Britannica Sources used in this answer

How do gamma rays and neutrons create initial radiation hazards after a nuclear explosion?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

U.S. hydrogen bomb test in the Marshall Islands — nuclear weapon A test of a U.S. thermonuclear weapon (hydrogen bomb) at Enewetak atoll in the Marshall Islands, November 1, 1952.

Initial radiation, often called prompt radiation, is a critical hazard generated within the first minute of a nuclear detonation. This radiation consists primarily of gamma rays and neutrons, which are released as part of the explosive energy of the weapon.12

These particles create significant hazards for living organisms due to their high penetrating power, allowing them to pass through most structures over considerable distances. While they account for only about 3 percent of the total energy released in a nuclear explosion, they are responsible for a substantial proportion of casualties.1

The biological impact of this radiation is severe because both gamma rays and neutrons can cause extensive damage to human tissue. Furthermore, neutrons are particularly effective agents of mutation, often causing more biological damage than other forms of ionizing radiation. Because of their ability to travel long distances and penetrate shielding, these emissions pose an immediate and lethal threat to anyone in the vicinity of the blast.13