Ground Zero

Offset Distance (Nuclear). The distance the desired ground zero or actual ground zero is offset from the center of an area target or from a point target... 

Experiments with explosives have demonstrated16 that the overpressure can be estimated using an equivalent mass of TNT, denoted mTNT, and the distance from the ground-zero point of the explosion, denoted r. The empirically derived scaling law is... 

Fallout Radioactive material that falls back to earth after a nuclear explosion. Contains highly radioactive materials from the original weapon, vaporized material from ground zero, and other materials pulled into the mushroom cloud. The amount of fallout and spread of radioactivity depends on weapon yield and meteorological conditions. 

Ground zero Location of a nuclear explosion. Exact location may be in the air (using a bomb or missile) or underground but is assumed in this text to be detonated on the ground, where it will do the most damage. 

Mushroom cloud Giant mushroom-shaped cloud extending from ground zero well into the atmosphere initially contains an immense fireball and highly... 

Note Actual fallout ranges depend on local meteorological conditions. Fallout direction relative to ground zero can be highly variable. 

The second column of Table 5.1 presents the radius of complete destruction following a nuclear explosion. It is assumed that an individual within this radius will not survive. If an individual near ground zero lives through the massive destructive power of the nuclear explosion, he will likely succumb to the intense heat and radiation. Table 5.2 supplements Table 5.1 and lists various levels of destruction, ranging from... 

Level of Destruction versus Distance from Ground Zero ... 

The third column of Table 5.1 presents the radius of 50% mortality from the air blast of a nuclear weapon. The blast (or shock wave) travels in all directions from ground zero at approximately the speed of sound. The blast alone can be fatal, but the risk of serious injury or fatality increases significantly because the shock wave picks up any materials in its path (e.g., shards of glass, metal, etc.). At the speed of sound, the air blast plus flying shrapnel travels at a speed of about 1 mile every 5 seconds. Thus, an individual 5 miles from ground zero has about 25 seconds to take cover before the air blast arrives. The same air blast speed applies to almost any size nuclear weapon.2 The risk of injury from the blast drops with increased distance from ground zero. 

The fourth column presents the radius of 50% mortality by thermal burns. The fireball from a nuclear explosion can reach temperatures in the tens of millions of degrees Fahrenheit and cause thermal burns at large distances. This intense heat can also cause temporary or permanent blindness and can ignite materials far from ground zero. Heat from the fireball will be felt instantly in all directions from ground zero thus, the longer a person remains out in the open, the more intense the thermal burns will be. However, the heat from the fireball lasts only several seconds and can be shielded by solid materials like brick and earth (e.g., behind a wall or hill, in a ditch or subway tunnel, etc.). The risk of thermal burns drops with increased distance from ground zero. 

The final column presents the radius of 50% mortality from fallout 1 hour after the explosion. Of all of the threats described, fallout is the hardest to predict because of the influence of local, regional, or even global weather patterns. The mushroom cloud can rise into the atmosphere as far as 80,000 feet, where wind and rain influence the time and location for fallout to occur.2 Individuals several miles from ground zero and well outside any radius presented in Table 5.1 can receive significant or even lethal radiation doses from fallout. However, while the air blast, thermal burns, and initial radiation are threats in all directions, fallout is a threat downwind from ground zero. Wind speed and direction vary at different altitudes, and it is safest to assume that fallout is a potential threat in all directions from ground zero. Individuals outside the blast zone generally will have several minutes to an hour or more to seek shelter before fallout arrives. 

Time is precious for anyone within a few miles of ground zero. Such individuals have no time to watch the mushroom cloud, gather personal items, calculate the distance from ground zero, or estimate the weapon s yield. As a general rule, if an individual can see a mushroom cloud, he is exposed to the initial radiation and heat. 

An individual located well away from ground zero may be tempted to flee the area a few minutes after the explosion (refer to Tables 5.1 and 5.2 for relative distances) because it could take several minutes to an hour or more for the fallout to arrive downwind. However, the last place to be when fallout arrives is trapped in the open or in a traffic jam. Everyone else may try to escape too, and that will create traffic congestion. Staying in a designated or even a makeshift shelter is better than being stranded in an open area where chances of survival are severely diminished. Regardless of location relative to ground zero, the best procedure is to stay in a protected shelter until authorities confirm it is safe to evacuate. 

The average individual can do little in the short term to help the victims of a nuclear explosion. In fact, people who move toward ground zero in an effort to help can become victims and thus make a terrible situation even worse. The fewer people who must be rescued, the more effective emergency responders will be. 

In summary, individuals within the light destruction radius should seek longterm shelter as soon as possible. Individuals further from ground zero have some time to gather resources and to build up additional radiation shielding. In all cases, individuals should plan to stay in their shelters as long as 14 days or until authorities confirm it is safe to evacuate. 

Samples with highest concentrations, August 1964 Bi, sediments Ce, marine algae Cs, land invertebrates Co, sediments °Co, marine invertebrates Mn, sediments ° Ru, sediments Sb, groundwater Seawater, 1972, Fe Sediments 1958 vs. 1972, Fe August 1964, ground zero... 

James M. Barquest, Ground Zero Pharmaceuticals, Inc., Irvine, California, Role of Quality Systems and Audits in Pharmaceutical Manufacturing Environment... 

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