What Are Nuclear Weapons, What Happens When They're Set Off? Russia Declares Nuclear Alert

Russian President Vladimir Putin declared on Sunday that his country's nuclear forces are being placed into special "combat readiness." Despite the heightened state of alert President Biden has opted not to change America's nuclear alert status, The New York Times reported.

Professor at the Harvard Kennedy School and one-time adviser to former President Bill Clinton's Office of Science and Technology Policy, Mathew Bunn, told Vox: "I think there is virtually no chance nuclear weapons are going to be used in the Ukraine situation."

Despite the United States choosing to downplay the threat of a nuclear confrontation, the situation resulted in an increase of online searches for information about nuclear weapons and the potential results of a nuclear blast.

In 2021, the Arms Control Association estimated that the United States had 5,550 nuclear weapons, while Russia had 6,257 nuclear weapons. In both countries around 1,800 of these are retired, while 1,500 are deployed as warheads on ballistic missiles and at U.S. bomber bases.

The weapons of the U.S. and Russia have the potential to kill millions, according to Our World In Data, but the effect of their detonation on agriculture could go on to kill billions.

What Is a Nuclear Weapon?

The Centers for Disease Control and Prevention (CDC) defines a nuclear weapon as a device that uses a nuclear reaction to create an explosion. They can come in the form of bombs dropped by aircraft or missiles that can be launched.

Modern nuclear weapons work by combining chemical explosives, nuclear fission and nuclear fusion, according to the Union of Concerned Scientists.

Fission occurs when the protons and neutrons that make up the nucleus at the heart of an atom are split. This has the result of breaking down large atoms that make up heavy elements into small elements with lighter atoms.

The difference in mass between the heavier atoms—usually plutonium-239 and uranium-235 in nuclear weapons—and the lighter atoms that are created is released as a tremendous amount of energy.

In modern nuclear weapons, this is triggered by chemical explosives placed around a pit of plutonium-239 and uranium-235 with blast directed inwards forcing the atoms of these elements together. Once this reaches a critical mass neutrons are injected triggering a fission chain reaction and a subsequent nuclear blast.

In some weapons, this fission process triggers a further fusion reaction. Fusion is almost the reverse of fission, with smaller atoms forced together to create larger atoms, something that also releases excess energy.

A fusion weapon can create a fireball that can reach several tens of millions of degrees, temperatures similar to those found in the center of the sun according to the Union of Concerned Scientists.

What Happens in a Nuclear Explosion?

The key difference between a nuclear explosion and a conventional explosion is the amount of energy that is released in their detonations. AtomicArchive.com says that the detonation of a large nuclear weapon could be millions of times more powerful than the largest "conventional" detonation.

A large proportion of the energy released in a nuclear blast comes in the form of heat and light. As a consequence, while the main source of destruction for both weapon types is the blast and shock waves they create, the temperatures generated in a nuclear explosion are also vastly greater than those generated in a conventional blast.

This means that a nuclear blast can cause fires and skin burns at great distances from the immediate blast. It is estimated that a one-megaton nuclear weapon with an explosive yield of a million tonnes of TNT would destroy a region of 80 square miles.

The shock and heat of a nuclear blast account for 85 percent of its total expelled energy, with 50 percent blast energy and 35 percent thermal energy.

The remaining 15 percent of a nuclear blast's energy is accounted for by radiation. Five percent of this is released immediately as energetic gamma rays and as neutrons, particles that make up atomic nuclei with protons.

The remaining ten percent comes from delayed nuclear radiation which is released over time from the products created and the residue and debris left behind by a nuclear explosion, AtomicArchive.com says.

What are the Short- and Long-Term Effects of a Nuclear Blast?

The CDC says that the immediate effect of a nuclear blast is felt by people at the blast site, with widespread destruction caused mainly by the blast wave. This destruction spreads to a wider area as fires resulting in burns. Because much of the energy of a blast is released as light, blindness can also result from a nuclear explosion.

As well as causing burns to the skin, which can show immediately or manifest a few days after exposure, radiation resulting from a nuclear blast can cause radiation sickness, or acute radiation syndrome (ARS). The CDC says ARS occurs when a person is exposed to a high dose of radiation which was able to reach internal organs or the entire body was exposed.

Initial symptoms of ARS include nausea, vomiting, headache and diarrhea, but can progress to a seriously ill stage with symptoms like loss of appetite, fatigue, fever, nausea, vomiting, diarrhea and possibly even seizures and coma.

Because of radioactive fallout, particles and gases released by a nuclear explosion can travel for great distances and ARS can be experienced by people far away from the blast zone. This can happen when food or water sources are contaminated with fallout.

The CDC says in the event of potential radiation exposure resulting from a nuclear incident people should head indoors immediately and close and lock all windows and doors. While staying away from walls and windows, all fans and air conditioners should also be shut off.

When coming in from the outside, outer layers should be shed to avoid bringing irradiated materials like dust and debris inside. Uncovered parts of the body should be washed and clean clothing should be put on.

If a person can't get inside immediately, the CDC advises that mouths and noses should be covered to limit the risk of inhaling radioactive material.

Follow the latest updates from Ukraine on our Live Feed here.

Russian President Vladimir Putin speaks during his address to the nation at the Kremlin in Moscow on February 21, 2022. As the fighting continues in Ukraine, Putin has put Russia's nuclear weapons on high alert. ALEXEY NIKOLSKY/GETTY

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