Nuclear Weapon Factsheet and FAQ

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A nuke is complex. It’s rocket science and nuclear physics all rolled up into one. But we don’t need to be Einstein. What really matters can be understood by everyone.


What was the size of the blast range at Hiroshima and Nagasaki?

For both Hiroshima and Nagasaki everything was destroyed up to 3 miles away. Glass broke as far as 12 miles.

How many people were in Hiroshima and Nagasaki when the bombs dropped?

350,000 lived in Hiroshima – 90% were civilians. 240,000 lived in Nagasaki, nearly all of them civilians.

How many died at Hiroshima and Nagasaki?

By the end of 1945, there were 140,000 dead in Hiroshima and 73,884 in Nagasaki.

Since 1945, the United Nations report a further 400,000 deaths as a result of the bombs.

Are there any photos just after the explosions?

Yoshito Matsushige took a photo of the mushroom cloud 2 minutes after the bomb at Hiroshima. He then went into the city and took five more photos of the immediate aftermath. These are the only known photos taken that day at ground level.

Yosuke Yamahata entered Nagasaki the day after the bomb. He took around a hundred photos over about twelve hours – the only record of the immediate aftermath of an atom bomb.

See also: (with detailed explanations) and

Nuclear Weapons

How does a nuclear weapon (nuke) work?

There are two types: atomic bombs (A-bombs) and hydrogen bombs (H-bombs). H-bombs can be a thousand times more powerful than A-bombs.

A-bombs work by splitting atoms. Each time an atom splits, power is released, and more atoms are split. These all combine to create an atomic explosion.

The H-bomb is an A-bomb plus hydrogen. The heat from the A-bomb forces hydrogen atoms to fuse. This fusing gives out extra power.

What’s the difference between a missile and a warhead?

The missile is a rocket attached to the warhead. The warhead is the part which explodes.

The word ‘missile’ is sometimes used to describe both the rocket and warhead.

What’s the difference between plutonium and uranium?

Plutonium is more reactive than uranium, so you need less of it to make a bomb.

What’s the difference between plutonium and uranium bombs?

The Hiroshima bomb used uranium, Nagasaki used plutonium. The explosions were about the same. Just different designs.

When a uranium bomb explodes, a small piece of uranium is fired into a bigger piece. When a plutonium bomb explodes, the plutonium metal is compressed and made denser.

Why does the atomic explosion chain reaction stop?

A chain reaction happens when one atom splits and causes other atoms to split. The result is an atomic explosion.

But a chain reaction only works if the warhead stays in one piece. Once the bomb explodes nothing is left, so the chain reaction stops.

How hard is it to make a nuke from scratch?

It’s very hard and very costly. The first two A-bombs cost billions of dollars, employed over 130,000 people, and took over three years to finish.

Does a hydrogen bomb produce radiation?

Yes. A hydrogen bomb is made up of two parts: hydrogen plus A-bomb. Hydrogen doesn’t produce radiation, but the A-bomb does.

How is nuke waste dealt with?

It’s similar to other nuclear wastes, but there is much less of it. Further details are unclear.

Present Dangers

Could a cyber-attack launch a nuke?

Yes. The main (but not only) concern is that cyber-attacks could fool leaders into thinking an attack was in progress. The result could be the launch of thousands of nukes.

Could terrorists get a nuke?

Some have already tried. So far they have failed, but it may be just a matter of time.

The only sure way of stopping them is to get rid of all nukes and their materials.

How many nukes would it take to kill everyone on the planet?

A few thousand are enough. The reason is that nuclear war triggers nuclear winter.

In a nuclear war, cities and forests would burn out of control. Millions of tons of smoke and dust would rise into the upper atmosphere. In just a few days a shroud of smoke would surround the globe. Smoke would block out the sun, causing temperatures to plummet. Crops would be wiped out. Global famine. Extinction.

Even a ‘small’ nuclear war, with just a hundred Hiroshima-sized bombs, would cause major global cooling. Enough to kill one in four from famine.

Could fire cause nukes to detonate?

UK nukes are designed to cope with fires – there would not be an atomic explosion. This might not be true for other countries.

But even without an atomic explosion, fire is still a major hazard. It could leave radiation scattered over a wide area. That’s why the routine transport of nukes on Britain’s roads is of concern.

How can you survive a nearby atomic explosion?

In 1980 the UK govt issued a pamphlet called Protect and Survive. It advised taking shelter in a nearby (preferably pre-prepared) building.

Advice from the US govt is similar: Get Inside; Stay Inside; Stay Tuned.

However, both govts assume that there is a building to take shelter in. But if you live within five miles of the blast all buildings would be destroyed.

And both govts assume that help would arrive. But in an all-out nuclear attack, no help would come.

It all adds up to a very low chance of survival if you’re near an atomic blast.

How long does radiation stay around after an atomic blast?

For a modern weapon, it would take about twenty years to get down to safe levels.

Will other countries get nukes in the next decade?

Since the 1970s roughly one new country each decade has obtained nukes. So we should not be surprised if one or two more get them in the next decade.

What is the Doomsday Clock?

The Doomsday Clock is a symbol that predicts the chance of a nuclear disaster. The closer the hands are to midnight, the closer we are to nuclear catastrophe.


Some countries oppose the new Ban Treaty. What pressure could change their minds?

First, political pressure. The United Nations has wanted to ban nukes since 1946. And today the majority of nations in the UN want a ban.

Second, legal pressure. It can be argued that existing law already requires a ban.

Third, economic pressure, such as sanctions.

Lastly, moral pressure. Nukes could destroy the human race. By any moral standard that’s as bad as it gets.

What happens to bombs that are no longer in use? How do you get rid of them?

The warhead is first taken out of service and placed in storage. Then it’s taken apart piece by piece in the opposite way to its assembly.

The US had a novel way of getting rid of nukes. Until 2013, one in ten US light bulbs was powered by old Russian warheads. Twenty thousand nukes were disposed of that way. Sadly, this no longer happens.

Is it really possible to ban all nukes?

Yes. The world has banned other terrible weapons, such as biological and chemical weapons, so why not nukes?

In fact it’s easier to ban nukes as once they are gone it would take vast amounts of time and effort to make them again. Time enough to prevent new ones being made.

More Questions?

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Protect And Survive, Home Office, HMSO, 1980.
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Until 2013, 10% of US electricity came from disassembled Russian nuclear warheads, Rosen A, Business Insider, Published February 20, 2015. Accessed February 2, 2019.

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