FALLOUT FACTS
So what are the facts around a nuclear event and how can you guard against them. To begin with there are two types of nuclear blast from a weapon: air burst and ground burst.
An air burst describes the type of explosion when a bomb is detonated above the ground. This would have a ‘good’ effect on the target, there would be widespread blast and thermal damage but only in a specific area.
Ground burst weapons explode on contact with the ground in order to destroy a hardened target or devastate an area. These types of burst cause the classic mushroom cloud. This sucks up dust and debris which forms the cloud. Eventually this, now radioactive, dust will fallout of the cloud, carried by the wind, spreading radioactive contamination across a much wider area.
There are a couple of key things to know about the aftermath of a nuclear detonation. There are three main types of radiation: Alpha, Beta & Gamma. All three will be generated by a nuclear explosion. The Alpha particles are the least troublesome as they will not penetrate thick clothing. If they are inhaled or land on a cut then they may cause cell damage. Beta particles travel faster than Alpha and could pass through clothing. They wouldn’t pass through masonry though. Because they travel fast they could cause burns and damage to the eyes and respiratory system.
The third type is Gamma. This is the most deadly. If you see the blast from a detonation then you have already received a fatal dose of Gamma radiation. Gamma is like an invisible light, travelling as fast. It moves in a very random way, not like light rays. It passes through the body and damages the DNA strands that it touches. This is what leads to severe radiation sickness. Your best hope in a strike is to wait inside until the light has passed before moving to your shelter before the fallout starts to appear.
No shelter is going to save you if you are within the central zone of an explosion. If you are a few miles from the explosion and you are already in a shelter then you stand a good chance of surviving. The further you are away and downwind of a detonation the more likely you are to survive.
There is some good news though, the levels of radiation diminish significantly over time. For every sevenfold increase in time, there is a tenfold decrease in radiation levels. So after two days the levels drop dramatically and after two weeks you reach a level where you can move around without the need for lots of protection.
So what can the shelter do to help you in the critical two days after an incident? Well, we need to understand halving thicknesses and protection factor.
The halving thickness is what is used to describe the protective thickness characteristics of different materials. In our case we are burying our shelter, so compacted soil is used. The halving thickness of soil is 3.6 inches. This means that for every 3.6 inches you reduce the radiation penetration by 50%. So if we double that we reduce the radiation by 75%, another layer takes it to 87.5% and so on.
The protection factor for modern shelters is PF1000, this means that the shielding is thick enough to reduce any radiation penetration down to 1/1,000th . The required depth or thickness of compacted soil for this PF is 36 inches.
