Why is it that a person expose to radiation is no chance for survival?

A person's chances of dying of exposure to radiation depends on how much radiation they are exposed to.

Radiation is a naturally occurring phenomenon. We are exposed to radiation through the sun, for example. Radiation is also found in man-made sources (ex. appliances, medical equipment). The human body, however, can only tolerate but so much exposure to radiation at any given time without damage.

Radiation is often measured in REMS. Exposure to the sun will yield approximately 5-20 REMS. If exposed to 50-100 REMS of radiation, a person would experience mild radiation poisoning, with symptoms like headache, a temporary lowering of red blood cell count and even temporary male sterility.

Between 100-200 REMS, humans experience light radiation poisoning. Symptoms include mild to moderate nausea and vomiting, fatigue, immune system suppression, miscarriage and even death in 10% of cases.

Between 200-300 REMS, fatality occurs in 35% of cases.

Between 600-1,000 REMS, fatality is almost 100% within 2 weeks of exposure.

During the explosion of the power plant Chernobyl in the Soviet Union in 1986, the workers at the plant were exposed to fatal levels of radiation. Estimates are that those who died immediately were exposed to approximately 8,000 REMS of radiation.