Which part of making an atomic bomb is the hard part and how many people know how to do that? [closed]

Question

I mean which part of the process of making an Atomic bomb is the hard and how many people know how to do that on Earth. Is it in hundreds or less i.e. 20 - 50 people or even less?

Don't get me wrong but I don't get it, because the USA has A-bomb from July 16, 1945 (Trinity) so it is almost 70 years!

How can by it so difficult with today technology that has advanced tremendiously?

Answer 1

The hard part is getting the material — enriched uranium or plutonium :-)

Other than that it's trivial to make gun-type device similar to the Hiroshima one, but it requires much more material as you need a critical mass to sustain a chain reaction.

A more advanced implosion version crushes the material and so increases its density, so you need less material. The usual method is to make the material into a sphere and symmetrically detonate chemical explosives around it. The hard part is ensuring these charges denotate symetrically, as even several microseconds' delay between their detonations prevents the material reaching critical density.

About "getting the material", you could enrich uranium by reacting it with fluorine to make uranium hexafluoride, and spin it in a powerful centrifuge. Ordinary uranium contains mostly heavier U-238 (not useful in your case) and lighter (useful) U-235. The centrifuge very slowly separates the useful isotope from the less useful "depleted" uranium.

As for politically hard part, try building such a centrifuge and you'll soon have the IEAE (or worse) knocking on your door!

Answer 2

It is still difficult because the physics involved in nuclear weapons did not change over time and is fortunately quite involved. Some of the challenges are listed in the Wikipedia article about nuclear weapon design.

Even if technology has advanced you need complex models involving the reactions and the outcome on very small timescales. One example is how to compress a metal sphere using explosives absolutely evenly in microseconds. The faster computers help you only a bit, as you still need accurate models that can often only be calibrated using extensive data from experiments. This data is almost exclusively classified so only few things changed compared to decades ago in terms of published or generally accessible knowledge.

I do not want to speculate about the number of people who might have enough knowledge as this is off-topic here. One should not forget though that it is not only about the knowledge but also about the access to a lot of technologies and materials.

Answer 3

To develop an A-bomb from scratch you have to make tests. Such tests cannot be made unnoticed by other nuclear powers (they are easily detectable from space, by seismic sensors and by radiation pollution dosimeters).

Once you have your tests detected, you face strong political response and possible sanctions.

Answer 4

Organising the administration.

The Manhattan project employed 100,000 people - many of them physicists or mathematicians. Even organising a room full of physicists and mathematicians and keeping them concentrated on a common goal for a longer than a tea break is impressive. Managing 1000s of them for many years in secret is almost un-imaginably difficult.