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How Does A Nuclear Bomb Work?

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Nature has got millions of secrets in even the smallest and unimaginable things existing in the universe and scientists revealed many of them in the initial years of the twentieth century. Many of these ground breaking discoveries were made in Physics after the remarkable contribution of Albert Einstein who is famous for his Theory of Relativity published in 1905. This theory directed the process leading to the creation of the Atomic bomb.

When Einstein published this theory, he demanded that there should be no attempt to create a weapon out of it. But after his death, the US started the top secret Manhattan Project, responsible for the creation of the Atomic Bomb. Lets see how the bomb works?


Basically, a nuclear bomb is made by using radioactive elements Uranium and Plutonium. The word radioactive means that the atoms in the elements are unstable and therefore they release energy. Atoms of elements consist of a nucleus and an electron, which revolves around it.

A Nuclear bomb explodes when the energy inside the nucleus of a radioactive atom is released. There are two types of processes in which energy can be released.

  • Nuclear Fission
  • Nuclear Fusion

The nucleus contains two sub-atomic particles, Protons and Neutrons. In Fission, the reaction occurs when a free Neutron strikes the nucleus of the atom and then it breaks down releasing a huge amount of energy. While in Fusion, atoms of hydrogen fuse together to form an atom of Helium and thus huge amount of energy. This is how the sun works.


Nuclear fission

In Nuclear fission, highly enriched Uranium and Plutonium are used. Their scientific names are U-235 and Plutonium239. Literally, fission means splitting of heavy nucleus in which energy is released as a reaction, but the inside of fission is quite complicated and can be only understood by people who are studying Physics. I will try to make the context simple and comprehensible. In nuclear fission, there are two types of processes:

  • Gun-triggered
  • Implosion

Gun-triggered fission

A gun-triggered fission process is a process in which highly enriched Uranium is used. Enrichment process is done in highly sophisticated devices and the radioactivity in increased. Initially, the atomic number of Uranium is 232 but after enrichment it becomes 235.

In such a bomb design, there are two different types of Uranium objects. First one is the Subcritical Mass, a mass used to start a gun-triggered fission reaction, containing Neutrons; and the second is the Supercritical Mass, the mass containing the fuel for the explosion, which contains the highly enriched uranium. The Tamper is a coating to prevent loss of energy stored inside the highly enriched Uranium and is made of Uranium-232. The bomb explodes through the following process:

  • The Trigger receives the signal to shoot the bullet (Subcritical Mass)
  • The bullet shoots and strikes the Supercritical Mass
  • The core expands exerting pressure on the Tamper.
  • The Tamper starts expansion
  • Expansion stops and pressure is exerted on the core.
  • Fission takes place
  • The bomb explodes

This process sounds very long but, believe it or not, the complete process takes just an 100th part of a second. This process shown through the picture was used in older nuclear devices, but nowadays it's modified and is more sophisticated. This is how Little Boy, the bomb dropped on Hiroshima exploded, releasing an energy equivalent to 15 Kilotons; i.e. 15,000 kg of TNT and only 15 kg of Uranium was used.


Early in the Manhattan Project, secret US programme to develop the atomic bomb, scientists working on the project recognized that compressing the subcritical masses together into a sphere by implosion might be a good way to make a supercritical mass. There were several problems with this idea, particularly how to control and direct the shock wave across the sphere. But the Manhattan Project team solved the problems. The implosion device consisted of a sphere of uranium-235 (tamper) and a plutonium-239 core surrounded by high explosives. When the bomb was detonated, this is what happened:

  • The explosives fired, creating a shock wave.
  • The shock wave exerted pressure on the Tamper
  • The tamper started expansion
  • Expansion stopped exerting pressure on the core
  • The fission reaction began.
  • The bomb exploded.

Fat Man was this type of bomb and had a 23-kiloton yield (power). These bombs exploded in fractions of a second. The fission usually occurred in 560 billionths of a second.

In a later modification of the implosion-triggered design, here is what happens:

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  • The explosives fire, creating a shock wave.
  • The shock wave propels the plutonium pieces together into a sphere.
  • The plutonium pieces strike a pellet of beryllium/polonium at the centre.
  • The fission reaction begins.
  • The bomb explodes.

Nuclear fusion

This process is highly complicated and destructive. The bomb designed through this technique is known as a thermonuclear device as it involves both Fission and Fusion. But this fusion reaction involves other types of fuels known as Deuterium and Tritium. Fission bombs worked, but they weren't very efficient. Fusion bombs have higher kiloton yields and greater efficiencies than fission bombs.

To understand this bomb design, imagine that within a bomb casing you have an implosion fission bomb and a cylinder casing of uranium-238 (tamper). Within the tamper is the lithium deuteride (fuel made by deuterium) and a hollow rod of plutonium-239 in the centre of the cylinder. Separating the cylinder from the implosion bomb is a shield of uranium-238 and plastic foam that fills the remaining spaces in the bomb casing. Detonation of the bomb causes the following events:

  1. The fission bomb implodes, giving off X-rays.
  2. These X-rays heat the inside of the bomb and the tamper; the shield prevented premature detonation of the fuel.
  3. The heat causes the tamper to expand and burn away, exerting pressure against the lithium deuterates.
  4. The lithium deuterate is squeezed.
  5. The compression shock waves start fission in the plutonium rod.
  6. The fissioning rod give off radiation, heat and neutrons.
  7. The neutrons goes into the lithium deuterate, with the lithium and make tritium.
  8. The combination of high temperature and pressure are sufficient for tritium-deuterium and deuterium-deuterium fusion reactions to occur, producing more heat, radiation and neutrons.
  9. The neutrons from the fusion reactions produced fission in the uranium-238 pieces from the tamper and shield.
  10. Fission of the tamper and shield pieces produce even more radiation and heat.
  11. The bomb explodes.

All of these events happen in about 600 billionths of a second (550 billionths of a second for the fission bomb implosion, 50 billionths of a second for the fusion events). The result is an immense explosion that is more than 700 times greater than the Little Boy explosion: It has a 10,000-kiloton yield.


Modern nuclear techniques

Nowadays, nuclear warheads are fitted inside a ballistic missile or they're simply dropped off a bomber. But these bombs are so destructive that they can easily destroy the world. The explosion would not only give off heat and radiation, but a long-term problem would occur.

As the bombs would explode, they would produce dust clouds and gases in the atmosphere and will form a thick layer. Eventually they would block sunlight reaching the earth surface and the planet would become frozen and this would cause mass extinction. This theory is known as the Global Glaciating Theory. It is believed that the mass extinction of dinosaurs happened because of a meteoroid striking the Earth. Nuclear bombs are deadly and they should be dismantled or some day it might get into wrong hands.


Author on May 07, 2012:

You have no idea what you are talking about.

ben on May 06, 2012:

thanks it really helped

talon on April 18, 2012:

this information was very useful but you cant have a super critical mass to start with they collide two subcritical masses one bigger than the other but if you have a preset supercritical mass then it would explode the second it became a supercritical mass but i don't blame u A lot of people get that wrong

mel on April 10, 2012:

world leaders have enough nuclearwepons to distroy the world when are they going to learn once these weapons are used in a war etc they don't need them the nextday because there will not be one so why do they still need the need to increase there weapons

A bad good boy on March 17, 2012:

Einstein finished his one man journey in research in 1955

still we have no one person = Einstein ?

My answer is : we have

every one have n number of einsteins in mind but the problem is if some one try to show his one small invention then others try to suppress and they will give one good name "fool".

Keep it up your own explanation and you don't bother about the issues

kate on March 09, 2012:

what is hubpages stand for

lonewolf on March 09, 2012:

a government scientist used einsteins theory, he made machines, made a nuclear bomb. thank you ralph bergstresser for making nuclear bombs,called the manhatten project.also ralph did phillydelpha experiment.the men on the ship,were sent 300 miles back in time and when they were bought back,they were yelling, imped into the ships wood and could not get out.

nutrition on February 27, 2012:

i used this for my writing to obama

notorious on February 15, 2012:

in the wrong hands, which country have used it? It has always been in the wrong hands

Shyam sharma on January 01, 2012:

Gr8 it was so easy to understanding

kushwar S.Rawat on December 30, 2011:

yes it is very useful for energy but war is very painful

rahul on December 23, 2011:

i like it so much

giridhar on December 12, 2011:

It's nice.Very interesting and usefui

Moses teka on December 11, 2011:

I wold like to 10q for this material

Vigneshwaran on December 02, 2011:

mass convert to energy atom bomb proves that then what about energy convert to mass i think accelerators doing the job can any tell me the answer

john mark mores on November 17, 2011:

have a nice work

pppeeeaaaccceee on November 12, 2011:

Nukes are an extremly volatile weapon therefore i would not recommend small children play with them, let them play with plastic explosive, its like playdow

smurf on November 08, 2011:

gee for simple tearms this is soooooo hard to understand..... dictionary here i come!!!!

meh on October 16, 2011:

if you got a problem... nuke it!!!!!

Unknown on October 09, 2011:

Tom, you're wrong. Einsteins formula E=mc2 does relate to the a bomb, which corresponds to the h bomb as well, considering the h bomb was somewhat derived from the a bombs research. WHAT NAOW, YOU MAD?

hassam (author) from Pakistan on September 29, 2011:

Hi, Tom I welcome your criticisms but may be it is you who are taking my statements in a different way, I mean to show no arrogance in my articles. My articles are meant for students or learners who could understand the very basics of technology and science.

Obviously such complex sciences are not easy to understand as scientists devote their lives in trying to develop such sciences and Engineers implement it in a practical form we could put to some use.

Even I consider myself a learner not an expert in any subject as there is always something to learn, even from my readers who could be better in a subject in which I may have lesser knowledge.

And I don't know where you saw my article biased, even if it is, I must say every author has a view point which is reflected in his work.

Tom on September 29, 2011:

Einstein's Theory of Relativity had nothing to do with the creation of nuclear weapons. It argued for the relativity of all observations and the absolute value of the speed of light (the only thing being the same for all observers). And E=MC2 simply describes the relationship of energy to mass.

Also, your statement, "but the inside of fission is quite complicated and can be only understood by people who are studying Physics," reflects an arrogance common in certain cultural backgrounds and is intended to let the peons know they should keep their mouths shut and let the grown-ups (experts) make the important decisions. Anytime anyone tells me I CAN'T understand something, that I must defer to the "experts", that gets my hackles up!

I don't know if you actually feel this way, but your language implies you do.

Never condescend to your readers.

We're smarter than you think in subjects you might know next to nothing about (like history, as your errors make clear).

Also, this is a science article. Please try to keep your personal biases out of it.

jo on September 17, 2011:

bombing i don't like sorry

hero of war on September 11, 2011:

you hippie with your mother earth crap go shove a crack pipe down ur throat i know a book that's just right for you read tom clancy rainbow six skip to the end there is a whole group of naturalist extremeists that try and fix the world by using bio weapons so fu you are no different from the rest of humanity.......... good info niceley done and presented i didn't know about the implosion one nice good info i rate 4/5 p.s. the hippie thing was aimed at mother earth boy a few posts up lol :P

I am sick with ratio activeity on September 08, 2011:

This explanes fall out the video game you may want to cheak out fall out three you want to see a nuke go of go to megton and arm the bomb to explode than go to tpenny tower and go to the top press the button ha hah ha

ramakant on August 09, 2011:

there is no need to make nuclear weapons for protection against our earthbeings.Nuclear energy should be use to give benefit human beyond of boundaries not for killing them.

Zach Barnica on February 10, 2011:

very interesting reading material. really helped thank you.

Arjun babita from attractive on February 09, 2011:

nice, it`s very useful

praisy on January 26, 2011:

what do u meant for tamper

iyyanar on January 24, 2011:

even a good invention like nuclear and radioactivity will be used by wrong persons like hitler and many terrorists.

surya on January 24, 2011:

there are two infinite things in the world they are universe and human dirty imaginations like hitler does.

Apoorv on January 08, 2011:

Bombs.....wrecks the mother Earth and humanity from stratosphere to seafloor

Joe Buddrick on October 08, 2010:

man kind must end war or it will end man kind

jumper on October 05, 2010:

war is bad (a blond comment)

base on August 17, 2010:

it was a bad idea to make one because if a person gets it and launches it in the place you are your done

Michael Fischer on July 04, 2010:

you state that the manhattan project started after the death of einstein.this is false.he died in 1955 !

Derek1 on June 15, 2010:

Nice Hub. A lot of good info here.

Daniel on February 06, 2010:

Hi Buddy, how is raw uranium ore converted into enriched uranium? What process go into it.

Leah on September 21, 2009:

Thanks, it really helped

Rod on September 04, 2008:

Gun - triggered fission

The small and large masses of uranium are BOTH subcritical

A supercritical mass EXPLODES

The small mass is fired into the large mass to quicklyf form a SUPERCRITICAL mass which then EXPLODES

Rod on September 04, 2008:

Einstein died in 1955. The manhattan project wasstarted in June 1942. Atomic bombs used against enemy targets on 6 August 1945 and 9 August 1945. Einstein was still alive!

rb11 from Las Vegas on July 23, 2008:

For such a destructive device they end up making a pretty picture.

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