The Effects of Nuclear Detonations
A nuclear detonation differs from a conventional explosion in several ways. It produces an immediate large, hot nuclear fireball and air blast wave, prompt nuclear radiation, residual nuclear radiation, thermal radiation, electromagnetic pulse (EMP), interference with communications signals, and – if the fireball interacts with the terrain – ground shock.
Nuclear Fireball. A typical nuclear weapon detonation produces X-rays, which heat the air around the detonation to high temperatures, causing the air to expand and form a large fireball within a small fraction of a second. A 1 kiloton weapon produces an approximately 17-meter radius fireball for an underground burst and a 30 m radius fireball for an air burst, a 10 kt weapon produces a 36 m fireball for an underground burst and a 65 m fireball for an air burst, and a 1 megaton weapon produces a 315 m fireball and a 560 m fireball respectively.
Air Blast. In the case of surface and low air bursts, the fireball expands, immediately pushing air away from the point of the detonation, causing a wall of air to travel at great speed away from the detonation. A 1 kt weapon produces approximately 1 pound per square inch over the nominal air pressure causing shattered windows at approximately 2.2 km, 2 psi over the nominal air pressure causing shattered wood siding panels at 1.3 km, 4 psi of overpressure causing wood frame building collapse at .8 km, 6 psi of overpressure causing shattered concrete walls at .6 km, and 7 - 9 psi causing concrete building collapse at .5 km. A 10 kt weapon produces 1 psi of overpressure causing shattered windows at 4.7 km, 2 psi causing shattered wood siding panels at 2.9 km, 4 psi causing wood frame building collapse at 1.8 km, 6 psi causing shattered concrete walls at 1.3 km, and 7 - 9 psi causing concrete building collapse at 1.1 km. A 1 MT weapon produces 1 psi at 21.6 km, 2 psi at 13.2 km, 4 psi at 8.1 km, 6 psi at 6.1 km, and 7 - 9 psi at 5.1 km.
Ground Shock. Given surface or near surface detonations, the fireball’s expansion and interaction with the ground causes a shock wave to move into the ground in all directions. As a rule of thumb, a 1 kt surface detonation can destroy an underground facility as deep as a few tens of meters, and a 1 MT surface detonation can destroy the same target as deep as a few hundred meters. Only a few meters of penetration into the earth is required to achieve a coupling effect, in which most of the energy that would have gone into the air with a surface burst is trapped by the material near the surface and reflected downward to reinforce the original shock wave. This reinforced shock wave is stronger and can destroy deep underground targets to distances usually two to five times deeper than those destroyed through the employment of a surface burst.
Initial Nuclear Radiation. Nuclear radiation is ionizing radiation emitted by nuclear activity consisting of neutrons and electromagnetic energy in the form of gamma rays. Initially, these radioactive materials are in the fireball. A 1 kt weapon produces a 150 Centi-Gray (cGy) exposure dose causing threshold symptoms – an increased risk for contracting long and mid-term cancers – at 1 km, 450 cGy of exposure causing performance impairment – and is considered the lethal dose for 50 percent of the population (LD50) with medical assistance – at .8 km, 650 cGy causing delayed casualty – and is considered a lethal dose for 95 percent of the population in weeks – at .7 km, and 3,000 cGy causing prompt casualty and death within days at .5 km. A 10 kt weapon produces a 150 cGy of exposure causing threshold symptoms – an increased risk for contracting cancer – at 1.5 km, 450 cGy causing performance impairment and LD50 at 1.3 km, 650 cGy causing delayed casualty – and is considered a lethal dose for 95 percent of the population – at 1.2 km, and 3,000 cGy causing prompt casualty and death at .9 km. A 1 MT weapon produces a 150 cGy of exposure causing threshold symptoms at 2.8 km, 450 cGy causing LD50 at 2.6 km, 650 cGy causing delayed casualty at 2.4 km, and 3,000 cGy causing prompt casualty at 2.1 km.
Residual Nuclear Radiation. Residual nuclear radiation consists of gamma rays emitted from radioactive nuclei. Fallout is the release of small radioactive particles that drop from the fireball to the ground. If the detonation is a true air burst in which the fireball does not interact with the ground or any structure, it rises to become a long-term radioactive cloud, and the cloud travels with the upper atmosphere winds and circles the hemisphere several times – over months – before it dissipates completely. This phenomenon is called worldwide fallout. If the fireball interacts with the ground or any structure, it also includes radioactive material from the ground or structure induced with neutrons. For a true surface burst, a 1 kt detonation would extract thousands of tons of earth into the fireball, but it has no potential to carry thousands of tons of material. Thus – as the fireball rises – it releases radioactive dust, which falls to the ground and produces a radioactive fallout pattern around ground zero and in areas downwind. The radioactivity in this area would be hazardous for weeks and is called early fallout. Induced radiation on the ground is radioactivity caused by neutron absorption, and it takes approximately five to seven days for induced radiation to decay to a safe level. Induced radiation in the air is caused by the production of carbon-14 by nitrogen absorbing neutrons.
Thermal Radiation. Thermal radiation is electromagnetic radiation in the visible light spectrum that can be sensed as heat and light. It can cause burns to exposed skin directly – or indirectly if clothing ignites or an individual is caught in a fire ignited by the heat. A 1 kt weapon causes 1st degree burns affecting the outer layers of skin producing redden or darkened skin and moderate pain at approximately 1 kilometer, 2nd degree burns affecting all layers of skin producing blisters and severe pain at .9 km, and 3rd degree burns affecting tissue under skin producing charred skin and extreme pain at .7 km. A 10 kt weapon causes 1st degree burns affecting the outer layers of skin at 2.8 km, 2nd degree burns affecting all layers of skin at 2.3 km, and 3rddegree burns affecting tissue under skin at 1.7 km. A 1 MT weapon causes 1st degree burns at 19, 2nd degree burns at 13.7 km, and 3rd degree burns at 11.1 km.
Electromagnetic Pulse. EMP is a short duration pulse of low frequency or long wavelength electromagnetic radiation (EMR). Any unprotected equipment with electronic components could be vulnerable to EMP. At low levels, this can cause a processing disruption or a loss of data, but at increased levels, certain electronic components can be destroyed. A surface or low air burst produced local EMP with severe intensity – traveling through the air to distances of hundreds of meters – but electrical lines and telephone wires carry the pulse to possibly 10 km. A high altitude or exo-atmospheric detonation within a certain altitude range generates an EMP that could cover a large region of the Earth’s surface as large as 1,000 km across.
Blackout. Blackout is the interference with radio and radar waves resulting from an ionized region of the atmosphere. A surface or low air burst produces an ionized region of the lower atmosphere that could be as large as tens of kilometers in diameter, and this low altitude ionized region interference would continue for up to a few tens of minutes. A high altitude or exo-atmospheric detonation produces a large, ionized region of the upper atmosphere that could be as large as thousands of kilometers in diameter, and this ionized region interference continues for up to several hours.
Major Variables
The yield of the weapon is one of the most important factors in determining the level of casualties and damage. Other factors include the type and density of target elements near ground zero (GZ), height of burst, terrain or objects in the area that could interfere with various effects moving away from GZ, and weather in the target area. A 1 kt detonation produces severe damage approximately one quarter of a mile from GZ, and within the severe damage zone, almost all buildings collapse and 99 percent of people quickly become fatalities. Moderate damage extends one half mile, and moderate damage includes structural damage to buildings, prompt fatalities, severe injuries, overturned cars and trucks, component damage to electronic devices, downed cellphone towers, and induced radiation at ground level that could remain hazardous for several days. Light damage would extend out 1.5 miles, and light damage includes some prompt fatalities, some severe injuries, and the effects on infrastructure as stated for medium damage. Some fatalities and injuries may occur beyond the light damage zone. A 10 kt detonation produces severe damage effects one half mile from GZ, moderate damage extends one mile, and light damage ranges three miles. A 1 MT detonation produces severe damage beyond two miles from GZ, moderate damage extends beyond four miles, and light damage encompasses beyond 12 miles.