Why hydrogen bombs are much harder to make than atomic bombs
John McKenna, Formative Content
If it has, it joins an elite club.
Nine countries are believed to have developed nuclear weapons, but only five are thought to have tested H-bombs: the US, China, Russia, the UK and France.
This is because developing hydrogen bombs is notoriously difficult.
Splitting atoms
Nuclear weapons come in two forms: atomic bombs and hydrogen bombs.
Atomic bombs are made by splitting atoms of enriched uranium or plutonium — a technique called nuclear fission. It is the same process that is used to generate civil nuclear energy.
Just to get to this stage is no mean feat: there are limited sources of uranium around the world, with mines in Australia, Canada and Kazakhstan accounting for more than two-thirds of global uranium ore production.
Once a country acquires uranium, it must be enriched before it can be used as the fuel in nuclear fission.
This is because only 1% of uranium in its natural state is easily split with neutrons. This 1% comprises an isotope called Uranium 235, while the remaining 99% comprises an isotope called Uranium 238.
Uranium enrichment refers to the process that separates these two isotopes, and is usually carried out by placing uranium in its gas form into a centrifuge.
The key difference between the enriched uranium used by nuclear power plants and weapons-grade uranium is that the latter is more highly enriched, or “fissile”.
Recreating the Sun’s energy
While the ability to enrich uranium is a giant leap towards splitting atoms in an atomic bomb, it is only a small step towards building a hydrogen bomb.
Thermonuclear bombs, as they are also known, use the nuclear fission process from an atomic bomb as just the first stage of a process that aims to replicate conditions on the Sun.
The huge energy generated by the Sun and other stars is created by nuclear fusion.
Nuclear fusion squeezes atoms together, causing their nuclei to fuse.
In the Sun, massive gravitational forces create the right conditions for fusion, but on Earth they are much harder to achieve and require a huge amount of energy.
H-bombs use the energy from an initial atomic explosion to trigger nuclear fusion.
This explosion heats hydrogen isotopes in the bomb to temperatures reaching 100 million degrees Celsius, causing their nuclei to fuse together.
The energy released by the nuclear fusion is so powerful that it can split apart atoms of unenriched uranium.
This resulting nuclear fission can create explosions thousands of times bigger than the atomic bomb dropped on Hiroshima in the Second World War.
Barriers to building an H-bomb
Even if a country like North Korea had all the technology and expertise in place to develop a hydrogen bomb, there are still two substantial barriers to overcome.
First, hydrogen isotopes like tritium that are used in thermonuclear bombs are rarely found in nature. Instead they must be synthesized in specially designed reactors, which aren’t easy to build and generate tiny amounts of tritium at a time.
Second, H-bombs like the Tsar Bomba — the biggest bomb ever dropped — are too large for most aircraft, let alone long-range missiles.
Creating an H-bomb small enough to fit on a nuclear warhead but still capable of devastating damage is therefore extremely difficult.
Experts believe it’s likely that North Korea has created a “boosted” atomic bomb. This contains a small amount of hydrogen isotopes that trigger a small fusion reaction. The fusion reaction boosts the overall power of the atomic explosion from nuclear fission.
When North Korea claimed it had developed a hydrogen bomb in 2016, experts claimed it was more likely to be a boosted-fission device.
However, with initial seismic data from the explosion’s tremor suggesting it is an order of magnitude bigger than any previous nuclear test in the country, scientists are now considering the possibility that North Korea has in fact finally successfully developed a genuine H-bomb.
Have you read?
- North Korea’s nuclear test? Here’s what the science can tell us
- These are the countries with nuclear weapons
- What is nuclear fusion? The science explained
Originally published at www.weforum.org.
