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Lest We Forget: The Health and Environmental Effects of Nuclear Weapons

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Lest We Forget: The Health and Environmental Effects of Nuclear Weapons
Section 5.0 Effects of Nuclear Explosions

Nuclear explosions produce both immediate and delayed destructive effects. Immediate effects (blast, thermal radiation, prompt ionizing radiation) are produced and cause significant destruction within seconds or minutes of a nuclear detonation. The delayed effects (radioactive fallout and other possible environmental effects) inflict damage over an extended period ranging from hours to centuries, and can cause adverse effects in locations very distant from the site of the detonation. These two classes of effects are treated in separate subsections.


In the Hiroshima attack (bomb yield approx. 15 kt) casualties (including fatalities) were seen from all three causes. Burns (including those caused by the ensuing fire storm) were the most prevalent serious injury (two thirds of those who died the first day were burned), and occurred at the greatest range. Blast and burn injuries were both found in 60-70% of all survivors. People close enough to suffer significant radiation illness were well inside the lethal effects radius for blast and flash burns, as a result only 30% of injured survivors showed radiation illness. Many of these people were sheltered from burns and blast and thus escaped their main effects. Even so, most victims with radiation illness also had blast injuries or burns as well.

With yields in the range of hundreds of kilotons or greater (typical for strategic warheads) immediate radiation injury becomes insignificant. Dangerous radiation levels only exist so close to the explosion that surviving the blast is impossible. On the other hand, fatal burns can be inflicted well beyond the range of substantial blast damage. A 20 megaton bomb can cause potentially fatal third degree burns at a range of 40 km, where the blast can do little more than break windows and cause superficial cuts.


An explosion closer to the ground (close enough for the fireball to touch) sucks large amounts of dirt into the fireball. The dirt usually does not vaporize, and if it does, there is so much of it that it forms large particles. The radioactive isotopes are deposited on soil particles, which can fall quickly to earth. Fallout is deposited over a time span of minutes to days, creating downwind contamination both nearby and thousands of kilometers away. The most intense radiation is created by nearby fallout, because it is more densely deposited, and because short-lived isotopes haven't decayed yet. Weather conditions can affect this considerably of course. In particular, rainfall can "rain out" fallout to create very intense localized concentrations. Both external exposure to penetrating radiation, and internal exposure (ingestion of radioactive material) pose serious health risks.


Effects of Nuclear Weapons and Nuclear War


Figure 2.15. The mushroom cloud formed in a nuclear explosion in the megaton energy range, photographed from an altitude of 12,000 feet at a distance of about 50 miles.

2.16 The dimensions of the stabilized cloud formed in a nuclear explosion depend on the meteorological conditions, which vary with time and place. Approximate average values of cloud height and radius (at about 10 minutes after the explosion), attained in land surface or low air bursts, for conditions most likely to be encountered in the continental United States, are given in Fig. 2.16 as a function of the energy yield of the explosion. The flattening of the height curve in the range of about 20- to 100-kilotons TNT equivalent is due to the effect of the tropopause in slowing down the cloud rise. For yields below about 15 kilotons the heights indicated are distances above the burst point but for higher yields the values are above sea level. For land surface bursts, the maximum cloud height is somewhat less than given by Fig. 2.16 because of the mass of dirt and debris carried aloft by the explosion.

2.17 For yields below about 20 kilotons, the radius of the stem of the mushroom cloud is about half the cloud radius. With increasing yield, however, the ratio of these dimensions decreases, and for yields in the megaton range the stem may be only one-fifth to one-tenth as wide as the cloud. For clouds which do not penetrate the tropopause the base of the mushroom head is, very roughly, at about one-half the altitude of the top. For higher yields, the broad base will probably be in the vicinity of the tropopause. There is a change in cloud shape in going from the kiloton to the megaton range. A typical cloud from a 10-kiloton air burst would reach a height of 19,000 feet with the base at about 10,000 feet; the horizontal dimensions would also be roughly 10,000 feet. For an explosion in the megaton range, however, the horizontal dimensions are greater than the total height (cf. Fig. 2.16)




The details of the actual fallout pattern depend on wind speed and direction and on the terrain. The fallout will contain about 60 percent of the total radioactivity. The largest particles will fall within a short distance of ground zero. Smaller particles will require many hours to return to earth and may be carried hundreds of miles. This means that a surface burst can produce serious contamination far from the point of detonation.

This map shows the total dose contours from early fallout from a surface burst of a 1-megaton fission yield.

From the 15-megaton thermonuclear device tested at Bikini Atoll on March 1, 1954 - the BRAVO shot of Operation CASTLE - the fallout caused substantial contamination over an area of more than 7,000 square miles. The contaminated region was roughly cigar-shaped and extended more than 20 miles upwind and over 350 miles downwind.

Fallout can also enter into the stratosphere. In this stable region, radioactive particles can remain from 1 to 3 years before returning to the surface.


Nuclear Weapon Effects Calculator

This interactive tool is intended to give an idea of the devastating blast effects of ground-level, shallow subsurface, and low-altitude nuclear weapon detonations. It is relevant to traditional nuclear weapons, potential terrorist attacks, and next generation nuclear weapons such as "Bunker Busters" or "Robust Nuclear Earth Penetrators" (RNEPs). (Despite the name, "Earth Penetrators" will not penetrate far into hard rock and can be considered "surface" bursts when using the bomb calculator.)

High definition aerial maps of selected U.S. cities have been provided. The size of the bomb can be chosen by selecting the weapon's yield, as measured in kilotons (KT) or megatons (MT) of TNT equivalent. There is also the option of having the bomb delivered using an automobile at ground level or using an aircraft flying at an altitude that produces the widest area of destruction.


Effects of Nuclear Earth-Penetrator and Other Weapons

Committee on the Effects of Nuclear Earth-Penetrator and Other Weapons, National Research Council
Authoring Organizations

Underground facilities are used extensively by many nations to conceal and protect strategic military functions and weapons stockpiles. Because of their depth and hardened status, however, many of these strategic hard and deeply buried targets could only be...

<Read More>

The Nuclear Winter: by Carl Sagan

Except for fools and madmen, everyone knows that nuclear war would he an unprecedented human catastrophe. A more or less typical strategic warhead has a yield of 2 megatons, the explosive equivalent of 2 million tons of TNT. But 2 million tons of TNT is about the same as all the bombs exploded in World War II -- a single bomb with the explosive power of the entire Second World War but compressed into a few seconds of time and an area 30 or 40 miles across

In a 2-megaton explosion over a fairly large city, buildings would be vaporized, people reduced to atoms and shadows, outlying structures blown down like matchsticks and raging fires ignited. And if the bomb were exploded on the ground, an enormous crater, like those that can be seen through a telescope on the surface of the Moon, would be all that remained where midtown once had been. There are now more than 50,000 nuclear weapons, more than 13,000 megatons of yield, deployed in the arsenals of the United States and the Soviet Union -- enough to obliterate a million Hiroshimas.

But there are fewer than 3000 cities on the Earth with populations of 100,000 or more. You cannot find anything like a million Hiroshimas to obliterate. Prime military and industrial targets that are far from cities are comparatively rare. Thus, there are vastly more nuclear weapons than are needed for any plausible deterrence of a potential adversary.

Nobody knows, of course, how many megatons would be exploded in a real nuclear war. There are some who think that a nuclear war can be "contained," bottled up before it runs away to involve much of the world's arsenals. But a number of detailed analyses, war games run by the U.S. Department of Defense, and official Soviet pronouncements all indicate that this containment may be too much to hope for: Once the bombs begin exploding, communications failures, disorganization, fear, the necessity of making in minutes decisions affecting the fates of millions, and the immense psychological burden of knowing that your own loved ones may already have been destroyed are likely to result in a nuclear paroxysm. Many investigations, including a number of studies for the U.S. government, envision the explosion of 5,000 to 10,000 megatons -- the detonation of tens of thousands of nuclear weapons that now sit quietly, inconspicuously, in missile silos, submarines and long-range bombers, faithful servants awaiting orders.


Medical Consequences of Nuclear War

Our understanding of the potential human devastation of a single nuclear explosion is rooted in the terrible experience of Japanese citizens in Hiroshima and Nagasaki. But the weapons used in 1945 were tiny in comparison to most of the tens of thousands of warheads that will remain in today's nuclear arsenals even if all of the START and 1991/1992 initiatives to reduce the superpowers' nuclear arsenals are fulfilled. A single modern weapon, exploded either intentionally or accidentally over a large city, is capable of slaughtering more than one million people. If a larger number of weapons are exploded in warfare, the overall consequences will include not only short- and medium-term medical injuries but also severe environmental effects, disruption of transportation and the delivery of food, fuel, and basic medical supplies, and possible famine and mass starvation on a global level.

According to a summary of the 1986 Report on the Medical Implications of Nuclear War, published by the Institute of Medicine of the U.S. National Academy of Sciences, "Each successive study of the possible human destruction that would result from a nuclear war -- either a limited exchange (were that possible) or a total exchange of existing stockpiles -- draws a grimmer conclusion about what the human costs would be. Instead of speculating that the casualties might amount to only a few tens of millions, recent studies have indicated that the casualties are more likely to number a billion or more, and even the survival of human beings on earth has been questioned."

The following descriptions summarize only the immediate injuries resulting from a single explosion of a one-megaton warhead detonated on the ground -- the equivalent of 1,000,000 tons of TNT, but less than 1/8000 of the destructive force that will remain after all current arms reduction plans are implemented. The immediate human casualties stem from three different sources of injury: the blast effects of the explosion itself; the burns resulting both from direct exposure to the intense heat generated by the explosion and from the resulting massive fires; and the radiation released by a nuclear detonation, delivered in the form of fallout of radioactive material downwind from the explosion itself. The most important factor in predicting most of these injuries is the distance of human beings from the explosion itself, although other factors including the weather may be critical (on a rainy day the moist atmosphere will absorb more of the heat energy released by the explosion, and burn injuries may be reduced).

To estimate the effects of a nuclear explosion in your own city or town, take any map, pick a location at which the nuclear detonation might take place, and draw four concentric circles, with a radius of 1.5 km, 5 km, 10 km, and 20 km respectively. The summary below describes the nature of the destruction and injuries that will rake place within each of those circles.


Radiological Dispersion Weapons: Health, Social, and Environmental Effects


Perhaps the simplest and least expensive way for a terrorist group to use radiation as a weapon would be to acquire fissile materials, ranging from weapon-grade plutonium to spent nuclear fuel from a civilian power plant, and to disperse them over a populated area with a conventional explosive device. Such radiological dispersal weapons, which are far easier to produce than fission or fusion bombs, would cause less destruction and fewer immediate casualties than an actual nuclear weapon, but would nevertheless result in long-term health and environmental damage and could cause incalculable social and economic disruption.

Radiological weapons, with the controversial exception of depleted uranium weapons used by the US in the 1991 Gulf war and again in the1999 Balkans war, have not been deployed or used in conflict for both practical and ethical reasons. They have never yet been used deliberately to cause harm by irradiating a population or an environment. In terrorist hands, the objective would not be military advantage but the damage and panic that would result from the dispersal of radioactive materials in a highly populated area. Even a small radiological weapon could contaminate a large urban area, would increase the cancer danger to the affected population, and would have a psychological impact far exceeding the one we have witnessed during the recent anthrax scares.

The actual effects of radiological weapons would depend on several factors:

*the types and amounts of isotopes dispersed;
*environmental conditions such as season, temperature inversions, humidity, and prevailing winds;
*the size and population density of the affected area.

In 1996, IPPNW commissioned a study of the effects of a crude plutonium dispersal weapon (35 kilograms of radiological material) detonated in a major population center, comparable in size and density to London, using a sophisticated computer model (COSYMA) that could account for variations in all of the above factors. (It should be noted that there are other radionuclides more readily available than plutonium, with far greater radioactivity per unit weight and much greater physical health hazards due to either penetrating gamma radiation and/or mobility in the environment.) The results, presented within generally accepted dose standards established by the International Council for Radiological Protection (ICRP), were sobering.




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