The likely effects of a nuclear attack

Light and Heat

A nuclear explosion produces an intense flash of light lasting several seconds, which can blind anyone seeing it. The heat flash can set fire to buildings at a certain distance from the center of the explosion, depending on the haziness of the atmosphere at the time. Skin exposed to the heat flash could suffer burns. However, any shelter that can withstand the blast would provide protection against the heat flash. Any exposed parts of the shelter made of flammable material could catch fire. Exposed plastic would not catch fire but might distort in the heat, weakening the resistance of the shelter to the subsequent blast wave.

Initial Nuclear Radiation (INR)

This highly penetrating radiation is emitted from the fireball within one minute of the explosion. The distances from one megaton explosion and above, at which people require shielding from INR, are less than those distances at which there would be total destruction.

Blast

At the moment of explosion, a blast wave would be generated, traveling at a tremendous speed and creating extremely strong winds that may last for several seconds. When the blast wave passes over a building, the sudden increase in pressure and the following wind may cause the building to either explode or collapse.

Tremors

The tremors or shock waves from a ground blast extend for a short distance only and would not affect buildings beyond those already destroyed by the blast. The effect on shelters below the ground would depend on their ability to withstand ground movement and on the nature of the soil. Depth in the ground, shape, and flexibility would be important.

Fallout

An explosion on or near the ground sucks up a large amount of earth and debris, which is vaporized as it rises to a great height and becomes highly radioactive. It then condenses to sand-like particles that are carried along by the wind and drop to the ground. This fallout can come down very near to the explosion or may be carried by the wind for hundreds of miles. The fallout dust is usually visible to the naked eye but emits ionizing radiation, similar to X-rays, which cannot be seen or felt. Radiation is dangerous, and heavy doses cause sickness or death. Fallout dust remains radioactive for several days after the explosion and can, in certain circumstances, still be dangerous after several weeks.

Radiation and Fallout after a Nuclear Attack

If a nuclear attack were to happen, it's important to understand what fallout is and what happens to it. Fallout is the mixture of radioactive particles and debris that falls to the ground after a nuclear explosion. The radiation emitted from fallout decreases rapidly at first and then more slowly over time. For example, after 7 hours, the radiation emitted will be 10% of its original strength and after 2 days, it will be 1% of its original strength.

Once radiation levels have dropped to a safe level, the government will use various communication methods to inform the public. These methods include text messages, phone notifications, social media posts, emergency alert systems, and public address systems. You'll be advised when it's safe to emerge from your shelter for short periods. Initially, it may only be safe to spend an hour or so a day outside, but gradually, this safe period will increase until it's safe to stay outside all the time.

In the worst-affected areas, it may be safe to leave the shelter after about two weeks, while in most places, this period will be much shorter. It's important to follow the advice of the authorities and not leave the shelter until you're told it's safe to do so. By doing so, you can protect yourself from the harmful effects of radiation and keep yourself and your loved ones safe.

When outside the shelter, no special clothing is required, but it would be advisable to wear outdoor clothing and rubber boots or heavy-duty shoes to avoid contamination of indoor clothes. These clothes should be removed before re-entering the shelter. Shelters offer varying degrees of protection against blast and fallout. They will also provide protection against the heat flash, provided no flammable materials are exposed. No shelter can protect someone close to the site of a nuclear explosion. However, for those who are far enough away to survive the initial effects, the principal danger after the explosion is from radioactive fallout.

Protection Against Radiation and Fallout

Dense materials around a shelter can reduce the risk of harm from radiation as long as you remain inside. Generally, the thicker the material, the better the protection. However, some protective materials are more effective than others. The following list includes common materials likely to be used in shelter construction, and their effectiveness in reducing radiation by half:

• 2 inches of lead is equivalent to 3.5 inches of slate

• 4 inches of concrete

• 6 inches of packed earth

• 8 inches of bricks

The protection provided by buildings or shelters can be expressed as a protective factor. A typical house will reduce the power of radiation to one-fifteenth of that outside, which is a protective factor of 15. Shelters constructed of the right materials can give a much greater protective factor than this.