TYPES OF NUCLEAR WEAPONS AND THEIR EFFECTS

Given the fragile state of affairs on the Korean peninsula, fears of a nuclear incident are higher than at any time since the Cold War. With good reason, most people associate use of nuclear weapons with devastating outcomes. Few, however, know much about the different types and their actual effects.

(by the way, It’s pronounced “noo-clee-ar”, not “noo-cu-lar”)

TYPES OF NUCLEAR WEAPONS

Until the recent missile launches by North Korea, most people were concerned about the use of “dirty bombs“ by terrorists. A dirty bomb is not technically a nuclear weapon. It uses conventional explosives to disperse radioactive material in the general area. Usually, the effect of the explosion causes more damage and casualties than the radioactive elements.

Our concept of an “atomic bomb“ as developed by the Manhattan Project in the 1940s is one that uses “nuclear fission”. The explosion is caused by a chain reaction that splits atomic nuclei. The result is a wave of intense heat, light, pressure, and kinetic energy equaling thousands of tons (also called kilotons) of TNT. This is followed by the release of radioactive particles in a cloud that resembles a mushroom (if a ground blast). Mixed with dirt and debris, the particles fall back to Earth, contaminating crops, animals, and people. This will happen in the area of the detonation, but will also be blown elsewhere by the prevailing winds.

Atomic bombs gave way to hydrogen bombs, which are best described as “thermonuclear” weapons due to the generation of extreme heat during detonation. H-Bombs use a process known as nuclear fusion, which takes two light nuclei and forms a heavier one, using variations of hydrogen atoms called “isotopes”. This fusion process requires high temperatures and usually involves a fission reaction as discussed above to initiate. H-Bombs don’t just generate power in the kilotons; they can reach levels in the megatons (millions of tons) of TNT.

Another type of thermonuclear weapon is the “neutron bomb“, which generates much less kinetic energy and thermal damage, but much more radiation. Enhanced radiation weapons like the neutron bomb generate a fusion reaction that allows neutrons to escape the weapon with only a limited blast. Originally designed by the United States to counter massive Soviet tank formations, the neutron bomb is an example of a tactical nuclear weapon. The effect is to leave infrastructure mostly intact while wiping out human targets due to massive radiation.

DAMAGE CAUSED BY A NUCLEAR ATTACK

The impact of a nuclear bomb is dependent on its “yield”, a measure of the amount of energy produced. The Hiroshima A-Bomb had a yield of 15 kilotons, while the “Tsar Bomba” detonated by the Russians in 1961 had a yield of 51 megatons (51,000 kilotons!). Most of the weapons stockpile of the U.S. and Russia consist of bombs in the 100 to 500 kiloton range, much stronger than Hiroshima and much weaker than Tsar Bomba. This is because they are meant to be fired at major cities in clusters rather than one large bomb, which would be easier to intercept than, say, 20 smaller ones.

Damage is caused by:

• Blast effects (kinetic energy) – damage due to the explosion and resulting shock wave
• Heat (thermal energy) – damage generated by extreme heat
• Radiation (initially and later via fallout) – both local and, later, far-reaching
• Electromagnetic pulses (EMPs) – disrupts telecommunications, infrastructure

You can expect a generally circular pattern of local damage, but various factors come into play besides the yield of the weapon. The altitude of the explosion, weather, wind conditions, and nearby geologic features play a role. The U.S. government estimates the distribution of damage for fission bombs to be distributed in the following manner:

• 50% shockwave
• 35% heat
• 5% initial blast radiation
• 10% fallout radiation

(Note: I don’t have the data in front of me, but it stands to reason that H-bombs would likely cause a higher percentage of heat damage while Neutron bombs would cause more radiation damage than the above model for a standard fission bomb.)

The atom bomb dropped on Hiroshima in 1945 flattened buildings over a roughly 4 square mile area and killed 60,000 people immediately. Another 90,000-140,000 succumbed later to injuries and radiation exposure. Although this represents a total of 150,000 to 200,000 fatalities, the entire population did not perish. At the time of the explosion, there were about 350,000 people in Hiroshima, including 43,000 soldiers. This shows that, although horrific in its effects, that distance from ground zero and other factors play a role in a nuclear weapon’s lethality, as does the power of the bomb itself.

A 50 megaton H-Bomb like the Russian “Tsar Bomba“, however, would cause a much larger circle of devastation than the Hiroshima bomb, with widespread fatalities at least 20 miles from ground zero and third-degree burns 50 miles away. Windows were reported shattered from the test detonation as far away as Norway and Finland.

You might think there isn’t anything you can do in a nuclear attack, and if you’re at ground zero at the moment of detonation, you’re right. But your chances of survival, given some time, distance, and protection, may be better than you think. Well talk about’ what you can do to increase your chances of survival in future articles.

Joe Alton MD

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