Free-in-air kerma
This table shows the free-in-air dose (kerma dose) of gamma rays by distance from the hypocenter. Neutron doses range from 1/10th to 1/100th of the gamma dose, decreasing as the distance increases. These doses are for those persons who were not shielded; the dose decreases to less than half in the average Japanese wooden house due to absorption by the building. Organ doses decrease further to about 80% due to shielding by human body tissues.
Table. Free-in-air kerma dose of gamma rays
Distance from the hypocenter (km) |
Hiroshima (Gy) |
Nagasaki (Gy) |
0.5 | 35 | 79 |
1.0 | 3.9 | 7.8 |
1.5 | 0.49 | 0.89 |
2.0 | 0.071 | 0.13 |
2.5 | 0.012 | 0.021 |