How much does it cost to build a nuclear bomb?

Answer 1

Probably on the order of $100,000 and most are likely less. The majority of the cost is the high purity nuclear materials.

There are several major costs in building a nuclear bomb, which can be categorized as such:

Weapon Design: the scientific and engineering effort required to fully understand how a nuclear weapon works and make a functional design. This includes a significant amount of computer hardware to do simulation, a moderate number of highly-trained physicists, and a larger number of engineers and technicians to build and test various components. A conservative estimate to design a very basic, reliable "gun-type" Uranium bomb would be many tens of million dollars. A plutonium implosion bomb likely would require several hundreds of millions, with a "boosted" advanced atomic bomb design being slightly more expensive. A reliable hydrogen bomb design would almost certainly costs tens of billions of dollars, as they are incredible complex devices.

Fuel Costs: acquiring the atomic fuel (weapons-grade u-235 or pu-239) is astronomically difficult. Theoretically, it might be purchasable on the black market, for $10-50 million PER BOMB, but that's assuming you can find it (and don't get caught by one of the big country's spy networks). Making it costs tens of billions, as obtaining the raw materials isn't simple; you would need 100x the bomb fuel's weight in reactor fuel, or 10,000x the amount in raw uranium ore to start with, and the purifying plant is a huge complex filled with expensive equipment, and requires an enormous amount of electricity to run. Tritium/deuterium production is slightly less expensive, but not that much cheaper.

Bomb construction: making the actual bomb from a solid design is modestly expensive, as you need high-quality machine tools able to produce the parts to a very high level of tolerance. Overall, through, it should not be that expensive, perhaps a few million dollars to buy the machine tools and parts.

Thus, if you want to make multiple nuclear bombs, and have a reliable design that will work 99% of the time, then you probably need to spend $50 billion or so to make a simple A-bomb, $60 billion for an advanced A-bomb, and $200 billion or more for a H-bomb. After that, each bomb should run several million dollars each to make, regardless of type.

"Terrorist"-level bomb-making:

If all you want to do is build a crude, gun-type Uranium-fueled atomic weapon, that has a reasonable chance of working, then, assuming you have enough weapons-grade uranium on-hand, you can probably build one for a few tens of thousands of dollars, provided you can order certain machined parts from suppliers, make the rest yourself at a local quality tool-and-die shop, and have access to a few dozen cheap PC computers. I'd say you could easily build one for $100,000 or less. I'd give your bomb less than a 50% chance of working properly, though.

There is no ability to "home-make" anything other than a crude gun-type Uranium bomb. The design and construction requirements for an implosion devices require the resources of a large-sized company, at the very least, and such weapons will not work unless there is significant effort put into the design (you can't cut corners on the design or components of an implosion device, unlike a gun-type device). That is, even if I gave you 30 pounds of weapons-grade Plutonium, you'd still need 10-20 million dollars to produce an implosion device that might work (and, I'd give it a low-probability of functioning properly).

Hydrogen bomb design and manufacturing is impossible for anything outside a major government-level effort.