Lecture 15

Prompt Radiation Effects from a Nuclear Bomb

Monitoring radiation intensity

1. The so-called dosimetry units (rad, rem) determine the amount of damage radioactive radiation can do to the human body. They depend on the kind and nature of the incident radiation (X-rays, gamma-rays, beta-particles, alpha-particle, or neutrons).
2. They also depend on the energy loss of the particular radiation and the associated ionization effects in the human body material.
   

Radiation Exposure & Dosimetry

1. Radiation is measured as the amount of energy E deposited by radiation into a body part of mass m. (unit Rad or Gray).
2. Units of Radiation Measurement
   
3. 1. The Sievert is a measure of the biological effect.
   2. 1 Gray (Gy) = 1 Joule/kg  (Energy/mass).
   3. 1 Sievert (Sv) = Gray x Q, where Q is a "quality factor" based on the type of particle.
   4. 1. Q for electrons, positrons, and x-rays = 1.
      2. Q = 3 to 10 for neutrons, protons dependent upon the energy transferred by these heavier particles.
      3. Q = 20 for alpha particles and fission fragments.

  Sources of Natural Radiation and Radioactivity

1. Cosmic Ray Bombardment
   1. Cosmic Rays originate from: solar flares; distant supernovae.
2. Long-lived K-40 Radioactivity (in US).  K-40 has a half-life of T1/2=1.28·109 years its natural abundance is 0.021 %.
3. Internal Gamma Glowing
   On average, 0.27% of the mass of the human body is potassium K of which 0.021% is radioactive 40K with a half-life of T1/2=1.25·109 [y].  Each decay releases an average of E avg= 0.5 MeV  radiation, which is mostly absorbed by the body, but a small fraction escapes the body.
   
4. Radon
5. 1. Radon is a radioactive inert gas.
   2. Radon progenies build up in confined space and are breathed in.
   3. Basal cells in bronchial epithelium are believed to be target cells for cancer.

Fission products

Dose received from bomb tests