclear reaction there is an accompanying release of a certain amount of energy related to the decrease in mass. These mass changes are really a reflection of the difference in the internal forces in the various nuclei. It is a basic law of nature that the conversion of any system in which the constituents are held together by weaker forces into one in which the forces are stronger must be accompanied by the release of energy, and a corresponding decrease in mass.
In addition to the necessity for the nuclear process to be one in which there is a net decrease in mass, the release of nuclear energy in amounts sufficient to cause an explosion requires that the reaction should be able to reproduce itself once it has been started. Two kinds of nuclear interactions can satisfy the conditions for the production of large amounts of energy in a short time. They are known as "fission" (splitting) and "fusion" (joining together). The former process takes place with some of the heaviest (high atomic number) nuclei; whereas the latter, at the other extreme, involves some of the lightest (low atomic number) nuclei.
Â The materials used to produce nuclear explosions by fission are certain isotopes of the elements uranium and plutonium. As noted above, uranium in nature consists mainly of two isotopes, namely, uranium-235 (about 0.7 percent), and uranium-238 (about 99.3 percent). The less abundant of these isotopes, i.e., uranium-235, is the readily fissionable species that is commonly used in nuclear weapons. Another isotope, uranium-233, does not occur naturally, but it is also readily fissionable and it can be made artificially starting with thorium-232. Since only insignificant amounts of the element plutonium are found in nature, the fissionable isotope used in nuclear weapons, plutonium-239 is made artificially from uranium-238.
When a free (or unattached) neutron enters the nucleus of a fissionable atom, it can cause the nucleus to split into two smaller parts. This is the fission process, which is accompanied by the release of a large amount of energy. The smaller (or lighter) nuclei which result are called the "fission products." The complete fission of 1 pound of uranium or plutonium releases as much explosive energy as does the explosion of about 8,000 (short) tons of TNT.
In nuclear fusion, a pair of light nuclei unite (or fuse) together to form a nucleus of a heavier atom. An example is the fusion of the hydrogen isotope known as deuterium or "heavy hydrogen." Under suitable conditions, two deuterium nuclei may combine to form the nucleus of a heavier element, helium, with the release of energy. Nuclear fusion reactions can be brought about by means of very high temperatures, and they are thus referred to as "thermonuclear processes." The actual quantity of energy liberated, for a given mass of material, depends on the particular isotope (or isotopes) involved in the nuclear fusion reaction. As an example, the fusion of all the nuclei present in 1 pound of the hydrogen isotope deuterium would release roughly the same amount of energy as the explosion of 26,000 tons of TNT.
In certain fusion processes, between nuclei of the hydrogen isotopes, neutrons of high energy are liberated. These can cause fission in the most abundant isotope (uranium-238) in ordinary uranium as well as in uranium-235 and plutonium-239. Consequently, association of the appropriate fusion reactions with natural uranium can result in an extensive utilization of the latter for the release of energy. A device in which fission and fusion (thermonuclear) reactions are combined can therefore produce an explosion of great power. Such weapons might typically release about equal amounts of explosive energy from fission and from fusion.
A distinction has sometimes been made between atomic weapons, in which the energy arises from fission, on the one hand, and hydrogen (or thermonuclear) weapons, involving fusion, on the other hand. In each case, however, the explosive energy results from nuclear reactions, so that they are both correctly described as nuclear weapons. In this book, therefore, the general terms "nuclear bomb" and "nuclear weapon" will be used, irrespective of the type of nuclear reaction producing the energy of the explosion.
TYPES OF NUCLEAR WEAPONS
There are two basic types of nuclear weapon. The first type produces its explosive energy through nuclear fission reactions alone. Such fission weapons are commonly referred to as atomic bombs or atom bombs (abbreviated as A-bombs), though their energy comes specifically from the nucleus of the atom. In fission weapons, a mass of fissile material (enriched uranium or plutonium) is assembled into a supercritical mass-the amount of material needed to start an exponentially growing nuclear chain reaction-either by shooting one piece of sub-critical material into another (the "gun" method) or by compressing a sub-critical sphere of material using chemical explosives to many times its original density (the "implosion" method).
The latter approach is considered more sophisticated than the former and only the latter approach can be used if the fissile material is plutonium. A major challenge in all nuclear weapon designs is to ensure that a significant fraction of the fuel is consumed before the weapon destroys itself. The amount of energy released by fission bombs can range from the equivalent of less than a ton of TNT upwards of 500,000 tons (500 kilotons) of TNT.
Figure 4.0: The two basic fission weapon designs
The second basic type of nuclear weapon produces a large amount of its energy through nuclear fusion reactions. Such fusion weapons are generally referred to as thermonuclear weapons or more colloquially as hydrogen bombs (abbreviated as H-bombs), as they rely on fusion reactions between isotopes of hydrogen (deuterium and tritium). However, all such weapons derive a significant portion, and sometimes a majority, of their energy from fission (including fission induced by neutrons from fusion reactions). Unlike fission weapons, there are no inherent limits on the energy released by thermonuclear weapons. Only six countries-United States, Russia, United Kingdom, People's Republic of China, France and India-have conducted thermonuclear weapon tests. (Whether India has detonated a "true", multi-staged thermonuclear weapon is controversial.
Using the Fast Neutron-Induced Gamma-Ray Observer (FIGARO) detector array, LANL scientists performed extensive neutron-production measurements at WNR. The FIGARO array contains 20 neutron detectors that can, by using pulse-shape discrimination, distinguish between neutrons and gamma rays. The neutrons are detected in coincidence with a signal from a fission chamber that indicates a fission event occurred. The energy of the neutron produced by the fission event is determined by the time between the event signal and detection of a neutron in the FIGARO array (time of flight). The slower a neutron moves, the lower its energy. With the neutron-production measurement data obtained with FIGARO, Los Alamos scientists are able to provide our simulation and modeling teams with the information necessary to improve weapons computational codes.
Figure 4.1: Data of Los Alamos model
Neutron spectral data (average neutron energy) measured with the FIGARO array compared with a current Los Alamos computer model. The discrepancies at approximately 8 MeV and above 14 MeV demonstrate the need for improved modeling of neutron spectra. BRC stands for Bruyeres Research Center at the Bruyeres-le-Chatel Center of the CEA (the French equivalent of the US)
TYPES OF NUCLEAR EXPLOSIONS
The immediate phenomena associated with a nuclear explosion, as well as the effects of shock and blast and of thermal and nuclear radiations, vary with the location of the point of burst in relation to the surface of the earth. For descriptive purposes five types of burst are distinguished, although many variations and intermediate situations can arise in practice. The main types, which will be defined below, are (1) air burst, (2) high-altitude burst, (3) underwater burst, (4) underground burst, and (5) surface burst.
Provided the nuclear explosion takes place at an altitude where there is still an appreciable atmosphere, e.g., below about 100,000 feet, the weapon residues almost immediately incorporate material from the surrounding medium and form an intensely hot and luminous mass, roughly spherical in shape, called the "fireball." An "air burst" is defined as one in which the weapon is exploded in the air at an attitude below 100,000 feet, but at such a height that the fireball (at roughly maximum brilliance in its later stages) does not touch the surface of the earth. For example, in the explosion of a 1-megaton weapon the fireball may grow until it is nearly 5,700 feet (1.1 mile) across at maximum brilliance. This means that, in this particular case, the explosion must occur at least 2,850 feet above the earth's surface if it is to be called an air burst.
The quantitative aspects of an air burst will be dependent upon its energy yield, but the general phenomena are much the same in all cases. Nearly all of the shock energy that leaves the fireball appears as air blast, although some is generally also transmitted into the ground. The thermal radiation will travel long distances through the air and may be of sufficient intensity to cause moderately severe burns of exposed skin as far away as 12 miles from a 1-megaton explosion, on a fairly clear day. For air bursts of higher energy yields, the corresponding distances will, of course, be greater. The thermal radiation is largely stopped by ordinary opaque materials; hence, buildings and clothing can provide protection.
The initial nuclear radiation from an air burst will also penetrate a long way in air, although the intensity falls off fairly rapidly at increasing distances from the explosion. The interactions with matter that result in the absorption of energy from gamma rays and from neutrons are quite different, as will be seen in Chapter VIII. Different materials are thus required for the most efficient removal of these radiations; but concrete, especially if it incorporates a heavy element, such as iron or barium, represents a reasonable practical compromise for reducing the intensities of both gamma rays and neutrons. A thickness of about 4 feet of ordinary concrete would probably provide adequate protection from the effects of the initial nuclear radiation for people at a distance of about 1 mile from an air burst of a 1-megaton nuclear weapon. However, at this distance the blast effect would be so great that only specially designed blast-resistant structures would survive.
In the event of a moderately high (or high) air burst, the fission products remaining after the nuclear explosion will be dispersed in the atmosphere. The residual nuclear radiation arising from these products will be of minor immediate consequence on the ground. On the other hand, if the burst occurs nearer the earth's surface, the fission products may fuse with particles of earth, part of which will soon fall to the ground at points close to the explosion. This dirt and other debris will be contaminated with radioactive material and will, consequently, represent a possible danger to living things.
A "high-altitude burst" is defined as one in which the explosion takes place at an altitude in excess of 100,000 feet. Above this level, the air density is so low that the interaction of the weapon energy with the surroundings is markedly different from that at lower altitudes and, moreover, varies with the altitude. The absence of relatively dense air causes the fireball characteristics in a high-altitude explosion to differ from those of an air burst. For example, the fraction of the energy converted into blast and shock is less and decreases with increasing altitude. Two factors affect the thermal energy radiated at high altitude. First, since a shock wave does not form so readily in the less dense air, the fireball is able to radiate thermal energy that would, at lower altitudes, have been used in the production of air blast. Second, the less dense air allows energy from the exploding weapon to travel much farther than at lower altitudes. Some of this energy simply warms the air at a distance from the fireball and it does not contribute to the energy that can be radiated within a short time .In general, the first of these factors is effective between 100,000 and 140,000 feet, and a larger proportion of the explosion energy is released in the form of thermal radiation than at lower altitudes. For explosions above about 140,000 feet, the second factor becomes the more important, and the fraction of the energy that appears as thermal radiation at the time of the explosion becomes smaller.
The fraction of the explosion energy emitted from a weapon as nuclear radiations is independent of the height of burst. However, the partition of that energy between gamma rays and neutrons received at a distance will vary since a significant fraction of the gamma rays result from interactions of neutrons with nitrogen atoms in the air at low altitudes. Furthermore, the attenuation of the initial nuclear radiation with increasing distance from the explosion is determined by the total amount of air through which the radiation travels. This means that, for a given explosion energy yield, more initial nuclear radiation will be received at the same slant range on the earth's surface from a high-altitude detonation than from a moderately high air burst. In both cases the residual radiation from the fission products and other weapon residues will not be significant on the ground.
Both the initial and the residual nuclear radiations from high-altitude bursts will interact with the constituents of the atmosphere to expel electrons from the atoms and molecules. Since the electron carries a negative electrical charge, the residual part of the atom (or molecule) is positively charged, i.e., it is a positive ion. This process is referred to as "ionization," and the separated electrons and positive ions are called "ion pairs." The existence of large numbers of electrons and ions at high altitudes may have seriously degrading effects on the propagation of radio and radar signals (see Chapter X). The free electrons resulting from gamma-ray ionization of the air in a high-altitude explosion may also interact with the earth's magnetic field to generate strong electromagnetic fields capable of causing damage to unprotected electrical or electronic equipment located in an extensive area below the burst. The phenomenon known as the "electromagnetic pulse" (or EMP) is described in Chapter XI. The EMP can also be produced in surface and low air bursts, but a much smaller area around the detonation point is affected.
If a nuclear explosion occurs under such conditions that its center is beneath the ground or under the surface of water, the situation is described as an "underground burst" or an "underwater burst," respectively. Since some of the effects of these two types of explosions are similar, they will be considered here together as subsurface bursts. In a subsurface burst, most of the shock energy of the explosion appears as underground or underwater shock, but a certain proportion, which is less the greater the depth of the burst, escapes and produces air blast. Much of the thermal radiation and of the initial nuclear radiation will he absorbed within a short distance of the explosion. The energy of the absorbed radiations will merely contribute to the heating of the ground or body of water. Depending upon the depth of the explosion, some of the thermal and nuclear radiations will escape, but the intensities will generally be less than for an air burst. However, the residual nuclear radiation, i.e., the radiation emitted after the first minute, now becomes of considerable significance, since large quantities of earth or water in the vicinity of the explosion will be contaminated with radioactive fission products.
A "surface burst" is regarded as one which occurs either at or slightly above the actual surface of the land or water. Provided the distance above the surface is not great, the phenomena are essentially the same as for a burst occurring on the surface. As the height of burst increases up to a point where the fireball (at maximum brilliance in its later stages) no longer touches the land or water, there is a transition zone in which the behavior is intermediate between that of a true surface burst and of an air burst. In surface bursts, the air blast and ground (or water) shock is produced in varying proportions depending on the energy of the explosion and the height of burst.
Although the five types of burst have been considered as being fairly distinct, there is actually no clear line of demarcation between them. It will be apparent that, as the height of the explosion is decreased, a high-altitude burst will become in air burst, and an air burst will become a surface burst. Similarly, a surface burst merges into a subsurface explosion at a shallow depth, when part of the fireball actually breaks through the surface of the land or water. It is nevertheless a matter of convenience, as will be seen in later chapters, to divide nuclear explosions into the five general types defined above.
Effects of nuclear weapons .There are several different kinds of effects from a nuclear explosion, effects which vary with the altitude at which the bomb explodes. For there to be widespread thermal or immediate radiation effect, it must detonate in air, at least 2000 feet/620 meters. This means it must be delivered by aircraft or missile, since that is above the height of the tallest buildings.
Regardless of the height of the burst, the spot on the ground directly below the center of the explosion is called [actual] ground zero. Designated ground zero (DGZ) is a term used in planning attacks with nuclear weapons; the DGZ is the point on the ground, either below an air burst or the actual point of a surface burst, where the weapon is aimed.
Table 6.0: Effects of weapons
Classes of weapons effects
Type of effect
Bomb yield and burst altitude
Symmetrical around ground zero, decreasing by inverse cube
Immediate ionizing radiation
Biologically significant absorbed radiation (SI units of Grays)
Bomb design (i.e., radiation enhancement), yield, burst height
Symmetrical around ground zero, decreasing by inverse square
Delayed ionizing radiation (fallout)
Biologically significant absorbed radiation (SI units of Grays)
Bomb design ("clean"vs. "dirty"), yield, burst height (or subsurface depth)
Wind patterns; radioactivity is greatest downwind of burst
Bomb yield and burst altitude, clouds and precipitation
Symmetrical around ground zero, decreasing by inverse square
WEAPONS PROGRAM SNAPSHOT
This programs show the data on how the weapons program are performing. In the programs weapons there are three critical areas which are; (1) Level 1 and Level 2 programmatic milestones; (2) safety; and (3) security.
7.1 Level 1 and 2 Milestones (FY10 Quarter 2)
Level 1 (L1) milestones - very actual, multiyear, supposed to involve many, if not all, sites
Level 2 (L2) milestones - support achievement of L1 goals, annual milestones are reported to NNSA program management on a quarterly basis. Progress on milestones is entered into the Milestone Reporting Tool (MRT).
Figure 7.1: Level 1 and 2 Milestones chart
7.2 Safety Trends (October 2009 through February 2010)
Total Reportable Cases (TRC) - those that result in any of the following: death, days away from work, restricted work activity, or transfer (DART) to another job, or medical treatment beyond first aid or loss of consciousness as a result of safety incidents
Figure 7.2: Graph of safety trends
7.3 Security Trends (October 2009 through February 2010)
Incidents of security concern (IOSCs) are categorized based on DOE's Impact measurement Index (IMI) in Figure 7.3. The IMI roughly reflects an assessment of an incident's potential to cause serious damage to national, DOE, or LANL security operations, resources, or workers or degrade or place at risk safeguards and security interests or operations.
Figure 7.3: Security Trends
IMI-1 - Actions, inactions, or events that pose the most serious threats to national security interests and/or critical DOE assets, create serious security situations, or could result in deaths in the workforce or general public.
IMI-2 - Actions, inactions, or events that pose threats to national security interests and/or critical DOE assets or that potentially create dangerous situations.
IMI-3 - Actions, inactions, or events that pose threats to DOE security interests or that potentially degrade the overall effectiveness of DOE's safeguards and security protection programs.
IMI-4 - Actions, inactions, or events that could pose threats to DOE by adversely impacting the ability of organizations to protect DOE safeguards and security interests.
DISCUSSION AND RECOMMENDATION
8.1 Predicting Nuclear Weapon Effects
The DOE, through the NNSA also in alliance with the DoD, is responsible for guaranteeing the US possesses a safe, secure, and reliable nuclear hindrance. NNSA is responsible for transforming the Nuclear Weapons Complex into a responsive infrastructure that supports specific stockpile requirements and maintains the essential US nuclear capabilities needed for an uncertain global future. In addition, the US nuclear hindrance will transition from one that relies on deployed forces to one that relies more heavily on weapons' capabilities.
NNSA's responsibility is to design, provide, and test nuclear sources for NWE tests. DoD as well as NNSA share responsibilities for several nuclear weapon issues by a memoranda of agreement, including the following:
Hard and deeply buried target defeat - Forecast weapon energy transfer into the terra firma for motley devices and penetration depths, propagation of terra firma shock through complex, heterogeneous geologic media, and response of underground facilities to terra firma shock.
Agent defeat - Forecast thermal along with radiation environments in a chemical or biological agent storage facility, container and agent response to those environments, turbulent agent sweep up additionally mixing within a rising fireball, and the effects of these events on the agent itself.
No ideal air blast - Forecast weapon output into air and propagation of shocks in complex settings and particularly for devices at low yield or non ideal height of burst.
Primary and secondary fire - Forecast fire ignition and spread from nuclear detonations and resultant collateral damage, particularly in urban settings.
Dust cloud, fallout - Forecast transport of bomb and activated target debris to low and high altitudes and the subsequent fallout. Focus on heavily debris-laden plumes, chemical or biological agent-containing plumes, and complex terrain and weather.
Figure 7.0: General vulnerability phenomena and their effects on the reentry body
8.2 Controlling Radiation Hazards
When determining the appropriate controls to put into place, radiation protection professionals must consider ALARA principles and whether the potential exposure is from external or internal sources. Typically, external radiation hazards are present with radioactive materials or radiation generating devices (e.g., x-ray machines) that emit penetrating radiation. Photon (gamma rays and x-rays) and neutron radiation can penetrate and harm the entire body. Beta radiation is considered low penetrating and can cause damage to the skin or lens of the eye. External radiation is typically controlled by minimizing time of exposure, maximizing the distance from the source, and using shielding to reduce exposure rates.
Radiation can also cause harm from internal sources. Radioactive materials can be taken into the body through inhalation, ingestion, absorption through skin, or directly through a wound. Alpha emitters (plutonium and transuranic nuclides) are generally the most harmful internal radiation hazards, often collecting in specific organs/systems and causing localized damage. Internal radiation hazards are controlled by preventing radiation from entering the body through the use of engineered controls and personal protective equipment (PPE).
The NPR balances several important issues and concerns in a reasonable and responsible way. It recognizes the diminished role that nuclear weapons can play in a 21st century environment in the protection of vital US national security interests, while recognizing that nuclear deterrence can and should continue for the US and international security partners. Los Alamos National Laboratory and Stanford University have played a role in these developments, and the implications for the future of the national laboratories and the nuclear weapons complex are profound. The goal of this fellowship was to bring this technical perspective to a more policy-focused environment, expanding upon the knowledge at Stanford's Center for International Security and Cooperation (CISAC) to connect the social and physical sciences addressing national security. For the first, there was a strong desire to focus on technical elements and means on how might nuclear policy, the nuclear stockpile, and the nuclear complex itself be configured to preserve the benefits of deterrence in an environment of further stockpile reductions? The weapons complex as a deterrent component poses many highly technical questions, many of which are the core of my research. Key questions include the timing and capacity of the nuclear weapons complex for reconstitution and the survivability and redundancy of the complex-especially the vulnerability of a capability based deterrent to a first strike. In addition, military deterrence issues must be addressed-particularly the reconstitution of delivery systems and platforms. Historically, most of the weapons in the stockpile were designed to deter the Soviet Union. A shift in US strategy beginning in 1970 resulted in the removal of most tactical nuclear weapons and adoption of a deterrent-rather than war fighting- role. Since arms control agreements have been reached, both Russian and US stockpiles have decreased dramatically. The discovery of how to release nuclear energy was a fact, not a choice, a new understanding of the natural world. It revealed that there was no limit to the amount of energy that might be packaged into small, portable, and relatively inexpensive weapons; that there could be no defense against such weapons, each of which could destroy a city; that therefore a policy of common security in the short run and a program of abolition in the long run would be necessary to accommodate the new reality and avoid disaster. Recoiling from such urgencies, which would require negotiation, compromise, and measure humility, we chose instead to distend ourselves into the largest scorpion in the bottle. Obstinately misreading the failure of our authoritarian counterpart on the other side of the world, to out shame and misfortune, we continue to claim an old and derelict sovereignty that the weapon themselves deny.