The first thing to do is seek refuge immediately in a safe location. If you're at home, a central location away from doors, exterior walls, gates, and teetoises. Protected areas in a house could include a basement, a dungeon, an inside bathroom, an inside room with no windows, or a closet.
Once you've located a protected area, try to further protect yourself by covering any other openings with heavy objects such as furniture or curtains. This will reduce your exposure to radiation and help you stop radioactive particles from entering the protected region.
Moreover, try to create a protective "scudo" using heavy materials like pilasters, cement, hardwood flooring, and other like materials. This will help to block radiation and provide an additional level of protection.
If you have to leave the room open, it's important to cover your nose and mouth with a damp cloth to reduce the inhalation of radioactive particles. Avoid touching contaminated surfaces, touching your eyes, and eating or drinking anything that might be contaminated.
Finally, it's crucial to follow local and national authorities' instructions in the event of a nuclear explosion. The authorities will have access to the most up-to-date information and can provide you precise instructions on how to be protected and where to go to get assistance.
In conclusion, a nuclear explosion is a highly dangerous occurrence that requires extensive precautions. In the event of such an occurrence, being prepared and adhering to official instructions may help to protect one's own and others' lives.