Nuclear weapons: distance by thermal radiation level

The explosion of a nuclear weapon releases energy in three major forms; blast energy, thermal energy, and nuclear radiation. Thermal energy accounts for around 35 percent of that released by a nuclear explosion, and this can cause a catastrophic amount of damage in addition to the destruction caused by the blast.

Effect on humans

Near ground zero of a one megaton nuclear explosion, thermal radiation is strong enough to vaporize a human body, although most people in this area would be killed by the blast force. At a distance of up to six miles, thermal radiation would be around 13 calories per square centimeter (cal/cm²), which would be strong enough to inflict third degree burns to all unprotected skin, causing damage on a muscular or skeletal level. Around half of unprotected people would experience third degree burns at 10 cal/cm² (6.9 miles), around half of unprotected people would experience second degree burns at six cal/cm² (8.6 miles), and around half of unprotected people would experience first degree burns at three cal/cm² (11.5 miles).

Effect on non-living objects

For non-living objects, fabrics would catch fire in areas where thermal radiation was 18-20 cal/cm², unpainted wood would burn at 15 cal/cm², and newspaper would catch fire at eight cal/cm². Again, this is compounded on top of the destruction that would be caused by the force of the blast, which would cause winds with peak velocities similar those of the strongest hurricanes at around 4.5 miles from ground zero.